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N900WM
07-07-2006, 08:34 AM
Hey Guys,
New to the forum and my 91 prostar. Although I've owned a few boats in the past, never and inboard.

My boat has an Indmar 351 with 900 hours and electronic ignition. It runs very well and is in top mechanical condition. However, I could use a bit more speed to haul my fat a$$ barefooting and I have ordered the GT40 heads and the Edelbrock intake.

Has anyone performed this upgrade and do you have any additional thoughts on what else should be done?

It seems a shame to change this stuff out without changing the cam while I'm at it. But I've not seen where many people are changing cams. The stock cam may be the best option?

Any thoughts or insight would be appreciated.

starman205
07-07-2006, 10:32 AM
Consider buying a CNC prop from Acme. That will also improve your hole shot. :wavey:

P.S. Welcome to the board. Check out the Frequently Asked Questions Thread for additional information, and Doug should be along shortly.

east tx skier
07-07-2006, 11:46 AM
Welcome. My boat came with the GT40 heads and I already had the acme 13x12 three blade on there. A CNC'd prop is a great add on for sure.

I added the performer intake last year and the torque increase was great. If you're looking for more top end though, you might consider going for the rpm intake

I can think of about 3 issues you will encounter with the intake swap. Both have to do with the fact that you do not have very much room under your engine box and the new intake will add height.

You absolutely need a low-profile flame arrestor. Ski Dim used to sell them, but last I heard, they don't anymore. I know someone on here was doing the search. If you call SkiDim, they may be able to tell you what part number to look for.

Next, even with the low profile flame arrestor, your sound dampening may (and I stress may) be in contact with the flame arrestor. In my setup (new sound dampening material), I had to cut out the area above the flame arrestor and replace it with foil tape (foil tape won't work with the OEM material, but works great with the foil backed stuff I used from overtons). I think my stuff is thicker than the OEM material; hence my problem. If you have the stock stuff, you may be okay.

Last issue, and this was the biggest pain to figure out. Be mindful of your throttle cable. With the higher manifold, and due to the fact that the throttle cable is partially supported by a plate on the manifold (and probably due in part to the fact that my throttle cable is attached to one of my hoses at the perfect pass servo), raising the back end of it up while the front part that was attached to the hose stayed the same height created problems. Basically, you want that throttle cable to stay pretty much level. If it isn't, it will bind where it breaks (where it runs by the carb). When it binds, you will notice that it hangs at about 1,200 rpm when you try to bring it back to neutral). If you encounter this problem, you will need to buy a taller mount for the back of the thottle cable for the manifold. It runs about $36.

In the end, it was all worth it. Loads more low end when combined with the GT40 heads.

As for the cam, that's definitely a good way to get more out of the motor. I've been warned by skidim though not to go too aggressive with them. Something about sucking water into the cylinders (but don't quote me as memory fades).

Another option is to take the newly acquired GT40 heads to a machine shop and have the cylinders shaved a bit to get a bit better compression ratio than the stock 8.5:1. This should run you about $100 per side or so. I thought about doing it, but after the new intake, I decided I had no compulsion to do anything else. I was very satisfied with the increased torque and have no need for more top end.

bikeman
07-07-2006, 10:43 PM
I'd be very curious to hear someone's experience on getting their heads ported and polished as well as shaved as compared to "new" GT40s which I'm guessing have larger valves? do they have some significant flow characteristics (aside from the manifold adder)? I've been considering polishing up mine as they are now 10 years old and sit half the year and I'm sure are gunked up.

east tx skier
07-07-2006, 11:07 PM
I think someone here mentioned putting the GT40Ps on their boat, but I can't for the life of me remember who it is.

TRBenj
07-08-2006, 10:27 PM
I'd be very curious to hear someone's experience on getting their heads ported and polished as well as shaved as compared to "new" GT40s which I'm guessing have larger valves? do they have some significant flow characteristics (aside from the manifold adder)? I've been considering polishing up mine as they are now 10 years old and sit half the year and I'm sure are gunked up.

Buying new GT40 or GT40p heads will give you much more bang for your buck over having your stock heads professionally p/p'ed. You'll need a pro to do it to get anywhere near the flow of the GT40 or GT40p's. The valves are a little bigger, but thats not the entire reason they flow better- they are just a better design. The GT40p's actually have the same size intake and a smaller exhaust valve than the standard GT40's, and the P's outflow them all across the board. The P's also have a smaller combustion chamber, so you'll see a performance improvement from the bump in compression as well. New GT40's or GT40p's can be had for $550 if you know where to look, and as low as $200 used in decent condition.

There is no danger in putting a better performing cam in your boat- as long as you know what youre doing. There is the possibility that too much overlap on the intake and exhaust could result in reversion (sucking water back into the cylinders) since we have wet exhaust. Some people recommend 112 degree lobe seperation to be safe. I am getting a cam from a place called Cam Research- who only do Fords and have experience with ski boats- and they said I would have no problem with 110 degrees, and it would perform a little better than 112.

Some people claim that low end torque is all-important in a ski boat. Torque is definitely king, but not necessarily low-end. When I take off WOT from an idle, I get an instant 3k RPM from my 240 horse 351w so you should see similar- the prop slippage acts like a high-stall torque converter on a car. I argue that midrange torque and throttle response are more important than low end. My cam was matched to the other components I will be installing (Weiand Stealth intake and GT40p heads) and the powerband will be 2500-5200 RPM. I expect to turn all of 5200 with the mods, as I currently can turn a strong 4600.

rcnjson
07-11-2006, 01:35 PM
I am new to the forums but not new to the small block fords. I put a set of Canfield aluminum heads that I had laying from my mustang on my boat. The heads are 195 CC intake runners and 2.02 intake valves (big time HP heads). Along with the heads, I did the Performer intake and a Barry Grant carb. I haven't got the setup sorted out quite yet, the carb is giving me fits, but it should rip. The heads also have 1.6 roller rockers which is what I would recomend for anyone who wants an easy 25-30 HP's out of their current setup. I'm not sure what the different boat engines came with for heads, but mustangs (302W and 351W use the same heads) came with 1.5 ratio stamped rockers. The 1.6 ratio gives you a little more lift without changing the cam, and that is lift through the whole cam profile. Going to the roller instead of the stamped rocker reduces friction in the valvetrain to free up some HP's. If you really want to uncork it you could go with a 1.7 roller rocker on a stock head. Not an option for me because of the huge intake valves and piston to valve clearance. The pedastal mount roller rockers are a simple installation, just pull off the rocker boxes, unbolt the old ones, bolt on the new ones. No messing around with backlash or lifter preload on the pedastal mount (stock setup). They are available all over the place for 100-150 used for a good set or like 200 new.
k

east tx skier
07-11-2006, 01:39 PM
Some people claim that low end torque is all-important in a ski boat. Torque is definitely king, but not necessarily low-end. When I take off WOT from an idle, I get an instant 3k RPM from my 240 horse 351w so you should see similar- the prop slippage acts like a high-stall torque converter on a car. I argue that midrange torque and throttle response are more important than low end.

You are correct IMO. While I may have said low end, I should have added mid range. As you said, 3k rpms is reached in a seeming immediate fashion.

TRBenj
07-11-2006, 03:04 PM
I am new to the forums but not new to the small block fords. I put a set of Canfield aluminum heads that I had laying from my mustang on my boat. The heads are 195 CC intake runners and 2.02 intake valves (big time HP heads). Along with the heads, I did the Performer intake and a Barry Grant carb. I haven't got the setup sorted out quite yet, the carb is giving me fits, but it should rip. The heads also have 1.6 roller rockers which is what I would recomend for anyone who wants an easy 25-30 HP's out of their current setup. I'm not sure what the different boat engines came with for heads, but mustangs (302W and 351W use the same heads) came with 1.5 ratio stamped rockers. The 1.6 ratio gives you a little more lift without changing the cam, and that is lift through the whole cam profile. Going to the roller instead of the stamped rocker reduces friction in the valvetrain to free up some HP's. If you really want to uncork it you could go with a 1.7 roller rocker on a stock head. Not an option for me because of the huge intake valves and piston to valve clearance. The pedastal mount roller rockers are a simple installation, just pull off the rocker boxes, unbolt the old ones, bolt on the new ones. No messing around with backlash or lifter preload on the pedastal mount (stock setup). They are available all over the place for 100-150 used for a good set or like 200 new.
k

I am no expert, but I believe you are incorrect on the 1.5 rockers coming stock on Fords. I believe windsors (including 302w and 351w) had 1.6 rockers stock. Small block Chevies came with 1.5 rockers from the factory, I believe. A decent Ford upgrade would be to go with 1.6 roller rockers, decreasing valvetrain friction. The 1.7 rockers would give you more lift, but should be used cautiously as they may impact piston-valve clearance (as you mentioned). They may also push your powerband beyond the RPM that our boats turn- so they should be matched carefully to your specific cam. They may work well with a mild (stock)cam though.

I've been told that aluminum heads may not be a good idea on a FWC marine engine for 2 reasons- the different expansion rates of the iron block/aluminum heads and the effect of electrolysis on the aluminum. I know PCM's ZR6 (6L) has iron block/aluminum heads and uses closed cooling- is the LQ9 the same? I believe some Donzi owners are running AFR heads on their boats, and I think are having good experiences with them. AFR offers the option to have the heads anodized on all exterior surfaces as well as inside the water passages, which is interesting.

Ive heard great things about the Barry Grant carbs- I bet once you get everything tuned your boat will fly with that carb+heads!

rcnjson
07-11-2006, 03:37 PM
yep stock is 1.6, my bad, first post and already I muddied the waters... Anyways, I wouldn't worry about the aluminum - cast iron interaction between the heads and block. Aluminum heads on cars expand and contract too as a function of the heat they see. The cars run hotter than the boats so the heads are actually expanding more on the car (so is the block) but aluminum expands faster than the cast iron so at a higher temperature the difference in expansion is actually greater.

There may be a disadvantage to using the aluminum heads in a salt water environment. I know that the aluminum will turn to dust complements of the salt and temperature. Freshwater shouldn't be a problem.

I'll get back when I have the carb sorted, a couple of my friends have MC's and they wanna race so we'll get some results maybe this weekend? One has a early 90's Tri star and the other has an 87 190? maybe. We'll see I should have 'em covered, if not who knows, maybe its time for a stroker motor.

TRBenj
07-11-2006, 06:11 PM
When I contacted AFR, they said the anodizing wasnt necessary on a fresh water only motor, but I wouldnt take any chances after spending that much money! I just know that there are people out there that think aluminum heads on a boat are a bad idea.

I think a stroker motor is a great idea. When it comes time to do a full rebuild on mine, I dont think I could resist a 393w with AFR's!

N900WM
07-17-2006, 08:34 AM
Hey Guys,
Thank you very much for your input. Good input and very much appreciated.
Installation is scheduled for next week. I'll report back once she's operational.

rcnjson
07-18-2006, 12:30 PM
N900WM,
This may go without saying, but if you are putting new heads on use new head bolts. ARP head bolts would be better than stock replacements, they cost a bit more, but they are better and reusable. The stockers are torque to yield so they actually stretch at the final torque setting. The ARP bolts do not yield (or stretch) when they are torqued. Some 302's and 351's used different size head bolts. If you are interested, I can get you the part number for the bolts I used, they are like $50.00 through Summit. I also have recommendations for gaskets if you are interested.
Jason

TRBenj
08-02-2006, 08:16 AM
I finally got my heads, intake and cam installed (GT40p's, Weiand Stealth and Cam Research Cam) last week, and got back on the water last night. WOT RPMs increased from 4600 to just over 5000 RPM, top speed is somewhere around 48-50 (previously 43). Holeshot and midrange power are both great. I get an instant 3200 RPM out of the hole and it gets to 4800 real fast. Overall, I'm very pleased.

N900WM
08-02-2006, 01:30 PM
I finally got my heads, intake and cam installed (GT40p's, Weiand Stealth and Cam Research Cam) last week, and got back on the water last night. WOT RPMs increased from 4600 to just over 5000 RPM, top speed is somewhere around 48-50 (previously 43). Holeshot and midrange power are both great. I get an instant 3200 RPM out of the hole and it gets to 4800 real fast. Overall, I'm very pleased.


Do you have specs on the cam?

TRBenj
08-02-2006, 10:10 PM
This cam was recommended based specifically on my intake, heads and intended use. It is installed 3 degrees advanced, as recommended by Cam Reasearch. Specs:

RPM Range: 2500-5200
Duration @.050" (I/E): 218/222
Lift w/ 1.6 Rocker (I/E): .490/.490
LSA: 110 degrees

I lined up against my dad's '03 SN 196 with the 330 Excalibur motor and I put a quick couple of boat lengths on him that I held up to top speed. Tremendous midrange power.

N900WM
08-04-2006, 01:03 PM
TRBenj,
I finally got on the water this morning with the new heads and intake. The boat is an animal!
I'm turning 5200 rpm at WOT. Speed is about 46mph. Lotsa torque!
Previous to the upgrade, the boat saw 4600 rpm at WOT.

I'm running a 13x13 prop as was recommended by Skidim. I didn't expect it to turn 5200.
What prop are you running?

east tx skier
08-04-2006, 01:42 PM
Did you go with the GT40p heads? If not, 5,200 sounds high with the standard performer. Sorry, I've not reread the thread (maybe you have a different intake than me). Can you refresh my memory?

TRBenj
08-04-2006, 04:03 PM
I saw a strong 48 MPH at 5100 RPM last night. The prop was a 12.5x15 Acme 3-blade (I have a '90 Nautique with the 1.23:1 tranny). Gaining 600 RPM is extremely impressive- good for you! I think I have a little more top end to gain by rejetting. It gets to 4800 real fast and 5000 isnt far behind. Ill have to read the plugs and see if Im lean.

DooSPX
08-05-2006, 07:05 PM
did you have to get a low profile flame arrestor to fit under the stock 91 motor box?

N900WM
08-07-2006, 11:20 AM
East TX skier- yes, GT40 heads and Edlebrock intake.

DooSPX- stock flame arrestor fits nicely with stock plstic cover.
I had previously re-insulated the engine house with 1/4" foil insulation. This no doubt made some room.

east tx skier
08-07-2006, 11:49 AM
Edelbrock Performer intake or Edelbrock performer RPM?

I'm surprised you had room under the box. I have the same setup (same insulation and had to go low profile and cut out the insulation, which was thicker than stock, to get the box to close with any clearance over the flame arrestor.

N900WM
08-07-2006, 02:02 PM
Performer.
Throttle bracket was ok as well. The geometry did change a touch but all works well. Had to change the return spring to a weaker spring but that's all.

east tx skier
08-07-2006, 02:13 PM
Part of my issue was with the location of the perfect pass servo as well.

I'm still amazed you had room under the box after all was said and done. I'll bet going stock to GT40s and a new intake was pretty impressive change.

N900WM
08-09-2006, 07:47 AM
VERY Impressive!
I finalized some carb adjustments last night. GPS shows 49mph.
NICE!

dchatagnon
12-05-2006, 04:49 PM
Hi,
I'm having a ford 351 HO and I'm considering about the intake manifold upgarde. EastTX did you install this one : http://www.skidim.com/prodinfo.asp?number=EDL-2181
I'm having the 4160 holley carb. What else do I need? Once you have installed the new intake, do you still need the spacer plate ?

Thanks.

east tx skier
12-05-2006, 05:21 PM
That's the one. I kept the spacer plate on there. Check your clearance and hunt for a low profile flame arrestor.

TRBenj
12-05-2006, 05:37 PM
Whether you need the spacer plate depends on where your PCV is plumbed in. Newer 4160's have a vacuum port you can use that will allow you to get rid of the spacer. If you need the spacer for the PCV, then youre best off keeping it. Some people have plumbed it into the intake manifold itself, but you run the risk of leaning out one cylinder.

I have a used Edelbrock Performer for sale. Shoot me a PM if youre interested.

east tx skier
12-05-2006, 05:40 PM
TRBenj, I've got a newer 4160 and would love to lose the spacer. Can you show me on this picture where it would be plumb in absent the spacer?

/edit, although you can't see the PCV, it appears to be plumbed into the spacer. Where on the carb would it attach?

TRBenj
12-06-2006, 01:04 PM
ETS, Ive been told that the newer Holleys have vacuum ports for the PCV. If you have one, it should be a 3/8" port somewhere on the base plate of the carb. Ive never actually seen one myself.

Jim@BAWS
12-06-2006, 01:39 PM
Doug,

If you want a LITTLE extra out of that FORD 351.Bang out the baffles in tose mufflers or go straight PVC. You will see and increase

Jim@BAWS



TRBenj, I've got a newer 4160 and would love to lose the spacer. Can you show me on this picture where it would be plumb in absent the spacer?

/edit, although you can't see the PCV, it appears to be plumbed into the spacer. Where on the carb would it attach?

east tx skier
12-06-2006, 02:39 PM
Thanks TRBenj, I'll give it a look.

And thanks, Jim, for the suggestion. But after the performer intake install, I stopped wanting for anything more in the power department. The low to midrange bump I got from the intake was just the ticket. Felt like a whole new boat.

The only thing I'm wondering about is reducing the low clearnance. I figured out that the small cutout in the noise reduction material I made to get the engine box down was starving the boat for air at 2,175 rpm and only there. I cut a little channel in the foam and finished it off with foil tape and problem solved. If I could drop it two inches, I could put the shroud back on.

etduc
12-06-2006, 05:47 PM
TRBenj, I've got a newer 4160 and would love to lose the spacer. Can you show me on this picture where it would be plumb in absent the spacer?

/edit, although you can't see the PCV, it appears to be plumbed into the spacer. Where on the carb would it attach?

The newer carbs, are cast into the carb main body (back of carb)

On my Edlebrock, it can be drilled and tapped (or press fitted) with a 3/8" tube,at the rear of carb body.

Isn't that a 3/8" tube, I see attached to your flame arrestor?

Some flame arrestors, have the a pvc tube fitting directly on the arrestor. My old jet boat did.

DooSPX
12-06-2006, 07:28 PM
Doug,

If you want a LITTLE extra out of that FORD 351.Bang out the baffles in tose mufflers or go straight PVC. You will see and increase

Jim@BAWS

Im still thinking off removing my big silentmaster and putting in two pvc pipes.
how much increase are you talking about?

TRBenj
12-07-2006, 10:19 AM
The newer carbs, are cast into the carb main body (back of carb)

On my Edlebrock, it can be drilled and tapped (or press fitted) with a 3/8" tube,at the rear of carb body.

Isn't that a 3/8" tube, I see attached to your flame arrestor?

Some flame arrestors, have the a pvc tube fitting directly on the arrestor. My old jet boat did.

You want to plumb the PCV to a vacuum source- the flame arrestor is not one of them. It must be at the base of the carb, on the spacer, or directly to the intake manifold. A valve cover breather, on the other hand, is fine to run to the flame arrestor. Breather hose is usually 5/8", while PCV is usually 3/8", but I suppose that could vary.

Jim, is it fine to run PCV in place of a long stretch of exhaust hose? That hose sure is expensive. Any things to be careful of?

TMCNo1
12-07-2006, 11:30 AM
10' of 3" aluminum conduit from a electrical contractor you may know or a electrical supply house would be your safest alternative to use to replace the mufflers. The cost would be around $80 + tax in most areas for a walk-in retail customer and if you know someone in the electrical industry it will probably cost somewhat less wholesale. 2 replacement mufflers are around $275.

east tx skier
12-07-2006, 12:18 PM
You want to plumb the PCV to a vacuum source- the flame arrestor is not one of them. It must be at the base of the carb, on the spacer, or directly to the intake manifold. A valve cover breather, on the other hand, is fine to run to the flame arrestor. Breather hose is usually 5/8", while PCV is usually 3/8", but I suppose that could vary.


Let me put it this way, going from memory, if my PCV is plumbed somewhere other than the spacer, is there any need for the spacer?

TRBenj
12-07-2006, 01:50 PM
ETS, as long as you have a suitable vacuum source for the PCV, then you dont need the spacer. The flame arrestor is not a vacuum source, as suggested above. If you have one on the carb, youre golden.

The spacer probably also adds a little bit of HP, but not much. I think its effect would be decreased with the improved intake manifold. I am looking to gain a little more clearance as well. I think I can get just enough by going with a slightly shorter flame arrestor and going from a 1" to a 1/2" spacer. Im gonna add the PCV port to the shorter spacer since my carb is older and doesnt have a vacuum port.

east tx skier
12-07-2006, 02:44 PM
Well you've got more room under there than I do. Are you running one of the taller intakes than the regular performer? I can see a downside to dropping everything back down since it took me so long to get the throttle cable lined back up so it wouldn't bind when coming off plane. I may just subscribe to the "if it ain't broke, don't fix it" philosophy and enjoy my winter.

TRBenj
12-07-2006, 03:01 PM
Yup, Im running a Weiand Stealth intake which is an inch taller than the Performer. I made my own bracket to make the throttle level. Right now I cant close my motor box. I think I will be able to get an arrestor like yours from a friend that will give me a little more room.

http://i41.photobucket.com/albums/e260/TRBenj/7-31007_small.jpg

east tx skier
12-07-2006, 03:08 PM
That's a tall intake.

My low profile flame arrestor has a number on the top of it, which I, of course, can't recall, in case you need it (I can look) to cross reference.

I've given some thought to fabricating a little collar to clamp to the floor, and to which the motor box could be attached (mini clam shell). Would be helpful keeping stuff (ropes, cases, etc.) out of the bilge and would give me the inch or two in clearance t'boot.

TRBenj
12-07-2006, 04:26 PM
I spoke to SkiDIM a few months ago and they were able to tell me the part number of your arrestor: R145006A. It looks like the same (or VERY similar) arrestor was installed on some mid-late '80s Nautiques. I have a friend who may be able to trade with me since he has no clearance issues.

Ive seen bases that raise the motorbox before, and they can look good when done right. If you can get carpet to match, that would really look nice.

east tx skier
12-07-2006, 04:46 PM
When it warms up, I'll take it out and put it through its paces with the new longer channel in the NR foam. If that doesn't do the trick, I'll explore my options.

etduc
12-08-2006, 09:17 AM
Here's a link to the spark arrester, I mention. Top of the page.

http://www.skidim.com/products.asp?dept=1060

I have owned about a half dozen, carburated vehicles (1972-1986). All vented the pcv, directly into the oem air cleaner. While it may be cleaner to vent after to carb (looking), there in no performance difference. In fact, some motorcyle drag racers vent the pcv directly to the exhaust pipe. (Well, downstream of the header!) Not recommended for our lake applications.

In the motorcycle industry, most vent pvc directly into the airbox, prior to the carbs or throttle bodies.

Just trying to help.

east tx skier
12-08-2006, 09:59 AM
Thanks, etduc. I may start looking and asking more questions if/when I pull the cover off this weekend.

TRBenj
12-08-2006, 11:49 AM
Here's a link to the spark arrester, I mention. Top of the page.

http://www.skidim.com/products.asp?dept=1060

I have owned about a half dozen, carburated vehicles (1972-1986). All vented the pcv, directly into the oem air cleaner. While it may be cleaner to vent after to carb (looking), there in no performance difference. In fact, some motorcyle drag racers vent the pcv directly to the exhaust pipe. (Well, downstream of the header!) Not recommended for our lake applications.

In the motorcycle industry, most vent pvc directly into the airbox, prior to the carbs or throttle bodies.

Just trying to help.


The PCV needs a vacuum source to operate properly. The spark arrestor is NOT a vacuum source. The 5/8" fittings on the spark arrestor are for a breather tube, not a PCV tube. There are setups where both valve covers are vented to the flame arrestor with 5/8" hose- but these breathers do not have PCV valves. A vacuum source (carb base, carb spacer of intake manifold) is necessary for a properly functioning PCV system.

The PCV valve usually requires a 3/8" (ID) hose.

Laurel_Lake_Skier
01-07-2007, 04:11 PM
Are there any issues with spark plugs clearing the exhaust manifolds with the GT-40p heads on the Indmar engines? From what I have read, the spark plugs are relocated in those heads......I've got a tight squeeze on a couple of them with the stock heads....the PCM exhaust set-up gives quite a bit more room around the plugs.

east tx skier
01-07-2007, 05:11 PM
Rear plug on the port side is a real pain to get to depending how you feel about dislocating your shoulder. But it fits.

Jim@BAWS
01-07-2007, 06:49 PM
Are there any issues with spark plugs clearing the exhaust manifolds with the GT-40p heads on the Indmar engines? From what I have read, the spark plugs are relocated in those heads......I've got a tight squeeze on a couple of them with the stock heads....the PCM exhaust set-up gives quite a bit more room around the plugs.


Pretty sure AUTOLITE 24s. DO NOT use the same plugs that came out of your original heads

Jim@BAWS

east tx skier
01-07-2007, 10:29 PM
Pretty sure AUTOLITE 24s. DO NOT use the same plugs that came out of your original heads

Jim@BAWS

I use AL 764s

TRBenj
01-08-2007, 08:48 AM
Pretty sure AUTOLITE 24s. DO NOT use the same plugs that came out of your original heads

Jim@BAWS

Nope, the 24's are the correct plugs for the original heads. GT40p's use the same plugs as the standard GT40's, Autolite 764.

The P's have a different plug angle than the standard GT40's. On my PCM, this actually improves their accessibility. PCM and Indmar use the same style exhaust manifolds- you should have no problem at all with them.

Laurel_Lake_Skier
01-08-2007, 07:32 PM
Rear plug on the port side is a real pain to get to depending how you feel about dislocating your shoulder. But it fits.

Doug

Do you have the GT-40 P heads or the regular GT-40? One of the sites I saw mentioned that the Ps have a different location for the plugs. They were talking automotive applications and said headers could give clearance problems. I'm wondering about the maine manifolds since there isn't much wiggle room around them with my stock heads.

east tx skier
01-08-2007, 10:24 PM
Standard cast iron GT40 heads on mine. It's not all that bad. Per JimN's sage advice, I have an old plug wire cut off that I pop on there to get it unscrewed. Works like a charm.

TRBenj
01-09-2007, 10:01 AM
Doug

Do you have the GT-40 P heads or the regular GT-40? One of the sites I saw mentioned that the Ps have a different location for the plugs. They were talking automotive applications and said headers could give clearance problems. I'm wondering about the maine manifolds since there isn't much wiggle room around them with my stock heads.

Laurel, Ive got the GT40p's on my boat. Plug angle is better than the stock heads or standard GT40's. PCM's and Indmars use the same style 351w exhaust manifold (they are interchangable).

The fitment problems with automotive headers is unrelated. Automotive headers curve down, marine headers curve up. You wont have any problem putting the P's on your boat.

Laurel_Lake_Skier
01-09-2007, 08:16 PM
Thanks....been hoping to find someone that has them in place.....Do have them on an Indmar or PCM? I have worked on a friends PCM in a Nautique and there is a lot more room around his plugs than on my MC.

east tx skier
01-09-2007, 11:39 PM
TRBenj has a '90 SN IIRC.

TRBenj
01-10-2007, 11:55 AM
ETS is correct, I have a PCM.

Perhaps your friend has different heads on his boat that would account for the difference in how accessible the plugs are? E7 (240hp) heads, GT40 and GT40p heads will all be a little different.

On the GT40p's, the location of the plug isnt different- the angle is. Regardless of which exhaust manifolds you have, they will give you more clearance than the E7's or GT40's.

I have a better picture that shows the plug angle, so Ill have to search for it. Heres another shot of the motor:

http://i41.photobucket.com/albums/e260/TRBenj/Myarrestor.jpg

DooSPX
01-10-2007, 07:53 PM
One of these years I will get around to installing some "p's" and a performer!
but first I want to get a CNC

Laurel_Lake_Skier
01-10-2007, 09:41 PM
The picture helps....your manifold is different than the Indmar. If you can find the close-up showing the plugs that would be great. Those manifolds you have are the same as my buddy's. The runners are angled to allow more clearance to the plugs. All of his are a piece of cake to get at and two or three of mine are real projects to get in and out.

Here's a photo borrowed from TMCNo1 to show the MC/Indmar manifold.

TMCNo1
01-10-2007, 10:05 PM
The picture helps....your manifold is different than the Indmar. If you can find the close-up showing the plugs that would be great. Those manifolds you have are the same as my buddy's. The runners are angled to allow more clearance to the plugs. All of his are a piece of cake to get at and two or three of mine are real projects to get in and out.

Here's a photo borrowed from TMCNo1 to show the MC/Indmar manifold.


I don't know about the PCM combo, but on the 240 hp heads the plugs angle up toward the exhaust mainfold and need to be broke loose with a deep offset boxend wrench and screwed out by hand. I always apply a small amount of Lubrimatic Anti-Corrosion wheel bearing grease to the threads of every new plug and start by hand then screw in by hand or with a old spark plug boot (as ETS suggested) and tightened as far as possible before the deep offset boxend wrench is used to tighten them down snug.

TRBenj
01-11-2007, 10:08 AM
I see the difference now. It looks like the Indmar water jacket extends a little further down, which would make plug clearance a little tighter.

PCM and Indmar used the same heads on the 351w: 240hp = E7 heads, 285hp = GT40 heads. On my E7's, only one plug required a box end wrench- the rest I could get with a socket. With my GT40p's, I can get a socket on all 8.

Like TMC1 mentioned, the plugs angle up towards the manifolds on the E7 heads. On the P's, they angle down more. While this causes header fitment problems on Mustangs, its good news for our marine exhaust manifolds.

Ill post a better pic if I can find it, but I dont know how much it will help. Either way, the GT40p's will give you more clearance than the stock heads.

Laurel_Lake_Skier
01-12-2007, 09:48 PM
TRBenj

Do you still have the performer manifold for a 351? What are you asking for it? Why did you decide not to use it on your upgraded engine? I tried a PM but you are full......

Thanks for your info/photos on the GT 40-P heads. I'm checking out sources for them now.

TRBenj
01-13-2007, 12:37 AM
TRBenj

Do you still have the performer manifold for a 351? What are you asking for it? Why did you decide not to use it on your upgraded engine? I tried a PM but you are full......

Thanks for your info/photos on the GT 40-P heads. I'm checking out sources for them now.

Laurel, Ive already sold the intake. Sorry!

I went with the Stealth because it is the intake manifold of choice for a lot of the Mustang guys. The midrange power is really impressive.

For the GT40p's, I recommend this place: Tri-State Cylinder head (http://www.tristatecylinderhead.com/catalog/) You can find used sets cheaper (ebay, etc), but by the time you have a valve job done and new springs installed (recommended for upgraded cams) you come out ahead with Tri-State. If I were to do it all over again, this is the way I would go.

I cleaned out my PM box, so feel free to send me any questions you may have.

Plug angle pic:

http://i41.photobucket.com/albums/e260/TRBenj/GT40Pplugangle.jpg

TMCNo1
01-13-2007, 08:20 AM
Plug angle pic:

http://i41.photobucket.com/albums/e260/TRBenj/GT40Pplugangle.jpg

I would be wonderful to have that easy access to the plugs on the regular heads!

TRBenj
01-13-2007, 08:25 AM
I would be wonderful to have that easy access to the plugs on the regular heads!

TMC1, the GT40p's are not an expensive upgrade. $540 for the pair at the link I posted above. Figure in shipping and gaskets, you should be out the door for under $800. Well worth it for that improved spark plug angle, dont you think? Consider the extra 50hp a bonus!

TMCNo1
01-13-2007, 08:32 AM
TMC1, the GT40p's are not an expensive upgrade. $540 for the pair at the link I posted above. Figure in shipping and gaskets, you should be out the door for under $800. Well worth it for that improved spark plug angle, dont you think? Consider the extra 50hp a bonus!

:uglyhamme :uglyhamme :uglyhamme It would just about be worth it! AH, just forget about the HP gain, lose 50 lbs., take all the junk out of the boat, run it with 1/3 tank gas and you've gained 35hp more.

willschilling
08-07-2007, 12:43 PM
What head gaskets is everyone using when swapping GT40p heads on their marine 351s? The Felpros I bought from skidim seem to have port openings that are too small for the GT40p heads. Also, I know the bolts on the 351 are 1/2" so what size drill bit do you use on the heads to open up the bolt holes to the proper size? Can you reuse the factor bolts or do you need to buy new ones?

Thanks!

Will

TRBenj
08-07-2007, 12:59 PM
What head gaskets is everyone using when swapping GT40p heads on their marine 351s? The Felpros I bought from skidim seem to have port openings that are too small for the GT40p heads. Also, I know the bolts on the 351 are 1/2" so what size drill bit do you use on the heads to open up the bolt holes to the proper size? Can you reuse the factor bolts or do you need to buy new ones?

Thanks!

Will

Not sure what you mean by port openings on a head gasket. I used these (http://skidim.com/prodinfo.asp?number=RM0018) gaskets from SkiDIM with my P's and had no issue.

I highly suggest you have the bolt holes drilled out by a machine shop- they should be able to open up the holes to 1/2" for cheap. This is not a job for a home mechanic without the proper tools and know-how. If you bought them new/remanufactured, you should have this done before they were shipped to you (easier and cheaper). If you bought the heads used then you should really have them gone through. Get a basic valve job done to make sure theyre in good shape and ready to bolt on. FYI, I bought a used set of heads off ebay for cheap that were supposedly straight- and my machine shop found 2 bent valves. For the price, remanufactured heads are a much better deal!

The factory head bolts are "torque to yield" and should not be reused. Invest in some quality ARP head bolts.

willschilling
08-08-2007, 03:35 PM
Sorry, I meant the intake and exhaust manifold gaskets. Not the head to block gaskets. Any suggestions? The intake and exhaust ports on my heads are slightly larger than the marine gaskets I purchased through skidim in their "valve grind gasket kit." I had them double check they sent the right ones already. I purchsed brand new bare heads that have had no port work done.

rcnjson
08-08-2007, 04:16 PM
I PM'ed you yesterday but so everyone else knows...

Fel-Pro
Head 1011-1

Intake 1262

Exhaust 1415

You will not be disapointed with these and they will fit. The only issue is the water passage on the 1262's. There is a little "L" of gasket that goes into the water passage. I just cut that out with a razor blade easy peasy no problems. I get them from summit although you can probably get them at autozone or something like that with the fel-pro number. As far as head gaskets go these are probably the best you can do for a mild NA motor in terms of the reliability you need and the cost.

k

TRBenj
08-08-2007, 04:22 PM
Sorry, I meant the intake and exhaust manifold gaskets. Not the head to block gaskets. Any suggestions? The intake and exhaust ports on my heads are slightly larger than the marine gaskets I purchased through skidim in their "valve grind gasket kit." I had them double check they sent the right ones already. I purchsed brand new bare heads that have had no port work done.

Interesting. I got my intake and exhaust manifold gaskets at SkiDIM as well, and though I didnt buy them as part of the valve grind kit one would assume they are the same.

Both matched right up. The exhaust manifold gaskets are rectangular rather than oval (head ports), but they werent smaller. They matched my PCM exhaust manifolds perfectly- thats the side they will stick to anyways (the metal side goes toward the head).

Where did you find brand new bare heads? I didnt think they were in production anymore- they havent been installed on a car from the factory in 5+ years, and they were never touted as a "performance head." Are you sure you didnt buy a remanufactured set?

willschilling
08-09-2007, 11:58 AM
Interesting. I got my intake and exhaust manifold gaskets at SkiDIM as well, and though I didnt buy them as part of the valve grind kit one would assume they are the same.

Both matched right up. The exhaust manifold gaskets are rectangular rather than oval (head ports), but they werent smaller. They matched my PCM exhaust manifolds perfectly- thats the side they will stick to anyways (the metal side goes toward the head).

Where did you find brand new bare heads? I didnt think they were in production anymore- they havent been installed on a car from the factory in 5+ years, and they were never touted as a "performance head." Are you sure you didnt buy a remanufactured set?
Ya, they are brand new still have stenciling form Ford with a '97 manufacture date. A guy on ebay a few months back had several brand new bare sets that he was selling for $200 a pair. I think he used to have a speed shop and/or race team.