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jfw432
07-12-2012, 03:35 PM
So I bought some GT40P heads and the Edelbrock Performer 2181 intake manifold a couple weeks ago because of the excellent reviews from everyone. I did the heads first and then did the intake partly because of when the parts arrived and partly because I wanted to feel a difference in both.

The first day I took the heads out, I noticed my top end speed was a hair better but less 1mph as seen on my Stargazer GPS. First day I skied behind it, we had a full boat and a so-so driver so I couldn't really feel a difference either which depressed me a bit. The second time I went out, I did notice a little more get up when I was behind the boat. I was never really able to tell a true difference from the drivers seat. I think I use less throttle to get wakeboarders up now with full balast and a friend commented that I get him up faster now but that could just be because the nose doesn't rise as much when I use less throttle. Hard to say...

The one thing that I didn't ever hear about was the difference in sound that the new heads make. The old heads sounded throaty and the GT40P heads sound a little more throaty and more like an old muscle car than a boat at idle. I thought it was just me listening too hard but have had two people on separate occasions say the same thing.

As for the intake... I didn't notice any difference at all. Not in top end speed or with the seat of the pants feel when getting up. It looks prettier and is a whole lot lighter but that's about it from what I can tell.

O2BESOHUGE
07-12-2012, 05:36 PM
Makes Me Wonder About Adding That To Mine. Is It Really Worth It? How Much Did You Spend?

SeaCup
07-12-2012, 05:45 PM
It's funny how some people will tell you about how great the mods they did are. Any drag racer will tell you it takes a lot of hp to shave a few tenths. This winter I did a bunch of performance upgrades to my boat as well. I did the GT-40 p's with heavier springs and opted for the Weiand Stealth manifold. A new cam might wake things up some. It all has to work together.

You may want to play with the carb some. From the factory it's close but not quite right. I found that after understanding the way the carb worked and properly tuning it was when things came to life for me. Not a drag boat but a lot better than it was.

jfw432
07-12-2012, 09:37 PM
Yeah I was looking at the plugs and thinking I may need to richen up the mixture a bit but I need to do a plug chop before I go messing with things to be sure.

I bought my heads used instead of getting the remanufactured ones and stepped up the holes myself with a step drill. Picked up both heads for about $250 shipped and got the intake for $130 shipped. Both off ebay. Then got the gasket kit from JEGS for about $50 because it was cheaper to order the entire kit than just the gaskets I needed. The heads did require some cleanup though so it's a tradeoff for sure.

east tx skier
07-12-2012, 09:40 PM
I don't know the difference between the GT40p heads and the regular 351 heads, but with the intake over my stock GT40 heads on my old MC, even my wife let out a wow on our first hole shot. Goes to show what I have always said---perception of performance on the water really depends on a lot of factors.

imracin68j
07-13-2012, 12:25 AM
motor looks awesome. Did you boot the MC plastic cover over the air cleaner?

thatsmrmastercraft
07-13-2012, 12:27 AM
motor looks awesome. Did you boot the MC plastic cover over the air cleaner?

It sure does. That is seriously clean.:cool:

SeaCup
07-13-2012, 09:46 AM
motor looks awesome. Did you boot the MC plastic cover over the air cleaner?

Sorry to disappoint everyone but that is the engine in my Supreme, no MC cover.

imracin68j
07-13-2012, 10:04 PM
Well in that case it sucks. lol jk.

SeaCup
07-15-2012, 02:42 PM
Trying to stay on point with this thread. Get some parts for that Holley and take the boat out by yourself one night and start playing with it. I purchased a few sets of jets, QC spring kit, pump cam kit and a couple of new nozzles and went to town. A timing light and a vacuum gauge should be used as well

Take some 0-40 times and compare what you find, make a change and see if it gets better or worse. Can be a little time consuming and tedious but well worth it in the end.

j.mccreight@hotmail.com
07-16-2012, 08:24 AM
Yeah I was looking at the plugs and thinking I may need to richen up the mixture a bit but I need to do a plug chop before I go messing with things to be sure.

I bought my heads used instead of getting the remanufactured ones and stepped up the holes myself with a step drill. Picked up both heads for about $250 shipped and got the intake for $130 shipped. Both off ebay. Then got the gasket kit from JEGS for about $50 because it was cheaper to order the entire kit than just the gaskets I needed. The heads did require some cleanup though so it's a tradeoff for sure.

Can you post the cylinder head casting marks of the both sets of heads. The markings will be on the underside.

jfw432
07-16-2012, 10:14 PM
Can you post the cylinder head casting marks of the both sets of heads. The markings will be on the underside.

Do you mean underside as in under the valve cover like the casting marks by the valve springs or the marks at the front and back showing 3 bar vs 4 bar? I don't remember seeing anything on the underside by the valve openings.

j.mccreight@hotmail.com
07-16-2012, 10:41 PM
Do you mean underside as in under the valve cover like the casting marks by the valve springs or the marks at the front and back showing 3 bar vs 4 bar? I don't remember seeing anything on the underside by the valve openings.

Yes under the valve cover and on the end like you said 3 or 4 bar also on the head gasket side near the combustion chamber on the intake manifold side. Its a four digit number starting with a letter Like this http://www.google.com/search?tbm=isch&source=mog&hl=en&gl=us&tab=wi&q=ford%20head%20casting%20numbers&sa=N&biw=369&bih=615#i=25

jfw432
07-17-2012, 09:47 AM
Well I only have limited pictures from before I installed the heads and a couple of them were ebay pictures that I can't seem to download right now. The attached picture shows "GT40P" under the valve cover. The other casting mark appears to be "6K18" or something like that. It's upside down and a little blurry though so I'm not sure.

The ebay pictures show F77E (maybe F7ZE?) on one of the intake runners and also the 4 bars on the side of the head. Here is the link to the auction. http://www.ebay.com/itm/370625473313?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

One of the things that's interesting are the casting marks on the exhaust side. There is GTP stamped on both sides. Currently installed on my engine there is a casting mark "5" on the #5 cylinder by the valve cover gasket. There is also a "7" on the #2 cylinder and "8" on the #7 cylinder but those are under the spark plugs. It's hard to tell which way is actually forward but I based my decision on the "5" casting mark. Can you install the heads backwards?

Kyle
07-17-2012, 12:36 PM
Ok I have the GT40p heads, intake, and cam added to my set up.

I have the power slot tranny and there was a drastic difference when I added the heads, cam, intake.


I may have missed something but I do NOT see where you added a cam to your list of upgrades. I looked at your profile and the boat owned says OTHER. Can we start out with what year and brand of OTHER boat do you have. Pre 91 Indmar had very low output cams.



When I added the upgrades to my boat I instantly gained top end and loads of torque. I went from being a max speed of 40.5 or so to 46.5 ish with a power slot reduction gear tranny. It is real hard to get a reduction gear to push 45+ mph.

Where I really notice a huge difference is loaded down. I can foot multiple footers around 44 mph. Another thing that I notice is, I can load 2 coolers loaded full of beer, ice, food, and 9 friends and I can still run 44.3-44.6 mph. Now at that speed with the over weighted the boat will start bouncing around or try to fly if I try to go over a jet ski wake. Loaded down I roll 30 to 32 mph to save fuel and it is a extremely smoother ride. If I had my old set up I dont even think that I could plane out with that kind of weight on board.

I have a friend with a '98 Air Nautique and if I load 9 people and he loads 9 people my hole shot will kill his. Most of the time if we race back to the dock I will beat him. Were his boat is superior to mine is in choppy water. My 190 is not designed to take chop and with the over weight it really starts to become unstable in rough water. It is not worth damaging my boat or hurting a passenger to beat him back to the dock.


Lets get more information about the boat before deciding this was a waste of money.

j.mccreight@hotmail.com
07-17-2012, 02:11 PM
Well I only have limited pictures from before I installed the heads and a couple of them were ebay pictures that I can't seem to download right now. The attached picture shows "GT40P" under the valve cover. The other casting mark appears to be "6K18" or something like that. It's upside down and a little blurry though so I'm not sure.

The ebay pictures show F77E (maybe F7ZE?) on one of the intake runners and also the 4 bars on the side of the head. Here is the link to the auction. http://www.ebay.com/itm/370625473313?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

One of the things that's interesting are the casting marks on the exhaust side. There is GTP stamped on both sides. Currently installed on my engine there is a casting mark "5" on the #5 cylinder by the valve cover gasket. There is also a "7" on the #2 cylinder and "8" on the #7 cylinder but those are under the spark plugs. It's hard to tell which way is actually forward but I based my decision on the "5" casting mark. Can you install the heads backwards?


They are gt40p heads, I was thinking that you might have been sold early explorer gt40 heads. Can you post your original cylinder head casting numbers?

tockit
07-17-2012, 02:17 PM
Ok I have the GT40p heads, intake, and cam added to my set up.

I have the power slot tranny and there was a drastic difference when I added the heads, cam, intake.

I may have missed something but I do NOT see where you added a cam to your list of upgrades. I looked at your profile and the boat owned says OTHER. Can we start out with what year and brand of OTHER boat do you have. Pre 91 Indmar had very low output cams.

When I added the upgrades to my boat I instantly gained top end and loads of torque. I went from being a max speed of 40.5 or so to 46.5 ish with a power slot reduction gear tranny. It is real hard to get a reduction gear to push 45+ mph.

Where I really notice a huge difference is loaded down.

Lets get more information about the boat before deciding this was a waste of money.Did you do anything to the bottom end of the engine before you installed your heads?

Thanks!

Kyle
07-17-2012, 02:56 PM
Did you do anything to the bottom end of the engine before you installed your heads?

Thanks!


Yes and only because I had no choice..........

I went back with a .040 block and hypereutectic pistons.


http://mastercraft.com/teamtalk/showthread.php?t=36324








Now for info on this current thread something is really fishy. There should be no way that you could not feel a difference when adding the intake or heads. Something else is not right. If you have the low output cam then that is a problem and if the carb is not set right then there is another problem.

I have driven my boat against a factory 285hp HO engine ps205 and there is a drastic difference. NOT because I have a ps190 and I am feeling the difference against the ps205, there is just a huge power difference that can be felt.

SeaCup
07-17-2012, 03:58 PM
These are NOT just bolt on and go parts. There are a lot of factors that contribute to all these changes that need to be factored in. Just with the heads you need to know how much if any the block was decked, how much if any the heads were cut (changes volume and compression), upgrade the springs (no cam manufacture would ever recommend not changing the stock one's with higher lift cam), calculate proper pushrod length, rocker setup and shimming to get the proper geometry.

Kyle
07-17-2012, 04:19 PM
These are NOT just bolt on and go parts. There are a lot of factors that contribute to all these changes that need to be factored in. Just with the heads you need to know how much if any the block was decked, how much if any the heads were cut (changes volume and compression), upgrade the springs (no cam manufacture would ever recommend not changing the stock one's with higher lift cam), calculate proper pushrod length, rocker setup and shimming to get the proper geometry.

agree with you...

I had the shop that did my heads calculate all of the details and install the proper valve springs.



I am still willing to bet that the cam is not the HO or better cam in this situation.

We still do NOT know max RPM, Max speed, what degree the timing is set, what brand of boat or year of boat this guy has either. All of the above items need to be answered before real advice can be given.

jfw432
07-17-2012, 05:46 PM
First off, please don't get me wrong. I'm not hating on either mod and I fully understand that some carb tuning may be required. I haven't gotten too serious on tuning just yet because the plugs look identical to my old ones. That said, my boat is an 86 Dixie Super Skier 299 with the 351w and 1:1 velvet drive tranny. My prop is one of the machined Acme 524 (13/11.5). No I did not touch the cam or the valve springs and can only imagine that I do not have the HO cam. I tried checking the timing a week or so ago. The marks are really faded and hard to see but looks to be around 6 at idle. There were timing marks in nail polish and the idle and high rpms marks were dead on but I wasn't able to see exactly what the high rpm mark actually said.

I did notice a difference getting up with the new heads alone but can't feel it driving the boat. "Seat of the pants" says I got nothing from the intake. Sorry I don't have max rpms with my current setup but if the rain clears up tonight, I'll check. My old setup with a worn out 13x13 forged prop would get me to 3760rpms at 39.6mph (Stargazer GPS) by myself. My new setup with heads, 13x11.5 prop, and intake gets me to around 41mph (no clue on rpms). The prop change alone got me to 40.5mph though.

The casting marks on the old heads were E5AE with CA written underneath.

edit: I haven't confirmed my engine compression yet either because my gauge doesn't fit this thread size....go figure.

jfw432
07-17-2012, 06:20 PM
Update: Tonight my max rpms were 4430 at 40.6mph.

Kyle
07-17-2012, 07:05 PM
The cam you are running is a POS.

Not bashing you or your boat. Just ask phntmski in my friends. He has a '91 and he had a POS cam and heads. I built his engine for his boat over the winter and it was the same engine as mine but a slightly different cam. He absolutely loves that new engine. He calls or texts me every time he drives the boat commenting on how bada$$ his new engine is.

Buy a new cam and your rpm will increase to where it should be @4800-4900.

Another thing I would do is freshen up the bottom end. It will eventually self destruct like mine did because it can not handle the mods. Put new rings and bearings in it.


Your problem is the cam. Trust me

tockit
07-17-2012, 07:11 PM
I got nothing from the intake.
What intake are you running?

Kyle
07-17-2012, 07:27 PM
So I bought some GT40P heads and the Edelbrock Performer 2181 intake manifold a couple weeks ago because of the excellent reviews from everyone.

What intake are you running?

I assume that he is talking about the Edelbrock Performer 2181

jfw432
07-17-2012, 08:49 PM
Yes I was talking about the Edelbrock 2181 intake.

So would any valve springs or anything need to be changed to accommodate the new HO cam? What cam would you recommend?

Keep in mind that the heads, intake, and prop were a fairly cost effective way IMO to get just a little more help when the boat is loaded down. Once I changed the prop, my engine never had a problem pulling people up or planing off but the law of man dictates that something runs well can always run better... If I can change the cam and keep the rest, it might be worth going that route. If changing the cam means changing valve springs, rocker arms, push rods, rings, and bearings then it's time to call it quits for a while.

Kyle
07-17-2012, 09:28 PM
Personally I would have already done the bottom end. The heads will change things enough to effect the lower parts in the engine.



I posted the cam that I am running in the cam thread.

http://mastercraft.com/teamtalk/showthread.php?t=49202&page=2


There will be folks that suggest a little wilder cam but I really like my cam that I have. It produces lots of power and I find it plenty for me. Would I like more, well yeah but I am completly happy with the power I have now.

jfw432
07-17-2012, 10:02 PM
Thanks for the info. I will probably wait until winter at least before I tackle that job.

Kyle
07-17-2012, 10:08 PM
Thanks for the info. I will probably wait until winter at least before I tackle that job.

That is what I would do...... You will love it, I would hate to have to read a thread about you having to replace your whole engine. When mine let go my cam was in 6 pieces and it destroyed everything accept the intake and carb. I had 5 bent valves and had to have my heads completly reworked. It was a total Bish and I just dont want that to happen to you. It even destroyed my distributor. Everything was trashed pretty much.

jfw432
07-18-2012, 09:27 AM
Alright well I can at least start planning and doing research then. You recommended freshening up the engine with new rings and bearings when the cam is done. Is that enough or was that a temp freshen up to cover me for a little while? I guess what I'm getting at is; would you recommend going ahead and getting a new crankshaft, pistons with a fresh bore, and rods if waiting until winter to do the work?

TRBenj
07-18-2012, 12:22 PM
A cam alone is not going to add 5mph. The stock 351w cam is on the order of .440-.450, so the "hot" .460 cam is an extremely mild upgrade. The P heads alone, coming from the E7's should easily add 45hp. A proper cam (closer to .500 of lift) and a good intake will get you another 30-40hp. But the heads are the biggest piece of the puzzle.

I think something else is wrong. Did you set the proper lifter preload? Have you compression tested the engine? I assume the ignition and fuel systems are up to snuff? Go into more detail on those- stock? Upgraded? Whats your timing set at (initial and final)?

I would have absolutely no hesitation in running a stock 351w bottom end with an upgraded top end like we're describing. At well below 1hp/ci, and RPM's in the low 5k range (at best) there are absolutely no weak points in the windsor bottom end that would cause me to lose a wink of sleep. Assuming it was properly cared for, isnt low on compression, or showing high wear, etc. Im closing in on 1300 hrs on a stock bottom ended 351w with a 350hp top end that I spin north of 5200rpm on a consistent basis.

Kyle
07-18-2012, 01:55 PM
A cam alone is not going to add 5mph. The stock 351w cam is on the order of .440-.450, so the "hot" .460 cam is an extremely mild upgrade. The P heads alone, coming from the E7's should easily add 45hp. A proper cam (closer to .500 of lift) and a good intake will get you another 30-40hp. But the heads are the biggest piece of the puzzle.

I think something else is wrong. Did you set the proper lifter preload? Have you compression tested the engine? I assume the ignition and fuel systems are up to snuff? Go into more detail on those- stock? Upgraded? Whats your timing set at (initial and final)?


I kind of agree with you on the cam. Truthfully we have no idea what cam is in the boat right now though and we are guessing. That being said, it is real hard to say if it is good or bad.

As far as going bigger I will agree that I wish that I had gone slightly bigger and that is why I am seriously considering the roller rockers going to a ratio of 1.7 but I am waiting until winter because I am just too busy.

He said timing was at 6* and that could easily be moved to like 10-11* and should free up a few rpm.

He also did not mention the lifters or push rods being changed. If he just changed the heads out and used the same push rods and lifters and torqued the pedestal mounted rocker arms, technically the preload should not be an issue.

Compression test is a fantastic idea too.






Where I question the cam and not worrying about it comment is due to this reason.

phantmski has the same identical engine as I do and almost the same size cam but I can turn mine 200-300 more rpm and mine is faster. Everything in that engine is the same but the cam. His lift is actually more than mine too, so by saying add lift and you have a better cam is kind of misleading. Lift, duration, and overlap effect the performance greatly.

I am still stuck on the cam being the problem.

Right now he is spinning 4430 rpm and a cam change will get it up to 4800 or so. Then the prop starts coming into the mix.

I also agree on checking fuel system and carb adjustments.

TRBenj
07-18-2012, 02:24 PM
I think its safe to assume he has a stock cam in the boat? Those specs were posted recently.

My father swapped GT40 heads onto his '92 Ski Nautique years back. It went from 4400 to 4700-4800, and performed essentially equivalent to a Pro Boss (HO 351w) engine. I did a similar thing on my '90 Ski Nautique, but added an intake and a cam at the same time... instead of picking up 300-400rpm, I picked up 600rpm. So I still think its safe to say that the heads are more than 1/2 of the picture when it comes to upgrading the top end with these components.

Totally agree on the cam selection... there are a TON of parameter to consider beyond the gross lift numbers. But looking at the gross lift gives you an idea how it will perform with this common upgrade, assuming the cam design is half way decent (good phasing on the valve events, duration, LSA, etc).

Yes, timing should be bumped up to 10-12 initial, and final should be verified with a light. It should be all in by 3k rpm and total should be in the ballpark of 35deg.

Yes, he *should* be able to reuse pushrods and rockers when going from E7's to P heads, but shimming is most likely required, unless he got brand new P castings (very doubtful) AND got very lucky that the geometry matched the stock heads perfectly. If those heads were refurb'd, then they were probably resurfaced a few thousands at a minimum. Excessive preload could be a contributor to his issues if it was not verified properly following the valvetrain install. This is not something that can be ignored.

To be honest, with the prop and engine modifications coming at the same time, we have very little actual data to go by in terms of performance changes. There are blanks that would be really helpful to have filled in, as we have multiple variables that could all be contributing to the performance (or lack thereof). Is it safe to assume that all data currently being collected is using a known-accurate tachometer and a GPS for speed?

Kyle
07-18-2012, 02:41 PM
The cam specs posted are the one out of a HO engine. I have never seen cam specs out of a boat that is the non HO engine. Cam specs that have been posted are out of vehicles posted by James.



The poster has heads that were bought used. Who knows if they have been resurfaced, or had any kind of valve work done to them.

We kind of need more information.

TRBenj
07-18-2012, 03:41 PM
Agreed, we need more info.

I have always been told that the non-HO and HO cams were very similar (if not the same), and both very conservative. What Jason posted makes perfect sense to me.

The performance of my father's former '92 (non-HO with GT40 heads added after the fact) seemed to help confirm that theory, since it performed similarly to a factory HO engine on that hull. I know of several older boats that had heads added (and not cams) and they picked up a world of performance as well.

j.mccreight@hotmail.com
07-18-2012, 04:56 PM
Just to throw gas on the fire... Op stated his original heads are e5ae-ca which have a 67-70 cc chamber not the e7te which have 60-64 cc. The gt40p are 58-61 cc an increase of .8 or so in the compression ratio. I question his prop 13x11.5 is this acceptable for a 1:1. I know my 89 1:1 with oj force 13x13 4 blade I can do 45 mph on the gps @ 4600-4700 rpm all day long with just a weiand intake if i'm running light I can get 46. if e7 were original he might not "feel" much of an increase but with the e5ae he "should have" felt a huge increase if the basics were done correctly.

TRBenj
07-18-2012, 05:04 PM
Im not sure if we agree, but he should have felt a substantial performance boost going to the P's whether coming from the E5's or E7's... both are lousy.

13x11.5 is perfectly acceptable for a 1:1, especially an Acme. Their 13x12 (540/541) runs consistent RPM's with the OJ and Federal hand finished 13x13's.

We dont know much about the hull- could be big, heavy, slow... or not. Another variable that isnt going to help us diagnose how big of an issue there is- but it sure seems like something is amiss.

j.mccreight@hotmail.com
07-18-2012, 05:19 PM
Im not sure if we agree, but he should have felt a substantial performance boost going to the P's whether coming from the E5's or E7's... both are lousy.

13x11.5 is perfectly acceptable for a 1:1, especially an Acme. Their 13x12 (540/541) runs consistent RPM's with the OJ and Federal hand finished 13x13's.

We dont know much about the hull- could be big, heavy, slow... or not. Another variable that isnt going to help us diagnose how big of an issue there is- but it sure seems like something is amiss.

I think we agree more than either of us will admit to, I totally agree on the hull thing...

jfw432
07-18-2012, 06:30 PM
This thread has been massively helpful even though I wasn't really expecting help from it. I did weeks of research on this mod from this site, correctcraftfan, and various mustang forums expecting to find an assortment of things saying I would have to deal with valve spring adjustment, lifter issues, push rod issues, and rocker arms. I thought to myself that some of this would HAVE TO be done when changing heads but I really don't know that much about 4 strokes so I relied on what others have said to guide me. I couldn't find squat! Everything I read seemed to say "you just have to drill the holes to 1/2" and you'll be good". I even asked about carb settings and the closest answer I got said "with any engine mod you should check your carb settings but mine didn't really change when I swapped heads". The more I looked, the more reassurance I got that everything was just plug and chug. No adjustments, no tuning, nothing...

I come to this site and everyone is talking lifter preload, pushrod and rocker shimming, etc. I'll try to look into that stuff and see what needs adjusting. I do have a light valve tap. UGH exhaust manifold removal again......

Actually all of my mods were done independently of each other. Yes the rpms and speeds are all based off of my Stargazer GPS Perfect Pass which has the digital rpm gauge. I do assume my hull isn't quite as fast. The hull is slightly deeper than nautiques and mastercrafts of that period and my hull weighs 500-600lbs more as well. My weight distribution is probably a little different too since I have seats in the bow which could cause a little more plowing at speed.

TRBenj
07-19-2012, 08:26 AM
I did weeks of research on this mod from this site, correctcraftfan, and various mustang forums The more I looked, the more reassurance I got that everything was just plug and chug. No adjustments, no tuning, nothing...

I come to this site and everyone is talking lifter preload, pushrod and rocker shimming, etc. I'll try to look into that stuff and see what needs adjusting. I do have a light valve tap. UGH exhaust manifold removal again......
If you spent more than 5 minutes reading the GT40p head swap threads on CCFan, I find it very hard to believe that lifter preload was never mentioned. Not sure what youre talking about with pushrod shimming or valve taps. You shim the rocker arms in order to set the proper lifter preload. This is standard practice whenever installing new (to you) heads.

Actually all of my mods were done independently of each other. Yes the rpms and speeds are all based off of my Stargazer GPS Perfect Pass which has the digital rpm gauge. I do assume my hull isn't quite as fast. The hull is slightly deeper than nautiques and mastercrafts of that period and my hull weighs 500-600lbs more as well. My weight distribution is probably a little different too since I have seats in the bow which could cause a little more plowing at speed.
Unless I missed it, the performance numbers quoted were a mix between old heads/new heads and old prop/new prop. If you have WOT RPM and GPS speed numbers for just the the old vs. new heads (same prop so its out of the equation) that would be very helpful.