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View Full Version : GT40 recommendations please!


XavierSPL
06-19-2013, 04:50 PM
I've read a few threads about this topic already but am hoping I can get some specific recommendations as I'm planning on getting everything in the next week and engine internals are def not my strong suit.. Hoping some of you with 1st hand experience can make some recommendations on what I should do or get:

I'll preface by saying that right now my goal is to get back in the water asap without blowing a ton of cash - this winter I'll be doing a full restore to the boat and can push off major expenses to the drivetrain to then if any are needed.
While looking at an engine swap on my 88 PS190 with a 1:52 velvet, I think I've decided to go with a rebuilt/reman short block and add some freshly rebuilt GT40 heads I found locally. The engine I've been looking at is internally OE spec, not built up or anything. Ideally if I could get in the area off 300hp I think I'd be happy, nothing crazy but better than stock would be good for me. I just had my 4160 rebuilt in preperation so have been planning on keeping that.
So what I'm looking for help with would be specific recommendations or advice on what else I need to make the package all work well together:
Any recommendations on a better than stock intake manifold that would work well but be reasonably priced? (any concerns about externals lining up?)
Do I need to get a better cam? (Any specific recommendations with a budget in mind?)
Do I have to change out the springs (or anything else) in the GT40 heads assuming they're all OE spec?
Are standard rockers suitable? If not, any thoughts on specifics I should consider?

Any advice on these is really appreciated, I'm taking the week after next off and hoping to be able to start wrenching then so need to start ordering everything yesterday. If there's any thoughts on these things as far as nice-to-have vs. must-have that would be helpful as I just don't know what I don't know.:rolleyes:

Thanks!

j.mccreight@hotmail.com
06-19-2013, 05:28 PM
My recommendations are as follows,
* use an edelbrock performer manifold, will line up perfectly
* use gt-40 heads, if using a stock camshaft the existing valve springs will suffice (just barely)
* standard rockers acceptable
* if your truly wanting 300 hp then a camshaft swap is a must, and then so is lifters, pushrods and valve springs.
* ensure brass freeze plugs are used.
* after all this you will likely need a new propeller

I did a top end kit on my boat but I went about it very differently than most folks that just wanting a few more hp. if you want my specifics PM me and I'll be more than happy to share.

CantRepeat
06-19-2013, 05:29 PM
/paging Kyle

j.mccreight@hotmail.com
06-19-2013, 05:32 PM
/paging Kyle

Hey my 351w is no slouch8p

thatsmrmastercraft
06-19-2013, 05:36 PM
My recommendations are as follows,
* use an edelbrock performer manifold, will line up perfectly
* use gt-40 heads, if using a stock camshaft the existing valve springs will suffice (just barely)
* standard rockers acceptable
* if your truly wanting 300 hp then a camshaft swap is a must, and then so is lifters, pushrods and valve springs.
* ensure brass freeze plugs are used.
* after all this you will likely need a new propeller

I did a top end kit on my boat but I went about it very differently than most folks that just wanting a few more hp. if you want my specifics PM me and I'll be more than happy to share.

All good advice. With the GT-40 heads and Performer you should be looking at roughly 280 hp which would certainly be a huge difference. If you choose for more hp, the cost goes up quickly.

XavierSPL
06-19-2013, 05:41 PM
My recommendations are as follows,
* use an edelbrock performer manifold, will line up perfectly
* use gt-40 heads, if using a stock camshaft the existing valve springs will suffice (just barely)
* standard rockers acceptable
* if your truly wanting 300 hp then a camshaft swap is a must, and then so is lifters, pushrods and valve springs.
* ensure brass freeze plugs are used.
* after all this you will likely need a new propeller

I did a top end kit on my boat but I went about it very differently than most folks that just wanting a few more hp. if you want my specifics PM me and I'll be more than happy to share.

This is really helpful - thanks so much. I was hoping to be able to use the stock cam and head components until this winter. Upping to a better cam is the type of thing I'd be fine with putting off until this winter when I have the time and let the wallet cool down a bit.

Since I'm getting the heads and block seperately, I'm assuming I need to get lifters and pushrods, anything specific needed for these? Anything else I'm missing besides gaskets and bolts? Also, I've been assuming I can use my MC valve covers, is that correct?

j.mccreight@hotmail.com
06-19-2013, 05:49 PM
yes use new lifters and pushrods. your MC valve covers can be reused. One thing to check that a lot of people don't is lifter preload it needs to be around .020"-.030", theoretically you can just torque the rockers down and go with it and they "should" be within specs. Personally I would check and get the correct length pushrods.

XavierSPL
06-19-2013, 05:56 PM
yes use new lifters and pushrods. your MC valve covers can be reused. One thing to check that a lot of people don't is lifter preload it needs to be around .020"-.030", theoretically you can just torque the rockers down and go with it and they "should" be within specs. Personally I would check and get the correct length pushrods.

Ok, this may be a stupid question but the engine I'm swapping out had 400 hours on it and was in great shape until the block was cracked due to not winterizing and then last for the last couple years - any chance that any of these parts (rockers, pushrods, lifters) would be re-usable or should all be considered scrap?

03 35th Anniversary
06-19-2013, 05:59 PM
Do GT40-P if you are that far into it.

Just My Opinion.

j.mccreight@hotmail.com
06-19-2013, 06:02 PM
Ok, this may be a stupid question but the engine I'm swapping out had 400 hours on it and was in great shape until the block was cracked due to not winterizing and then last for the last couple years - any chance that any of these parts (rockers, pushrods, lifters) would be re-usable or should all be considered scrap?

You may reuse pushrods (if correct length, again check lifter preload) but pushrods are cheap I would use new, you may reuse rocker arms, but you need to use NEW lifters regardless.

XavierSPL
06-19-2013, 06:06 PM
Do GT40-P if you are that far into it.

Just My Opinion.

If you're referring to the heads, they are the P's - need to have them drilled out.

XavierSPL
06-19-2013, 06:08 PM
You may reuse pushrods (if correct length, again check lifter preload)
Here's where my ignorance to internals come in - I have no idea how to check for correct length or preload.

I also see different specs on the lifters, should I just be looking for 351W OEM?

TRBenj
06-19-2013, 06:12 PM
My recommendations are as follows,
* use an edelbrock performer manifold, will line up perfectly
* use gt-40 heads, if using a stock camshaft the existing valve springs will suffice (just barely)
* standard rockers acceptable
* if your truly wanting 300 hp then a camshaft swap is a must, and then so is lifters, pushrods and valve springs.
* ensure brass freeze plugs are used.
* after all this you will likely need a new propeller

I did a top end kit on my boat but I went about it very differently than most folks that just wanting a few more hp. if you want my specifics PM me and I'll be more than happy to share.
I agree... mostly.

- New pushrods are not required on a cam swap. If the old ones are damaged or the new valvetrain geometry is significantly different, thats a different story. Most times, when switching between Ford factory iron heads (GT40 and GT40p included), you can shim the rockers to dial in your lifter preload using your stock pushrods.

- Very rarely will mild top end engine mods drive a prop size change. Of course, a new modern prop is the best bang youre going to get for your buck (way better than any engine upgrade), but youre not going to want a different sized prop unless youre doing something very out of the ordinary. Typical mild upgrades to the top end of the engine will simply push your peak hp to the right- so you will spin the factory sized prop a higher RPM and take advantage of the new hp. Only when you start to go beyond the 1hp/ci range on a top end build, or if you add cubic inches (stroker) do you need to start thinking about a steeper prop (more pitch) to bring your WOT RPMs back down to where the engine makes peak hp.

-An Edelbrock Performer RPM or Weiand Stealth would offer better all around performance than a standard Performer... the only downside is that theyre taller and *might* impact motorbox clearance. Check and see what you have to work with.

- GT40p heads are better than GT40 heads in this application. They flow a little better both intake and exhaust in the lift ranges that are typically used on a ski boat (.500 and below), despite having smaller exhaust valves. They also have smaller combustion chambers, so they give you a compression ratio increase, so free hp. (GT40's have the same size chamber as the stock heads, so you end up around 8.5:1 instead of 9.5:1 with the P's). The P's also do not appear to have an issue with external cracking of the water jackets like the regular GT40's are prone to do. Oh, and GT40 heads are significantly cheaper and more readily available. Probably because the Mustang guys dont like them as much due to the different spark plug angle (and the need to run special headers)... though that spark plug angle works in our favor with our upswept marine manifolds.

- I'd have to see the specs, but I do not believe a spring change would be required on stock GT40 heads if you went that way, even with a mild cam upgrade. Those were performance heads from the get go and only came on Mustang Cobras and Lightning pickups. P heads, on the other hand, were emmissions heads that happen to flow well and came on Explorers and Mountaineers with baby cams... so those do need better springs if upgrading the cam to anywhere near .500.

TRBenj
06-19-2013, 06:20 PM
Damn, I need to type faster.

Checking Lifter Preload with Non-Adjustable Rockers (http://www.cranecams.com/pdf-tech-tips/hydro-lift.pdf)

You need to check every single rocker/valve... I have found that they can vary quite a bit (.060") from one to another on the same head. Shim accordingly with a kit like this. (http://www.summitracing.com/parts/fms-m-6529-a302)

XavierSPL
06-20-2013, 12:57 PM
Picking Up The Gt40p Heads Tonight, Looking At The Performer Rpm Intake, Going To Try And Reuse The Rockers And Pushrods From The Old Heads If Straight, Not Sure On Which Lifters Though. Anyone Point To Specifics For This Application?

thatsmrmastercraft
06-20-2013, 06:07 PM
Be sure to verify that you have enough clearance to use that Performer RPM, she sits a little higher than your stock intake or the base Performer.

XavierSPL
06-20-2013, 10:02 PM
Be sure to verify that you have enough clearance to use that Performer RPM, she sits a little higher than your stock intake or the base Performer.

Sounds like others have had this same configuration in a PS190, anyone else have issues? Do I have to re-use the carb spacer from the stock setup?

Kyle
06-20-2013, 10:49 PM
Gt40p heads like everyone has said.

I'd do performer not performer rpm. I run the performer and have 1/4" between flame arrestor and the engine box. If you sit or stand on the box then you can feel it touch the top of the arrestor. The rpm sits taller than the performer.

Push rods are cheap but not required unless longer or shorter rods are needed.

If replacing the cam always replace lifters. Always like never reuse the old lifters on a new cam. If removing and reinstalling old cam then the old lifters need to go in the same hole as they came out of.


I disagree on the prop. If you add more HP then you will turn the current prop at a higher rpm. I gained 4400-5200 by doing the engine mods. I repropped my boat to bring rpm to 4900. I run an honest 46 mph out of a '93 190 designed to go 41. If I add people to the rear then I've hit 47~48 GPS confirmed. The weight changes the shaft angle and will help lift the boat up in the front for a little less of a wetted hull. I quit throwing cash to hit the 50mph mark.

I've footed 3 long line adult men behind my boat at 44~45 confirmed on my stargazer.


Now I'm not going to dog on my friends boats on here but I have rats boat with a 285 non slot and phntmski and my boat with 330+HP with slots. All boats top out 46 ish. I walk rats 205 and phntmski 190 by .5 mph ish. Phntmski has a different cam but everything else is the same. There is a difference in the amount of power between the factory 285 vs our 330 HP engines. Unfortunately I have not compared 2 non slots, one with the factory 285 vs what I've built. All I know is my factory engine to what I have now was a for sure noticeable difference. The seat dyno was nice.

If you have any questions just pm phntmski. He seriously texts me saying thank you every time he takes his boat out. He loves the more powerful engine.

XavierSPL
06-23-2013, 11:55 PM
Thanks again for all the tips everyone. Picked up the GT40Ps for $340, sprayed em with some high temp gloss black, gave the rockers from the old heads a bath and installed them, have new lifters on the way. Cleaned the pushrods, all were straight so hopefully they'll be the correct length.

Among many other things, I figured better safe than sorry so ordered up an edelbrock performer intake..

Kyle
06-24-2013, 12:48 PM
Sounds like you are making good decisions.

Pushrods should be the same

Performer will fit tight. The rpm I think you will be lifting the doghouse.

Dino Don
06-24-2013, 11:31 PM
I have an 87 190 and ran into box clearence issues with stock spacer using the reg performer intake. My engine is built along the same lines as Kyles and performes very well. I bored mine and used flat top pistons. I did not want to raise my box so I had my spacer machined down to gain the space I needed. Apparently not an easy task but doable. Without the spacer and with a marine 4160 carb I ran into mixture issues using intake vac on the PCV valve on the val cover. I had to go back to the spacer to get it to run correctly. Had no issues at all until I changed the intake. I built the engine and ran the original intake set up and then changed intakes several weeks later.

XavierSPL
06-25-2013, 09:36 AM
I have an 87 190 and ran into box clearence issues with stock spacer using the reg performer intake. My engine is built along the same lines as Kyles and performes very well. I bored mine and used flat top pistons. I did not want to raise my box so I had my spacer machined down to gain the space I needed. Apparently not an easy task but doable. Without the spacer and with a marine 4160 carb I ran into mixture issues using intake vac on the PCV valve on the val cover. I had to go back to the spacer to get it to run correctly. Had no issues at all until I changed the intake. I built the engine and ran the original intake set up and then changed intakes several weeks later.

I'll keep my eye on it then - I'd probably just go the route of raising the box an inch or so as it'll be getting all new vinyl and carpet this winter, should be easy to do it without any trace..