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  • GT40 recommendations please!

    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.

    Thanks!
    My restoration thread here!!

  • #2
    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.
    James

    1989 MasterCraft TriStar 190 SE
    sigpic

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    • #3
      /paging Kyle
      Tim
      Gone, surfing.

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      • #4
        Originally posted by CantRepeat View Post
        /paging Kyle
        Hey my 351w is no slouch
        James

        1989 MasterCraft TriStar 190 SE
        sigpic

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        • #5
          Originally posted by j.mccreight@hotmail.com View Post
          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.
          - Peter
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          • #6
            Originally posted by j.mccreight@hotmail.com View Post
            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?
            My restoration thread here!!

            Comment


            • #7
              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.
              James

              1989 MasterCraft TriStar 190 SE
              sigpic

              Comment


              • #8
                Originally posted by j.mccreight@hotmail.com View Post
                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?
                My restoration thread here!!

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                • #9
                  Do GT40-P if you are that far into it.

                  Just My Opinion.

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                  • #10
                    Originally posted by XavierSPL View Post
                    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.
                    James

                    1989 MasterCraft TriStar 190 SE
                    sigpic

                    Comment


                    • #11
                      Originally posted by 03 35th Anniversary View Post
                      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.
                      My restoration thread here!!

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                      • #12
                        Originally posted by j.mccreight@hotmail.com View Post
                        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?
                        My restoration thread here!!

                        Comment


                        • #13
                          Originally posted by j.mccreight@hotmail.com View Post
                          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.

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                          • #14
                            Damn, I need to type faster.

                            Checking Lifter Preload with Non-Adjustable Rockers

                            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.

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                            • #15
                              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?
                              My restoration thread here!!

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