'86 5.0 GT40P head swap questions

[sm41]

Hi guys. I picked up a very cheap set of GT40P heads and did the clay test. With a pre-used head gasket (old one came out in one piece), stock cam, rockers, and true flat top pistons, I had .112 clearance on the intake and .209 exhaust. I know you need to have at least .08 to be considered safe. I still need to get them decked to ensure a good seal. Do I have enough room for 1.7 rockers? I've heard the '86 had a unique cam, but I'm having a hard time finding the specs to do the math and see how much clearance I'd lose.

I'm also having a much harder time finding valve springs this time compared to when I last built a 5.0 a few years ago. None of the popular Mustang sites seem to have stock type, no machining required springs anymore. I've heard the name AlexParts a few times. Any other providers? Nothing against them (no experience, good or bad) but I like having multiple options.

Thanks for the input!

[Lowetlx]

Trick flow makes a nice set of springs for about $150. I used them on my 3bar heads and they are very easy to install and shim to height. How much are you having them take off the heads? .010”? Now you only have .102”. If you knew how much lift the cam is at when the piston is at and near tdc you could determine how much extra lift you will have with the 1.7 rocker. For instance if the cam is at .100 lift the 1.60 rockers will be at .160” and the 1.7’s at .170” essentially .010” more for every .100” of lobe lift. But the cam is at low lift during that time so you might clear. It would be best to clay again. You may be very close to that .080”

[sm41]

That's a good point about the cam positioning. This is the first '86 I've done a head swap with, and I know everything is kind of a gray area as far as whether it's all going to fit. I might see if I can borrow some 1.7s to test fit. If not, I'm not too worried about the couple extra hp I'd leave behind by staying stock.

Depending on how much they have to mill off, I may get the thicker head gaskets.

[Lowetlx]

Thicker head gaskets is a whole new discussion. you have to make sure you keep the quench clearance in spec. How far above or below is the Piston at tdc? If your between 0 and .010” below I would run a .038” thick gasket.

[sm41]

I was thinking the .042 if they have to take a fair bit off, since that would balance it back out. Though I could be misunderstanding quench.

They're definitely below deck, which I'm guessing is why I have enough clearance. I didn't think to measure the distance though.

[STL79Coupe]

I used Alex's Parts drop in springs on my last explorer motor. I was using an E cam, 1.7RR, and my heads were shaved 30. The springs saw a few missed shifts that resulted in zinging to the moon and still were fine. You can also get a tool to flycut your pistons while they're still in the block. It might be worth looking into using the tool.

[sm41]

The more I hear about Alex's the more I think I'll end up going with them.

If I was going to try and put a cam in it, I might fly cut, but it's really not worth it to me. This car is just a cruiser, and will be plenty fast for my tastes with the stock cam and GT40Ps.

[STL79Coupe]

The more I hear about Alex's the more I think I'll end up going with them.

If I was going to try and put a cam in it, I might fly cut, but it's really not worth it to me. This car is just a cruiser, and will be plenty fast for my tastes with the stock cam and GT40Ps.

I would just use Alex springs then. I was amazed that none of them broke while zinging to umpteen grand.

[sm41]

Finally got a weekend to put it all together. Runs like a charm, pulling hard all the way to 6k! Not the fastest thing in the world, but it's a whole lot better than with the E6s.

https://youtu.be/DoPnwv6q4D4

[viking]

Looks pretty fast to me. Seems like it sounds a little different.

[sm41]

I'm pretty happy with it! That would be an exhaust leak at the H-pipe, which has since been adjusted. The engine note did change a little though, I'm guessing since the compression ratio is a little higher.