Engine Question about old GT40y heads

nothwoods · Apr 11, 2021

I've got a stock 94 shortblock with E303 cam. I'm putting on a set of the early aluminium gt40's with 1.94 intake valves and 1.7 rockers. Anyone ever run that setup? Just worried about piston to valve clearance.

nickyb · Apr 11, 2021

You gotta check that clearance for " your" engine. Better to be safe then sorry.

nothwoods · Apr 11, 2021

I know I should check it, but I figured a million people must have run this setup back in the day when these were considered good cylinder heads. Gotta be some consensus out there about whether it's a workable arrangement?

7991LXnSHO · Apr 12, 2021

Clearance will depend on your cam and it’s timing, and also head gasket thickness. So while the parts are a good starting point, this is about as strong of a yes as you can get.

2000xp8 · Apr 12, 2021

I had a similar setup, can't remember if it was my E cam or crane 2031, but it should work, but always check.
If you really want to make the best of it, take the heads to the machine shop for a valve job, bowl cleanup and seat pressure. It will make a big difference, probably should cost about $200-$250.
I like x and y heads but out of the box they are flawed.

nothwoods · Apr 12, 2021

A long time ago I had an engine with a B cam on a stock lower end with iron 3 bar GT 40's and the same 1.7 Crane/Cobra rockers. That amounted to .510 lift vs .530 that I'll have with the E cam, but the E cam has a bit less duration. Also the iron heads had 1.84 intake valves vs 1.94 on the aluminium ones. I thought there would be a lot of opinions on this, lol

2000xp8 · Apr 12, 2021

nothwoods said:
A long time ago I had an engine with a B cam on a stock lower end with iron 3 bar GT 40's and the same 1.7 Crane/Cobra rockers. That amounted to .510 lift vs .530 that I'll have with the E cam, but the E cam has a bit less duration. Also the iron heads had 1.84 intake valves vs 1.94 on the aluminium ones. I thought there would be a lot of opinions on this, lol

I don't think anyone is willing to put their name or reputation on it definitively.
Used parts can't always be trusted.

nothwoods · May 17, 2021

So I did a clearance check on this if anyone's interested. Again this is a stock 1994 short block with hypereutectic pistons, E303 cam, and the early GT-40Y aluminum heads, with 1.94" intake valves. I did the check with Crane/Cobra 1.7 rockers, and without a head gasket installed, my findings are as follows: I'm using Fel-Pro 9333 PT-1 gaskets which list a .047" installed thickness. No problem on the exhaust side, would've ended up with around .300". On the intake side I was right at zero clearance, the valve just, and I mean JUST kissed the piston, so it would've been at about .045" with the gasket, which you're looking for .080" minimum on the intake, .100" on the exhaust. I'm going to get some 1.6 rockers and that should put it at about .076". A little on the tight side but I think it will work.

WhiteCobra95 · May 17, 2021

That's what I remember from back in the day. 1.9" intakes are too big for stock pistons. The only way around it was TFS heads due to the angle changes. Otherwise, you're limited to the smaller intake valves. I've helped several friends fly-cut their stock pistons, but those were all the older forged factory 5.0L pistons which had a lot of meat to them. I don't know if you can do that with the later pistons. (In fact, the '86 short block needed fly cuts for iron GT40's with an E-cam and 1.7 rockers.)

7991LXnSHO · May 17, 2021

nothwoods said:
So I did a clearance check on this if anyone's interested. Again this is a stock 1994 short block with hypereutectic pistons, E303 cam, and the early GT-40Y aluminum heads, with 1.94" intake valves. I did the check with Crane/Cobra 1.7 rockers, and without a head gasket installed, my findings are as follows: I'm using Fel-Pro 9333 PT-1 gaskets which list a .047" installed thickness. No problem on the exhaust side, would've ended up with around .300". On the intake side I was right at zero clearance, the valve just, and I mean JUST kissed the piston, so it would've been at about .045" with the gasket, which you're looking for .080" minimum on the intake, .100" on the exhaust. I'm going to get some 1.6 rockers and that should put it at about .076". A little on the tight side but I think it will work.

Glad you checked!

nothwoods · May 17, 2021

The stock pistons should be fine with the 1.6 rockers. Actually the Crane's are listed as being 1.72, so I should have about .082" clearance even with the 1.94 valves.

nothwoods · May 17, 2021

Something else I just remembered... have to check with my friend but I’m almost positive that this engine had the old Performer heads on it, which had 2.02 valves, and it had this cam already. Don’t remember what it had for rockers but there were no marks on any of the pistons, (other than #7 missing a ring land very shortly after he changed the blower pulley). He won’t know what rockers were on it but he still has the heads on his new motor. This was like fifteen plus years ago.

Engine Question about old GT40y heads

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I gotta say i never painted my nuts, Never Ever

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Engine Question about old GT40y heads

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