I have a roller tappet engine with '86 flat top pistions (no valve reliefs) that come up even with the deck, stock HO cam, and E7 heads shaved .005". Piston to valve clearance is OK for exhaust valves and just below minimum for intakes. Since the engine won't be seeing high RPMs, I decided to risk it and everything is fine. Now thinking about power adds and wondering about GT40 heads. Can anyone tell me how piston to valve clearance would be with GT40 heads vs E7s?
not sure of the exact clearance but my buddie has same setup 86 pistons and e7s but he has 460 rockers and a .512 lift cam and had no clearance issues.
I use an '86 short block, with the non-releived pistons, a B303 cam (480 lift) and stock rockers with no problems.
We were going to build my brothers 86 engine with his GT40 heads. I searched all over the web and it was a 50/50 split on if it would work or not. If you already have the parts then mock it up and check it. But if the E7s were already too close it's going to be even closer with the GT40s and any bigger cam will just make it worse. On my brothers car it ended up one of the heads was bad so we never got to fire it up and run it but it did not hit a piston when mocked up. He ended up getting a pair of Trick Flow Heads. these are the best heads for a 86 piston and allow about any cam you want becasue the valves are straighter and dont hang down as low.
Don't have the GT40 heads and my engine is in the car and running. Just considering options now. I got the same 50/50 odds when polling about the '86 pistions and E7 heads combo. Figured I'd be in the good 50% since the engine won't see high revs. The clay showed my intake valves .020 closer than minimum recommended clearance so I certainly wouldn't want to make it any tighter. Sounds like GT40 heads on my current engine would be a bad idea. Maybe I should build a stroker replacement.
i have an 86 ho block which is going to have an f303 edelbrock estreet heads 1.90 valve with 1.73 comp cam roller rockers, but i have a complete forged rotating assembly with valve relife pistons. im hoping for high 300hp. my first plan was keep the stock 86 block with gt40 heads. if i remeber corectly it was going to so close that i just decided to build an engine i wanted.
GT40 heads (not the P versions) have larger exhaust valves too. Bad idea. Build a new short block with pistons and reliefs. Better yet, build a stroker short block then top it with the heads of your choice.
Going to Charlotte tomorrow to check this out. http://cgi.ebay.com/ebaymotors/347-...r_Truck_Parts_Accessories&hash=item27bb5d7c78 Talked to the owner on the phone and he sounded like a good guy to deal with. But, I'm wondering if those heads and that cam are a little too aggressive for a well-mannered, dependable driver. I drive it around town and on road trips with the wife. We'll talk about a build with different heads and cam. Maybe 9.5 - 10:1 compression. I'll keep the current Doug Thorley shorties and Thrush Turbos. Would like to get close to 300 RWHP in a dependable, smooth, carbed engine with NO MORE than 2500 stall converter. What do you think, is that realistic?
Depends on what cam is there. The more cubes there is, the tamer the cam will be as opposed to a smaller displacement motor. I've got a Z303 in my 331 with 1.7 rockers (228*/228* @ .050, .587/.587 lift, 112*LSA) and it combined with the 1.94 valved canfield heads (equal to AFR 165) and the highrise dual plane 3x2, it's surprisingly mild mannered on the street for everyday driving. It's got a wicked lope at idle, but the power comes on at 1500 rpms and pulls to around 6500. The dual plane/small carbed (250 cfm Primary) helps to lower the rpm range downward too.
I've run it in front of both a Toploader 4 speed and the Comet's C-4 with an unknown, but mild stall converter (that according to my transmission guy who looked at it) It'll light up the 295/50's out back with just a lite touch of the go pedal and brake. Very streetable. Gears are 3.50's in a 9" with Trac-Loc
