Valve clearance

1172 Views 10 Replies 5 Participants Last post by gork1rogues, Mar 12, 2006

Ford66

Discussion Starter · Mar 11, 2006

I have a 1991 302 block with .030 over forged speed-pro four valve relief pistons. Plan on buying edelbrock RPM heads
with 1.90 intakes. Will I have any clearance problems ?????

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If so you should have no clearance issues, Tim runs that same setup and he said he has .180 on the intake and .200 on the exhaust; of coarse your cam will affect the actual clearance but you should be fine, this is the same setup I am putting together

Ok, just thought I would add that these are hypers, you probably have different pistons but if they are cut for 1.90 valves then there should be no issues

[ This Message was edited by: mikemustang289 on 3/12/06 4:07am ]

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Ford66

Discussion Starter · #3 · Mar 11, 2006

Nope the reliefs are not that big. the cut in the piston is 1.5 in. across

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mikemustang289

· #4 · Mar 11, 2006

ok, the reliefs are not typically cut for the full diameter of the valve since the valves are not parallel to the pistons once they in the heads, I would pull a valve out and match up the ouside diameter of the valve to the piston to make sure the valves fit the same diameter of the notches.

If the reliefs are too small you will see the valve contact the edge of each relief.

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71hotrodpinto

· #5 · Mar 11, 2006

Stock 302 valve reliefs historicaly will clear a 1.94 intake valve with reasonable valve lifts. Except for 86 302 which has a true flat top piston with no valve reliefs
Good luck

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mikemustang289

· #6 · Mar 11, 2006

I have 1.85 intakes on my 351's and they wouldn't clear a stock piston, I had to retard the cam and still ended up with .075 clearance, that was with a 278 ([email protected]) cam with .498 lift.

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71hotrodpinto

· #7 · Mar 11, 2006

That sure seems weird because thats the stock valve size on the early 351s. strange

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mikemustang289

· #8 · Mar 11, 2006

bad wording, the 351 heads are on a 289 with stock valve reliefs for 1.78/1.45 valves

With another .050 in diameter from 1.85 to 1.90 I'm sure my clearance would be even less.

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1 Bad 88 GT

· #9 · Mar 12, 2006

On 2006-03-11 12:56, Ford66 wrote:
I have a 1991 302 block with .030 over forged speed-pro four valve relief pistons. Plan on buying edelbrock RPM heads
with 1.90 intakes. Will I have any clearance problems ?????

No.

BTW are they the EDL-60229?

[ This Message was edited by: 1 Bad 88 GT on 3/12/06 7:12am ]

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Ford66

Discussion Starter · #10 · Mar 12, 2006

reasonable valve lifts ???????? What about .540 lift ????

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gork1rogues

· #11 · Mar 12, 2006

It is not so much the lift that is important, but the duration and timing events. It would be best if you were to check it instead of just slapping it together and not knowing how much clearance there actually is.

Check this page out:
http://www.fordmuscle.com/fundamentals/pistontovalve/index.shtml

[ This Message was edited by: gork1rogues on 3/12/06 11:56am ]

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