302 Piston & Valve Clearance

MRITTER · #1 (**permalink**) 08-30-2001, 07:33 AM

I have a '92 model 302 EFI in my FFR and I am getting conflicting info from two different, and very knowledgeable, mechanics about piston valve clearance.

I want to put in a Ford F-cam and 1.7 roller rockers. Ported and polished stock heads and valves. One mechanic says that the '91 and later motors have reliefs that will allow for this with no problem. The other says that I will only end up with about 10 thousands of an inch clearance and that within 500 miles I will knock the bottom out of the motor.

Does anybody have any info on this subject.

Thanks in advance for any help.

Mike

mikiec · #2 (**permalink**) 08-30-2001, 08:31 AM

The only way an F cam will work with 1.7 rockers is to notch the pistons.

I'm running the F cam with GT40-P heads but using the 1.6 rockers. Runs and sounds great. The motor is a 92.

To make sure this all works I suggest you check piston to valve clearance. That way you will know for sure.

Mike

Matt M FFR 1502 · #3 (**permalink**) 08-30-2001, 01:30 PM

Remember when the valve is at its highest point, the piston is near the bottom of the cylinder. It duration that kills valves and pistons, not lift. The 1.7 lifters should be ok, but I wouldn't put a motor together without checking the clearance. IMHO Matt

Having said that, I run 1.6 rockers with the F cam.

Christian · #4 (**permalink**) 09-01-2001, 11:17 AM

Engine Factory always clay checks the valve to piston contact
when putting on cylinder heads. Usually anything over .500 lift
is a good idea. I realize that this is difficult to do when engine
is already installed. www.enginefactory.com

MRITTER · #5 (**permalink**) 09-04-2001, 07:07 AM

Well, I appreciate the replies. We went ahead and installed the 1.7 roller rockers and no problem. Car runs great. Just thought I would post the results in case someone else wanted to go there.

Mike

CobraEd · #6 (**permalink**) 09-04-2001, 07:23 AM

I have a 74 motor but with the Edelbrock aluminum heads. I have .488 lift with the standard 1/6 roller rocker ratio. I have been toying with going to the 1/7 ratio which would take me to .518 lift. I am hesitant to do this because of clearance issues. Does anyone know if the older 302s have more or less valve clearance than the later "5.0"s?

Ed

MRITTER · #7 (**permalink**) 09-04-2001, 08:14 AM

I know that the '87 and later model 302s have valve reliefs in the top of the piston that allows more room. The 86 motors do not and you can't do anything to the valvetrain in them w/o clearance problems. If there are valve reliefs in the pistons you probably will be ok but I'm just not sure about the older 302s.

Mike

CobraEd · #8 (**permalink**) 09-04-2001, 08:18 AM

there are valve reliefs, I just don't know how effective they are.