Valve-piston clearance w/1.70 rockers - FFCars.com : Factory Five Racing Discussion Forum

Matt Levine · 10-31-2005, 03:05 AM

I want to install roller rockers, and If I get 1.70 ratio rockers - 302 with aluminum GT40 Y heads, Ford Racing B303 cam w/.48 lift I&E - there will be an additional .051 valve lift. Can someone tell me if this will be cause a problem with valve to piston clearance. .051 doesn't seem like much to me, but I sure wouldn't want to be wrong.

powerhouse · 10-31-2005, 12:42 PM

If you have enough clearance now, you should be ok. The opening and closing points aren't changing,just how fast the valve is opening. Max. lift isn't really an issue with piston/valve clearance as at max lift the piston is pretty far down in the bore. The area of concern is on the overlap stroke when the ex. valve is closing and the intake is opening.
The only way to know for sure is to physically check the clearances. Andrew

Matt Levine · 10-31-2005, 03:12 PM

Any way to check the clearance without removing the head?

powerhouse · 11-01-2005, 01:08 AM

you could install a light tension valve spring and mount a dial indicator to read off of the retainer. you would use the rocker arm as the lever, rotate the engine from roughly 50* btdc to 50* atdc on the overlap stroke. check the clearance every 5* . do this on both intake and exhaust

Gordon Levy · 11-01-2005, 02:48 PM

You won't have a problem unless you exceed .530 valve lift. The lift on the B cam isn't enough to be concerned about with 1.7 rockers.

Matt Levine · 11-01-2005, 07:50 PM

Thanks Gordon, I sure appreciate the help.

Tims 88GT · 01-25-2006, 12:52 AM

is this a 5.0 mustang or a motor out of a 5.0 mustang? because you can go about .540 lift with stock valve springs but the retainers dont like more that .500 lift. i run .522 and have not had a problem, i say you would be better off with a differant cam the b303 cam is only so so. there are better cams.