1.7 RR

[50canuck]

Can you put 1.7 RR on the 86gt stock heads?and get any gain from them? Will it cause any p/v issues?

 

[shttygtstang]

should of did a seach but you could use em

 

[v8only]

i'd be super careful there, your 86 pistons have no valve cutouts. I "thought" you could only run 1.6's, maybe I'm wrong, just be very careful.

 

[fiveoboy02]

The only way to know for sure is to check the clearance, either with clay or a dial indicator.

 

[Michael Yount]

P to v clearance is minimal during overlap -- when the intake is just opening, and the exhaust is just closing, and the piston is passing through tdc at the end of the exhaust stroke and the beginning of the intake stroke. Consequently, the valves are only open around .07-.08" at that point in time. Do the math - a change in rocker ratio only reduces p to v by about 5 THOUSANDTHS of an inch. Nothing to worry about unless you're right on the ragged edge anyway. And if everything else is stock, you're not on the ragged edge of clearance.

The switch from 1.6's to 1.7's on a stock 86 won't cause any clearance problems. Now, if you're running an aftermarket cam, and have reduced p to v because of that - then you need to do the math. What was you clearance with the 1.6's (you did measure, right?)? Subtract .005" from it, and you'll have a pretty safe approximation of what your clearance will be with the 1.7's.