Mike 92LX

Intake and exhaust. Thanks

bill mcdonald

Worried about clearance?
I did on a ZZ9, 64cc combustion chamber AFR heads.
Zero decked block.
2 reliefs in the pistons, 10:1 compression.

aklim

On a stock engine? I wouldn't. Those springs are old and tired. Also have to dremmel the drip tabs off if you do.

Mike 92LX

I would never run a cam with stock springs. I am aware of the drip tabs.

Not worried about clearance..since 1990 I run 1.6 on intake and 1.5 exhaust on all the cars I built. Big debate before about using 1.6 on both sides with these cams

aklim

A lot of people I see just toss 1.6 all around on a tired motor, feel the power (much of it placebo) and get carried away. Many get away with it too but if your luck runs out......

I wouldn't want to risk it myself but YMMV

Mike 92LX

if compression is good and the right spring is used it shouldn't be a factor in terms of stress. I have added tons or rockers to LT1s and L98s since 1990 probably around 100 of them. I am just curious since the ZZ4 was designed for a 1.5 rocker and TPIS likes the 1.6 on intake side and 1.5 on exhaust if anyone is running 1.6 on both intake and exhaust. I am doing two cars with these cams and they want 1.6 on both sides...

-=Jeff=-

I did.. well, I actually ran 1.6 intake and 1.5 exhaust on my 89 vette with ZZ9 cam.

but I also had CNC'ed Stock Heads, (I forget the model # of the springs), Miniram and headers with exhaust..

GREGGPENN

Who is "they"?

Both cams are ground with quite a bit more lift/duration on the exhaust side. They are "legacy" cams (grinds) that were created in an era where exhaust flow represented as much/more obstacle to air flow. Plus, you gotta think the option of adv/straight/ret setting -- in conjuction with rocker lift could give SOME control to how the cam was installed for creating low/high-end power.

1.6 rockers on the inlet side gets you closer to what the exhaust life/duration is "providing". Of course, other factors in the build should be considered.

Personally, I assume you're asking as a matter of wondering if you'd run into valve float putting 1.6 rockers on those exhaust lobes? Considering the duration, I would think the lobes are gradual enough to handle the higher ratio.

I'm sure TPIS could confirm.

If you're wondering about actual performance/result, the heads used would play an equal factor.

Mike 92LX

"They" meaning owner of both cars.

I will try it then