That'* not why the 7.0" pushrods come in.
Our lifters can only compensate for a .015-.020" difference in valvetrain geometry after that they collapse. Stock is pr'* are 7.05. So, milled 40 over or 30 over with .052" head gaskets will only have a difference of .01".
But, even so, increasing the lift by .04" doesn’t put the valves anywhere near the piston.
Just look at the lift on the more aggressive cams. Your retainers are going to hit your valve guides way before the valve will hit the piston.

I did the exact figures. It'* just over .3" from top of [both exhaust and intake] valves to the top of the piston [where the valves are on the piston]. So you have quite a bit of 'room for fun.' Mind you, this on an SI LN3.. so your SII L36 could vary.


-justin

you're too god damned smart you know that?

Now if i was really smart i'd be able to figure out why i've got knock on a n/a engine.

Thanks for the ZZP link. I'm definitely not going that far with these heads, lol.

So you're telling me I can take .030" off my heads and keep the stock pushrods? Moving to shorter rods would negate the effects of the milling wouldn't it? I'm going for more compression, so dropping .050" on the rod length would put me right back where I started. Where would my CR be after a .030 deck job?

Also, do you guys know if anything has to be done to the PCM to run higher compression? I'll probably be getting a dyno tune, but could I run a stock PCM to drive the car to the dyno?

Ok, disregard that last post.... somehow I read "pushrods" and my brain said "connecting rods." Yeah, I'm an idiot.

I would still like an answer to this question. Any takers?

yeah, you could do it.. but don't be surprised if the car runs like ****.


-justin

As long as you have everything flowing really good, your stock timing should be fine. But upping the compression on an otherwise stock motor will most likely lead to KR.
I'm not really sure what else you have planned but if you 30 or 40 over your heads, you should have p&ped heads, at least pems, headers would be better, and a cam.

How is higher compression going to run like ****? He'll need to reduce timing somewhat, or go to higher octane.