Schrick camshafts passing Cali smog?

[nando]

Originally Posted by =======Live Fast!

Yea. Im curious as well. I know plenty of folks that race in Spec E30 that take the head and block down to the absolute minimum required in the rules. I havent heard about any problems theyve had as a result of it...

SpecE30 builds are required to use all stock parts, so their motor builds are always a compromise.

the primary thing with an aftermarket cam is piston to valve clearance. even without a decked head and block, it's likely you will have piston and valve contact at TDC with the schrick 284/272.

It's a certainty if you deck the head and block any amount that the intake valve will hit the piston and destroy your motor. You'd have to cut the valve pockets a little deeper to meet the minimum valve clearance of 1.5mm - but this is a hairy edge to ride on. safer to target at least 2mm clearance at TDC. the exhaust side isn't so close, it's the intake side you have to worry about.

the other problems are the cam timing as mentioned (can be dealt with using an adjustable gear), but a bigger effect will be on the quench area of the combustion chamber which are certainly thought out & engineered elements on the stock M20B25.

a normal surfacing won't be a big deal, but if you're trying to cut enough to reach say, 9.5:1 then there's not going to be much left of the original combustion chamber design, and it's likely the pistons themselves will hit the head anyway.

Basically the .2 difference in CR isn't worth the drawbacks - it's still not enough to match a 284/272, anyway. if you're forced to use all stock parts (SpecE30), then that's just what you have to do, but it's really not comparable once you start modifying stuff.

[=======Live Fast!]

Originally Posted by Wild Ride

I have gone down this road over the past two years:

Im at 10.2:1 with a decked head and a 288 and a 2.7l diesel crank b27 rods and b25 pistons double overbore. As long as you don't have headers and intake you will pass the visual. The distance between the cam and crank timing gears will change when you take material off the head. You will need an adjustable timing gear to fix your timing or the car will run like s**t. You will absolutely need a very good tune that is optimized for your setup like a miller war chip megasquirt etc. Don't adjust your fueling with a adjustable fuel pressure regulator it is just a band aid for a proper tune. A good tune optimized for your setup coupled with a good cat will pass smog. It will idle very lopey at 1100 rpm which will spook many smog guys so make sure yours is very lax or ignorant.

All together you are looking at 2k plus to create a perfect setup between cam, injectors, tuning, cam gear, wideband, machine work etc.

Yea JP did recommend I get the miller maf/w.a.r setup. Its next on the list...need to save up! Just blew close to 4k in labor and parts redoing the whole head with port and polish...

[=======Live Fast!]

Originally Posted by nando

SpecE30 builds are required to use all stock parts, so their motor builds are always a compromise.

the primary thing with an aftermarket cam is piston to valve clearance. even without a decked head and block, it's likely you will have piston and valve contact at TDC with the schrick 284/272.

It's a certainty if you deck the head and block any amount that the intake valve will hit the piston and destroy your motor. You'd have to cut the valve pockets a little deeper to meet the minimum valve clearance of 1.5mm - but this is a hairy edge to ride on. safer to target at least 2mm clearance at TDC. the exhaust side isn't so close, it's the intake side you have to worry about.

the other problems are the cam timing as mentioned (can be dealt with using an adjustable gear), but a bigger effect will be on the quench area of the combustion chamber which are certainly thought out & engineered elements on the stock M20B25.

a normal surfacing won't be a big deal, but if you're trying to cut enough to reach say, 9.5:1 then there's not going to be much left of the original combustion chamber design, and it's likely the pistons themselves will hit the head anyway.

Basically the .2 difference in CR isn't worth the drawbacks - it's still not enough to match a 284/272, anyway. if you're forced to use all stock parts (SpecE30), then that's just what you have to do, but it's really not comparable once you start modifying stuff.

You my friend are a wealth of information. I always appreciate the breakdown!

[Anguz]

i just passed smog with my 272.

[RobE30]

I'm pretty lucky that I didn't have any clearance issues after I installed my 284/272 cam. It's been in for almost 10k miles, I would imagine I shouldn't sweat it now, right?

[nando]

you got extremely lucky. it's foolish to install an aftermarket cam and run the motor without checking the clearance of the intake valves.