if you feel like fabricating go with a holley 4bbl the increase in size will also increase the air flow thru the turbo and they seem to be stable in rough conditions as for the water injection start asking around the draw thru turbo group most of thos guys have had turbocharged cars longer than I've been breathing

so the best combo for what we are up to is a sss with 81-83 z28 pistons with a dish? if i did my research right there are two diffrent pistons one flat and one dished. go water injected (with what size jet?)and most of all get rid of the intercooler.what carb setup would be best? you have to remember we are dealing with steep hills and rough conditions so it has to fairly easy to tune for such thanks for all the replies again

unless you want to spend big bucks on forged slugs you will have to try oem replacements. as for the head the sss 38cc is too much you will need something with a bigger chamber say 41cc or biggerthat will lower your comp some keep in mind even the u67 open chamber head is usable for boosted applications.

here are rough comp #s with stock L-20 dished pistons

41cc head a87 type 9.0:1
45cc head u67 type 8.5:1
38cc sss head 10.8:1

if you use a reduced deck piston you will not cause detonation on the contrary it will help by reducing the compression further

U67 head turbozx pistons 8.0:1
u67 head Z20 pistons 6.5:1
a87 head Z20 pistons 7.5:1
sss head Z20 pistons 8.0:1

I hope this is usefull personally I'd go with the last combo, it will be the most resistant to detonation due to the larger squish area of the head and the reasonable compression. you should be able to run rediculous boost with this setup. I would also recomend looking into a bigger carb and water injection if you plan on staying with a draw thru setup.

on a suck through set up, you do not run an intercooler as a rule so once you get rid of it, lower the boost, tune the car and you should increase the boost gradually. You should be right, as mentioned earlier, the lean condition would melt your pistons.
have you checked out the suckthrough turbo group on yahoo.com?

draw thru turbo club

there is also the blowtrough group.

blowthrough

ok chris we get rid of the intercooler no problem. now what piston head combo now?

The problem with draw through and the intercooler, is that while driving fast, the fuel would drop out of the mist and condense on the cool intercooler surface, and never make the engine, that would be a nightmare to tune. This is why EFI engines position injectors so that they squirt onto the intake valves. This stops the metered fuel mixture from forming large droplets and settling in the intake. That would be a fire hazard waiting to happen, imagine the fuel laying in the base of the intercooler after a run...I'd almost bet this caused a lean condition, which would cause the pistons to meltdown.

I'd definitely get rid of the intercooler on a draw through turbo setup. These are for blow through or EFI only I'd think.

Chris

no chance of a dyno but could install once running a o/2 sensor and meter ratio as well but was wanting to get running first with aleast the right parts and yes these engines get get beat up severely they are thru the rpm range probably more than any other driving that why i'm asking for help with this matter

its a draw thru and i have heard of sneazining sould we get rid of intercooler and just go to a holley or posible injection as in pro injection?also water/alky injection would that help as well?I personally have a 2300 cc air cooled vw with t-4, gm injection with 52 lbs injectors with intercooler water/alky inject 8-1 comp with no problems with 20 psi boost

are you blowing thru the carb or drawing thru, if you are drawing thru, your intercooler has all of your fuel in it and that is your problem. one sneeze and you would blow thew front off of your car.

So there's no chance of getting the vehicle on a dyno, so appropriate A/F ratios can be checked throughout the rev range?

Tuning by ear/eye is not the best way. Especially when you want to go out and thrash the engine to within an inch of it's life.

Chris