Spun up my newly aquired 305 roller L03 from an 89 TBI Camaro and got anywhere from 190 to 210 pounds on the guage !!! Motor looks like it has never been apart and looking in the plug hole, pistons have a slight dish with small valve reliefs. Can that be right ??? Thanks.

 

should be a 9.5:1 c/r motor, and that's what mine would pump out was 190-210psi when i was still running my old 305.

 

Does that mean a premium gas diet is required ???

 

My 383 produces around 195-200 psi. Its' compression ratio is 9.5:1.
Doesn't necessarily mean it will need premium.

 

if you want to run lots of timing, then yes, or this will result:

but if your easy on the timing, you'll be fine. say around 8* advance at idle with no more than 36* total.

 

WOW - what are those pistons from - a 350 or 305 and are they flat tops ??

Before I install the engine, I do have a set of head gaskets that are about .040 thick, I think the stock gaskets are about .028. Should I install the new head gaskets to drop compression a little or just leave it alone ? Maybe they should be replaced anyway with 140,000 miles on it ???

 

gotta say interesting way to break an engine in there mw. just out of curiosity how do the cylinder walls/bearings and everything else look after that?

 

I'd suggest leaving it alone, if there's nothing wrong with it. There's CERTAINLY no point in deliberately downgrading it to even weenier than stock. Unless you just want to refresh it, which is a different matter entirely. If you pull the heads, I'd suggest gettting SOME OTHER HEADS, such as 081 casting off a TPI or LG4 or L69 motor (Monte Carlos had those), and DO NOT spend any money on the swirl-port ones you have now. When you put it back together, use regular head gaskets, and have the heads decked a little bit, basically just enough to clean up the surface; your CR will come back out about the same as it was before.

Even a low CR motor will give very high readings on a compression gauge, if it has a very small cam. Which of course pretty much describes the L03 situation. Moderate compression, weenie cam.I'd suggest leaving it alone, if there's nothing wrong with it. There's CERTAINLY no point in deliberately downgrading it to even weenier than stock. Unless you just want to refresh it, which is a different matter entirely. If you pull the heads, I'd suggest gettting SOME OTHER HEADS, such as 081 casting off a TPI or LG4 or L69 motor (Monte Carlos had those), and DO NOT spend any money on the swirl-port ones you have now. When you put it back together, use regular head gaskets, and have the heads decked a little bit, basically just enough to clean up the surface; your CR will come back out about the same as it was before.

Even a low CR motor will give very high readings on a compression gauge, if it has a very small cam. Which of course pretty much describes the L03 situation. Moderate compression, weenie cam.

 

those are 305 four valve relief pistons. actually, the bore looks great. i plan to run a honing stone down it, grab another piston and a set of rods and have that be my spare motor. i've got a set of 416 heads here at the house i'm going to do up and put in one of the summit cams. i haven't pulled the crank out of that motor yet, but the rod bearings looked OK.