Ok, I was always taught take 3 complete sets of readings (not just three in a row on each cylinder), average the numbers and then compare the lowest cylinder to the highest cylinder. The lowest cylinder should not be more than 10% lower than the highest cylinder. However, I was taught for stock application and not sure if high performance engines needs to have closer tolerances. I did the dry test runs with all plugs out to ensure if there was blow by between cylinders I would see it. I also kept a charger on the car so the starter didn't slow down and affect the numbers. I have not done a wet test yet. My numbers averaged out as follows:

1: 170 , 3: 173 , 5: 166 (lowest) , 7: 171

2: 173 , 4: 176 (highest) , 6: 174 , 8: 169

based on that 10% of the highest number is 17.6 psi and the actual difference between the highest and lowest is only 10 psi which comes out to a little less than 6%. The engine is a fairly new rebuild (approximately 2k miles on it) does that sound appropriate and other than maybe doing a wet test, which I am thinking isn't needed with these numbers is there anything else I need to do?

 

did you do it with the throttle blades open?

 

I would repeat the was the throttle open question.

What is the cam?

A bone stock b-body LT1 with 10:1 compression will usually crank up in the 190s, lowest I ever saw was 180psi BUT it was a dirty 185K mile engine and with some short oil change intervals and some ester based oil to do some cleaning even that was up to 195psi by the time it hit 190k miles.

Was the engine built for performance or just "rebuilt"? Did the shop that did the work understand appropriate LT1 compression ratios?

 

to answer your questions, first nope I honestly forgot to prop open the throttle body. It has been awhile since I have had to do a compression test so I didn't even think about it. The engine was rebuilt for preformance and I looked up to my original post to see if this is the one I listed all the info about the engine in and of course it is not. I posted another thread today about the spark plugs and in that post I included all the engine info.

The parts list was picked out by a speed shop here locally that specializes in corvettes and camaros and was originally put together by them. I won't mention their name because they did a crap job and I ended up having to tear it down to the block and replace alot of it myself. Primarily the valve train components and opti cap and rotor were the things they really screwed up and I had to replace, but that's a long story.

Ok the 93 LT1 was rebuilt as a LT4 383. The machine work to blueprint and clearance the block along with head and intake work was done by a very reputable shop in my area. The intake and heads came off a 96 Corvette with the LT4. The heads were ported and polished and reworked with larger valves and the intake ported to match and polished. The cam is Crane cams 109661 230/238 duration @.050, with .575/.595 lift with 1.6 fully roller rockers, 112 degrees seperation with +5 degrees advance built in to the grind, comp cams bee hive style springs, retainer and locks, BBK 58mm throttle body (which I forgot to prop open) and shorty headers, eagle specialties street and strip balanced rotating assembly with hypereutectic pistons, I beam rods and steel crank, injectors were upgraded to 36 lb EV1 style injectors. I am running a MSD 6AL with MSD billit opti and blaster coil along with their 8.5mm super conductor wires.

I know I probably forgot something but hopefully that helps get some of the information you wanted in here. I do not know what the actual compression ratio is on the engine. As I said the shop did a crap job on many things and it ended badly so alot of things I just never got info on. But I do know it was supposed to have a lower compression ratio to it as the cam grind is set up for 10.0 - 11.5 for use with manifold nitrous or Roots supercharger 15lb. max boost.

Oh and the engine has only 2k miles on it since the rebuild.

 

Rule of thumb is cylinders should be within 10% of the highest reading. I think with that cam your compression is fine. If you are really concerned I'd suggest getting a leakdown instead of doing a compression test.