I finally have everything just about done (to the point the engine cranks and such) so i decided to do a compression test. I bought this engine back in October and it has sat a while before that by the looks of it. It had been involved in an accident where the oil pan was damaged, crank pulley was knicked and timing cover smashed. The engine was sold as a 99 LS1 but had 241 heads on it so it turns out to be a a late 2000 or so.

The engine had been kept in my dining room since i bought it. I took the pan and windage tray off and looked at each cylinder at TDC (from the bottom) and all of the cylinders still have crosshatching on them not damage that i could see. There are no loose rods or bearings that i could tell. I went ahead and installed the cam in my sig, patriot golds, 7.450 pushrods, new timing chain, LPE high flow oil pump and everything else in my sig.

When cranking it over the engine makes 55psi oil pressure. I checked all of the cylinders letting each one compress about 4 times. I had 6 all make about 60psi. One was making about 10 so i cranked it a little more and it jumped up to 60psi. Then i had one cylinder make 135psi. So is my motor toast? I figured the bearings would have gone before the rings and i wouldnt be making oil pressure.

When i replaced the valve springs i did notice all of the cylinders leaking with 130psi in them from my compressor. I'm going to go ahead and start it anyway but i was just curious if anyone knows what and engine should be that has sat so long. I am figuring it has sat for atleast a year and a half, i just installed new springs and valve seals. I'm just hoping its because the engine hasnt been heat cycled in a long time. What do you guys think?

 

I know what really matters is the compression being close between cylinders as different setups give different numbers, but 60 psi sounds REAL low. I have very low compression (8.6:1) and I get 155 psi in each cylinder. I would check to make sure your valve train is set up right (valves adjusted and fully closing). Also, when you checked the pressure,, did you hold the throttle open? If not, it may give numbers like you're getting.

Derrick

 

if the rings have not had oil in a while put a little oil in the cyl and crank it for like 15 sec and remember to hold the throttle wide open when doing a compression test hope this helps

 

60 PSI is low. Very low. I'd personally pull the plugs and oil the upper cylinders. Any cylinder is going to leak down. You really need a leakdown tester to see where it's leaking. It's a red flag that 7 cylinders are exactly 60psi... You might not be getting the valves all the way closed. What you could do is turn the motor to TDC and pressurize the cylinder with the same fitting you used to change the valves... If you hear excessive air in the intake or exhaust, focus on the valvetrain... If it's all crankcase, then just go with the upper cylinder lube and hope the rings settle in.

 

As said before 60 is low. I would take the spark plugs out and shoot some oil in the cylinders. If it's been sitting that long the rings are going to loose some it's seal because it's dry. Also make sure you put the timing chain on right. If it's off a tooth or so that could effect it too because the valve timing would be off.

Shoot some oil in it, try it again and get back with us. Good luck.

 

Well the throttle was wide open as there is no intake and no headers on the engine as of right now so i know nothing was blocking the ports. I have read that larger duration cams will lower the reading as well. I know it wouldnt lower it THAt much though but i was figuring it could be part of the reason.

I'm 99% positive it's the rings as the valves all sealed fine when installing the springs. Could it be that i installed pushrods that are too long? I measured with a pushrod checker and added .080 pre load. Yeah i was fine with the 60psi until i hit the cylinder that gave me 135psi. It was the second cylinder from the front on the right side (facing the engine).

If it might be my timing chain off, could i loosen the rockers some and see if that helps? That would in theory lower the duration of my cam as well too right? How much oil should i shoot in the cylinders? Like a tea spoon full? Just regular motor oil right? I double and tripple checked my timing chain being lined up dot to dot and even stopped and called a friend in the middle of it because i didnt like how the timing chain was slack (old and new) but i was told this was normal.


Here are the cam specs if anyone catches anything that might be contributing to my low readings

235/235 .647/.647 110+4LSA (according to cam card)
Open intake 11 BTDC
Open exhasut 51 BBDC
Close intake 43 ABDC
Close exhaust 3 ATDC

 

Engine started up on the first try today and runs perfect! I just cant get the idle down although ive narrowed it down to problems with the carb. Sounds pretty nasty too. I'm gonna start it up and heat cycle it a few times then do another compression test and see.

 

I finally got around to doing a compression check today. Let it warm up for about 30 seconds so i wouldnt burn my hands on the headers lol. Every cylinder put out 149-152psi. I cranked each until the needle stopped going up, about 4 strokes each. Not bad for a $200 longblock.

 

score,

nice work