lq4 compression test results

[tmills213]

Compression test. 2002 lq4 with 205K miles. drove it home, pulled it, sat for 2 weeks until now. I think I know the outcome of this.... is there anything I could be missing. I read some stuff about carbon build up and valves. The heads were coming off anyway so I can see what things look like but if it all looks ok... demmit. I was hoping to avoid lower end work. I know the cranks are "good" up to maybe 1k horse but would it be a simple ball hone, rings, and rod bearings if I were to redo it... or do I go to forged goods? its going to get boost some day, if I ever stop pulling this string on the sweater.. :/



Dry Wet difference
1 160 170 10
2 135 150 15
3 130 145 15
4 135 155 20
5 125 175 50
6 150 155 5
7 135 180 45
8 135 175 40

[clinebarger]

Cranking compression numbers don't mean jack, There are far too many variables involved. A Leak Down Test is far more accurate.

[tmills213]

well I was convinced to pulled the heads. overall looked good until i pulled the other side tonight. few scuffs in 3 cylinders but one #8 has a deep scratch in it. It catches a fingernail.



I hope I can take a min amount of bore and fix it. I don't like the idea of a turbo with thin walls. Suppose I have to get new pistons and keep pulling the string from the sweater???

disregard the horizontal marks, they are from my fingers/smudges. just the long vertical one.

[truckdude239]

Broke ring? Yiu can still see the honing cross hatching at 200k if your worried about thin walls have it sleeved and bored back to stock size.

[clinebarger]

That don't look to bad to me, I would throw some LS9 head gaskets on, ARP Head Bolts, & Have a good Valve Job done along with whatever Springs you need.

[tmills213]

I am on the fence of going with no point of return. I want to do it right. I am most likely going to sell my Buell moto to fund this (kids do that usually) and am thinking of boring and doing bottom end work now. unsure, waiting to hear back for quote

[crazy longhorn]

Originally Posted by clinebarger

That don't look to bad to me, I would throw some LS9 head gaskets on, ARP Head Bolts, & Have a good Valve Job done along with whatever Springs you need.

It don't look that bad to me either....at 140 K, my 5.3 was top end only. Pressure tested the heads, surfaced/grind? fresh springs (gm blue springs),ARP bolts/multi layer gaskets... stock cam shaft. I did not bother to run a comp test, or leak down on it....just read the plugs. None of the holes were pushin oil...other than a light bit of piston slap , on cold start, no issues> She pulls 45 psi pressure @ idle (hot)....damn fun to play with. Longhorn

[truckdude239]

They did a 4.8 build somewhere that they thought it was a 5.3 but was a 4.8 and it had a spot worst then that and tbey tubro buikt it making 1k horsepower on it