Just bought a complete 1998 LS1 short block with 23k on it, been in storage. What would the compression be with mt stock 5.3 862 heads? The motor is a short block no heads. I am going to replace the short block with all my parts and see how it runs.

 

You may raise the compression but the ls1 heads outflow the 5.3 if I remember correct.

 

Thought it was the other way around?

 

i have a n LS1 in my truck with the 706s. Mine is around 10.9ish. Heads aren't milled but ported

 

Found this on Tech:
Head CC volume vs Compression Ratio:
______________________________________________

The below CR numbers are with the stock GM 5.7L displacement LS1 graphite head gaskets installed.

Installing the thicker 2003 GM MLS head gaskets will decrease your compression ratio by approx 0.1 - 0.2

72.27cc = 9.1 CR
71.71cc = 9.2 CR
71.05cc = 9.3 CR
70.59cc = 9.4 CR
70.03cc = 9.5 CR
69.74cc = 9.6 CR
68.91cc = 9.7 CR
68.35cc = 9.8 CR
67.79cc = 9.9 CR
67.23cc = 10.0 CR
66.67cc = 10.1 CR (stock LS1 head spec)
66.11cc = 10.2 CR
65.55cc = 10.3 CR
64.99cc = 10.4 CR
64.43cc = 10.5 CR (stock LS6 head spec)
63.87cc = 10.6 CR
63.31cc = 10.7 CR
62.75cc = 10.8 CR
62.19cc = 10.9 CR
61.63cc = 11.0 CR
61.07cc = 11.1 CR
60.51cc = 11.2 CR
59.95cc = 11.3 CR
59.39cc = 11.4 CR
58.83cc = 11.5 CR
58.27cc = 11.6 CR
https://ls1tech.com/forums/advanced-...ume-vs-cr.html

Dam that would be a 11.1 5.7 with stock 5.3 heads. Is that too high?

 

Witch head gasket is better/or use?

1)The graphite gasket 12498543 0.051 thickness
2)MLS gasket 12498544 0.059-0.057 thickness

 

i used the MLS

 

ready to see what this motor can do in your truck!

 

im running 862s off of my 4.8 on my ls6 and i havent had any problems. I was told c.r. was around 10.8-11.1 I really wasnt concerned about it. It runs damn good compared to my 4.8.