Shaun H-A
Lv 7
9 years ago
Favorite Answer
Those are low numbers. If you are questioning ring seal, you should be checking that with a dual gauge leak down tester, not a compression gauge.
Where the cam is phased (Advanced or Retarded) plays a huge role in cranking compression numbers and so does rocker arm adjustment. I've seen cranking compression numbers move as much as 50 PSI by simply advancing or retarding the cam. I routinely see 20 PSI on normal every day stuff. The chain retards the cam as it stretches. Plus, the factory cams were installed retarded because doing so help tweak the idle emissions. Other than that, retarding the cam for how the stock engine was used was a complete loss.
If the rocker arms have never been touched, loosen every one of them exactly 1/2 turn. They will still be within factory spec. I would replace the timing chain with this:
http://www.summitracing.com/parts/SUM-G6610-B/ this:
http://www.summitracing.com/parts/SUM-G002/ and this:
http://www.summitracing.com/parts/SUM-G1792/
Install the crank gear at the 2 degree advance mark IF you are keeping the stock cam in the engine. The timing chain I have specified has a built in thrust plate on the back of the cam gear because timing gears on Big Block Chevy's LOVE to eat the block from the cam gear rubbing against it. Plus, the thrust washer positively locates the cam in the block so the cam lobes are centered with the lifter bores.
Use a harmonic balancer puller to remove the balancer and use a harmonic balancer installer to install it again. DO NOT hammer the balancer back on the crankshaft with a hammer. You will destroy the rear thrust on the rear main bearing and also destroy the balancer. You will need to drop the oil pan down about 1/4-1/2 inch so the timing cover will line back up with the pan and gasket. Do not over torque the bolts on the pan or timing cover.
After you replace the timing chain, I bet you see a 20-30 PSI gain in cranking compression.
I bet you also see a 15-20 PSI gain with your rocker arm adjustment which will also be a very noticeable gain in both drive ability/performance AND fuel economy.
FYI: I make a cam for this engine that is close to a 100 HP and 100FT lb torque gain over the stock cam, is a mileage improvement and it idles almost undetectable. It is a power improvement over the stock cam even from idle and of course throughout the entire RPM range. I'll make you a 100% money back guarantee on the cam as well. Love it or I will refund you. All designed to work with stock parts but I would suggest a valve spring change if you do it. I can give you a valve spring for it as well.
Use a 3 arm puller to remove the old crank gear. Just be sure to protect the threads in the front of the crankshaft.
Email:
[email protected]
While I am still going to perform a leak test today to determine if there is any excessive leakage, I started to think of cam timing and how it effects compression pressure.. Then I found this ?