Is this right? Timing marks...

[jns]

Edelbrock timing set, pretty sure I have #1 cyl at TDC. How can I know if the cam gear is 180 degrees off or not? Looks like the o on the crank gear is at 12 o'clock, if it's not clear in the picture. Engine ran good and seemed strong but had 60psi in every single cylinder. Engine is supposedly a recent rebuild. If it were worn out, doesn't seem like all cylinders would be 60psi. I'm hoping that the timing is off (retarded several degrees?) since that seems to be a possible cause for low compression on all cylinders. Thanks!

 

[mikestertwo]

The cam timing looks correct. The chain is a little loose but other than that it looks ok. Are you sure your compression gauge is accurate? I think you have some other issue.

 

[pacecarta]

dot to dot is straight up as you have it (not advanced not retarded)

its at @1 tdc ,

i think its time to check with another compression gauge

and fwi its not posible to put a cam 180 out , cam sensor can be installed 180 out but cam is technically 180 off the dot every crank rotation since it takes two turns of crank (720deg) to move cam gear 360 deg
and bolts in cam can only go in one way

 

[jns]

Thanks...yeah, dumb question I asked about the cam being 180 off. Just frustrated and not thinking clear. Tried two compression testers and both read the same. Just don't understand what it could be....sure seemed to run strong though I haven't been in another GN to compare it to. Think the chain's ok? I imagine there's no way to tighten it so replacement would be the only option if needed?

 

[Nick Micale]

Too bad you did not conduct a leak-down test to confirm cylinder integrity?

Other possible issues could be a bad valve job or rings not seating properly.

I have had 2 engines in the last month with 60 psi max compression, and one was over heated and killed the rings, other had serious detonation and pre-ignition which killed the pistons.

Simple test for the heads/valves is pour a liquid, like solvent, in the combustion chambers and see if it leaks into the ports.

"and fwi its not posible to put a cam 180 out , cam sensor can be installed 180 out but cam is technically 180 off the dot every crank rotation since it takes two turns of crank (720deg) to move cam gear 360 deg​

and bolts in cam can only go in one way"​

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Paul is correct here with a stock style cam, but a billet cam CAN be improperly installed! ​

 

[jns]

I had performed a leakdown test and all cylinders seemed to hold pressure with no air escaping except for cyl #4 had air rushing out the intake port so I guess it was a leaky valve. Just did a compression test on my truck and the gauge I had used showed 150 on the truck so the gauge seems fine. The car passed smog a few months ago so it was running good enough for that. Just had a problem with start-up smoke that lasted a few minutes but quit after that(plugged up pcv, etc). I picked up some rebuilt heads I was going to put on as well as a new 204/214 cam but not sure if I should put the engine back together with this mysterious 60 psi compression reading. Could a wiped cam cause the low compression readings? Maybe a decked block causing too much pressure on stock pushrods to keep valves from sealing completely? Any other ideas? Thanks for the help so far!!!

 

[Chuck Leeper]

IMO, that engine is not a recent rebuild... As filthy as it is, makes me wonder how many yrs it's been run.
The heads are off. Pull the lifters and see what the bottoms look like. You may have a wiped cam, but not likely all lobes are gone.