Variation in compression

[James aka fastfugitive]

I took these measurements from a cold 1700cc W code engine a couple of days after a 50mile 50mph highway drive

#1 = 135psi
#2 = 139psi
#3 = 160psi
#4 = 165psi

Is this sort of variation acceptable and/or is this indicative of one side having been put together differently and now has a different static CR?

Oh plug readings;
#1 = fouled - running rich
#2 = fouled - running rich
#3 = light brown - so about right
#4 = light brown - so about right

Or are the different readings simply explained/caused by the clearly apparent carb+mixture inbalance?

cheers,
J.

[MASSIVE TYPE IV]

It looks like a couple of cylinders are tired... The tired cylinders are not burning as clean as the others and therefore the richness is explained...

The next step is a leak down test- compression tests are rather worthless as indicators of where the problem exists. A leak down check will tell you not only how bad the issue is, but also where it is very clearly.

[James aka fastfugitive]

Thanks - thats the next step after resetting the valves, timing and upgrading to twin 40DRLAs

Jake - do you have any experience with 9164-1 emulsion tubes or is it really only worthwhile using -2's...?

[udidwht]

How many miles on the motor?

Were the valves adjusted prior to the compression check? Also set the dwell then timing after valve adjustment, unless you have an electronic ignition.

Do you know the history of the motor?


If not, adjust valves, check timing then give it a compression test. I'd say #3 and #4 are a bit high. When my motor had the 1.7 in it the compression readings were normally between 135psi - 145psi. Could be carbon build up in the rings, loose cylinder head bolts on 1 & 2 side, valves out of adjustment, poor ignition, etc... Lots of variables.

If all else fails time for leak down test.