Results of compression test

[Cowracer]

I finally cumshawed a diesel compression tester. I tested 1-3-5 and 7.

here are my results

Engine throughly warmend up, ECT at ~160 Degrees

I spun the engine over until the compression gauge stopped climbing Approx 6-9 "puffs"

Cyl 1= 275 psi peak
Cyl 3= 430 psi peak
Cyl 5= 420 psi peak
Cyl 7= 425 psi peak

I also tried to let each cyl leak down for 5 mintues. I saw a "slight" decay on #1 (maybe 2-3 psi) the others held steady.

So, that's it. Definatly something amiss on the #1 hole. After all my protestations to the contrary, you guys were right. The hydro-lock bent something. When I am wrong, I'm big enough to admit it.

The only thing other thing. Do those PSI numbers on the other holes seem high for an 18:1 engine? I would expect to see those on a stock CR truck.
Maybe its due to the fact that this thing dont have more than 400 miles on it since rebuild.

Will this mystery be solved? Will Tim ever catch a break? Will my wife mind if I go to a peeler-joint this weekend?

Stay tuned to "AS THE BEARING TURNS"...

Tim

[Kennedy]

So is the piston protrusion/deck height the same as the others?

A leakdown would be a nice next step.

[Cowracer]

I checked the piston height, or I tried.

I used a piece of 3/8 keystock across the cyl as a bridge and a dial indicator to measure piston height. I thought that the heights were the same, but a much more mechanically gifted guy told me that the rusults of that method would be highly suspect.

I had to give the compression test rig back, so an actual leak-down is not possible right now. I think that I have enough to go on as far as getting a warranty replacement.

Tim

[john8662]

The three high numbers you're giving might not be so high, you have to count compression strokes, you want exactly 6. The gauge will continue to climb after that.

I'd be interested in your readings at 6 puffs to know the compression of the 18:1.

I've been told that you should have about 350-360 PSI with 18:1.

[tom.mcinerney]

A comp test is only reliable for comparative measures between cyls, unless performed by someone experienced, routinely, under controlled conditions [as John's stipulation of '6-puffs'].

I realize the comp test was agreed on as a Go/NoGo warrantee check subsequent new head installation. But if the relevant pushrod(s) are bent , that alone might be adequate to drop the comp on one cyl . And here more puffs would be more indicative, i should think , as with more puffs , eventually the marginal psi-increase will flatten to nil .

I would hazzard that to reliably ascertain the damage , the tapped holes for head studs , and those for adjacent main caps should be checked for cracks , the main webs adjacent #1 should be checked for cracks , the rod should be carefully checked for alignment/distortion , and the piston should be replaced, since the crowns and pin bosses crack as it is . The crank would also need magnaflux , at minimum . Or else , look to pushrods , replace if bent , re-check comp --
Then run till 'conditions warrant' if comp OK, or have torn-down/new-engine otherwise .

There's a decent chance the compression discrepancy noted on #1 results from distorted rod , since just a little variation in piston height shows in compression.

All a result of a little water in wrong place. J.K.'s advice of using the 'Cadillac' coolant seal tabs is good practice , but they may well not have been able to seal the .030" block porosity documented. Worse [really looking dark, now] , the tabs may have only sealed temporarily!

[Cowracer]

Originally posted by tom mac 95:
A comp test is only reliable for comparative measures between cyls, unless performed by someone experienced, routinely, under controlled conditions [as John's stipulation of '6-puffs'].

I realize the comp test was agreed on as a Go/NoGo warrantee check subsequent new head installation. But if the relevant pushrod(s) are bent , that alone might be adequate to drop the comp on one cyl . And here more puffs would be more indicative, i should think , as with more puffs , eventually the marginal psi-increase will flatten to nil .

I would hazzard that to reliably ascertain the damage , the tapped holes for head studs , and those for adjacent main caps should be checked for cracks , the main webs adjacent #1 should be checked for cracks , the rod should be carefully checked for alignment/distortion , and the piston should be replaced, since the crowns and pin bosses crack as it is . The crank would also need magnaflux , at minimum . Or else , look to pushrods , replace if bent , re-check comp --
Then run till 'conditions warrant' if comp OK, or have torn-down/new-engine otherwise .

There's a decent chance the compression discrepancy noted on #1 results from distorted rod , since just a little variation in piston height shows in compression.

All a result of a little water in wrong place. J.K.'s advice of using the 'Cadillac' coolant seal tabs is good practice , but they may well not have been able to seal the .030" block porosity documented. Worse [really looking dark, now] , the tabs may have only sealed temporarily! Tom_mac

You summed it up pretty nicely. As far as any additional work/testing... Nope. Ain't gonna happen. At least not by me.

I have completly exhausted my willingness to wrench on this thing, at least regarding this issue.

Tim