Math was not my favorite subject,,,,

Buggyboy

Member
OK, on my current TO20 project, I ran a compression test to get a better idea of actual condition of donor engine before joining front to rear. Glad I did as # 1, #2 and #4 were right at 65# ,,,but #3 was way down at 25#,,,,aw Chit,,!! I had filled cylinders with ATF/Acetone mix while I worked on the rear main seal and trying to resolve the oil filter issue,,,,,
I've about decided to pull the pistons to check for stuck rings altho all the cylinders looked really clean,,,?
I miked the cylinder liners and get 3.010 on all of them. The book I have says std bore on a TO20 is 3 3/16". "IF", IF I do have to replace the rings,,,what size am I gonna have to order??
Thanks for all help.
 
3 3/16 = 3.1875. So, somethings wrong.
How do the valves look? The very low compression cylinder could be a valve stuck or burned up.
 
(quoted from post at 11:02:18 09/20/21) 3 3/16 = 3.1875. So, somethings wrong.
How do the valves look? The very low compression cylinder could be a valve stuck or burned up.

Well, Jim L,,Thanks for the reply,,looking like my Toolie-wak is the blackest on this one,,,LOL. I was using an electronic caliper,,and even tho it repeated those numbers several times,,I was still in doubt. So, based on your doubts, I went and dug up my "Old" but trusty Starrett dial caliper and now the Starrett is telling me the ID of cylinder liners ranges from 3.300 to 3.304,!! I took the batteries out of the HF electronic caliper, let it set 30 mins then reinstalled batteries,,,and,,,,and,,It now reads exactly like the Starrett,,,,, ( I feel better now),,lol,,,sorry bout that,,,,LOL,!!
My calculus says liner ID's are .113 BIGGER than the stock ID of 3.187. That seems like an awful lot of "wear" and if so, would explain the low compression numbers.
WHAT am I missing here, Jim,,,,,?????
 

Well, Tom,,glad you chimed in, cause my head is spinning with all these numbers,,,, You mean the PO had the liners bored out to next size of 3 5/16,, OR is the 3-5/16 an available oversize liner?? I always thought it not too good an idea to bore out any liners as there is not too much Meat there to begin with,,,,??
Are the rings gonna be readably available for the 3-5/16 liners?

I went ahead and pulled all the pistons to verify what I do have and glad I did,,,,. The two compression rings on #1 and #4 pistons were stuck and when I got em broke loose,,a quick end gap check in their liners blew my mind,,,How about a 1/4" end gap, didn't need any feeler gauges,,,,LOL. # 2 and #3 had 3/16" end gaps!! #4 piston never had am chance to control oil and compression blowby as the two compression ring gaps were almost in line and the two oil rings WERE IN LINE,,,,( I KNOW that guy ain't ever gonna touch any engine of mine)
The oil rings were not stuck but were not doing anything as they had closed in on the pistons,,,No telling where this utterly cheap set of rings came from,,,,

Another item of concern,,when I pulled the pistons I noticed the rod caps on #3 and #4 had the notches on the caps on opposing sides,,,????? I always read to install the notch on the rod on SAME side as the notch on the cap,,,? All the rod bearings look good with a grayish color with no scoring,,,AT LEAST I got one positive thing going for me,,,,LOL.
 

The huge ring end gap suggests standard sized rings forced into oversized pistons .

I would get rid of the lot and install a new matched rebuild kit . Much more expensive but at least you will know that there are no nasty ' oddments ' floating about waiting to ruin your efforts and waste your money .
 
Buggyboy, I got out of this conversation as I've never been into one of these Continental Engines. There are plenty of more knowledgeable folks on here that can advise you. But keep us informed on your progress.
 

OK, Tom, I checked out the Parts section and they do list the rings for the 3 5/16 liner (2 compression rings and 2 oil rings, so thats good. Now, on the rod bearings, The rod journals mike at 1.930 on all four rod journals. The specifictions page states Con Rod journals are 1.937-1.936. I believe these are .010 undersize bearings so if you include oil film clearance of .002 they should be ok,,,,? .001 should not be a great concern,,(fingers crossed) I was able to contact Federal Mogul Bearings to verify the stamped numbers on backs of rod and mains but all he could do was give me part numbers that did not help with identifying which undersize bearings I have.
The only way I can be sure of crank bearing sizes is to open the whole engine down to remove and measure the crank journals and I sure did not want to do that,,,?
Another method might be to plastigage the crank journals with the old bearings but that only tells you if clearances were OK but I already know that they were,,,????
 

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