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Compression question

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I decided to blow off the leak down test and just pull the head. I'm 99% sure it's the head gasket. I could see where the no's 1 and 2 cylinders were not sealing properly so I'm going to "O" ring it with some stainless or copper wire.

I talked with the Gasket Shop about it and he told me how to do it, but I'm thinking it may be better to super glue the wire to the top of the liners instead of the gasket. The end result should be the same and it should be a little easier, as well as a more accurate way to do it.

I'll see tomorrow when I run another compression test.

PeterK, you've got a good deal more clearance between the combustion chambers than I do, but I agree. I'm going to try the o-ring fix and see what shakes out.

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The good news is that I brought the tub and all the body panels to the paint shop yesterday! I told the painter that I want a "flawless" finish and he said, no problem...lol. We shall see!
 
Monkeywrench said:
I agree. Something sounds off. You should be seeing 180+ on all cylinders.


For fun, I threw some of your specs into Pipemax. I did a lot of guessing, so don't put too much stock into these numbers.

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Click to expand...

Pretty good guessing but my CR is no where near that high. It's supposed to be 10.5:1

I'm not sure about the rod length you used, The Pauter rods are 3/4" longer than stock with short deck J&E forged pistons.

Cool program though!
 
"I'm not sure about the rod length you used"

Big Block Chevy rods. They're about .5" longer than stock, and I'm pretty sure this is what some of the "long rod" people are using.
 
Note that according to conventional wisdom you shouldn't reuse a solid copper head gasket without annealing (which I hear is not the easiest thing in the world).
 
Bremer said:
Note that according to conventional wisdom you shouldn't reuse a solid copper head gasket without annealing (which I hear is not the easiest thing in the world).
Click to expand...
Might not be conventional wisdom, but I believe Mordy (of Gasket Works USA) has said that annealing does not seem to be required:
https://www.headgasket.com/preinstall.html
 
Well I guess I must have done something right. I did anneal the head gasket, then I made some o-rings from very thin copper wire, sprayed the gasket down with a copper head gasket sealing compound, readjusted the valves and cranked it up. Compression is now between 175 and 180 from front to back! It also runs a much better.

Thanks for everyone's help!
 
Good to know.

Q. What size wire, and was it off the shelf spool from the hw store?
Q2. Did you end up gluing it down to the top of the cylinder jugs?
 
Gasket Works recommends using a wire thickness that is no more than 10% the thickness of your head gasket. My head gasket is about .025. Their guidelines really didn't make much sense to me as a .0025 wire is not much thicker than a human hair, so I bought some 8 gauge electrical wire and removed some individual strands from it to use. The strands were about .010 thick. I applied them to the head gasket with Super Glue and then lightly tamped them down with a small hammer until they were slightly flattened out. Not extremely accurate all the way around, but we are dealing with a tractor engine here...lol. So far so good.
Worse comes to worse I'll have a new head gasket made. A close look at the head gasket revealed that it really wasn't cut properly because the cylinder openings for the number 1 and 2 cylinders went past the liners a little. I also used a good bit of copper gasket sealing spray. Not a huge amount, but enough to ensure a good seal...I hope.
 
Tab, I agree with the feedback above that 160 should be the target rather than the other lower cylnders. I would perform the wet compression test using at least 30 wt oil and squirting in no more then needed to seal the rings. I would check the setting on the throttle plates to insure they are allowing the same air flow during the test or you could plug each one off during the test just to see if your numbers matched closer. Can you rig up to measure crankcase pressure while the engine is running to set a bench mark and check it over the first several hundred miles to see if it goes down as the compression comes up on the other cylinders. If you have an intake valve leaking it should be evident when you have the engine running (intake talking); do you think placing a ballon on each Weber throat during its respective leak down test could provide a relative comparison of intake valve sealing? As you indicate, the work has been done by a competent machinist, the heads been milled and CC'd, if it's been CC'd I'd assume the valves were sealing at that time (no leakage), unless a sealant of some sort was placed on the valve faces. The leak down test should also help you spot one cylinder leaking to the adjacent cylinder/s. I'm hoping to hear each weekend you drive it they come closer in line with one another.

Stan
67TR4Ahardtale
 
Hey, Stan -

Let me welcome you to the party, if I haven't done so already.

If I'm not mistaken, Tab has been inactive for a while now, and I think he's sold his project.

But good info there, nonetheless!

:cheers:
Mickey
 
With intercylinder leaking, the adjacent leakers would both have the same compression. Have you oiled the cylinders to seal the rings and run the comp test? Others don't think it matters, but I like to have the throttles open for the comp test.
Bob

PS Before I wrote this,I didnt read enough to know you had the head off.
Bob
 
Or that he had already sold the car ?
:highly_amused:
 
With the wide range of compression pressures I wonder if the inlet flow of air is beings restricted more via the throttle plates on the lower compression cylinders; the more partial vacuum created the lower the compression pressure. but if you have Webers installed the two cylinders per carb should be close but I would at least examine the throttle plates position. If you haven't already I would perform the compression test with the throttle plates wide open. To determine if there is cylinder to cylinder leakage past the head gasket, I would open up the lash on all cylnders so all valves remain closed. Take the spark plug out of the adjacent cylnder you are testing and pressurize each cylinder and monitor for leakage out of the adjacent cylinders. You could break the electrode out of a couple spark plugs and put ballons on them to montor how quickly they fill.Corny I know, but I would do something like that. I would perform the wet compression test mentioned above using at least 30 wt oil and just enough squirted in to seal the rings. While the engine is breaking in you may want to measure crankcase pressure in inches of water, you can make a simple manometer with clear plastic tubing. As the rings break in the CC pressure should drop and hopefully your compression pressurses even out. I do agree 160 should be the target based on the head work you've done.

Hope to hear more as you get run hours on the engine,

Stan
67TR4Ahardtail
 
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Do me a personal favor and rerun what the results were for the compression imbalance on the engine; curious on what the results were??



Thanks, Stan
 
Stan, The guy is looong gone.
Look at the date that was posted..it's to be found in the blue stripe above the text.
 
Since we've revived a compression thread, I'll share the WOT compression numbers I got yesterday on my TR4 with 200 miles on a fresh rebuild:
#1: 150 #
#2: ~152 #
#3: 145 #
#4: ~152#

The motor is much smoother. The balancing of the crank and flywheel might have actually helped. It revs to 5k much quicker and smoother. Let's hope it keeps going for many miles...:smile:
Tim
 
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