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TR2/3/3A TR3 engine cylinder top clearance

jfcdo

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For a TR3 engine, I see in the manual that the clearance between the top of the cylinder and the top of the block should be 0.003 to 0.005 in. Is there a problem if the top of the cylinder sits too high above the top of the block? As I measure all around the cylinders, I find that the top of the cylinder is sitting about 0.012 (on average) above the deck. Some spots have 0.010 and one area (cylinder #4) had 0.015
Do I need to pull these cylinders and find a thinner Fo8 gaskets?
This is a new rebuild with new cylinders, pistons and rings. After assembling, the compression showed #1 150, #2 135, #3 120, #4 125
Ran the engine (ran rough) with no leaks (coolant/oil - no coolant in the oil). Head newly surfaced with new valves and valves adjusted.
Trying to figure out why there is such a difference in the compression in each cylinder.
I sure don't want to pull the cylinders if I don't have to.
Any advice, suggestions, ideas are appreciated.
Thanks, Jack
 

CJD

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The concern is that the head gasket will not seal the coolant jacket if the cylinders are to high. You also seem to have a large variance between cylinders...much more than normal. I would check to make sure the base of the block where the cylinders contact have all the scale removed. In a worst case...you may have to have the cylinders trimmed by a machine shop.
 

DavidApp

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Was the block clean when you installed the liners. A piece of trash may have chipped off the block walls as you lowered the liners.

David
 
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jfcdo

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Head gasket sealed well. There were no leaks. I had the block cleaned out in a hot tank. It was clean before I reassembled it. I thought about a chip lodging between the block wall and the cylinder, but that would have had to have happened for all 4 cylinders, and a chip would have likely resulted in a coolant leak into the oil and that has not shown up.
Trimming the cylinders...had not thought of that. I would hate to end up with cylinders that are too short.
I'm trying to figure out if the cylinders being too high would explain the differences in compression among the cylinders, and I beginning to think that I am going need to pull those cylinders any way. Such a hassle with the engine in the car now.
 

DavidApp

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Is it possible you have a mismatched set of liners? You would have to pull them to check the length from the seat to the top of the liners.

You have got them clamped down well when you take the measurements?
Block with hold down washers.jpg


David
 
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jfcdo

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Yup. They were clamped down when I measured the clearances. Mismatched set? The numbers all matched on the cylinder and piston set (Hepolite/AE) standard 86 mm. Looks like I will pull these cylinders and measure. What should that length be?
 

Graham H

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That is a lot of clearance, the block may have been refaced by a previous owner or the Fo8 seats could have scale embedded in them. If the block was refaced your only way forward would be to have each cylinder resized to get the best clearance however I wouldn't think 0.005/7in would have any dramatic effect on the compression and you could just run it in and keep an eye on the water and oil.

Graham
 
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jfcdo

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I did not check the clearances when I first installed the cylinders and pistons, and when it was all together, it started and it ran rough. I checked the compression and found to different readings with each cylinder. I rechecked the valve clearances and then rechecked the compression with no significant changes. I pulled the head and that is when I checked the clearances at the top of the cylinders. There had been no leaks at all. Thinking that I should take the head back to the machine shop and have them take another look at it.
 

bobhustead

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What type compression gauge are you using, press on or screw in? Are you spinning the engine enough turns on each cylinder? Do you have the throttles open during the test (some say this doesn't matter. I have no empirical evidence that it does, but it can't hurt)? Are all the plugs out and is the battery strong? If this is not a measuring error, possible culprits are in the valve train or rings. Are the pistons new? If not, did you clean all the carbon out of the lands by hand?
Bob
 

sp53

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Sounds to me like everything must have sealed between the head and sleeves and gasket with the sleeves too high or there would have been a big mess. Plus I think it would have given the correct compression for that engine. I would have thought there be oil coming out where the lifters sit on that thin wall and probably water everywhere. Usually the problem is not enough protrusion of the sleeves. This to me does not make sense. could there be an old figure 8 gasket stuck in the block

steve
 
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jfcdo

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Thank you for all the input from everyone.
I used a screw in type of compression gauge with all of the plugs removed. I turned the engine so that it compressed the cylinder that was being tested 8 times with each cylinder test. The battery is strong. The cylinders, pistons and rings are all new. When I put the head on, I used a Payen copper sandwich head gasket with a generous coating of copper spray-on gasket sealer, which may explain why I had no leaks. I am wondering, now that someone has mentioned this, has the deck of this block been shaved and this explains why the cylinders are sitting too high. Any way, it does not explain the differences in compression among the cylinders, so, once again, I am thinking that it is a problem with the head or with the valves. I should add that when first starting this engine, I was getting backfire through the carb on cylinder #4. This engine has a pair of the original Weber DCOE 42's that came as an option with these TR's. The carbs have been fully rebuild. It backfired through the carb on the cylinder that had the lower compression, #4.
 

bobhustead

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If the engine is still together, a compression test with oil in the cylinders might provide useful info, as would a bleed-down test. I am inclined to think you have two different problems that are not related.
Bob
 

CJD

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If the engine is already assembled and in the car...just try it and see how it works. The time to worry was during assembly.
 

DavidApp

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To skim the liners in place you would have to keep them clamped down as you machined part of the liner then move the clamps. Also not get any swarf in the cylinders if the pistons were still in place.

When I rebuilt my TR2 in the UK back in the late 1960 I did not know you could get replacement liners or they were too much so I took the liners to the local machine shop and had them bored to the next size up and got new pistons. Triumph parts were more common back then.

David
 
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jfcdo

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OK. So yesterday, I pulled the cylinders/sleeves and yes, sp53/Yoda, you were right. There was an old Fo8 gasket (steel) in the block, along with a copper Fo8 gasket. That combination likely cause the cylinders to sit too high on the deck. Gonna spend the time needed to thoroughly clean the block and then reset the cylinders and recheck the clearance. This will likely take some time because I want that area to be spotless before I reassemble. Any advice on how to remove an old Fo8 gasket that seems to be embedded. Thanks again to all.
 
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jfcdo

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By the by, when installing the cylinders, I plan to use Hylomar (the blue stuff) to seal the Fo8 gasket. Any thoughts on the best sealer. I have read about Wellseal and this stuff sounds similar to Hylomar.
 

sp53

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Here is what I did because I knew it would be sometime before I put the head in place. I took a can of sliver spray paint and painted the figure 8 gaskets with 2 to 3 coats of kinda heavy paint. The theory being rattle can spray paint never really dries and would stay soft and this would let me take my time without the goop drying unevenly. A machinist friend suggested it. I only have about 8 hours on the motor.

Back in the day the figure 8 gaskets came coated with something gray and they were made of a steel allow and not copper. After saying this, ever tr3 motor I have taken apart had some kind of sealer probably the wellseal stuff. However, I bet they put the head on that day within hours of assembly.

The copper probably would seal with nothing on the gasket, but again that depends on the block surface.



Peace out, steve
 
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