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Triumph TR6 - Compression Reading

Evening all. Does anyone know what value range I should get when I do a compression test? I will be doing the test on a 73 TR6. Thanks
JW BRAW

Hi JW,
Compression readings should be in the 100 to 170 range, most important the readings should be within 10lbs of each other ..for example if one is 80 and the rest are 135 approx then there are a couple of tests to do to see where the problem in that cylinder lie.. could be rings, valves etc.

Charlie
Charlie Ballard

Ahem,

You'll want to perform the compression check with a warm engine, ignition disabled, throttle wide open.

THAT is how you get accurate readings.

Two low cylinders next to each other can indicate head gasket issues.

If you find low compression pressure you'll want to determine whether valves or rings are contributing to the problem.

If, after squirting oil into the cylinder, your compression rises then you know it's a ring related issue. If, on the other hand, it does not rise then you've a good indication that it's a valve sealing issue.

As Sr. Ballard pointed out, you'll want them all pretty much the same. THAT is much more important than high readings (within reason of course).

hth,

Jim
Jim Deatsch

I've got 120-125 across the board. I'm a happy guy. Now if I can finish putting everything back together...
D Hasara

By throttle wide open I guess you mean hold the petal to the floor while turning over the engine? I imagine that might seem like a silly question to some of you, but I just wanted to make sure. Thanks
JW BRAW

You got it. And you take out all six of the plugs before testing so the motor spins freely.

I got 160 across the board on a high compression '69 head.

Tony
A. J. Koschinsky

OK the results are in. Cyl 1 106 Cyl 2 120 Cly 3-6 115
They are within 10 lbs of each other so I gues I am ok. Wonder what a new engine was. Mines a 1973 TR6 with 73,000 miles. Engine was rebuilt about 6 years ago. Engine seems to run strong, no oil burning, no pings. So come on sunny warm weather, I wanna drive drive drive, lol. Jim, where Penfield? I am in Saugerties. That's about 45 miles south of Albany. Thanks again for the answers.
JW BRAW

You're in good shape JW. Run 'er and watch 'er as they say.

Penfield is just a touch east of Rochester so we're almost neighbors.

J
Jim Deatsch

I,ve got a "ping" while acceleratying. Rings? I,ve added 3/4 new premium gas w/lead treatment since, buying it. (7-12-2004) 1960 TR3A, 36K MI, excellant condition, no rust, no overdrive, second owner,
...97% unrestored.
Thanks !!
Alec

alec@casaviejagallery.com

Alec

Rings will not cause ping.

Timing off or carbon deposits on piston top are most common. 3 has a fairly high compression ratio so the timing is a bit more sensitive.

Ping will not come in for a bit with carbon till motors warm so it just likely needs a tuneup since you don't mention only when hot.

Check your timing.

Bill
Bill Brayford

Your TR3 should have a dial knob on the side of the distributor. Decrease little by little until the ping goes away. You shouldn't have to run special fuel unless someone's milled the head too much.

Rings could let enough oil in to build up a carbon deposit, but you'd see lots of blue smoke on acceleration. And hard running would probably burn off any of these deposits. But don't run it too hard until you get the timing under control.

Your car will treat you well when you learn some little tuning procedures. The carbs should be adjusted as well. I tend to run mine a bit rich, it's better than too lean, but too much will cause deposits, too.

By the way, there's a TR3 thread, but it doesn't get as many subjects as this one.
Tom

JW,
To understand a little about compression ratios figure the atmospheric pressure at 14.7 psi at sea level. Divide your compression readings by the 14.7 and you will have the compression ratio. As per Mr. Koschinsky, 160psi divided by 14.7 and you get 10.8 compression ratio. Which I believe is what is called a 10 1/2 to one head. 8 to 8 1/2 to one is pretty normal, especially if you have a little wear on the rings.
Joe Justice
Joe Justice

This thread was discussed between 25/06/2004 and 30/07/2004

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