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Triumph TR6 - Compression check

Hi All,

I just did a compression test on my 70 TR-6. The test was a dry test with the engine warm. it read; #1 145 #2 145 #3 146 #4 141 #5 130 #6 136. Is this in range or do I need worry about # 5 and #6?
I'm going to do a wet test tommorrow, but I hope I'm OK. Any thoughts.

spj steve

5& 6 are usually the weak spots on this motor.
Don't know if a wet test will tell much. What do the plugs look like there. Is there excessive oil consumption?

The plugs were all black, but 5 and 6 were a little darker, haven't been burning oil, but my gas consumption has been high.

spj steve

Hey , when did this View Vehicle profile come on board?

When was the last time you adjusted the carbs?


Do a wet test. This is the real test.

view vehicle profile this is cool!!!
Rick Crawford

If you do a wet test and is still low all it will tell you is that it is in the rings , might try a leak down tester. That might pin point where the problem lies

Your compression numbers appear to be acceptable for an engine that has some miles on it. Your oil consumption seems to be ok. If your plugs are black and don't have anything else on them, (i.e. oil, antifreeze, etc.) I'd look into your air/fuel mixture for possible adjustments. Following up on Don's questions, at idle, what is your rpm? Does the engine die at idle? What kind of carbs are you using? Does your exhaust smell like gas?


What/where is this view vehicale profile you speak of.
M Macdonald

Looks next to Rick's name

Rick Crawford, Ontario, Canada View vehicle profile

Rick Crawford

Tried it. File too large. Suggest you check your CR. I think that you'll find that it's closer to 8.17 (or something like that, Steve Pike'd know) stock than 7.75.
Doug Baker

Doug UUUMMM shrink the file size???

I have also been meaning to ask. Don what is the LOGO all about?

Just re-read your second post Steve. Sounds like your back carb is running a little rich. For that matter both are a little rich. Plugs should be Brownish. What colour are they after a long run not just a drive around the block?
Also ,when was the last time the 2 carbs where synchonized?

You numbers look of. If I am not mistaken, you are within a 10% tolerance and this is OK.
Where is SteveP when you need him?
Rick Crawford

He really didn't have anything to add here as things looked to be pretty well covered so he was hanging out on the GL-5 thread wondering why Rick was singing from the refrain of a Darryl Rhoades and the Mighty, Mighty, Men from Gladd song.

To assess a compression ratio, you are looking at a volumetric measurement. Looking at compression numbers can provide some feel for the compression ratio, but they don't reflect a pure volumetric comparison. You have to think in terms of Charle's law and Boyle's law and how they work against each other in this situation as opposed to their combined effects in the ideal gas law. Having said all of that, the numbers don't really look all that odd, and they are within what I would consider an acceptable tolerance band for a TR-6 engine with unknown history, but appears to have had the head shaved to some degree in the past.

At least Rick wasn't singing the DR & TMMMFG parody of Helen Reddy's "I am Woman."

I am woman, hear me bitch
buy my records, make me rich...

...and it goes down hill from there.

What correspondence of a Compression test and the compression ratio have to do with this post?

Don't know where that came from

Rick, my avatar for my Wedge I designed

Rick Crawford

What I was asking was,in a back a$$ way.

What does Compression ratio have to do with his question

Don Kelly wrote:
"What I was asking was,in a back a$$ way.

What does Compression ratio have to do with his question"

Not that much really because cylinder pressures and compression ratios, while related are two different things. However, it had been raised previously and two posts specifically mentioned me, so I felt perhaps I should chime in and offer up my take on the situation and provide a little bit of information on why a compression ratio and cylinder pressures were not one and the same.

I'm sorry that this seems to present a problem for you Don.


Don, et. al.
To clarify further for your satisfaction, Rick's vehicle profile lists his compression ratio for his 71 stock engine as 7.75:1. I questioned that metric as I recall the stock early engine without smog control had 8.XX:1.
Doug Baker

Damn, I was still fixating on his compression question.
Did we, or he, ever solve it?

If my wife was to re-write "I am woman", it would probably go like this:
I am woman hear me bitch
I won't ride in a TR6
It rides rough and is a piece of shi*.
BTP Price

Berry, Buy a Wedge. She'll love it

This thread was discussed between 17/04/2011 and 23/04/2011

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