TR4/4A performance cam

[nbailey]

My recently acquired 67 Tr4a came with a sportcam installed. The previous owner does not know
what kind, or what valve clearances to use. Does anyone have any suggestions where I should start
when setting valves? Thanks

 

[tinman58]

I have a mild cam in my Tr3 and the valve clearance is .12 . I think you would be safe at that number.

 

[TR3driver]

Or, you could take some measurements and compare them to the table at
https://www.tildentechnologies.com/Cams/TriumphCams.html

As you can see, the recommended lash varies all over the place.

 

[KVH]

I've got a 66TR4A I bought a few years ago. It has some kind of modified cam. Some old notes from the prior owner say the cam is from Ken Gillandere at British Frame and Engine, Ryland Avenue, Temple City, CA. Notes I have say that the Exhaust Lash is .018 and the Intake Lash is .016. The Duration for each is 260.

Then I have a graph with those specs, and the graph says "Data for Degreeing Cam at .050 Tappet Rise," and that graph shows durations of 214 with no information about valve lash. Not sure what the graph is telling me, although is says the intake valve opens at 37 degrees and the exhaust closes at 37 degrees.

Do I use the .016 and .018 for the valve clearance when adjusting the tappets--instead of .010? Seems a bit extreme for variation. By the way, would this explain why this car is fast off the line but seems to top out quicker at high RPMs than my plain stock 4A?

Below are copies of my specs and graph.

 

[TR3driver]

Should be the other way around, running the lash too tight will emphasize high end power a bit, while cutting low end. My guess is that you have tired valve springs instead, or maybe some kind of exhaust restriction (like a collapsed baffle if you have baffle type mufflers).

And yes, I would at least start with the lash spec for your cam. The best lash depends on cam lobe design, which is exactly what changes for a 'hot' cam, so the recommended lash for any particular cam has little to do with the factory spec. Or if you want, follow the information at https://www.tildentechnologies.com/Cams/Tip_Lash.html and choose a value yourself

 

[MDCanaday]

The answer is it depends......on a screamer .015, for the street .012 is better. The racer needs
the oiling on the cam face at high speed and cares little for longevity. you should do well at .012.
MD(mad dog)