TR2/3/3A Idle Question...TR3 with Cam

[karls59tr]

I have a mild street cam in my 3. It tends to idle at 1200-1400 rpm and turns into a very lumpy idle when I adjust the idle screw to lower rpm. Are these rpm's way to high for an engine with a modified cam? I also have to kick the accelerator pedal occasionally to bring the idle down. Are there any common linkage or carb issues associated with this problem on the 3? Karl

 

[TR3driver]

Reasonably smooth @ 1200 sounds like the "3/4 race" cam I got from Bap Geon many years ago. You might try to double-check what the valve lash should be, as many of them take more than standard, and too tight will cause idle problems. Also double-check your tach, as it's not unusual for old ones to read a bit high at idle.

Lots of common linkage problems. The ones I fought with were the balls inside the pivots being worn oval (which would cause them to bind at idle when I tightened the joint enough to keep it from popping apart sometimes).

And the carb bodies/throttle shafts wore until the throttle plates would drag on the bores and refuse to close all the way until I blipped the throttle.

There are other possibilities too, those are just the ones I found.

 

[karls59tr]

Thanks Randall Good to know I'm not too far off the 1200 idle rpm. I have opened up the valve lash to .016 and it seems to run a lot better. When the engine was rebuilt we had set it at .010 and I think that caused some problems. I've done the throttle shafts at the carb rebuild. I'll check the pivot balls on the linkage. I finally put the 3 on the road for the first time this summer and it sure is a blast to drive with the extra grunt from the cam. Cheers Karl

 

[JFS]

My street TR3 is equipped with Elgin cam with 280 duration and .427 lift @ valves (1.65 Cambridge roller rockers). It also has 10:1 compression, polished and ported head, dual Weber DCOEs and header. It idles at 1000 RPM. What is your duration and lift?

 

[Geo Hahn]

...I'll check the pivot balls on the linkage...

If they are somewhat ovalled a quick fix can be to rotate them 90 degrees. On the one that threads in this can be done by putting a washer under it. Worked for me (though mine was popping out rather than binding).

 

[RonMacPherson]

OOOOOOH!


Sounds like a great setup. Can I ask, what are your carbs set to? venturi size, fuel stack buildup, air, emulsion tube, fuel, idle air and idle fuel? Doing some research. Friend's got problem with his, but he hasn't researched his cam, looks like we get to pull out the dial indicator and check it out.

 

[karls59tr]

To JFS I'm not up on my cam speak but here is what's on the bill: M.518cam...duration 227@.050".. .280"camlift....420"valve lift on 109lobe c/L

 

[JFS]

Ron, just got back from a little traveling. I have all the Weber numbers written down -- I'll run to the garage to find them in a bit -- but the idle jets were drilled out by Bob Prouty (now deceased) in Milwaukee and I don't think I have the size recorded.