TR2/3/3A Newbie

I had a 1960 TR3A when I was 15. (45 years ago) When I saw this one I had to buy it.
The engine was rebuilt but never tuned up. It chugged into my garage where I noticed that the chokes where stuck on. Once I freed them up and leaned the mixture, the idle doubled. Then I added 4 degrees of advance and the idle doubled again. Now it is purring like a kitten but the idle keeps hunting between 700 and 900 rpm. I'm thinking its the vacuum advance since I've eliminated my other guesses.
And Idea's why the idle would vary about every second, up and down.?

Thanks

Hi Steve. Welcome to BCF.

Just wondering - did you tune the carbs and ignition per the Instruction Manual? Hunting idle could be air leak around the throttle shafts. Also, disconnect and plug the vacuum line and see if that fixes the problem. Another tack: when was the last time the valves were correctly set?

Tom M.

NutmegCT said:

Hi Steve. Welcome to BCF.

Just wondering - did you tune the carbs and ignition per the Instruction Manual? Hunting idle could be air leak around the throttle shafts. Also, disconnect and plug the vacuum line and see if that fixes the problem. Another tack: when was the last time the valves were correctly set?

Tom M.

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Carbs. and timing are as good as I can get them and I checked the centrifugal advance which seems to be working.
I don't know a lot about the rebuild that was done to the engine but I assume the valves were set. They sound good, no tapping.
I thought I might have a vacuum leak through the advance hose but I can check the throttle shaft.
Thanks

Could it have a performance cam? Does the idle settle down at higher RPMs? Just throwing that out there.

It runs smooth when at about 1000 rpm. This car was raced in the 60's and came with a box of trophies so it is quite possible that the cam was modified.
Not sure what that means or what can be done to test this theory.

Steve

STeve 1958 said:

It runs smooth when at about 1000 rpm. This car was raced in the 60's and came with a box of trophies so it is quite possible that the cam was modified.
Not sure what that means or what can be done to test this theory.

Steve

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I'd bet money you have a longer duration cam if the car is a former racer. With the valves being open longer so it breathes better at higher RPM, it's going to be lumpy at anything below a grand (assuming you do have a hotter than stock cam). I had a mild cam in my TR3 and I could get it to idle at 8-900, but it didn't really settle into a nice purr unless it was at 1,000.
For sure pull the valve cover and check the clearance on the valves. I do that as part of any tune-up on my TR's, even when I know I set them with the last service.

On another note, with the throttle shaft connector loose, grab each throttle shaft and give it a wiggle. Anything more than a couple thousandths and you can pull extra air in well past the needle, doing all sorts of wonky things to your idle that won't be noticeable at open throttle. Could also spray some carb cleaner at the throttle shaft bushings with the car idling. If the RPM goes up, you're pulling air in past the shaft.

Saturday is here, so I'll pull the valve cover tomorrow. As well as checking for vacuum leaks.
I'm in the middle of restoring the interior with all new vinyl and carpet but tomorrow the seats go in so I can drive it again. Then I'll get serious about the engine, electrical systems and brakes.
Big job but lots of fun.

Steve

+1 on cam. You could try opening up the valve lash just a bit, that will sometimes help tame a wild cam. But easiest is probably to find the best balance between lopey idle and fast idle and just run it there.

I used to run a "3/4 race" cam and it loped even at 1200 rpm. If I tried to set it much slower than that, it would die at the bottom of the lope.

Hunting is always a lean mixture. Lean can be caused by any of the following:

1). Mixture set lean with adjusters
2). Bad carb gaskets
3). Bad manifold gaskets
4). Worn throttle shafts
5). Worn butterflies
6). Low fuel float level


A racing cam lopes, which is very different from rpm hunting. Lower the idle on a racing cam and it gradually loads up and slows to a stop without hunting. Hunting is always lean.

I have no experience with racing cams, and if that is not it, I would look at the distributor having slop in it. And yes for sure air getting in from a secondary source is always a problem, like with the throttle shafts, but again with that my experience is the idle just stays too high. There are some new after distributors that are priced well, and if you go that route, I would stay with points and condenser.

steve

Just in case ... if you want to test for air leaks at the throttle shaft openings in the carburetors, get the engine warmed up and idling, then spray some carb cleaner (or water, or starting fluid) directly where the shafts enter the carb throats.

If the engine changes speed with each "squirt", there's air leaking at that point. If so, time for re-bushing those openings.

Tom M.

Most of the TR3/4 engines that I have been around seem to even out at about 1000 RPM. Below that they are lumpy. I say enjoy the ride and don't expect this engine to do what the modern ones do.

charleyf said:

Most of the TR3/4 engines that I have been around seem to even out at about 1000 RPM. Below that they are lumpy. I say enjoy the ride and don't expect this engine to do what the modern ones do.

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Very likely true, but only because the carbs are worn out. The problem with high idle is you are engaging the vacuum advance ahead of schedule. If you have to idle above 800rpm on a stock cam something needs attention. On a racing cam it would be best to disconnect the vacuum advance completely, as it is only a mileage part anyway. Then you can raise your idle to whatever you need to keep it from stalling.

Good comments already but I will chime in that 700 is a pretty low rpm to get a Tr3 engine perfect. Both slop in a worn distributor, and slip in the carb throttle shafts will give you a little trouble to be smooth at that RPM. Have fun with your car!

Congrats on the new ride. Pictures or it didn't happen!

Thanks for all the advice. I started out by gapping the plug, gapping the points and then gapping the valves. All three were off and two valves had no gap at all.
Everything I do makes it run a little better but still lumpy. I'll chase down the vacuum leak issue next. I do think I'm running lean now CJD.