TR2/3/3A TR3 Carb help - crazy idle

[newmexTR3]

Hey guys,

I picked up my completely rebuilt set of carbs from Joe Curto on New Years eve (New throttle shafts! Yay!). I installed them that day but because of time constraints got them set only roughly. Still, it was running well enough to get it back to the lot and even in that state I could tell a SIGNIFICANT difference in the power. Apparently the needles the dpo had installed were from a TR2...

This evening I went to the lot (it's parked outside) and had a hard time starting it. Now I'm experiencing a strange problem. When the car starts running, the idle goes way up to about 2500 rpm for about 5 seconds, then just cuts out. This is with choke about 90% on. Once it's up to running temperature, I can give it some gas and it won't die, but then the idle goes really high again. I'm not sure what's going on... I had the carbs synched and idling around 1100 a few days ago when I installed them. Any ideas on what to look for would be great.

It is relatively cold - about 33 right now, if that makes any difference.

Thanks,
Gavin

 

[rlandrum]

If I had to guess, I'd say that the piston was sticking, probably because of the needle rubbing against the jet. (That might be because it's cold.)

Typically the needle should slide perfectly into the jet, with no (or very little) touching, until the piston makes a distinctive "clunk" sound.

It's been awhile since I rebuilt mine, but I belive the adjustment is made by loosening the sealing nut, then sliding the piston down until it's fully bottomed out, then lifting and dropping until that "clunk" is heard. Once heard, leave the piston in the down position and tighten the sealing nut.

 

[poolboy]

Does it rev up that high only when you are trying to let it idle ?
And how are you managing to get it up to normal temperature ?

 

[newmexTR3]

If I had to guess, I'd say that the piston was sticking, probably because of the needle rubbing against the jet. (That might be because it's cold.)

I kind of doubt this is the problem, as the carbs were just rebuilt a week ago by the best in the business, Joe Curto.

Does it rev up that high only when you are trying to let it idle ?
And how are you managing to get it up to normal temperature ?

It revs that high as soon as it catches from a cold start. Could it be the vacuum advance that is making it idle higher? I ran for years with out it and when I finally hooked it up recently I had some pretty serious vacuum leaks from the front carb throttle shaft. I'm getting to stay running by pumping the gas when it sounds like it's going to die.

Also, I'm using mobil 1 10-30 in the dashpots.

 

[mrv8q]

Also, I'm using mobil 1 10-30 in the dashpots.

I thought they liked 20W oil; an email to Mr. Curto is in order. Please post his response, I'd like to know what he recommends...

 

[TR3driver]

Sounds to me like you've got a big vacuum leak somewhere.

10W30 will work well enough. Whether it's optimum for your engine is a different question, but the effect is subtle enough that you need to worry about the major problems first.

The other thing to look for would be binding in the throttle linkage somewhere. You could try loosening the clamp where the linkage attaches to the front carb and see if that changes the idle. If so, there is clearly a problem in the linkage.

 

[poolboy]

Well that was my 2 thoughts on the matter, a vacuum leak as you suggest or a linkage problem like Randall said. The reving up and dying afterward would make a vacuum leak the # 1 suspect in my mind. Check the intake manifold for a leak and any other nipples that have a fitting or vacuum lines othewise attached.
I also agee with Randall about the oil. I've heard of people using, tranny fluid, 3 in 1, Mineral oil, 20w, 30w, all the multi weights, you name it.
All it really effects is what you might call "throttle response" when you accelerate.

 

[DougF]

If you haven't already, remove the air cleaners and start the engine at the solenoid button, if your car still has one. Watch the entire system for any mechanical glitches while these changes are happening. You may be able to narrow things down.

 

[rlandrum]

I kind of doubt this is the problem, as the carbs were just rebuilt a week ago by the best in the business, Joe Curto.

Even the best have their off days... Especially around Christmas... It's easy enough to check. Just lift the piston and let it slide back into place.

That said, a vacuum leak does make more sense, especially with the 90% choke.

 

[TR3driver]

Even the best have their off days...

One of our local club members had his carbs rebuilt by a respected professional; who apparently forgot to tighten the clamp nut after centering the jets. The jets got bumped while installing the carbs and were hugely off-center when I went to help him with it.

 

[newmexTR3]

Thanks for the tips guys, I really appreciate it. I did some work last night and figured out I had two problems:

1. The linkage was totally screwy and putting tension on the throttle shaft while at rest. I adjusted it so that it works well now, but then realized I had inadvertently changed the height of my gas pedal! doh! I'll fix that this weekend when I have someone around to eyeball it in the cockpit for me.

2. I have a vacuum leak on the front carb somewhere, possibly on the intake manifold / head mating surface. I installed some of those heavy duty intake/exhaust gaskets from Moss and I'm wondering if that has something to do with it. I didn't have enough time last night to explore the problem more.

Now for the good news. With the carbs newly rebuilt and choke set up properly, I experienced something I've never had happen yesterday- After being parked outside in 30 degree weather for 24 hours, the car started up on the first crank! It's like... a... new car! I've never had it start up that easily in cold weather, even when it is running really well. wow.

Also, even though I have the vacuum leak and there is some tuning to do, the power difference is quite simply stunning. Honestly it feels like I've got 2 extra cylinders going. And the car was not slow by any means before. I cannot wait to get everything dialed in. I've got a little rocket!

I told my wife all of this when I got home last night and she coyly said, "sounds like you probably don't need to put the Judson on then, huh?" Doh! Not sure how I'm going to justify that modification now!

 

[WA1KWA]

Vacum leak - spray some WD-40 or the like (you probably want to use the little red tube supplied with the can) in the obvious places it could be leaking. Especially the throttle shafts (I know they were just done, but I'm being a bit anal here). When the revs change, you've found your leak.

Colin

 

[DNK]

Vacum leak - spray some WD-40 or the like (you probably want to use the little red tube supplied with the can) in the obvious places it could be leaking. Especially the throttle shafts (I know they were just done, but I'm being a bit anal here). When the revs change, you've found your leak.

Colin

Always thought that was carb cleaner?