TR4/4A Engine Power

[KVH]

I'm still lamenting that I have twin TR4As, and one is more powerful than the other. I just can't figure it out.

After a cylinder head rebuild I thought I'd get to the bottom of it, but no. Even an engine rebuild doesn't seem to do it.

I still suspect my PCV valve and might disconnect it. I also suspect my pertronix ignition because I miss at exactly the same rpm nearly every time--maybe about 80%. Just a short little skip, them fine.

The feel is that something is gagged off. It's a new fuel pump and filter, so not that, I wouldn't think. Choked, gagged and restrained at 4200 rpms and above is how I'd phrase it. Runs great, except I know something isn't right on the heavy foot test.

Anyone have a better guess? I'm open about 8 flats on the carbs, and richer seems to result in black soot on my floor. PCV valve (I have a draft tube as well)?

The only hint I think I can mention is that my idle is always too high. If I unscrew the idle screws 'til they almost fall out, I'm still at 1200 rpms. So why too fast I don't know.

Thanks all.

 

[glemon]

What is different from car to car, same exhaust, carbs, distrubutor, cylinder bore, etc. ? Although the high idle speed should be checked, and there may be an issue there relating to top end power, I would also look at timing, do they both advance the same under a timing light at idle and through the Rev range? Are compression readings close? For giggles you could swap distributors, cap and plug wires just to make sure no differences there.

 

[JerryVV]

Lots of reasons. Timing and intake leakage come to mind. Also Carb linkage adjustment not allowing the butterflies to fully open or just out of balance. Throttle shafts leaking air or intake air leak at carb bodies or manifold connections. Those are just a few that come to mind.

 

[Brinkerhoff]

All else being identical ,the engines could ONLY perform the same if they had the same camshafts and a degree wheel were used to set the camshaft timing up. If you were just counting teeth and eyeballing the chain / gear relationship without actually checking when the intake valves start to open , even with the standard "per the book" method, your cam timing could be way off !

 

[vickxxx]

Your high idle does sound like a vacuum leak. I think JerryVV has the right idea. Make sure the linkage between the two carbs and even the throttle shaft lever are loose before adjusting the throttle. I'm not sure if you've gone thru and replaced the throttle shafts and discs. If the discs are not centered properly, they will cause leakage like this. This just recently happened to me after rebuilding the carbs on my TR.

Swapping out distributors with a known working one was another good suggestion brought up. I had a problem with my engine having difficulty getting above 3000rpm in 4th gear. I removed the distributor plate and found the weights to be sticking. After cleaning and lubing them up, the rpms came up dramatically.

 

[Foura]

You say that you have a draft tube as well as a PCV valve. Having been down the failed route of replacing the PCV valve with a catch tank, I wonder if that is your problem. Having the draft tube would mean that there would be no vacuum for your PCV valve. Hopefully, someone smarter than me can tell you what that would do to your mixture. I think that you should have one or the other but not both. The 4A came with the PCV so I would block off the draft tube and see what that does.

There have been a few threads on the forum on this subject. Might be worth a look.

 

[Merlin63Tr4]

Your high idle speed seems to indicate a vacuum leak.
A properly working PCV has no real affect on power output, unless the hose that connects it to the intake manifold is broken/loose resulting in a vacuum leak and a lean mixture. If it were my vehicle, I would remove the draft tube, block the hole, and leave the PCV to do its job.
Swapping the current distributor and checking the carb linkage as suggested are very good ideas.
It might also be worth your while to check your exhaust system for blockages.

M.

 

[KVH]

"A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools." -- Douglas Noel Adams (1952-2001)"

Love it. You know, I just can't find a leak. Spraying oil onto the carb shafts does nothing. The manifold is tight. The gaskets are new. The exhaust I carefully reassembled. The vacuum line from the dizzy is tightly connected. I usually time the car, then adjust the carbs. Should I have done it in reverse? Maybe the carbs were badly out of whack when I timed the vehicle. I timed is static then checked with a timing light.

 

[titanic]

The PCV valve would be at the top of my suspects list. When I had a TR4A, the PCV valve would produce a high idle speed and air leak. If may not be the cause of your problem, but temporiarly disconnecting it should be an easy way to eliminate it as a suspect.
Also, 8 flats down seems like it would produce a pretty lean mixture.
Berry

 

[charleyf]

Love it. You know, I just can't find a leak. Spraying oil onto the carb shafts does nothing.) QUOTE

Instead of spraying oil on the shafts I Was taught to spray carb cleaner or something very flammable. If the engine speeds up you know the fluid is getting by the shafts. Just don't get crazy with the spray. A little bit aimed directly at the shaft end is all that is needed. Somebody else can speak up if I am wrong here.
Charley

 

[tdskip]

Agree with Charley, it need to be something the engine can burn.

Offbeat idea, but one car having a lighter flywheel will change how it drives.