Poor running and SCARY sound

[EEtinkerer]

To all car nuts out there,

I have been totally stumped by this vehicle for quite some time. I have rebuilt several other old cars including a full restoration on a 1956 Chevrolet Bel Air that is a fairly hot street setup. Anyways, my 1974 TR6 is driving me completely nuts and no one that I speak to has any idea what is going on.

The car was purchased two years ago from a guy who installed a new cam, three 40DCOE weber carbs, rebuilt the frame and drivetrain and had it set up for club racing. Well I ended up going off to college with little time to play with this vehicle so it sat in the garage for awhile.

Coming home to work on it the car would never want to idle. It sounded almost like a two stroke with just terrible idle characteristics so I took the carbs off and rebuilt them all. Then I set them all back to the factory recommended tuning settings and it still ran poorly. Replaced the points, condenser, cap, rotor, wires, plugs and still stuck with the same problem.

I went back to school and it has been a year since I've been under the hood because it just doesnt want to run. Well, I started it up and it still runs horribly but something new came up. On a trailing throttle, there is a terrible squealing noise coming from the front of the engine. I disconnected the belt from the water pump and the squeal still occurs. I took the rocker arm cover off and adjusted the valve lash while I checked to confirm that all the rockers were getting properly oiled (and they were.) The oil pressure gauge works intermittently but has at least 50lbs cold pressure so the oil pump isnt dead. The engine only has about 5k miles on it since the guy rebuilt everything and we inherited it. I need to figure out what this horrible squealing noise could be. Even marvel mystery oil didnt ferret it out.

The poor engine running problem has driven me up the wall as well. I've rebuilt the carbs and soaked the parts in carb clean for 24 hours each and that seemed to help but that was over a year ago. The engine sputters and backfires terribly. At 3000rpms, the engine smoothes out and runs great. I've tried top end cleaners like Sea Foam and it just makes a large amount of smoke with no apparent running improvement. The engine doesnt idle and will absolutely not run at part throttle. I have to goose the throttle to keep it running. A slight tip-in condition will cause a stall condition so it's just stab throttle that will keep it running. I have tried turning the distributor static and while running and it doesnt seem to make enough of a difference. I also can't get it running well enough to check the timing with a timing light!

Any advice on ANY of these problems would be greatly greatly appreciated. I have never been so distraught or completely confused by a car. I hope someone here has an idea! Thanks in advance.

 

[Basil]

Hi and welcome to the forum! Since you said it was set up for racing - and this is just a wild hunch - but is it possible there is too much cam in the engine for normal street use?

Basil

 

[Guest]

Sounds like you have a RACE CAR that you are trying to use as a STREET CAR. Triple Webers, cam, etc...sorry to say but may never get it to calm down. That setup is designed to stay above 3000 rpm.

Bill

 

[EEtinkerer]

The vehicle's running characteristics have changed entirely from when we first got it. The squeal developed while it sat when I was at school. The poor running developed as it wasn't driven much while I was restoring my other vehicles. It has a rough idle but it used to "idle" at about 1000-1100. It wont even get close to that anymore. It should still run at part throttle conditions like it used to. The stab-throttle to keep it running seems a bit excessive.

I have a long/tall cam in my bel air and it's an entirely different type of lope. This just runs unevenly including backfires.

 

[Dave Russell]

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by EEtinkerer:
To all car nuts out there,
there is a terrible squealing noise coming from the front of the engine.

The oil pressure gauge works intermittently but has at least 50lbs cold pressure so the oil pump isnt dead.
<hr></blockquote>

Are you sure that it is just the gage & not the oil pressure itself that is intermittent?
D

 

[Mark Beiser]

Have you tried turning it over by hand with the valve cover off to check the travel of the rockers? The poor running could be caused by worn down cham lobes.

Worth checking anyway.

 

[coldplugs]

I not too familar with TR-6's but have worked with Webers a bit. I'd look at a couple of things. The "choke" mechanism that enrichens the mixture for cold starting can cause problems when they leak. They dump gas into a port behind the throttle plate. If there's a dark trail leading from the hole to towards the intake manifold this might be the problem. Since Webers usually have little trouble delivering lots of fuel without the choke, some folks just block the holes off by threading them with a tapered tap (6mm I think) and plugging them with a setscrew. Use locktite.

You could also look at smaller venturis. You said they were set to factory specs - which "factory" provided the specs?

Re the screech - it sounds like you're getting this in high-vacuum conditions. Any chance it's an air leak somewhere?

 

[Bob Buxbaum]

Here is a question that nobody asked; how old is the gas?!?!? If this thing has been sitting around as much as you say you have a tank full of crud! Try disabling the fuel system and hang a jug of gas next to the car and gravity feed it to see if runs any better (it will look like a hospital I.V. setup).

I had only a single 45DCOE hanging on a 1977 Honda Civic that I used to autocross and I learned that just ONE Weber will drive you crazy. The fact that you say that it USED to run okay means that the problem is getting worse, not better, hence my bad gas suggestion. The earlier question about the oil pressure gauge is a valid one. Fifty PSI when cold does NOT mean that your oil pump is good. It means it IS pumping! My TR8 (after complete rebuild) did exactly the same thing with 20W50 but went down to ziltch at 800 rpm until I reshimmed the pump to bring the pressure back up. Hook up a REAL pressure gauge and see what's going on. Last, the screeching is either the earlier suggested air leak or a deep problem (i.e. crank endplay causing the crank to move back and forth and rub things the designers never intended.

Try a fresh gas transfusion to see if you settle that question, then get a pressure gauge to answer that one. Then don't drive it 'till you "figger" it out, lest you blast a good engine all to heck. Good luck, and let us all know.

 

[Mark Beiser]

Good call Bob, we all neglected the obvious first thing to check!

 

[britishcarfreak]

Could be an ignition fault - i.e. jammed advance plate in the dissy. This may result in the acceptable running at only one rev range. However you mentioned that you tried moving the dissy about.

Triple webers are something I know nothing about but it does sound like a carb problem.

You say you haven't been able to get a timing gun on it at idle but you also say that you can get it to smooth out at 3k rpm. Why not check the timing setting at 3k rpm. Surely you could check what you have there and guess/work out backwards to what you should have at idle.

If it's turned bad on its own over time it seems like something stuck or deterioriated.

Are you getting a regular spark at all plugs. Some spark plug faults only show themselves at certain rev ranges. Even though you've replaced parts do NOT assume that they are of healthy functioning condition.

Have you read the plugs i.e. what do they look like? I expect that if you have a carb problem then a pair of plugs will look like crap. If it's an ignition or old fuel problem then they will all look like crap. The plugs will be the window to your motors soul.

The squeal is wierd. Check for crank end float - get someone to press the clutch pedal while you watch the crank pulley for movement. On a trailing throttle as dropping off of high revs you have a high vacuum at the throttle butterflies - any leak or issue here may be making the noise. Similarly a leak somewhere near there may be providing the rough running at low revs.

Have you got a manifold vaccuum gauge to use? It would be nice to know what you see on the gauge.

My Lucas Mechanical injection used to run lumpy until I installed a vacuum gauge and adjusted my throttle linkages to give the smoothest vaccuum reading. Runs much better now.

Enough rambling from me....