Thread: 1955 Thunderbird, new carb tuning issues

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Ok, doing a Flaming River rack and pinion install on the 55 T-bird and I had to replace the oil valley pan (long story) which meant I had to remove the intake. Since the intake was off, I got a Blue Thunder aluminum intake and Quickfuel Holley 650 Vacuum sec. carb. While everything was off I also replaced the head gaskets since I saw some signs of leakage down the sides of the block. I removed the rocker shafts and heads and reinstalled them without dialing anything in. I figured since the distributor was never moved I wouldnt have to adjust anything. I got everything back together and got the car running.
The problem is the engine now runs pig rich but idles high at 1100 rpms. The idle set screw is backed all the way out, and the idle mixture screws are about 1 1/2 turns out. I've played with them from 1-2 turns but it doesnt change much. I'm in Texas so I don't even have the electric choke setup. I havent checked the timing but it'll have to be the next step since everything else I've tried hasn't worked. At first I noticed that the fuel bowl was set too high so I lowered it back down. The quickfuel carb comes with sights which is nice. I also can't detect a vacuum leak nor do I hear one. The car runs great, but the exhaust burns the eyes and it's starting to get a little sluggish since I figure the plugs may be getting fouled. Am I missing something? Can a carb be jetted too high which would cause the idle to be too high? I've also found that the engine runs about 30-40* cooler now because the previous mechanic installed the head gaskets wrong and mismatched the head bolts which come in three different sizes. Could this have an affect. I would think if its running cooler I could up the timing but that would only raise the idle rpm.
I need the engine to idle at around 600-700 and not smell like a lawnmower. Its a 3-speed manual if that makes a difference. I'm thinking it either has a vacuum leak but would it still run so rich? Or the timing is out of whack but could it really affect idle by 500 rpms?
Thanks in advance, Scot Rod

Still have the Y-block engine in the car? I'm not familiar with the Quick Fuel carb you're running.....does it still have the choke plate in it? If so, is the linkage for it possibly hung up on the fast idle cam????

It's been my experience that most often Holley's come out of the box jetted too high and a 650 is a tad large, IMHO, for your application.

You need to set and adjust items in a "specific order" and not jump around as your post suggests. For example you can't adjust the mixture screws until you find out why it's idling so fast (at 1100 RPM). Maybe go back and try it in this order.

adjust the valves first, check the compression, make sure the carb linkage is free and allows it to return to idle and the choke fast idle cam is not sticking, set the dwell (if it's still got points), Then set the initial timing without vacuum connected, then check for total timing. Some of the Y-Block motors had a double diaphram distributor, one was for manifold vacuum and the other was for venturi vacuum. I'd only use the venturi vacuum port since your not using a stock "Teapot Holley" carb, and set it at 10 degrees before TDC. Make sure the old vibration dampener has not turned which would through off your timing marks. Make sure the secondaries are not sticking open (Holley's have/had a set screw on the base that was an adjustable stop). Are you certain that you don't have a intake gasket vacuum leak?

If it still runs at a high idle then look inside the carb.

Good luck

The carb came with 66s, and I stepped down to 64s. The timing was never touched during the job and the car didnt have these problems before. Carb on it before was a single inlet 600 vac. sec Holley which would run out of fuel at high rpms; did it in two different cars. With the new carb I don't run out of fuel. Just to test the timing, I loosened the dizzy and retarded the engine but only got it down to 900. Playing with the idle screws doesnt do anything. Linkage is not binding anywhere and the choke is open.
Also noticed that the rear sight was completely full of fuel so I adjusted it to get the level down but I don't think this would affect idle or am I wrong?
Should I spray down the gasket areas with carb cleaner?

Also, the reason it started running sluggish was because a plug wire came off the distributor.
Yes, the engine is still in the car. Car currently has 101,000 if the odometer is correct. Its not the original engine though since the 312 was not available in 55. It has 292 heads and a 312 block.

More info. Vacuum gauge is showing 11, screwed in the idle screws and it went to 12 but idle is at 1100. Also sprayed some throttle body cleaner on the runners but nothing happened. Also, the float level is lower now on the secondary but no change.

It sounds like you have a vacuum problem. Do you have all of the vacuum ports either being used or plugged. Also, assuming you have a '55 or '56 distributor the vacuum advance should be ported vacuum (above the throttle plates), not manifold. These distributors - pre '57 are only vacuum advance - not centrifugal, so it really makes no difference at idle (static only) as whether it's hooked up or not, but during operation when you do have some venturi vacuum action, that is when you need it hooked up. A 650 on a 312 is a bit big but I have run bigger on them and successfully - but that's ancient history now !!!

Originally Posted by Smockdoiley

More info. Vacuum gauge is showing 11, screwed in the idle screws and it went to 12 but idle is at 1100. Also sprayed some throttle body cleaner on the runners but nothing happened. Also, the float level is lower now on the secondary but no change.

I would think if the vacuum started to climb, the carb is just too fat.... Do the plugs read rich, too? I'd start leaning her down...see what powervalve it has, too.....

I can't go any smaller on the jets, the Holley kit only goes to 64. As for the distributor, it hasnt changed since I started this whole deal, and like I said before, it ran fine. The vacuum line is going to the correct vacuum signal on the carb, but it shouldnt be causing this problem at idle. I'm wondering if the powervalve is bad or something. Its always a bad sign when the engine is not changed when you screw the idle screws in all the way.

That would usually be the sign of a vacuum leak..... But you checked everything, right? Don't really see where the power valve would cause a problem in the idle circuit either....No way there is a fitting missing or loose on the intake....? an unlit propane soldering tank is a real good way to check for vacuum leaks on the gaskets and carb base.... What does the idle do it you take the linkage rod off it completely? I've had a problem occasionally with engines with a lot of cam that I had to drill some secondary air bleeds in the butterflys.... Could also be a plugged vacuum port in the metering block of the carb possibly.... Which I was there to mess with it...got to be something simple....

Setting here thinking about this-----back in 55 Ford didn't have any mech advance in the distributor--it was all vacume and was venturi at that--also vacume ran the wipers with a funny fuel pump deal---if the fuel pump/ carb/ distributor package has been changed around you probably have some compatibility issues---If so----get a dual advance ( what Ford called them in 57 from a later year 292 / 312--one from a truck will have less advacnce so you can run more initial--make sure the carb signal is hooked to venturi vacume---

this was fairle common issue back then---

Jerry

I know about the fuel pump deal, it was called a double action fuel pump. The wipers have been converted to electric years ago. If I remove the vacuum fittings then I get a vacuum leak which raises the idle even more. I'm fairly certain I dont have a vacuum leak. I've sprayed down everything, and I can get the engine to die if I cup my hand over the carb. Again, nothing has changed or been altered except the carb and intake. And the intake is a perfect swap from the factory setup. All the holes and fittings are exactly the same. I think its time to swap over to a carb that works correctly. I have a Holley 750 vac. sec. that runs fine. I think I may plop that on to see what happens.