Questions regarding idle on early Y-block

[zuburg]

I'm a new owner of a 1956 T-bird, unfortunately, it has a 235 Y-block with a bunch of Thunderbird bits bolted on instead of a 292. It has a Holley 4v carb. The current issue is a high idle of almost 1,000 rpms. I figured out how to lower it down to about 600 and it sounded pretty good at that speed. The issue is that when I put the automatic in gear (either drive or reverse) it dies at that speed. I had to increase the idle back up to 900 or more to keep it from dying.

I read that with an automatic, you may need to have someone help you by putting their foot on the brake and putting it in drive while you set the idle. I assume if I did that, once I put it back in neutral or park, the idle will be back up to 900?

I do plan to do a partial transmission rebuild to fix some serious leaking issues. Would this possibly help the situation?

Where should I start to address this issue?

thanks,

[scicala]

Have you tried to adjust the idle mixture screws when its warm for best idle quality (highest vacuum or smoothness at idle) when in drive ? Then lower the speed and re-adjust mixture ? Or have you been just turning the speed screw ?

Sal

[dmsfrr]

Originally Posted by scicala

Have you tried to adjust the idle mixture screws when its warm for best idle quality (highest vacuum or smoothness at idle) when in drive ? Then lower the speed and re-adjust mixture ? Or have you been just turning the speed screw ?

Sal

Sal,
What would a good idle vacuum be? About 20? I haven't had a gauge on one recently enough to remember.
Thanks.

[scicala]

"Sal,
What would a good idle vacuum be? About 20? I haven't had a gauge on one recently enough to remember.
Thanks."



Hi dmsfrr,

It will vary from engine to engine, but on a stock Y-Block in good condition I would expect to see from 17" to almost 20" of vacuum. I recently worked on a '54 Mercury 256 that was just rebuilt and good running that only had 17.5". I think the camshaft differences from year to year may account for the variation. Hard to say.

Sal

[darrell]

235 y block thats a new one anyway as others said a vacuum or carb problem.unless some fool put in a big cam.

[dmsfrr]

Sponsored Links (Register now to hide all advertisements)

Originally Posted by darrell

235 y block thats a new one anyway as others said a vacuum or carb problem.unless some fool put in a big cam.

235 is a typo, it's a '54 239.

I heard somewhere(?) that the '55 & newer y-block intake manifolds don't always seal well when up against '54 heads. So checking for vacuum leaks is a good idea.
.

[zuburg]

Thanks to all. Yep, it's a 239, I hate getting old. Since it seemed to be running pretty good, I was avoiding the idle mixture screws. Plus I didn't have a vacuum gauge. I will try to borrow one from a buddy and check them out.

[WestCoast]

some thing wrong here, t bird never had a 239 engine, first engine in 1955 was a 292, same with the 1956, and idle speed is 475, if you need more rpm to keep it from dying when put in gear I would suspect the torque converter, something is wrong with it, its not free wheeling, I think its locking up,

[dmsfrr]

Originally Posted by WestCoast

some thing wrong here, t bird never had a 239 engine, first engine in 1955 was a 292, same with the 1956, and idle speed is 475, if you need more rpm to keep it from dying when put in gear I would suspect the torque converter, something is wrong with it, its not free wheeling, I think its locking up,

You are correct about the engine sizes. Here's a link to the 2nd half of his original post/thread. https://www.fordbarn.com/forum/showth...=172555&page=2

My '55 Bird, also found to have a '54 engine, had similar dying in gear problems. It had several vacuum leaks along with carb & dist problems and the trans shop replaced the free-wheel mechanism in the torque converter.

.

[JeffB2]

What is the code on your intake manifold? If it's 9425-B on 239 heads you probably have a vacuum leak.

[dmsfrr]

Originally Posted by JeffB2

What is the code on your intake manifold? If it's 9425-B on 239 heads you probably have a vacuum leak.

I think zuburg found the number ECZ-9425-A on his intake manifold, at this link, when he was looking for the block casting number....
https://www.fordbarn.com/forum/showpo...0&postcount=17


.
.

[zuburg]

OK, I went ahead and ordered an inexpensive vacuum/pressure gauge, should be in next week. I started looking at where to connect the vacuum gauge and I believe all my vacuum lines are metal with fittings. I'm attaching a couple of pictures to confirm and ask where I should connect the vacuum gauge. I have marked 5 lines and listed what I assume they are below:
1 - fitting coming off back of carb, I assume this is a vacuum fitting that splits off to several components

2 - This is the largest line and goes to the power brake component (booster?)

3 - This line goes down to the fuel pump

4 - You can see clearly that this goes to the round thing next to the distributor (is this the vacuum for the vacuum advance?)

5 - This line goes from the round thing next to the distributor and connects to a fitting on the front of the carb (shown in picture 2). Is this a timed vacuum port?

What is the recommended connection point for the vacuum gauge to check the mixture screws? I'm guessing I could disconnect the line going to the power brake? If so, do I need a fitting to connect the vacuum gauge? Or can I just put the plastic tapered end that comes with the gauge kit in the opening?

[dmsfrr]

Originally Posted by zuburg

What is the recommended connection point for the vacuum gauge to check the mixture screws? I'm guessing I could disconnect the line going to the power brake? If so, do I need a fitting to connect the vacuum gauge?
Or can I just put the plastic tapered end that comes with the gauge kit in the opening?

Disconnect the rubber line to the brake booster (in yellow circle) and temporarily slide a short snug fitting rubber hose over that metal tube leading to the back of the carb. Then insert the tapered fitting for the vacuum gauge in the other end of that short temporary tube. (if the brake booster is leaking this disconnects it, but you can check it separately)

Or...
You could connect the vacuum gauge to the front end of line #3 where it slips onto the top of the fuel pump. But this won't let you know if the fuel pump booster diaphragm for the windshield wipers, or the wiper motor itself, is leaking.

[zuburg]

Thanks, dmsfrr, This should be an adventure. I'm thinking your idea of a problem with the torque converter makes sense. I will have that checked out when I get the transmission rebuilt, my number one priority. I'm still waiting for the state of NC to inspect my vehicle so I can get it registered. That is scheduled for Tuesday.

[dmsfrr]

WestCoast was the one who first mentioned the free-wheel / torque converter and reminded me of the similar problem in mine. Thank you.

After you connect the vacuum gauge in one of the 2 positions (above) for your carb adjusting take note of your final vacuum pressure. Then re-connect and swap the vac gauge to the other position. The vacuum reading from both should be the same, if the parts that were temporarily disconnected are in good internal condition.
If you don't get readings above 16"/17" (thanks Sal) you've probably got leaks to look for.
Keeping my fingers crossed.

Is your in-dash tach working?


.

[zuburg]

Thanks, yes the in dash tach is working. I was thinking of lowering the idle back down to normal with the car in park to check the vacuum in different places to check for vacuum leaks. Does that sound reasonable? Once I get the torque converter sorted out then I can set the idle in drive.

[oj]

You might check idle richness, if it is lean you'll experience what you are describing & have to increase rpm to get it to idle. Once you do get it to idle at 450rpm the torque converter will act right, it is acting stupid because the idle is high enough so it thinks you want to go somewhere.

[zuburg]

So should I adjust the mixture screws using the vacuum gauge with it in park? Then put it in drive to adjust the idle? Or does it have to be in drive when I adjust the mixture screws? I will be very happy if that is all is wrong, and the torque converter is OK.

[scicala]

You should get the mixture screws close to correct in park then put in drive (with emergency brake on, or someone else in the car), then lower the speed screw (by the throttle lever) until you get the RPM you want, then adjust the mixture screws again with the vacuum gage. Speed may go up again after that a little bit, so you may have to go back and forth.

Sal

[GREENBIRD56]

If the car has a working tachometer - then the distributor has to have been out of a 55 /56/57 'bird. A 239 is a "tang drive" motor - or it would have to have had a later oil pump stuck in there........ If the distributor is from the 55 / 56 models, then it would be a Load-O-Matic and the aforementioned Holley carb would not provide the necessary source vacuum to run the distributor's advance system. It would also need an adaptor to fit on a early four barrel manifold. I'm not trying to poop on the parade - but some stuff needs sorted out here......

Is there a chance this is a 272? - distributors would then mate and drive the oil pump. And there are "A" 4bbl manifolds on many 272's. The fitting of the later style Holley - with a Load-O-Matic is usually a recipe for trouble - so is it the later version or the T-pot?