I have a 1960 f-100 automatic,I just recently put in a rebuilt 292 v8 because I burnt the crank in the old one. Everything seems to run well except I have had trouble with the idol. Had an intake leak but I think I got it . The trouble I am having is when I step on the brakes and come to a stop it wants to die,also the idol is smooth but tend to fluctuate. Do I have an intake leak still or am I missing something else? Help???? Thend19

 

Kind of confusing, idol is smooth but wants to die? Flucuates? Do you mean it bogs down when you stop? Sounds like idle set too low. If you give more info you may well get more in return.

 

Does it still want to die if you shift in to neutral before stopping?

Scott

 

No, if I shift into N before i stop it will idol fine. It does'nt bog down it is as if the idol is set to low but in N. the idol is fine .I've tried setting the idol higher but then when shifting from P. to D. it shifts extremely hard. When i say it fluctuates i mean it sounds as if it is searching for the right spot but can't find it. My plugs are pretty white with a touch of pinkish color I have 55jets main and the exelerater pump maxed out .??????? what else can i tell u that might help?????

 

Does your distributor have a vacuum advance? Also Does your transmission have a diaphragm on the back of it? If yes make sure both of these are hooked to either the carb or the intake.

 

Yes my distributer vaccum adv. is hooked up to the carb , but the tranny doesn't have the diaphragm. I still have an intake leak on the throttle lever side of the carb I've been chasing it for 2 weeks does any one know a good way to cure it. I have a referbished two barrel holly that i recently bought and that is when the trouble started it seems. I got the new one because when I dropped a newly rebuilt 292 in my old carb had a leak in the trottle shaft. I've tried every thing i an think of even multiple gaskets , and rvt. If some one knows why this thing seems to be my gremlin PLEASE GIVE ME SOME OTHER IDEAS!!!! THANKS FOR YOUR TIME GUYS.

 

Have ya got power brakes by chance? If the booster or hydro-vac is bad it will kill the engine when ya come to a stop like at a stop sign. Just askin.

 

No , there are no power brakes or steering. I'm wondering if it could have something to do with the automatic tranny? I don't know much about them,but I'm pretty sure it has to do with my intake leak I can't seem to get rid of . ANY IDEAS ?????

 

My initial though was that the trans may not be disengaging completely when coming to a stop. Doesnt take much for a piston in the valve body to stick. There should be some sort of connection between the engine a trans so it can tell where the throttle is but my knowledge of these trans is limited to looking at one as I pulled it out of my 59.

Your intake leak needs to be fixed first of all IMO where was it leaking from and what have you done to try and fix it?

Scott

 

tbirdscott
I was wondering if the tranny could be the culprit? I'm not sure how the tranny knows therpm ,there is only a speedo cable and a small coolant be cooler next to the tranny to cool it as far as I can thell.how would I go about unstickinf a piston I have a pretty good feeling that it has been the issue.I don't know much about automatics .As far as the ontake leak I have saved down the manifold w/ a fine flat file,as well as the carb base plate.New gasgets,my space plate just beroke tonight I am getting tired of chasing the leak and am starting to just cranck the @#@$$ **** out of the mounting studs. It seems to be ok for a minute but then pops back up.right now it is barely idoling with the choke on some.If I come to a stop the only way to keep it running it to pull out the choke. Could this be a tranny issue and not a leak at all??? I know that when I spray carb cleaner at base of carb in the throttle side the rpms do change . I'm at a loss right know And could use a fresh pair of eyes so to speak.I want my babny back to normal DAMMIT!!! D.D.thanks

 

Thend,

Looks like to me that you have a worn throttle shaft or carb base throttle shaft bore. They do that, you know? Sure messes up the idle, for sure. Only reliable fixes are replace the carb base section with a known good one that has absolutely no slop in that bore, or, have a machinist rebore the base section and install a new bronze bushing matched to the throttle shaft OD. I do not believe you have a leak at the carb/manifold joint.

Also, you may need to install a throttle "dashpot" to just barely hold the throttle a little open momentarily after you stop to allow the trans to drop internal pressure, thus not dragging your engine RPM's down so far. These dashpots mount off the manifold or the carb and a small adjustable piston is aligned with your throttle linkage. These are spring loaded and retract slowly after the higher idle speed is not needed any longer

Hope this helps you out of your problem. Aloha.

 

Here is a pic of carb with a dashpot on it.



After re-reading the thread I gotta ask if you still have your old carb and if you have tried it? Sounds like you may have gotten a dud with your rebuilt carb since you said that is when the trouble seems to have started and it sounds like it could be on the lean side according to your plug readings.. How much shaft play is there on the rebuilt carb compared to your old one?

Scott

 

If the throttle shaft is worn bad enough, you may see gas puddles on the intake on either side of the carb. This is not an uncommon problem. Especially since you said it picks up when you spray it with carb cleaner. Here's a good fix if this is the trouble!

500 Holley 2 barrel perf carb carburetor 4412 Reman Bright Zinc Finish | eBay

There are tons of these things available.

 

I think you definitely have a vacuum leak and that is causing your idle problem. Sometimes carburetors just wear out and there's nothing you can do to correct the issue short of replacement...