I reciently replaced my 400 ci with a 460 ci in a 78 4X4. I need dependability so things are pretty stock except for an edelbrock manifold and carb. Stock dist, computer module, and exahust.Here is my delama, in the morning at cold start an exterme miss is there. I will allow it to run for say 5 minutes, shut the engine off , wait 1 minute, re-start and the miss is gone and will run great all day. This happens every morning. I thought maybe the vac advance was sticking so before starting I disconcted it, no change still missed. Good plugs, new stock dist. Could it be a bent push rod, bad lifter? Is ther anyone who has had this problem before that can help me. Please be gentel this is my first time in a computer forem.

Craig

 

Sounds more like a choke problem to me. Is it an auto or manual choke? Also if your truck is a 1978 it shouldn't have a computor control in it unless you retained it when you swapped engines.

 

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Thanks Deen for your response.
Its not a choke problem. The miss will continue after the engine has warmed to operating temp and the choke has fully opened. The miss only stops after I turn the engine off, wait 1 minute and restart. Also it is always cyl #8 thats missing. Im really scratching my head over this one. Also the original 400 came with an electronic dist. After purchasing an electronic rebuilt dist (the same as the 400 excet for a larger drive gear) I used it and the 400 computer modual in the new 460. Everything worked fine for about 20k miles.
This problem started about 1,000 miles ago.

Thanks again,
Craig

 

I have had a similar problem with my '82 F-250 4x4 after replacing the original 351w with a 460/c-6, mine would give me the most trouble after a rain or sitting unused for a week or so. There are many different answers to your problem, finding the right one for your situation is the kicker.
(A). I'd check distributor cap for cracks and carbon tracking or carbon buildup on the terminals(inside the cap)
(B). Check spark plug wire(s). On a cold night open the hood and start engine and see if you can see srarks jumping from the #8 wire if so relace all the wires, also make sure you don't let the #7 & #8 wires run parallel next to each other from distributor to the plugs since the fire one right after the other it could cause a miss. Keep them as far apart as possible with wire separators.
(C). Check the module against a known good module( usually these start acting up just before they puke).
(D). Look at the cowl to hood seal, if the seal is bad it will let water fall onto engine(#8's against fire wall right under seal), also it could leak water onto air cleaner where it'll settle into indention for wingnut and if the wingnut isn't totally sealed to air cleaner it could allow water to drip into intake manifold and since motor is tilted rear down the water could be settling in #8's intake tract causing a miss at start up.
(E). Check spark plug(s), it(they) could have a crack in the porcelin shell you could have missed.
I hope this helps in any way.
BB79RANCH

 

Hey BB79:

Thanks for the come back and info. You gave me a lot to check out but it will take some time Ill let you know what works.

Thanks again
Craig

 

A bad wire, cracked plug, etc. would not go away after you warmed the engine. I would pull the #8 plug to see if its oil or fuel soaked during the "miss" cycle. You can buy an adapter from NAPA or any other auto parts store that screws on the end of the plug that keeps it from fouling when an engine is burning oil, etc. It's not a fix-all but if you put one on and your problem went a way at least you would have an idea what's causing the miss. The plug extenders usually sell for around $5.00-6.00
A sticky lifter could also cause a miss in one cyclinder. Pull the valve cover on cold start up and see if that valve train is oiling. Deen

 

The Edelbrock carb has me wondering....My Edelbrock seems to have been jetted real fat and I have been gradually leaning it out over the last few months. Mine tends to miss when cold as well but the problem eases up a little more each time I make a jet or rod change. I am currently 8% leaner than stock in cruise mode and stock in power mode. I am reluctant to make anything more than minor changes each time due to the possibility of going too lean and getting some detonation because I am running around 10:1

DannyP
89 F-150 4x4 former EFI I-6 now carbed 351W, Edelbrock heads,cam,intake,carb.
MSD 6A, ZF, Sterling 10.25 with 3.55L's.

 

Danny:

Springs, rods, jets and that little book? I went thru the same cold problems you are having and ended up on the lean side also.
In fact I was dialing in the elect choke when this weird miss thing started. This isnt a carb, timing or pre ignition problem, the cyl is just dead until I turn it off and back on, warm or cold, then it runs like a top all day.

Good luck on yours,
Craig

 

After leaning it out to 8% under, I decided it didn't help so I went back to stock. I purchased a 4-hole 1 inch carb spacer and am trying that. So far it does seem to help. Don't run out and buy one yet tho, it still misses but not as bad. I plan on playing with the jetting a little more over the next few weeks or months. I'll keep you posted on any progress. By the way, the miss problem I have only occurs below 1500 rpm, especially noticeable when lugging.

DannyP
89 F-150 4x4 former EFI I-6 now carbed 351W, Edelbrock heads,cam,intake,carb.
MSD 6A, ZF, Sterling 10.25 with 3.55L's.

 

Danny:

Is your problem a miss or is it a backfire. Early on I had a backfire problem. What was happening was when cold, idel on curb, the venture vacuum was advancing the dist to far. I limited that advance with the alan screw in the vac port on my dist. Now that I solved my other miss problem I am going to resume fuel and timing settings and Id be interested in what you find out.

Craig