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Discussion Starter · #1 ·
ok i have a 351 having trouble with it surging, when i pull the vacum to the brake booster, i have good vacum but the idel dosent change with the vacum being unplugged, it has a new distributer ( installed correct ) and a new holly carb and new plug wires and a coil, it tends to start and run ( a little rough like a miss ) and it surges high rpm low rpm untill it stalls any ideas??

and its a clevlend not modified or 400

thanks alot Al
 

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Yep, sounds like a vacuum leak to me too. If it's not the carb gasket, check the manifold gaskets and possibly the EGR area (if you still have it installed).
 

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Discussion Starter · #5 ·
ok I just got threw checking all vacum and i have no leaks ?
i checked the points and reset them to .17 thousands

i just pulled a plug and found the gap to be .45 thousands, my book says they should be .32-.35 is this .10 gap larger my problem? they are new plugs and i have to admit i dident check the gap when i installed them? what do you think?
 

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Points? Why would you use that old style distributor? What exactly is this 351C motor in? The gap on the plug is not going to cause the problem you describe. Like I said before, if you pull off the hose to the booster the motor should fall on it's face.
 

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Discussion Starter · #7 ·
i pulled the vacum hose to the boster , no diffrence still ran a little rough, and it seems to stall and not restart when it gets hot?

i pulled all vacum line on the motor and pluged them all no leaks, i sprayed brake cleaner all over the manifold and carb no high revs like a leak ?

brand new holly carb seems to be working fine, could my coil be going bad? or the voltage regulator , i was going to put a duraspark system on it, but i think i need the electronic distributer from a 460 to fit , the 351-m/400 i think is taller but i think the 429-460 is a direct swap for a 351 clevland.

i dont think my problem is a gas or vacume problem, i think i have a electric problem somehow, the coil is lose does that matter? if the distributer shaft has play up and down does that matter, and if the plug gaps are all big does that matter?
 

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What exactly is this 351C motor in?
The voltage regulator has nothing to do with the way it will run.

The dizzy for a 351C is the same one used in a 351M, 400, 429 and the 460. A loose coil should not cause this problem UNLESS the wires are grounding out. Why not tighten up the coil bracket? All dizzy shafts have up and down play. Like I said before the plugs won't matter.

You need to find out if is an electrical, vaccum or gas problem. If you have no idea what you are looking for (anjudging by some of your questions) you might be better off to take it to a shop. Diagnosis over a computer screen is hard to do without seeing it first hand.
 

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Discussion Starter · #9 ·
what is the motor in? does the body style effect the ability to run?

it is out of a 1972 mustang put in a 1979 bronco that was striped, it ran perfect in the car, i have a new electric fuel pump, new gas tank new fuel lines, i cant figure this god**** problem out, could the timming chain have jumped a tooth? and i did just tighten down the coil, i found it was lose. i have all the plugs out checking gaps so i dident have the ability to test the lose coil problem yet! and as far as taking it to a shop, crap i live in kissimmee florida all the shops around here are for ricers ! you know how they love there hondas and toyota's!

everyone says vacume leak just like you , but from where???? i only have three vacume lines on the motor and i disconect and plug all those with no positve results, i sprayed the base of the carb , i have spayed the entire intake manifold, same thing ?? seems to run ( a little rough ) for about 3-5 minutes, dies and wont restart , starts at about 2 minutes revind up and down ( about a 400 rpm change ) am i missing a area where vacume could leak ( i cant think of any ) oh and oil pressure hot is 70 psi and compression is 163-165 , i have been working on my mustangs for about 12 years and this one is getting me, maybe a curse of this da** bronco
 

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Yeah, it matters what it is in. It helps me to try and figure out what your working on.

When you pulled this motor did you open it up at all and inspect it? Does it still have the nylon cam gear? Did you pull the dizzy out when you did the swap? You could be a tooth off on the camshaft with the dizzy gear. Have you checked the firing order and also set the motor to TDC and verified where the rotor is pointing? You do know that it is a CCW rotation correct? You also know the #1 hole is the passenger front right?

When you try to restart it does it seem to want to start and then just turn over real hard?
 

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Discussion Starter · #11 ·
yes i pulled the dist. it was locked in and wouldent rotate ( what a job geting it out was ) , yes it has the rotor pointing to one i verified it yesterday, i dont know if it has the nylon gear i dident pull the timing cover, the fireing order is correct.
as for trying to restart it kinda drags like a slow first turn over and then goes normal will fire but not actualy start.
by the way thanks for the help
 

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Discussion Starter · #13 ·
yes it backfired, i actually pulled the dizzy 3 days ago and resent it, it was off about a half inch, ran good the first time for 15 minutes, do you think if its a nylon gear it sliped again, its late here but im going to go chec it agian and see if it moved.
 

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It backfired? Do the step I posted above. If you know nothing of the motor it very well could have a nylon cam gear.

You might also want to pull that dizzy out and make sure the roll pin has not sheared on the dizzy gear. It is not that hard to stab the dizzy back in to the #1 spot.
 

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Have you put a timing light on it? It sounds like either a ignition or carb problem. Low float setting, missing vacuum plug, broke advance spring in dist. , something simple.
That would be my guess too. Either the vacuum advance or the mechanical advance is stuck/broken or both are.

In the good old days you could take your dist to a guy with a Sun console & he would check it for you.
 

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You say you pulled the vacuum line off your brake booster and nothing. It is possible to develop a vacuum leak through your power brake booster to the input of it underneath the cab where your pushrod comes through the firewall to the brake pedal.
If this motor ran well and you didn't mess with any of these things that the other guys are suggesting I would take a pause and check this first. Everything I've read is a valid suggestion for a motor with your symptoms, but it sounds like you are getting too much air with that vacuum hose on, otherwise like we all seem to agree, it should die when you pull it off.
Check the face of the power brake booster just below where the master cylinder bolts to it. a line of deteriorated paint or rust here is a sign that brake fluid is leaking into your power booster, making this 20X more likely the cause, or a contributing factor.
Please let me know if this turned out to be your problem.
 
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