Timing issue??????????????? or not?????

[ford1386]

I just got done with my 302 swap have a 302 ho motor, holley 670 cfm street avenger, msd coil, 6al ignition, and msd pro billet distributor, and im having what seems to be a timing issue i rebuilt the motor before the swap and i went by the haynes manual for a 302 ho and it says it needs 10 degrees of base timing so i start it up set timing to 10 degrees and if i feather the throttle i can get it to rev up to 5k and it idles fine at about 550 rpm that i set it at but the problem is that if i try and crack the throttle wide open from an idle it falls on its face and sometimes even stalls out so i changed the advance springs in the distributor so it would advance quicker and it does the same thing, so i dont know if its timing or a carb issue but the holley carb box says bolt it on and go...........................

 

[baddad457]

Adjust the slack out of the accellerator pump linkage. It may also want more base timing.

 

[dagoof]

I'll be watching this thread closely.

From what you are describing, I have the same problem.

I've got a Holley 4160 600 CFM on my 302, and it seems to run strong, but not quite like the animal that I intended for it to be. When I punch it, it falls on its face and sometimes even dies just like yours.

Also, mine is sometimes hard to start when it is heated up and you've just turned it off.

 

[dcwroth]

timing?

If you havent done it already, recheck your firing order, 302 and 302ho have different firing orders.

 

[ford1386]

Adjusted accelerator pump spring to zero lash at idle, and firing order is right for ho motor. I put a vacuum gauge on the carb. and at 10 degrees of base timing it only has 10 inch pounds of vacuum and should be around 20 i was told, in order to get to 20 i have to advance timing to 40 degrees, at which the motor seems to take throttle fine, so im thinking i have a vacuum leak somewhere because i shouldnt have to advance timing to 40 degrees........... i sprayed ether around the carb base gasket and intake manifold with engine running and it didnt seem to speed up any but im gonna try a new carb base gasket first.................... and when i crack the throttle from an idle it back fires through the carb so it is getting enough fuel and then vacuum falls to zero

 

[ford1386]

and the holley tech told me that if it hesitates for a second or less to increase one jet size, and if a second or more to increase two jet sizes but it doesnt hesitate it just stalls out like i turned the key off then backfires through carb................

 

[baddad457]

That's not a jetting problem. That's a problem with the accellerator pump. Look inside the carb as you work the throttle. You should see a stream of fuel the instant the throttle's moved off the closed position. iI don't know who you talked to, but he obviously doesn't know S--T about carbs.

 

[baddad457]

What intake are you running ? And give it at least 14* base timing, 10* may not be enough. The 670's a little on the big side for a stock HO 5.0, you may also want to swap the accellerator pump to a 50 cc unit.

 

[ford1386]

Edelbrock rpm air gap intake 14 degrees of timing doesnt do any better, and yea i see a stream of fuel when i hit the throttle but im only building 10 inch pounds of vacuum at 14 degrees so im gonna look for a vacuum leak and the vacuum gauge im using at 10 inch pounds says late ignition timing so i either have a vacuum leak or the dots on the timing gears arent lined up but i know for a fact that i put them exactly at 6 and 12.............

 

[doorgunner]

Rookie says FYI......my Holley 4150 replaced the worn out throttle body on my '93 350....I hung a gallon can of gas from the rafter to feed the carb & it worked like a champ on my home-made test stand....works even better in the truk with an fuel pump....20 lbs. of vacuum at 700 rpm----25lbs at 4,000 rpm-----22lbs on interstate at 60mph/2800rpm...no hesitation...no nothing but smokin tires in 1st & a little smoke in 2nd gear....I reduced the main jet size from original #64 down to #45...then it started bucking/coughing/etc.....I gradually increased the jets to #54....it went from 12mpg/#64 jets to 19 mpg/#54 jets (without Overdrive).....it'll still barks the tires going into 2nd, but won;\'t smoke em like with #64 jets(spark plugs were black with #64 jets....tan with #54 jets)

(I gets all my carb info from baddad's post when Holley info doesn't work....)

I did once install timing chain/gears a couple teeth off.....another time---had distributor installed way off....another time had carb floats set too low....it cause similar prob's that you have......you get the point...

double check everything......twice!

p.sssssss. now I gotta make sure it's pointed straight before I stomp it.....WAAAAAAAAAAaahahahahhaaaaa

 

[ford1386]

it was a carb base gasket it doesnt fall in its face and shut off and i now have 18 pounds of vacuum at idle and 14 degrees base timing, has only a 1 second hesitation now when i stomp the throttle from an idle so im thinking i need to to re-jet to smaller................................but gonna get exhaust bent up first so i can tune it with some backpressure

 

[baddad457]

has only a 1 second hesitation now when i stomp the throttle from an idle so im thinking i need to to re-jet to smaller.............

That's NOT a jetting problem. But go ahead and screw it up if that's what you think it is.

 

[1mean02hd]

My motor is basically a stock HO with a cam and I'm running WAY more timing than 14 degrees. Sure 14 degrees works on an EFI motor, but thats with the SPOUT connector unplugged. I think my base is about 17-18 and 34-36 degrees total timing.

 

[ford1386]

yea i just have the factory ho roller cam in it so that might make up for the difference in base timing, but i dont understand why it cant be jetted too big if its dumping too much fuel in when i smash the throttle it could be flooding out...........right, if not what could be causing the hesitation?

 

[baddad457]

How do you know it's dumping too much fuel ? A hesitation on opening the throttle is usually caused by a lean condition (99% of the time) That's an accellerator pump issue, this is what gives the engine more fuel as the throttle is opened until the main metering circuit and powervalve take up the slack. This fuel comes out of the squirters in the throttle bore. If you have fuel dumping out of the venturis as you open the throttle, then you've likely got a bad powervalve. The venturis are the round objects in the center of the throttle bores. Fuel is supposed to come out of them, but when everything's right, you won't see it, or you'll just see a fine mist below them.