why does it keep hesistating? help me!

[dbmx66]

okay, so.....

i had the truck outside a few times in the past week, trying to tune it up a bit.
its irritating the crap out of me. theres this hesitation.

when i sit there and get on pretty good just from idle, its hesitates for a second then i left off for not even a second and get back on it and it screams like it should.

when i sit there and spool the convertor up to 2500-3000 rpm then let off the brake and smash the gas it just falls on its face. again until i left off and get back on it.

the timing is set.

i have tried almost all the different accelerator pump cams and squirters. and still havent solved it.

the hesitation only got a lil better by changing out acc. pump cams and squirters.

what do i do!

is it too much carb? the engines a 350 bored and stroked to a 383, full forged eagle bottom end. 11.5 or so compression, high flow cnc ported heads with 2.05int and 1.60exh valves. with a .575 hydraulic cam, aluminum rockers, vic jr single plane intake with a holley 750 double pump on it.

please help me.

[team39763]

Mine acted like that when I went racing last November. It turned out to be trash in my carb and I also had water and other crap in my fuel cell.

[dbmx66]

Originally Posted by team39763

Mine acted like that when I went racing last November. It turned out to be trash in my carb and I also had water and other crap in my fuel cell.

mine has a fresh holley carb on it, i milled the choke horn off, i made sure every piece was clean and intact before putting it back together.

[vin63]

May I ask what size jets you have in the primary versus the secondary? Also, what is your fuel pressure at the bowls?

[dbmx66]

Originally Posted by vin63

May I ask what size jets you have in the primary versus the secondary? Also, what is your fuel pressure at the bowls?

jets are 70s and 72s, pressure is 5-6psi

[vin63]

Originally Posted by dbmx66

jets are 70s and 72s, pressure is 5-6psi

Is the 5-6 psi at idle? What type of regulator system do you use? Since it doesn't require a bunch of changes, I would try going down jet sizes on the primaries first to see if there is any change by increasing the spread between the primary and secondary jet sizes.

[68longhorn]

Have you tried different timing settings? I was chasing a simalar issue on a far less radical setup. Swore it was carb related, eventually started different timing settings and that fixed it

[dbmx66]

Originally Posted by 68longhorn

Have you tried different timing settings? I was chasing a simalar issue on a far less radical setup. Swore it was carb related, eventually started different timing settings and that fixed it

well the timing was set where we wanted it, i have and msd pro billet distributor in it, it came with different springs and what not, do you think the timing is coming in quick enough?

[1970C10truck]

I'm also curious to hear your timing specs. Did you actually verify tdc with your balancer and timing mark? Or check the balancer hasn't slipped?
Posted via Mobile Device

[dbmx66]

Originally Posted by 1970C10truck

I'm also curious to hear your timing specs. Did you actually verify tdc with your balancer and timing mark? Or check the balancer hasn't slipped?
Posted via Mobile Device

tdc is at the 0 degree mark on the balancer

[1970C10truck]

I run my timing at 12* initial 36* total and because I mostly drive on the street I have my vacuum advance hooked up. Vacuum advance is on full manifold and limited to 6*.

Your 8* sounds a little low in my opinion for the motor you listed.
Posted via Mobile Device

[dbmx66]

its set a 34 degrees at 2500 rpm

[Mykk]

My vote for ignition timing as well.

I have a vortec headed .040" over 350. 11:1 compression, XR276 roller cam. Mighty Demon 750. I had a bog/hesitation/ stumble off idle too.

Previously I had the distributor set up for 36 degrees max @ 3000rpm with a 24 degree busing, 12 degrees initial and a B26 vacuum advance on ported vacuum.

I just rebuilt/recurved my distributor, used a 21 degree bushing. Set the mechanical to 36 degrees max @ 3000rpm. I also used an adjustable vacuum advance maxed by 8" vacuum and running manifold vacuum. Cleared up all hesitation issues. The engine now fires up, idles and revs faster than it ever has in it's life.

It has 36 mechanical max, 15 cranking. 30 degrees at idle and between 38-51 degrees while low load high vacuum cruising.

YouTube - Vortec 357. New Engine Tuning

Also, if I may suggest. If your SBC is for street use, consider removing the Vic jr in favor of a RPM air-gap. Single planes are steetable, and they drive fine. But I've solved a hesitation in a built SBC by swapping those intakes. myself, I just went from a Super Vic copy single plane to a RPM air-gap copy with a four hole tappered 1" spacer and couldn't be happier with the engine response. Cheers ~Mykk

[1970C10truck]

I agree with the above minus the air gap manifold part.

[dbmx66]

didnt have anytime lately with school and work to get down and tinker with it. hopefully this weekend.

then engine isnt for street so i was planning on keeping the single plane.