carb stumble???

Old 07-22-2009, 06:03 PM
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whitey70ss
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Default carb stumble???

I recently changed the carb and intake on my sbc (350 .60 over .510 lift cam 292 duration,edelbrock rpm heads 10.5-1 comp. victor jr intake 750 dp) now when I feather the accelerator to take off (4 spd) it has a slight dead spot and it has a low speed miss?? But as soon as I get past that spot in the accelerator pedal it clears right up. I was planing on going to the track sat. for test and tune, and was wondering what I should be looking for to cure this problem, I already played with the accelerator pump adjustment and checked the floats, and low speed mixers. thanks in advance.
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Old 07-22-2009, 06:56 PM
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fla1976
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Have you read your plugs. Sounds like you need to rejet the carb.
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Old 07-22-2009, 07:16 PM
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whitey70ss
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no I have not read the plugs. I havent had it to the track yet or any place I could wind it up and shut it down . any other suggestions.
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Old 07-22-2009, 07:17 PM
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any idea what size jets I should be running with this combination?? I havent pulled the bowls off to see yet.
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Old 07-23-2009, 02:13 AM
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fla1976
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I'd pull the bowls and see what it has. Then, I'd jump the size a couple and retry it.
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Old 07-23-2009, 08:47 AM
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whitey70ss
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the fronts are 66 the rear is 72H does this sound right??
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Old 07-23-2009, 12:25 PM
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oldandtired
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Originally Posted by whitey70ss
the fronts are 66 the rear is 72H does this sound right??
What is the model number? That looks too lean for a 750.

4779 came with 75/76 and 8.5 PV
4779-1 came with 70/80 and 8.5 PV
4779-2 came with 70/80 and 6.5 PV
4779-3 came with 70/73 and 6.5 PV
4779-4 came with 70/80 and 6.5 PV
4779-5 came with 70/80 and 6.5 PV (same as the dash 4)
4779-6 came with 71/80 and 6.5 PV
84779 came with 70/73 and 6.5 PV

There are also some other OEM and marine part numbers.

Dave
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Old 07-23-2009, 03:11 PM
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whitey70ss
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I drove to the (local)speed shop today and talked to a guy that teaches a hi-po class at the local college. he told me I needed a 45 power valve I had a 65 and told me to jet it 72 in the fronts and 80 in the rears. I put it together and now its raining :cry: it does seem to have better throttle response now :roll: I guess I'll see sat.
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Old 07-23-2009, 05:14 PM
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OneBadGMC
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That's a pretty big jet spread. Rear cylinders are going to get more fuel than the front.

Last I heard (haven't run carbs in a long time), 4 jets were the biggest spread you want to do from front to rear.

Maybe someone with better carb knowledge can comment on that.
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Old 07-23-2009, 05:52 PM
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fla1976
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Default Jets

I always tried to run mine square. All four the same. I guess there is no real reason except that it was race only.
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