302 carb help

[BAD BOB]

I got a 302 with heads cam headers and msd ign and i put a holley 750 on it and it seems to be loading up. Any help on if i should change jets or something?

[WWhittle]

what jets are in it and what is it doing?

[LXtasy]

Which heads and cam? Dp or vacuum secondaries? Transmission? rear gear?

750 could be to much carb IMO.

[05Saleen]

I got a 302 with heads cam headers and msd ign and i put a holley 750 on it and it seems to be loading up. Any help on if i should change jets or something?

What do you mean by loading up??? Bogging, backfireing. Check you plugs they will usually tell you what you need to do.

[BAD BOB]

its a new motor and all i have done is let it sit and run just to make sure everything it working good. At first it smelled a little rich so i tryed adjusting it which helped out but all the sudden at the end of the day i was messing with it and it started to choke out. It would crank right back up but seemed like the plugs were a little fouled so i would rev to clean them up then it sounded good then all the sudden do the same. I know it was a little rich a first but now it seems to be real rich.

[slowgreen99]

shoot that bitch. Itll help lean it out

[WWhittle]

its a new motor and all i have done is let it sit and run just to make sure everything it working good. At first it smelled a little rich so i tryed adjusting it which helped out but all the sudden at the end of the day i was messing with it and it started to choke out. It would crank right back up but seemed like the plugs were a little fouled so i would rev to clean them up then it sounded good then all the sudden do the same. I know it was a little rich a first but now it seems to be real rich.



you adjust the floats?

[BAD BOB]

all i adjusted was the fuel mixture screw. The carb was on a stock 302 and ran fine but was rich so the man got a 600 so i fugured with the mod it would work ok

[BAD BOB]

you adjust the floats?

looking in the sight glass it looks like the fuel may be a little low before it is too high

[05Saleen]

That is your idle mixture screw! Use a vacuum guage to set. Set your float level to the bottom of the site glass and use a vac guage to set your idle adj. adj till you have the highest vacuum reading and run for a while and ck. your plugs. If they are wet then you need to go to smaller jets...

[WWhittle]

I dont see these getting diagnosed over the internet.

[BAD BOB]

right and thats all its been doing and all the sudden it started running rich again i guess. I going to maybe try some new plugs and see if will help out

[05Saleen]

See the post 3 above. Slow typing.....

[05Saleen]

If you can catch me on the weekend probably on a sunday. Give me a call and I can probably help you diagnose it or fix it.

[BAD BOB]

That is your idle mixture screw! Use a vacuum guage to set. Set your float level to the bottom of the site glass and use a vac guage to set your idle adj. adj till you have the highest vacuum reading and run for a while and ck. your plugs. If they are wet then you need to go to smaller jets...

thanks that will hopefully get me somewhere

[05Saleen]

Read previous post.

[Pesce Nero]

where is timing at?, there is more than one A/F screw, i would assume you ment the curb idle screw that you were messing with. if the carb has been sitting, i would kit it.

jets have no effect on what a carb does at idle nor does a power valve unless its blown out then you can get fuel dripping right into the plenum causing a rich mixture. if throttle plates are open to far, you will also have a problem with a carb pulling fuel from the transfer circuit.

how big a cam in the engine?

[BAD BOB]

when changing jets how much should you change a one time?

[BAD BOB]

where is timing at?, there is more than one A/F screw, i would assume you ment the curb idle screw that you were messing with. if the carb has been sitting, i would kit it.

jets have no effect on what a carb does at idle nor does a power valve unless its blown out then you can get fuel dripping right into the plenum causing a rich mixture. if throttle plates are open to far, you will also have a problem with a carb pulling fuel from the transfer circuit.

how big a cam in the engine?

its like 520 or so. I dont know exactly

[05Saleen]

I don't think you will be able to diagnoss this over the computer!

[Pesce Nero]

initial timing needs to be 16 or higher. i would take the carb off, turn it upside down and set your throttle blades, alot of times the rear throttle blade are slam shut. set your throttle blades so that all you see of the transfer slot is a small square. small screw adjusts the rear blades. put it on the car. depending on how many A/F screws you have, turn them all the way in, and unscrew them 1 1/2 turns. start car. set A/F screws to highest vacum reading. if idle is to low, bump up timing. if you cant get idle rpm high enough, it needs more air. i would drill tiny holes in throttle blades, tiny!

do not tuch curb idle screw after you set throttle blades. another thing is, new gas sucks, reg pump gas doesnt have a set vapor temp compared to race fuel. race fuel will vaporize at say 100 degrees where pump gas might not till 400 degrees. engine needs to be good and warm before any real tuning could begin

[BAD BOB]

Damn EFI is easier

[Pesce Nero]

its not hard, i would have done all that in 1 minute before i ever bolted the carb on in the first place.

also, there could just be junk in the carb so it may need a kit

[05Saleen]

Not once you get used to it......I don't know shit about efi!
Other that it costs you an ass load of money to buy a hand held tuner and then take it to someone to tune it and that isn't cheap!

[BAD BOB]

got the rich idle issue figured out. Drove down the road for the first time and at around 2500-3000rpm i guess(dont have a tach yet) and it seems to be surging i guess a little rich? It has 65 jets in the front. It also does this when i stall it up to try to launch it. I have a wideband wondering if i should hook it up and adjust fuel that way? Any help here?

[LXtasy]

Do you have an adjustable fuel pressure regulator? What is the fuel pressure set to? I would set it around 5.5 psi and go from there.

[Pesce Nero]

surging usually means a lean condition. yes, if you have a wideband, hook it up

[BAD BOB]

Do you have an adjustable fuel pressure regulator? What is the fuel pressure set to? I would set it around 5.5 psi and go from there.

fuel pressure is around 4.5 to 5 and yes a adjustable regulator

[BAD BOB]

surging usually means a lean condition. yes, if you have a wideband, hook it up

ill hook it up tomorrow and see what it shows. Should i go bigger jets or fuel pressure?

[Jeff]

I would go up on the jets for sure ! My car never even ran right til I got over 75's on the carb with the 650 . It did all the things you are talking about surging and idle issues all the good stuff . When we threw Darryls AED 950 on the car with 81 jets all the way around it ran damn good !

[BAD BOB]

ok wideband shows when its wot its a little rich but can live with it right now but with throttle open a little like cruising around 2-3 grand it leans out to about 16.0-17.0. Any help??

[Pesce Nero]

go up primary jet and down on secondary jet

fixed

[BAD BOB]

going dowm on the primary jets wouldnt that make it leaner?

[Pesce Nero]

my bad, YES!! do the oppisite of what i said:hysterical:

fixed now

[BAD BOB]

ok So as everyone can tell i dont know much about carbs but at low rpms(cruising) it uses the primaries and under heavy load it uses both??

[Robert Holton]

i got idea pull your carburetor off, turn it over and throw it into the trash can, call 1-800-345-4545 and order a new one, listening to everybody and there brother and sister will just end u up in left feild, just stick with one guy, it may take time but eventually will get you in the right direction

[slowgreen99]

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