Ive decided to rebuild the 2 barrel because i have never rebuilt a carb before and i figure its only $20 for the rebuild kit so why not learn now, If i rebuild it and i do it wrong or it still doesnt work that good ill go ahead and pull it back off and put the 4 barrel on.
the summit racing 600 cfm vac secondary electric choke would be a better choice on the 302 run the 2bbl till you can afford an upgrade sell the 750 to buy your new carb
I wish i had the 600 cfm but i got the intake and carb kit as a christmas present from my father and he thinks bigger is better but in this case its not.
Of course the 600 would be better sized for a smaller and milder motor.. but the difference in primary venturi size is negligible when you're running a dual plane which separates both banks of cylinders and helps booster signal immensely. This is why many street/strip guys are able to run very large cam's and carb's on moderately sized street engines without stalling at the lights. And I see annular discharge style 950's and 1050's on 300 - 350 ci engines all the time. Much more sensitive booster design.. but it certainly shows how a dual-plane tames a fairly radical setup on the street. The other thing to keep in mind is that the 2 bbl manifold is putrid trash from an airflow standpoint when compared to the 4bbl.. so you'll gain with just the manifold swap alone even if you ran the same 2bbl carb with an adapter. WELLLL.. worth the swap, IMO. PS. Besides the dozens upon dozens of combo's that I've seen, run up against, and friends that have done it.. I've run 750VS setups on 6 different smaller ci motors(283, 289, 3 x 302, 327) through the years and all you need do is tune the secondaries to make them responsive. Plus.. you'll have plenty of room to grow and a cam, stall converter, and gear makes them sing sweet music as they can come up on the boosters quicker. Expect to lose about 15 ft/lbs at or below around 2,500-3,000 rpm over the 600. Not earth shattering losses to say the least.
Probably. Simply because that carb is likely sized for a larger CI engine to begin with. Depending on the OP's induction, cam/valvetrain, and exhaust package.. he'll likely just end up running a slightly larger jet than normal on the primaries.. and stiffer spring on the back barrels because he won't use much of them anyways. That's the beauty of a Holley in the first place. Nearly infinite adjustability.
I put the 4 barrel intake and carb on and i am going to tune the jets down for economy for the tome being untill i can save up enough to buy a new carb, another thing is the 4 barrel has an electric choke and the 2 barrel did not, were would i go about wiring in the choke wire thanks.
With weak venturi action(air flow) vs what the carb was designed for you'll likely need to increase jet size plus increase pump shot so it will run decent... If you lean it out with smaller jets, it's likely going to be a pig on the street... In my book throttle response is paramount, want no part of a boggy, hesitating carb...
X 2, you may need to increase jet size, not decrease it. As I recall, I did nothing to the jets on that 3310 750 on my roller 302. It was fine as is. A bigger carb does not equal lower fuel economy, this is a carburetor, not fuel injection. The force that draws the fuel out of the bowls and into the airstream is pressure differential (vacuum created by the air flow thru the narrowest part of the throttle bore and thru the venturis). You will get a slightly lower "pull" on the fuel with the larger sized carb. The jets in that carb are likely a little on the large side as it's intended to be a performance carb, not an economy carb, so those jets may be fine as is. Running it awhile then pulling the spark plugs and reading them will tell you if it's OK. That choke ? That's the first thing I remove from a carb. You're likely in a warm climate in Kalifornia, you likely don't need a choke.
Ok i wont do anything to the jets untill i run the engine for a little while and i live in the bay area of california, it gets up to high 70s mid 80s here.
Sure carb's are very forgiving and it'll still run alright( I still regularly see cars with burnt pistons, popped head gaskets and missing on 2 of 8 cylinders(ignition and/or FI related issues) start right up on the first spin).. but I'll send you some free jets and other Holley tuning parts(secondary springs or whatever you need) if you ultimately figure out that a 750 cfm carb is already tailored to a 302 ci engine. Also.. although I was specifically speaking about jetting down on the secondaries.. you very well may end up doing the same on the primaries too because unless this motor has a really high compression ratio and/or well above stock CI size?.. it was likely never intended to be used for a small 302 CI combo when it was set up or last calibrated by the previous owner. The almost unilateral fact is that nearly all larger sized carb's (spreadbores would be an exception) on smaller motors(300'ish CID) WILL require smaller jets(front and/or rear) to keep A/F ratios in check with less air volume flowing through them. It's all proportionately tailored to each application and less air flow almost always requires less fuel(the main jet controls this ratio for the most part and this ain;t computer controlled FI that gets adjusted on the fly). Otherwise.. everyone running bigger CI motors would be jetting down and smaller CI motors would be jetting up to keep things proportionate to the specific applications "venturi pull". The reality of this design is that you usually just jet to a happy overall fuel curve medium with jet size.. and then get into emulsion tube/orifice size tuning to fine tune homogenization characteristics based on the venturi air speeds. But that's a whole other ballgame there. Another way to get my point across is this. Never seen a smaller street style 300 CID engine NEED more than a 76 main jet on the front side except where the power valve has been plugged and/or someone has moved to square jetting. Just figure around +6 sizes on the secondaries from where you end up on the primary sizing and you'll be damned close. I highly doubt you'll need much more than about a 70-72 main jet and about a 76 rear jet. I also highly doubt you'll need much spring in the rear either because that engine/carb size will gain most of the airflow requirement from the primaries alone. Good luck with it all.
Ok i slapped the intake and carb on their a couple days ago and today i finally started it and it runs great at idle bit when i put it into gear it will run for a little bit untill the choke closes then it dies and wont start again, so i would like to add the choke wire, i no it needs a 12 volts source but weres the best place thanks.
Other than the red/green wire on the solenoid AFAIK there is no ignition switched 12v under the hood... Problem using that wire is it also feeds to coil, could use a relay connect it's coil to the red/green and relay contact from battery side of solenoid...
If it starts and idles great, wire the choke mechaninsm open. Or remove the whole mess. You do not need it.
Alright my step dad came over and helped me out with the carb, i stalled the choke wire and adjusted the carb, but the driver side was popping alot so he poored some water down the carb and it semi went away but its still their so now i will poor some trans fluid in it and see what happens.
