Hey guys..its been a while. i havnet had a computer for a long time but im back now. well here is whats going on. i just got a holly 4 brl carb for my 302 mav. i got the adapter for the 2 brl intake but im having a gas leak around the gasket no matter how tight i get it. is there a good adapter that you guys reccomend? or should i just go ahead and get the whole new manifold? also there is ALOT of black smoke coming from the exuast now. it happend after i put the carb on. i was sure to be clean and kept dirt from the intake manifold. well its good to be back and complain about my car problems again! lol thanx guys-james
Get a good intake! Go ahead and get a good dual plane intake. The black smoke is from running too rich (too much fuel). How big is the carb?
carb I got the holly four barrel. do you know were to get a good intake that will fit on the 73 302? and you think the smoke will stop if i turn the fuel in the carb huh? another problem i have is that when i get up to 70 or 80 (i know, you dont need to go that fast) my car will start to jolt back and forth then slow down. i just had my tranny rebuilt and preped so that is why im replacing the carb. think im on the right track?
its a........ it's a 750 cfm carb. And it's brand new, and set to the factory settings. So the engine is at it's full rpms when I start it.
750 cfm sounds like a little much to me. I have a 302 and I run a 650cfm and sometimes I have problems keeping it in tune. These carbs are funny mysterious things. Sounds to me like you have a case of too small of an engine and too big off a carb. Just my $.02. Jeri
It sounds like you are running a little to much in the carb. department.Ive got a modified 289 with a 750 holley and im going to a smaller carb this winter.Id say a 600 or 650 c.f.m. at most would work great with a dual plane intake on your 302.
First off at best, you would only see a very small improvement in engine power thus waisting the investment in the carb and adapter. The 750 is way to much for a stock street engine. You need a dual plane intake of at least a stock iron 4 barrel manifold and no more that a 600 cfm vacuum secondary carb, set up properly for secondary tip in. Yes the engine can run on a larger carb but will not be at it's best operation. Your stock engine can only use about 495 cfm +/- at it's wide open throttle point so it will not flow enough air to even open the secondary bores. If the carb is a mechanical secondary type, the engine will go flat or bog from to much opening area.
No such thing as too big of a carb. When the engine's running 2000 rpm and the throttles are wide open, it's only "using" about 177 cfm. Therefore a 350 cfm 2 barrell would be too big. I do agree though that a smaller 600 cfm would have been a better choice for street driving, but the beauty of holleys is that you can tune it for ANYTHING! For instance, everyone says a 1050 is way too big for a 302. Well, I ran a 1050 dominator on my stock mustang's motor for over a month. Got a best of 22 mpg and great driveabilty. Took a helluva lot of tuning though! Only reason I did it was because it was the only carb I had at the time. If it was me, I'd save my pennies and get a good aftermarket dual-plane intake manifold that will accept that brand new holley carb easily. Then next thing you know, you'll be buying new rear tires
. This is a classic thing. You have a two barrel intake manifold and you're pumping fuel in with a monstrous four barrel carburetor. I don't care how much you lean out that mixture, you'll be getting too much fuel. That's why it's smoking. 750 CFM's is way too much for a stock engine. You'd only need that with a very modified street/strip motor that had 400+ Horsepower. Putting a four barrel carb on a two barrel intake is never a good idea. The name to the power game is component matching. All of you parts have to work together to get good performance. If you just throw random parts together, you'll get crap performance back out of it. What you're doing with that carb would be like me putting dual 4" exhaust pipes on my 200 straight six maverick. It just would't make any sense and would not help performance. Sorry if I'm sounding mean here because that's not how I intended it to sound, I just want to make sure you get the jist that it's not a good idea .
As far as that adapter leaking, they are aluminum and tend to warp with too much torqueing of the carb nuts. When this happens, the gasket won't set right. Get another, shouldn't be too hard to find. I also agree, the 750 is way too big.
