302 with 750 holley and 4" duel exhaust?? too much???

[kingstang]

I recently bought a mustang that the previous owner said was a 302, but i looked up the carb and it's a 750 cfm holley and the exhaust are 4" flowmasters.... it has headers and a cam, it sounds pretty built, but im curious what you guys think?

Is it normal to have these mods with a built 302??

[SunlitGold68]

Ridiculous actually, 480 CFM would be about right. Too many people think bigger is better, it is just a myth.

[kingstang]

ok, the car runs great, i just dont know a whole lot about it. Should I get a smaller carb? What about the 4" duel exhaust?? everything looks sort of new...

[Z06killinsbf]

How can you assume that a 480 is the answer? You know nothing about the motor!!

What other specs are there that you know? Heads, cam, compression? I used a 780 on my 289 for a bit while I was rebuilding the 600, and it ran exactly the same. It all depends what the engine needs. Now the 4" exhaust.... Did they think it was a diesel? That's a bit ridiculous, 3" max.

[kingstang]

all the previous owner told me was everything that could be done was done except aluminum heads. Every shop ive took it too, says its sounds great, why would I want to change something...... I'm still trying to figure out what year 302 the engine is and hopefully I can go from there....

I've just been searching on the forums and been reading a lot, so now im paranoid lol

[jdub]

If it has stock heads then it's way too mild for a 750 and the 4" exhaust is absurd (but probably not hurting anything). "Everything but aluminum heads" usually tells me it's a guy who built his engine backwards. A good set of heads is where you start, not where you stop.

If it has some heavily, heavily worked 351w/GT40 heads or iron Dart/World/RHS heads, 13:1 compression and revs to 8000rpms then I'll eat my hat on the 750 carb.

Still, I think that going and immediately swapping out the carb for a 480 and putting a 2" exhaust on there isn't the best advice either.

[kingstang]

ok thanks for all the info!! ill keep researching!

[buckeyedemon]

i think there is a typo in your exhaust size.

4" is probably bigger than your collectors.

[TommyK]

Originally Posted by buckeyedemon

i think there is a typo in your exhaust size.

4" is probably bigger than your collectors.

I agree.

If it is 4" I would like to see a picture of it.

[my66gt]

I doubt that your system is a 4" system. 4" inlets on the mufflers maybe. Unless your having drivability issues I wouldn't worry about the 750cfm carb. Plenty of folks have used them on 289's without issue and without aluminum heads. Some have had issues or heard of others with issues and will tell you what your doing will never work.

Your carb likely has vacuum secondaries anyway so for general driving your only using half the carb until the secs open. When they open is tunable. It sounds like your happy with the way it runs so don't worry about it there are plenty of other places to spend money on these cars.

[frdnut]

I ran a 750 on my "built" 302 for years..Worked great.Unless you are having problems I would leave it alone..Like the saying goes if it ain't broke don't fix it.

[66resto]

I thought the saying was "If it ain't broke, its only because I haven't gotten around to fixing it yet"?

If sounds good and runs well leave it alone...for now. I'm sure you will have the opportunity to fix it down the road.

Maybe the 4" dual exhaust is two 2" pipes? Try to imagine an import fart can running the entire length of the exhaust system for it to be a 4" diameter pipe. HUGE.

[6t9mach1]

Originally Posted by SunlitGold68

Ridiculous actually, 480 CFM would be about right. Too many people think bigger is better, it is just a myth.

What is ridiculous is suggesting a carb size without knowing anything about the engine. There are many 302's out there running 750's that run very, very well. Just because a carb cfm calculator says an engine only needs a certain cfm, it does not mean that it does not benefit from the reduced restriction. I guess that my 850 Mighty Demon that flows over 900 cfm is way too big

[tom991]

Originally Posted by TommyK

I agree.

If it is 4" I would like to see a picture of it.

Might be just 4" extensions on the end of a smaller pipes.

[Klutch]

I agree there are many variables for proper carb size. Yes, lots of people over-carb. But lots of people also run their carbs too rich. If you dial in a large carburetor correctly, it will run great on a small block.

I like to point out that the 69 and 70 Boss 302 Mustangs came from the factory with Holley 780's bolted on. One could argue that carburetor was too big. But I've never heard a Boss 302 driver complain about too much carb.