carb size opinions

[BRADVAN 10]

I'm going to be buying a new Edelbrock carb and I need help selecting the size. Here's some info:

 

I have a 69 coupe that started as a basket case. The 302 is not original to the car (block numbers E0AE D3c 3G13) making it from 1983. Car has a C4 automatic. Other things I know about the engine; standard heads, unknown cam (but seems pretty mild if any upgrade), Offenhauser 360 intake (was on the engine when I got it), HEI distributor, standard exhaust manifolds, 2 inch exhaust with H-pipe and "turbo" mufflers. PO gave me an old, dust coverd Edelbrock 600 that I never got to work right. I took the essentially new Edelbrock 600 off my 65 fastback (mildly built 302 with approximately 325 to 350 HP). The new Edelbrock make the 69 run great.

 

This 69 coupe will not be a race car, I'm looking for best daily driver-type performance, with gas milage a major consideration. I understand Edelbrocks a little and want to stay with Edelbrock. Can I put a 500cfm Edelbrock on this setup? What issues might I face? Opinions please. Thanks.

[MustangChuck 16]

The 500 CFM Edelbrock should work just fine. For your setup, 500 CFM is just about right.

 

M/C

[Lemon Owner 11]

If I understand correctly it currently has a 600 Edelbrock that is running properly? If so then I would leave it as is because the 500 will make little difference other than making your wallet lighter.

[BRADVAN 10]

I have to buy a new carb, either another 600 to put back on my 65 and leave the current 600 on the 69, or put the 600 back on the 65 and buy another (500?) for the 69. Just wondering what the "in theory" gas milage would be?

[MustangChuck 16]

"In theory", the 500 CFM will make slightly better gas mileage on the 69 than leaving the 600 CFM. I don't believe you will see any change in power.

 

M/C

[GypsyR 32]

There are any number of online "CFM calculators" that will tell you a 500 is more appropriate than a 600 for a mild to moderate 302. I agree. One of our drivers is a lightly modified 5.0 I put a 500 cfm Edelbrock on years ago. I don't plan on ever changing it unless I decide to make the car a full-on racer. At one time that car was my wife's daily driver and had a 2100 on it. The old carb had worn throttle shfts and instead of messing with it I threw on a stock intake and the 500. Wife was not at all thrilled when she saw it but begrudgingly drove it. She's one of those people who only puts $10 or so in the tank at a time. Within a week she had already noticed she had to put less gas in the car and decide she liked that carburetor just fine. I like it too but it doesn't seem to get very good mileage when I drive it. The rear tires seem to wear a bit more too. Can't imagine why.

[69302 10]

I have a 600 CFM Edelbrock on my 302 (bored over) with Performer heads, Crower Monarch 1500 Cam, Performer Air Gap intake, Long Tube headers, HEI / MSD. It runs great, but as these very knowledgeable guys state.. MPG isn't so great. I don't drive it daily, so I'm not concerned with that. If the 500 CFM works, go with it. From what I understand, most people over carburate when they start hot rodding. Good luck!

[jholmes217 65]

If you are experiencing some bog from a stop, it may be due to the intake manifold also. An Offy 360, even though it has a divider, is a single plane intake manifold. Single planes are usually for racing and high RPM and not low RPM generally from street driving. Replace that intake with a true dual plane intake, such as an Edelbrock Performer, Edelbrock Performer RPM, Weiand Action Plus, Weiand Stealth, or others, and your performace will be better for a street car stock to near stock build.

 

As others have already said, something in the 500 cfm range would probably also give better low in torque and gas milage.