390 carb recomendations

[cobra460jet 10]

Need help in determining a carb for my 390 powered 69 mustang. Was thinking along the lines of a Holley 750 double pumper. I like the double pumps for there instant response. Should I go with the 4-corner idiling? Should I go with vacumn or mechanical? What about the choke? Electric or mechanical? I live in nc so the weather is relatively mild. The 390 will have headers, mild cam 512 lift 280 dur, aluminum intake F-427, and a 325 gear in the rear. Not looking for a drag car. Just a fun street car with a little bite. Have heard the street avenger holleys are real good performers for the street... Any suggestions?

[69R-CODE 25]

Let me know what you end up going with. I am looking for the same type carb for my 428.

[jholmes217 65]

What kind of tranny do you have? For stick shifts, I prefer double pumbers, and for automatics, I prefer vacuum secondaries. I'd go with electric choke myself. I was in the 82nd ABN Division at Fort Bragg, NC, and I still remember scraping frost of my windows on my 67 coupe I had at the time as a daily driver in the 80's. For a mild 390 you may be better off with a 650 or 700 cfm carb. The 428 would probably be OK with a 700 or 750 depending on how hot your build is.

As far as 4 corner idle and other extra features, go with what your wallet and tuning abilities are capable of.

I have one of the Summit Racing 600 cfm carbs on my 302 car, and love it. They also make 750 cfm vacumm secondary and mechanical secondary models.

I have a originally 735 CFM carb on my 428 Cobra Jet, but I have rebuilt a Holley 750 double pumber to try on it, but that car is a 4 speed with headers, Blue Thunder intake, Petronix ignition, and I believe a prevoius owner put a hotter cam in it since it has a lope to the idle.

Hopes this helps. I don't like to go overboard on carbs for the street. My experience on a "over carbed" car is poor thottle response, black smoke out the exhaust, and carbon fouled plugs.

[SM69Mach 68]

What kind of tranny do you have? For stick shifts, I prefer double pumbers, and for automatics, I prefer vacuum secondaries. I'd go with electric choke myself. I was in the 82nd ABN Division at Fort Bragg, NC, and I still remember scraping frost of my windows on my 67 coupe I had at the time as a daily driver in the 80's. For a mild 390 you may be better off with a 650 or 700 cfm carb. The 428 would probably be OK with a 700 or 750 depending on how hot your build is.

As far as 4 corner idle and other extra features, go with what your wallet and tuning abilities are capable of.

I have one of the Summit Racing 600 cfm carbs on my 302 car, and love it. They also make 750 cfm vacumm secondary and mechanical secondary models.

I have a originally 735 CFM carb on my 428 Cobra Jet, but I have rebuilt a Holley 750 double pumber to try on it, but that car is a 4 speed with headers, Blue Thunder intake, Petronix ignition, and I believe a prevoius owner put a hotter cam in it since it has a lope to the idle.

Hopes this helps. I don't like to go overboard on carbs for the street. My experience on a "over carbed" car is poor thottle response, black smoke out the exhaust, and carbon fouled plugs.

 

 

This +1.

 

I had a 750 on my fairly stock 390 and felt it was a little too big. I would have been much happier with a bit better throttle respsone and and sacrificed a little power to get it. Just dont go too big.

[Jimjific 23]

I had a 67 fastback with a 390 4spd. It had a cobra jet intake and heads. Pop up pistons to bring the compression back up due to the head combustion chamber size increase of the CJ heads. I put on Hooker headers and and 750 vac secondary w/manual choke. Flat out the fastest car I've ever owned. I beat my buddy in his 71 454 Chevelle. Man I loved that! The best part of that set up was how it pulled through the whole range of RPM. The primaries pulled to about 3000 and then you could feel the secondaries open and it pulled straight to 6000. I'm hoping to recreate something like it with a 351W stroked to 408 or 428 in the future.

 

As for chokes? I like manual since it is the simplest.

 

Jim

[jholmes217 65]

I had a 67 fastback with a 390 4spd. It had a cobra jet intake and heads. Pop up pistons to bring the compression back up due to the head combustion chamber size increase of the CJ heads. I put on Hooker headers and and 750 vac secondary w/manual choke. Flat out the fastest car I've ever owned. I beat my buddy in his 71 454 Chevelle. Man I loved that! The best part of that set up was how it pulled through the whole range of RPM. The primaries pulled to about 3000 and then you could feel the secondaries open and it pulled straight to 6000. I'm hoping to recreate something like it with a 351W stroked to 408 or 428 in the future.

 

As for chokes? I like manual since it is the simplest.

 

Jim

 

What rear end gear did you have in this beast Jim?

[Jimjific 23]

Jeff,

 

I forgot to mention that. It had just a 3.00 gear in it. When racing my buddy, he was probably a little better off the line since his ratio was higher, but I had the weight advantage and he most likely suffered from needing to shift sooner than me. I thought about putting a 3.25 of 3.50 in it but I never did since it was so much fun the way it was. Out on the freeways was awesome too. I could go from 70 to 80 in what seemed like a slight pop of the throttle. So I'm an advocate for the 3.00 gear I guess.

 

That car was a stock 390 but not a GT. The guy I bought it from told me it was a 428 CJ. Which he and I knew didn't come that year but he was basing it on the head, intake and block casting #'s. We figured the person kid who restored the car put it in (Side story here. The kid who restored it tragically died along with his sister in Hawaii in a helicopter ride. Their parents were in a different helicopter). Since the Heads and Intake did have CJ #'s, I had no reason to think it wasn't. But then I got the heads redone and noticed the pop up pistons and thought that was odd. The pistons were stamped STD so I mic'd the bores and they were standard 390 bore. This was my first lesson that Ford does a horrible job in block casting since without pulling the heads, there was no way to tell what bore that engine was.

 

I'm thinking of building this same motor or maybe stroking a 390 to 410 for the GT 390 XR7 Cougar I have sitting in the barn.

 

Jim

[jholmes217 65]

Cool story Jim! I had two cars that were dogs off the line due to stock rear ends, but the 66 coupe with a hot 289 and 4 speed and 4:10 posi would shoot out of the hole. I sucked on the highway though tacking 4500 RPM at 55 mph in 4th gear.

[Cobramach1 10]

Jholmes217 hit the nail on the head. 650 is plenty for your 390 even if it's a little hotter than mild. It is really easy to go too large when it comes to carburetors especially for cruising around. You'll be happier with the improved throttle response of the 650 in your application.

[70Mach03 12]

Need help in determining a carb for my 390 powered 69 mustang. Was thinking along the lines of a Holley 750 double pumper. I like the double pumps for there instant response. Should I go with the 4-corner idiling? Should I go with vacumn or mechanical? What about the choke? Electric or mechanical? I live in nc so the weather is relatively mild. The 390 will have headers, mild cam 512 lift 280 dur, aluminum intake F-427, and a 325 gear in the rear. Not looking for a drag car. Just a fun street car with a little bite. Have heard the street avenger holleys are real good performers for the street... Any suggestions?

 

I have a 670 CFM Street Avenger on my 351C and it's a good carb, easy to work on, and adjust. Mine was a little lean out of the box and I upsized the jets a few sizes. With a 3.00 rear I'd stick with vacuum secondaries. Is your's a manual or auto? With a stick, you may could actually go with the 770 CFM Street Avenger.

[Ray 10]

I have a 69 s code 390 with c6 auto, 3.00 to 1 rear, edelbrock streetmaster manifold and holley 750 with vac secondaries and electric choke. The rest of the engine/drivetrain is stock and this combination works fine except for a small stumble off idle, the stumble was not there when I was using the original cast iron manifold so I am sure this is a problem caused by the much larger plenum in the manifold. I have no doubt the stumble can be tuned out by playing around with the power valve or accelerator pump cam. I am running a 1" aluminium spacer on top of the manifold plenum but I get a bit of heat soak/hard to start after a long drive but this also happened on the old manifold, I am going to fit a 1" phenolic spacer and see if this helps, anyway good luck with whatever combo you try.