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Old 06-09-2018, 12:36 PM   #1
uncle buck
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Default 8BA or 8CM and Holley 390 cfm vs other combinations

After reading the recent loadamatic distributor threads concerning the Holley 390 cfm and the other thread on the 2gc carb info I would like some input on experience with the Holley 390 and various other distributor options. I have a 52 Mercury flathead with EAC on the heads that I plan on installing in a 36. I have the single and dual carb intakes , all 3 bolt , and a Edelbrock 4 barrel intake too. I am leaning towards the 4 barrel with a 390 cfm Holley. If I do this I would use an aftermarket distributor such as a Mallory or Chevrolet conversion from Bubba. What about vacuum vs mechanical advance ? What are the thoughts on doing this as opposed to the 94 , 97 , or 2gc ? Thanks in advance for any input offered. Also , I do have tube and Fenton headers and aluminum heads available to use if needed.
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Old 06-09-2018, 01:17 PM   #2
flatjack9
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Default Re: 8BA or 8CM and Holley 390 cfm vs other combinations

Go with the Chev conversion with mechanical and vacuum advance. Multiple carbs have the cool factor, but you can't beat the reliability and simplicity of the 4 barrel. I've been running mine for 20 plus years without touching it.
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Old 06-09-2018, 02:32 PM   #3
19Fordy
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Default Re: 8BA or 8CM and Holley 390 cfm vs other combinations

I have a 239 8BA with a Holley 4 bbl and it runs fine. Double check and make sure your Edelbrock intake has the generator mount in the center so the fan pulley lines up with the crank. The OFFY intake is 1 7/8 in. offset. Not good. I am running a Mallory UniLite mechanical advance distributor. Folks say that Chevy dist. is a great conversion so you might want to try that. You have to install the 390 carb backwards so the throttle linkage will work. Also using FENTON headers. Heads are early style with 1 inch spacer.
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Old 06-09-2018, 04:29 PM   #4
flatjack9
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Default Re: 8BA or 8CM and Holley 390 cfm vs other combinations

What's the problem with the offset?
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Old 06-09-2018, 05:56 PM   #5
51 MERC-CT
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Default Re: 8BA or 8CM and Holley 390 cfm vs other combinations

Quote:
Originally Posted by 19Fordy View Post
The OFFY intake is 1 7/8 in. offset. Not good..
Quote:
Originally Posted by flatjack9 View Post
What's the problem with the offset?
There really isn't any problem with the offset, just be aware that it is offset
7/8" (.875") to the drivers side, not "1 7/8 in." Just check for any interference.
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Old 06-09-2018, 07:30 PM   #6
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Default Re: 8BA or 8CM and Holley 390 cfm vs other combinations

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I think you would be quite happy w/the Holley 4v setup . - F F
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Old 06-09-2018, 10:23 PM   #7
uncle buck
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Default Re: 8BA or 8CM and Holley 390 cfm vs other combinations

Thanks for the input everyone. I do have another question. While I have no experience with the 2GC 4 bolt carb nor do I have one, would finding one of those and matching intake be a better choice than the 390 Holley ? Thanks again
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Old 06-09-2018, 10:41 PM   #8
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Default Re: 8BA or 8CM and Holley 390 cfm vs other combinations

I go with Flatjack, the 390 is a great carb and coupled with the Chevy dist will give good performance as well as economy/ Had one on a 296 with L-100 and it got 20 mpg in cruise. Unfortunately the C4 wasn't so lucky in town
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Old 06-10-2018, 04:01 AM   #9
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Default Re: 8BA or 8CM and Holley 390 cfm vs other combinations

Quote:
Originally Posted by uncle buck View Post
Thanks for the input everyone. I do have another question. While I have no experience with the 2GC 4 bolt carb nor do I have one, would finding one of those and matching intake be a better choice than the 390 Holley ? Thanks again
I have run both setups. I had a 390 Holley on a 276 ci Mercury in my old '36 3 window with an MSD distributor. It ran fine, but had a tendency to run hot in traffic. Looking back with what I know now, I think the MSD had too much advance built in (the dreaded "SBC curve"). I don't remember having any problems with the carburetor except setting up the throttle linkage initially; I had to run a cable that had a 180 degree turn in it. Once I got it set up it was OK, but I was never 100% happy with it. I was always a little disappointed in how the car performed. It ran fine, but didn't have the "oomph" i had expected.

I have a 2GC on a bored out aluminum Canadian Merc manifold on the 255 ci '51 Mercury I have in my current '51 Ford club coupe. As I have said before, mount it backwards, and everything falls right into place except for the manual choke. However, the automatic choke ports on the Mercury manifold hooks up to the choke mechanism on the carburetor just by shortening the choke stove tube a little. I don't usually like automatic chokes in old cars, but once I had this one dialed in, it was "set it and forget it". I am completely satisfied with the performance of this setup. Its trouble free and really steps out compared to the tired 239 8BA it replaced. While I am quite happy with this combination, to be frank, my performance expectations for this car were a bit lower than I had for the '36.

Overall, for a relatively heavy car with a hood, I would go with the 2G hands down because of fitment and cost. I am also currently building a "Hot Rod" (open wheels and engine compartment). Of course, that will get dual carbs on an aftermarket manifold; a four barrel just wouldn't be right on that type of car. As a side note, I am very interested in flathead 4 BBL setups. I have Fenton, Sharp, and Edmunds four barrel manifolds and have rebuilt a Carter WCFB and a couple of Rochester 4G's. At the present time, I am experimenting with running a Quadrajet (yes, that's right; one of those 750 cfm monsters) on a flathead. With their small primaries and "on demand" secondaries, they would seem to be the ideal 4 BBL carb for these cars. Plus, they are easy to find and cheap to buy. Just try to find and/or buy an older square bore carburetor core these days; they are getting very scarce.

Last edited by tubman; 06-10-2018 at 04:07 AM.
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Old 06-10-2018, 08:20 AM   #10
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Default Re: 8BA or 8CM and Holley 390 cfm vs other combinations

When switching to a different intake system. One of the first thing you have to check is the AF ratio, especially with the Holley, they come rich out of the box. For an interesting read on carburetors, try JWL's book "Flathead facts'" He covers most of these swaps.
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Old 06-10-2018, 10:09 AM   #11
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Default Re: 8BA or 8CM and Holley 390 cfm vs other combinations

Quote:
Originally Posted by 51 MERC-CT View Post
There really isn't any problem with the offset, just be aware that it is offset
7/8" (.875") to the drivers side, not "1 7/8 in." Just check for any interference.
Thanks for the correction. I added the 1 by mistake.
I do recall seeing some postings about ways to correct the offset by modifying
or making a new fan carrier bracket.

Last edited by 19Fordy; 06-10-2018 at 10:16 AM.
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Old 06-10-2018, 09:10 PM   #12
flatjack9
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Default Re: 8BA or 8CM and Holley 390 cfm vs other combinations

Again, why would you worry about this offset or spend the time to change it?
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Old 06-11-2018, 12:17 AM   #13
51 MERC-CT
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Default Re: 8BA or 8CM and Holley 390 cfm vs other combinations

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Originally Posted by flatjack9 View Post
Again, why would you worry about this offset or spend the time to change it?
In my case I have a fan shroud.
After installing the manifold it was found that the fan hit the shroud.
Therefore a new fan mount was fabricated to bring it back to center.
The alternator is still off set.

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Old 06-11-2018, 07:54 AM   #14
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Default Re: 8BA or 8CM and Holley 390 cfm vs other combinations

Yep, that can be a problem.
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Old 06-11-2018, 08:37 AM   #15
19Fordy
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Default Re: 8BA or 8CM and Holley 390 cfm vs other combinations

51Merc-CT fan carrier bracket with built in offset is a
great solution. Well done. You can also make a modification
where the pulley can swivel to compensate for the offset and
also be adjustable up and down for fan shroud centering..
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Last edited by 19Fordy; 06-11-2018 at 09:03 AM.
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Old 06-11-2018, 09:24 AM   #16
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Default Re: 8BA or 8CM and Holley 390 cfm vs other combinations

Another vote for the 390 Holley , pretty foolproof......
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Old 06-11-2018, 01:35 PM   #17
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Default Re: 8BA or 8CM and Holley 390 cfm vs other combinations

I have a holley 390 with a davis unified distributor and it runs great. holley 390 can be hard to find and $ if you do find one..
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Old 06-11-2018, 03:12 PM   #18
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Default Re: 8BA or 8CM and Holley 390 cfm vs other combinations

If I can ask, has anyone had problems with the Holley 390 4 barrel ? I've always used Holley's on my cars (1960's C****'S and Ford's) over the years with excellent results. Recently, I put a new Holley 390 cfm 4 barrel on my slightly modified flathead (Edelbrock heads, offenhauser intake maniflold, with fenton headers). The car is a 40 Coupe. The previous owner did say it also has a Mercury crankshaft. The problem I am having is a stumble under light acceleration. So far, I have had the crab distributor rebuilt by a reputable Early V8 Member. The distributor was correctly setup on his distributor machine. The dwell, total advance, and timing is all within spec. After installing the rebuilt distributor, the car still stumbled under load. The only improvement was, the engine responded better when revving in neutral and it also idled better. Moving on, I checked the carburetor float level, checked the accelerator pump adjustment, adjusted the idle mixture (using a vacuum gauge). This yielded no improvement. Also, checked for vacuum leaks and found none.
I then increased the nozzle size, from.025 to a .031 nozzle. Some improvement, however still stumbles when accelerating. I also moved the stock accelerator Cam (orange) from the factory position (no. 2) to the no. 1 position on the throttle linkage arm and readjusted the accelerator pump. Slight improvement, however the stumble is still present.
Has anybody else running this carburetor had the same or similar issues? if so, what did you do to eliminate the problem?

Thank you in advance,

Scott
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Old 06-11-2018, 05:11 PM   #19
19Fordy
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Default Re: 8BA or 8CM and Holley 390 cfm vs other combinations

Modelacoupe3: I found that properly adjusting the secondary's on a 390 really makes a big difference in a smooth idle and throttle response. In the video below I replaced the factory screw with a hex socket head cap screw that permits adjustment of secondaries without having to remove carb from engine. Maybe this will help you also. Also, I used a power valve that is about 1/2 the number of the highest vacuum reading instead of the one that came with the carb. Stock jets are 51. Number stamped on air horn is 8007.
https://www.google.com/search?q=how+...hrome&ie=UTF-8

Last edited by 19Fordy; 06-12-2018 at 07:43 AM.
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Old 06-11-2018, 06:46 PM   #20
Ol' Ron
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Default Re: 8BA or 8CM and Holley 390 cfm vs other combinations

I have 2 390 Holley carbs, however, one has a larger secondary venturi. I called Holley, but they have no answers. One person suggested it might be a 450, but that has a different list number.
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