Primary carb- Front or back?

Ol' Ron said:
Aesthetics, that's what it's all about. How to put "DUAL" carbs on a stock engine so you can impress your fans. The best way is to place a block off plate under the rear carb, and don't run any gas to it. Engine will be happier.
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Ahh, the wisdom of Ol' Ron....The most astute response in this entire thread....
 
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tubman said:
I don't see anything in your post that would cause me to change my mind. Let me ask you : Have you ever spent any amount of time with these "rear-biased" manifolds?

Look at the way the manifold is made and THINK. That front carb is in the stock location for a reason.
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The answer to your question is yes. Obviously you have no idea how many engines I have tuned. You obviously also dont know the reason the front carb is close to but not in the exact location compared to a stock intake manifold. The reason the carbs are set back is so the generator can be located on the front of the intake manifold in the stock location. The two set back carbs are not set in those locations so the intake can run with one progressively. Now you learning something! Most of the engines I have tuned have the set back carbs with the generator in the stock location. The following two deuce flathead intakes were all made so the generator could be located in the stock location on the front of the intake Hexagon Tool, Offy ,Edelbrock ,Sharp ,Fenton, Burns, Almquist, Edmunds, Nicson, Weiand, and easily two dozen more brands of flathead intakes. And yes i have tuned engines using the names i listed.
Ronnieroadster
 
tubman said:
I don't see anything in your post that would cause me to change my mind. Let me ask you : Have you ever spent any amount of time with these "rear-biased" manifolds?

Look at the way the manifold is made and THINK. That front carb is in the stock location for a reason.
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The pictured "regular" dual intake is for pre-49 where the engines are "shorter" and the forward carb base is positioned to allow stock generator location. If you look at most '49-up dual intakes you'll see the carbs are more evenly positioned as the generator sits farther forward because of the "longer" water pumps and pulleys. One exception is the Edmunds which has very "strange" imo carb placement, but I ran one on my stock 239" '51 with straight 94 linkage with no issues. I eventually switched to an Edelbrock dual just because of better looking carb placement. I agree with Ronnie that straight linked dual carbs are the best way to go. If you take the time to make sure the carbs are the same and synced, you'll find good performance and economy. :)
 
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Running dual 94’s on a speedway intake with 2” spacers and straight linkage. 50 jets. 4.5 PV’s. Accelerator pump on #1. Ported vacuum to distributor. I rebuilt and tuned each carb on stock intake before swapping in the dual intake. Runs excellent!
 

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"Jockyshift41: - That manifold is not what I am talking about; it HAS to be run with straight linkage. To the rest of you, the engineers that developed these manifolds and the related progressive linkage systems they sold with them must have known something. On this one, I guess I'm just have to figure it out for myself. I'm kinda like that.:rolleyes:
 
Ronnie recently set up the 97's on an Almquist intake, straight linkage, modified gen mount on right cyl head,59AB. Runs like a rapxd ape. He IS a master.
Paul in CT
 
On my 39 EAB. I’m running dual edelbrock 94s rebuilt by CharlieNY (power valve sealed). Offy intake, direct linkage, car runs great.
 
I've been called many things in my life but "Astute" Is a first, now i havee to look it uo to see what it means?? Thanks anyway sounds good.
 
Wow, opinions are flying every which way.:) I'm tinkering on a dual Holley setup for a hotrod project. I normally post these bigger project so we can all learn something but some times a hotrod project can be looked down upon. Looks like I have about the same setup as Jockeyshift41. I'm building a Canadian 8BA, have Merc crank and EAB heads, probably end up .060 over. I'm looking at cams, don't want something too radical, want good drive-ability. I've been watching videos from Charlie at Vintage speed, he swears by progressive linkage.
 

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For what it's worth, I tried progressive on one of those offset type manifolds and found it more easy to make it work well when I switched to running both carbs at the same time.
same jets in both carbs, functioning but lower number power valves.

Re the suggestion to block off the rear carb. Actually I think this would be a good idea in this case, purely for testing purposes.

I'd remove the rear carb and just run one in the central location. Get it dialled in and running perfectly. Stock jets, 51s and a stock power valve.

I'd then swap in the other carb with exactly the same spec. get it dialled in and running perfectly.

Only by eliminating the twin progressive factor will you prove that the engine is running well. Condensor? Sticking valves? plug wires? get it running like gangbusters on one carb first. It will probably go quite well.

Then, try fitting both carbs. Leave the settings as stock (to start with). Set them up running in parallel. (Not progressive).

If there is an issue, address it. But make sure both carbs are exactly the same. From my experience, they might want slightly lower number power valves, but definitely not NO power valves.

If it runs better with them both on then great. If not, well, it's up to you.

But definitely get it running strong with one carb first, to eliminate all the "noise" that may be effecting your results.

Mart.
 
"Art Newland" - Even I have gone on record saying that you shouldn't even consider using anything but straight linkage on a manifold like that. I have to believe that the only reason Charlie Price recommends progressive linkage on one of those is because he makes more money on them than he does on a simple straight linkage setup.:mad:

"Mart" - Thanks for your contribution. It's valuable to hear from someone who has actually tried it. (I'd like to do some experimenting myself, but I've never really liked those things and would't spend the money.)
 
LQQKER said:
I struggled for too long with similar afterfire thru exhaust. I have twin 94s, synced linkage, blocked power valves.....started with 50 jets, went to 52s...slight improvement but very white spark plug porcelain. Finally got it running well with 54 jets and backed off the timing to 1 increment advanced. Good luck
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What distributor set up are you using? Stock? Mallory?
 
Running a Crab distributor from Bubba. Also a 3/4 Schneider cam from Reds Headers. NGK B-6L spark plugs. Echlin coil with internal ballast. Taylor 8mm suppression core wires. Hotton-Sullivan aluminium heads. 4" crank....Arias 3 ring forged pistons.
 
Have you had trouble w/ vacuum brake/ set-up? I have about 15"Hg but cant seem to get timing down pat. At WOT I have knock and low power. If I retard, no knock but even less power. I have tried setting crab at middle mark and adjusted brake w/ little effect. Crab was built by Bubbas. Currently running carbs sync'd.
 
47fordv8 said:
Have you had trouble w/ vacuum brake/ set-up? I have about 15"Hg but cant seem to get timing down pat. At WOT I have knock and low power. If I retard, no knock but even less power. I have tried setting crab at middle mark and adjusted brake w/ little effect. Crab was built by Bubbas. Currently running carbs sync'd.
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Might be worth the effort to mark the front pulley for TDC and several degree marks, then add a pointer and see where the timing really is. If 12v, all you need is a turn back timing light and a TDC mark and pointer.
 
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