The Jalopy Journal
Discussion in 'The Hokey Ass Message Board' started by swade41, Oct 18, 2007.
Offy has 1/2" forward spacers.
I just got off the phone with Holley's tech rep and he says the two carbs have different fuel curves do to the vacume. He said it might work at part throttle but nothing more and the back half of the motor would be lean. There goes that cooky idea right out the window...lol
Open to correction, but I think that the 4 bbl will flow 40% more (1.4 X as much). I might be off, but I think that's the ballpark.
But I'd sell the holleys, and use the money to buy a pair of small AFB carbs. Easier to jet; less hassle clearing a distributor.
That is correct on the ratings at different pressure drops.
2 bbls are done at 3",4 bbl at 1.5".
I might have a program that can convert between the two.
Plan A--Use an Offy 360 manifold:
Plan B--Use those door stoppers for door stoppers, buy some real carbs!
ha ha sucker, don't forget I know where you live...lol
How about a Mallory "Crab" cap, should work on a Unilite. It measures a little under 5" from top of cap to bottom of mounting flange.
According to Dyno 2000 by Motion Software,
500 cfm at 3" HG = 353.6 cfm at 1.5" Hg
Offy also make a bolt on cross ram adapter for that manifold which allows you to use your Holley carbs. You get a pair for $266 and they look real kool, linkage is also available.
Put 2 500 cfm Holley 2 barrels on it? Use the Ford kickdown tranny lever to activate the rear carb?
Second vote for crab dizy cap!
So what does that exactly mean in layman's terms ?....lol
I asume the 2 barrel will run out of fuel flow before the 4 barrel. Would it be something drastic or small enough to work ?
I would think the 2 barrel will run up through the higher rpm's because that's what all the stock car guys run on their 2 barrel classes.
Your biggest issue there will be fuel distribution which will lead to some driveability issues.
You already said this isn't some crazy race engine, so why make it too complicated to be reliable? Might as well grab a pair of motorcraft slide venturi carbs and run them sideways buring light diesel fuel boiled out of baby blue whale blubber...
It seems, in this case anyways, the AFBs win.
Just an update on this, the problem is solved, I went with a pair of Carters. A friend of mine had these so I traded the Holleys straight across for them. The distributor still looks a bit tight, but it does fit and have some adjustment.
Phil you will be happy with the Carter's..
I have the same set up on my 57 with two 500 Edelbrock's, and i running them straight, no progressive linkage. ( dont mind the long air cleaner studs...it has tall filters now.
Had to tune it, but once i did it start's and run's perfect. NO loading up, no bog...this is the third set up like this i've done, two with the Offy 360 intake, and one on my old 6.71 blower..
I realize that you have your clearance problem solved, but I thought I would add to the 2bbl vs 4bbl comparison.
When we were running IMCA/UMP style modifieds some of the tracks around here would allow you to run slicks if you ran a 500 cfm 2bbl or treaded tires if you ran a 390 cfm 4bbl. We did some dyno testing on the same engine with both the 2bbl and 4bbl carbs. The 390 cfm 4bbl was good for an additional 40 horsepower and there were fewer fuel distibution issues with the 4bbl.
Thanks Tony, do you have another picture of the other side of the carbs so I can get a look at your linkage setup. I'm going to swap this on after the show at Hamburg, so I can be ready for spring time. That linkage that is pictured in the forground is to short to work, but I need an idea of which holes to use so I can buy some rod to make it work.
If it was setup straight then they would go in the same holes on each carb right ? Progressive would need an arch to work through to pull the second carb open from what I could see, I think.
Does this help?-MIKE
Yes, setting it up 'straight' you would use the same hole's in each carb. I used the smaller hole's that are just below the mail linkage hookup. It's hard to see in this pic, but right now that's all i have.
I used a couple of those ball and socket joint's and 1/4 round stock. Just cut some threads on the rod and put it together using jam nut's at each end to lock it all together. It's a VERY simple idea.
I used the rear carb as my throttle hookup to the car and used the large upper hole there.
I myself don't like the feel when using the smaller hole's are the main hookup to the car's pedal. The movement is much faster because of the mechanical advantage of it being closer to the centerline of the throttle shaft.
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