multi carb setups
- Thread starter KAA
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Screaming Metal
Active Member
Because I build custom intake systems....yes, I have run them. On the dual log intakes on a (4x2) Nailhead, a old 392 Hemi (6x2) a customer had, a ford flathead (6x1), another ford flattie (4x1), and a ton more....
These intakes are for hotrodders that like like to tinker. Back in the day, there were no bonafide big racing carbs, there were the carter afb's, strombergs, holleys, Dell Ortos, SU's, etc. The more carbs you had, the more cfm flow you got....a lot of the old setups used stock carbs.
You had to tune them like anything else....
They looked cool, some of them ran pretty well, if the guys were really gearheads. I saw my fair share that would backfire and catch the whole motor on fire....and we'd all laugh.
You get out exactly how much you put into them....work wise, and tuning wise. One of the absolutely best running motors I've ever seen was a stroked 265 chevy in a altered back in the late 60's. It had 8 Harley Davidson Carbs on it, had a Howard cam and some old fenderwell exit headers with a hot little 'powerslide' behind it. Ran regular over around Bakersfield for about 4 years and it'd eat your lunch if your car wasn't lined out. Ted and 409 probably remember him....The altered had the big slicks on the back, had wooden looking spoke rims on the front, and it'd smoke the tires about 5/8's the length of the track and that thing was gone!
These intakes are for hotrodders that like like to tinker. Back in the day, there were no bonafide big racing carbs, there were the carter afb's, strombergs, holleys, Dell Ortos, SU's, etc. The more carbs you had, the more cfm flow you got....a lot of the old setups used stock carbs.
You had to tune them like anything else....
They looked cool, some of them ran pretty well, if the guys were really gearheads. I saw my fair share that would backfire and catch the whole motor on fire....and we'd all laugh.
You get out exactly how much you put into them....work wise, and tuning wise. One of the absolutely best running motors I've ever seen was a stroked 265 chevy in a altered back in the late 60's. It had 8 Harley Davidson Carbs on it, had a Howard cam and some old fenderwell exit headers with a hot little 'powerslide' behind it. Ran regular over around Bakersfield for about 4 years and it'd eat your lunch if your car wasn't lined out. Ted and 409 probably remember him....The altered had the big slicks on the back, had wooden looking spoke rims on the front, and it'd smoke the tires about 5/8's the length of the track and that thing was gone!
know a guy that is attempting to run 6-dueces, he wishes they would backfire and set fire to the whole thing because he is ready to light the match himself, not for the faint. All six have been rebuilt, it only takes one to not to want to play. I'd do triples in a heatbeat but 6 , no way in hell.
Screaming Metal
Active Member
Yea SS, i know a few folks that hate em', but they sure looked cool as hell as long as they'll play the game. As long as a person sits down, geta all the carbs exactly the same and is meticulous in their rebuilding and adjustments, then installs things, then balances them accordingly, they usually do pretty good.
The worst enemy of multi carb setups is dirt in the passages, and loose throttle shafts. And last but not least, someone jacking around with them just shooting in the dark.
I do have a flow bench I have 'adapted', much the same as SS used a F/A meter to adjust out his carb.
I mount a carb up there, I write down everywhere that carb is in need of adjusting. I put all of them up on the flowbench, get them really close. Therefor, when I mount them on a motor, I know they're really close to being the same.
After that, I mount them, then I start sorting them out. I get them to idle first, them I move thru the 1st transition, to mids, them from there to WOT.
Yes, you have to take your time, but I can't overstress the fact that you have to get these carbs on the same baseline....as close as possible.... to being the same. Then, from there, its easy to adjust. If you don't your doomed to failure right off the bat.
Attention to detail and being really patient is a virtue....
The worst enemy of multi carb setups is dirt in the passages, and loose throttle shafts. And last but not least, someone jacking around with them just shooting in the dark.
I do have a flow bench I have 'adapted', much the same as SS used a F/A meter to adjust out his carb.
I mount a carb up there, I write down everywhere that carb is in need of adjusting. I put all of them up on the flowbench, get them really close. Therefor, when I mount them on a motor, I know they're really close to being the same.
After that, I mount them, then I start sorting them out. I get them to idle first, them I move thru the 1st transition, to mids, them from there to WOT.
Yes, you have to take your time, but I can't overstress the fact that you have to get these carbs on the same baseline....as close as possible.... to being the same. Then, from there, its easy to adjust. If you don't your doomed to failure right off the bat.
Attention to detail and being really patient is a virtue....
I would agree Mr. 409, the least amount of those carbs you have working the better, unless WOT, then bring em on.
Screaming Metal
Active Member
I agree 100% 409, but sometimes I try to give folks my years of expertise of dealing with these setups, and when someone just does their own program, I just shake my head and go on. The Nostalgia drag folks are running some of these old setups, and the class is getting pretty popular.
Because alot of the old carbs have been picked over so many times, theres alot of junk out there. Well, most folks bite the bullet and get the new repop's or get the old looking new throttlebodys and EFI it and just be done with it.
The Progressive linkage tames things down alot, and with that linkage, keeps from jacking with both carbs if there were both dumping at one time. Alot easier to tune, a lot easier to keep tuned, keeps from dumping all that raw fuel down the motors throat especially on a TR.
But, some folks want to dump all 8 barrels at one time.
The old Caddys were popular with the 4x2's back in the day and ran good doing them, most were straight. You'd see the 6x2's on the Caddys from time to time, the better running ones had the old progressive linkage from Offy....we'd set up the 3x2 setup on each log....
2old2fast
Active Member
I've said this before but I'll repeat it , on a tunnel ram dual quad setup , when using the rear carb as the primary , you will over fuel the rear cyl's & under fuel the frt's. The savings in gas mileage over running 1:1 linkage is negligible & the driveability actually improves ,albeit slightly.
dave
dave
Screaming Metal
Active Member
OK in a open plenum, when the front 4 cylinders go thru their intake cycle, the vacuum pulls you intake charge thru the open plenum, into the lower 4 runners, into the front 4 cylinders. You have to remember the the Chevy firing order 1-8-4-3-6-5-7-2....balances the intake pulses somewhat, in the open plenum, with a progressive linkage.
We've done research into this with sensors in the intake, we've even used the Spintron and strobed the airflow pattern thru a plexiglass window in the side of the plenum.
Our tests showed a weakening of intake signal toward the front cylinders, ie, the fuel/air mixture arrived there, but it took longer. You've got to remember in a Tunnelram that vacuum pulls on a mixture that is atomized, so fluid dynamics in a mist is at work here.
That same signal weakness shows up in a dual plane intake....#3 intake valve is alot closer to your primary throttle bore than the #8 intake valve. And that mixture has to travel a long way in the horizonal plane.
That difference of those 2 vacuum signals in the dual plane, is very similiar to the signal in the TR. The larger the plenum, the weaker the signal. Thats how they came up with the Street Rams, they've dropped the plenum volume. Grumpy, and several others did some experimenting.
The older Scorpion intakes that had the carbs at a angle, guess what! We don't run the same jets in all 4 corners! And we made power to win races! Am I right Mango????
I know we're dealing with street motors here folks, and I'm not ragging on you 2O2F, but the Tunnels are made for alot of cam, with alot of carb. Alot of the time, folks don't realize that theres a big handicap running one of these on the street. You have to adjust and adjust and adjust.
I tune these things day in and day out with dominators, 850 doublepumpers....and even with the the new Killer looking Holleys. Mostly sheetmetal tunnels that are made for 1 thing, flowing air!
The old Weiand and the like, TR1Y's, could be tricky as hell to tune. The best tunnels running on the streets, in my opinion, are the single 4 models. Yes, the duals can be run, but you've got to tune them. And it takes time
Screaming Metal
Active Member
Screaming Metal
Active Member
Wild Mango
Member
I have had very good results withshort stacks underneath the carby inside the manifold on each bore. One of the many ideas of the late great Grumpy Bill, RIP. Idea being the large plenum damps out the intake pulses and the stacks help the fuel mix get down to the ports in a direct manner. Pictures in his book "The Chevrolet Racing Engine", a classic. No need for asymetric jetting and the throttle response is magnificent.
BTW off the thread but I never ever heard anyone shift a T10 like the Grump, and I expect I never will, either. Little bugger was fast and slick on the stick.
BTW off the thread but I never ever heard anyone shift a T10 like the Grump, and I expect I never will, either. Little bugger was fast and slick on the stick.
2old2fast
Active Member
O.K. screamin' , does that mean you believe that the frt cyl. run lean w/ progressive or no? [ when you're cruising at or around 2500 rpm] My experience says they do & there's no tuning around it !
mango , this is the 2nd time I've heard about these spacer stacks?? do you have anymore info?
dave
mango , this is the 2nd time I've heard about these spacer stacks?? do you have anymore info?
dave
Screaming Metal
Active Member
Not running lean, the further away your intake valve is away from yourprimary throttle bore, the weaker your vacuum signal. Its still getting a substantial gulp of atomized fuel/air.
Take for instance a I6 with a std 1bbl. carb. Is # 3 & #4 running rich while #1 and #6 running lean? No, the signal is weaker....
Screaming Metal
Active Member
Gone, but not forgotten....
Some of the Stinkiest cigars known to man, you can rest easy and watch us race awhile....
Some of the Stinkiest cigars known to man, you can rest easy and watch us race awhile....
Screaming Metal
Active Member
mango , this is the 2nd time I've heard about these spacer stacks?? do you have anymore info?
What Mango is referring to is a drop down carb spacer, with extensions on it. The Grump did this evil deed on occassions....worked too. Heres a modified version of it. Most of the ones you'll see is made from alum. sheetmetal. Looks like a carb gasket with 4 tubes extending down from it.
Grump made a run, waxed this guys ass. Guy protested, official looked at Grumps carb, opens the throttle, looking past the butterflys with flashlight. Official said,'Bill, you can't do that!', Grump looked at him, lite his cigar, 'Theres nothing in the rule books about it!', he smiled really big and walked off.
http://www.4secondsflat.com/carburetor_spacers.htm
I do the same thing by fastening a 4 hole spacer inside the open plenum just under each carb on a tunnelram. This reduces volume and dropping the charge down into the runner, stopping some reversion....
Offenhauser makes these things that go into the manifolds too....The Grump just modified their design some....
What Mango is referring to is a drop down carb spacer, with extensions on it. The Grump did this evil deed on occassions....worked too. Heres a modified version of it. Most of the ones you'll see is made from alum. sheetmetal. Looks like a carb gasket with 4 tubes extending down from it.
Grump made a run, waxed this guys ass. Guy protested, official looked at Grumps carb, opens the throttle, looking past the butterflys with flashlight. Official said,'Bill, you can't do that!', Grump looked at him, lite his cigar, 'Theres nothing in the rule books about it!', he smiled really big and walked off.
http://www.4secondsflat.com/carburetor_spacers.htm
I do the same thing by fastening a 4 hole spacer inside the open plenum just under each carb on a tunnelram. This reduces volume and dropping the charge down into the runner, stopping some reversion....
Offenhauser makes these things that go into the manifolds too....The Grump just modified their design some....
one finger john
Active Member
Screamin'. I remember tellin' ya about advice I got from Larry Ofria at Valley Head Service (Los Angeles, CA) in the early 70s about running an aluminum "skirt" down into the tunnel ram plenum to cut plenum volume. At the time I was running a 283 c.i. , 12.5 comp with a Weiand Street Tunnel Ram. Had two 600 cfm vac Hollys. Wasn't a torque monster but those inserts really picked up the bottom end. Motor was in my 57 with 5:38s in a Pontiac rear end. Ran a Sig Erson cam (.500 lift x 300* advertised duration x 108* separation). Around town it would cruise at 35-40 mph in 3rd gear, just "chatting" along until the cam, carbs and compression all came together and it would smooth out and gain a few mph all on its own. Kinda like when a motorcycle would come up on its cam. Everything just smoothed out and started working.
Miss those days. There was always something new to discover.
John
Miss those days. There was always something new to discover.
John
Screaming Metal
Active Member
Yes, Brother, miss those days too. I remember....I had the same thing in a mid 60's Nova. Great days back then, could fill your car up for not much more than 5 bucks....
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