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Username Post: Offenhauser Triple Carb Manifold        (Topic#367021)
Kyle G. 
Poster
Posts: 72

Age: 26
Loc: Delanco, New Jersey
Reg: 11-29-15
11-22-21 07:32 PM - Post#2831301    

I'm interested in improving the overall acceleration and gas mileage of my 1950 Chevy as its my daily driver.

Right now I'm getting 16 mpg in town and 20 mpg on the highway with a single barrel M-1 Fish carburetor on a 216 manifold on a 1960 235. A three speed overdrive and 3.55 gears makes up the rest of the driveline. Acceleration is good, but not spirited at the moment due to the extremely lean mixture setting.

I know these numbers are already pretty good, but I just took a look at the coloration of my sparkplugs and noticed that cylinders 3 & 4 were running slightly richer than the rest. A little bit of brown shading to the otherwise paper white plug.

From my experience with Japanese motorcycles and their propensity to give each cylinder it's own carburetor, I know the stock manifold isn't anywhere close to delivering the ideal air fuel mixture for all cylinders for all driving conditions. Which is why I'm interested with experimenting with a triple carb manifold.

My single question for the more experienced members of the board is will an Offenhauser triple manifold made for a 216 fit in a 1950 chevy deluxe without clearancing the vertical firewall brace?

1950 Chevy Styleline Deluxe w/ '60 235 engine and '58 torque tube 3-speed overdrive with 3:55 gears in the back

1946 Willys CJ-2A


Edited by Kyle G. on 11-22-21 07:33 PM. Reason for edit: No reason given.

 


Mercedes 
Contributor
Posts: 468

Reg: 07-09-18
11-23-21 04:06 AM - Post#2831311    
    In response to Kyle G.

I knew a guy in my prior years who messed around with the old 250 inline 6. He experimented with a lot of variations and built a manifold with a quadrajet. The problem was that the velocity pulled by the engine didn't match the quadrajet's design so the engine bogged and sputtered.

He later did two one-barrel carburetors and it ran great.

Adding multiple carburetors is more show than go. The larger the engine, you can get away with multiple carburetors. If you have a small engine, know that each carburetor is very small.



 
rrausch 
"16th Year" Silver Supporting Member
Posts: 14711
rrausch
Loc: L.A, Cal. & St. Louis...
Reg: 04-07-03
11-23-21 06:30 AM - Post#2831317    
    In response to Mercedes

You really have a Fish carb? Post some pictures of that bad boy.

That said, triple 1-bbls came on the '53-'54 Corvette 235s, but they had the correct (side-draft) carbs. I am not aware of any carbs that would work well on a 216 in a triple set-up. 20 mpg on the highway and 16 around town is not too shoddy.

1953 210 Convertible, 261 with dual Carter YF 966S carbs, P.S., Remote Bendix P.B. Booster... shade-tree restoration about done.




 
54delivery 
Contributor
Posts: 137

Loc: Salem, OR
Reg: 11-19-13
11-23-21 10:58 AM - Post#2831329    
    In response to Kyle G.

I have not run an Offenhauser triple, but have run the dual carb setup on a 235 and there was only enough room to run small air filters in order to clear the firewall rib.
I'm quite certain that running an Offenhauser triple setup will require firewall modifications to clear the back carburetor and you'll not have room for an air cleaner.
Of greater concern would be finding and adapting three carburetors small enough to work correctly on your stock engine. The 3 one barrel carbs the Offenhauser intake was designed to use are way too much for a stock 235 and will just reduce air flow through each carb to a point you'll never get them tuned to run right.




Edited by 54delivery on 11-23-21 11:04 AM. Reason for edit: No reason given.

 
High5 
Contributor
Posts: 271

Loc: Washington State
Reg: 07-14-13
11-23-21 11:03 AM - Post#2831330    
    In response to Mercedes

  • Mercedes Said:
I knew a guy in my prior years who messed around with the old 250 inline 6. He experimented with a lot of variations and built a manifold with a quadrajet. The problem was that the velocity pulled by the engine didn't match the quadrajet's design so the engine bogged and sputtered.

He later did two one-barrel carburetors and it ran great.

Adding multiple carburetors is more show than go. The larger the engine, you can get away with multiple carburetors. If you have a small engine, know that each carburetor is very small.



I ran two single barrel carbs on the 235 in my first '54 Chevy and they ran great. Only changes beyond the carbs was split exhaust and a slightly hotter spark plug. Those that tried to run triple carbs ended up changing cams and bumping compression. Too much fuel for stock components. Of the early 50's Chevy's I saw with triple carbs, all of them had the firewall gusset either bent outward or cut. I cannot remember the brand intake. Sorry.

1951 Chevrolet Sport Coupe 235 4 barrel 4spd
1954 Chevrolet 2dr Sedan Highboy 350 V8 set back 20% tilt front end '57 Olds rear 7" lift to front susp.
1955 Chevrolet 2dr Hardtop Highboy Olds tripower engine 4spd
1970 Corvette Stingray convertible


 
RAM_51 
"5th Year" Silver Supporting Member
Posts: 6136
RAM_51
Loc: Yakima, WA. USA
Reg: 12-28-02
11-23-21 11:15 AM - Post#2831331    
    In response to Kyle G.

I only saw one tri-carb set up at a car show quit a few years ago. Only the front two carbs were connected as there were clearance issues with the third....It was there, but I think he had it plated-off and nothing running to it. It was extremely close to the firewall. I can't remember what intake he was using.

1951 Fleetline Preservation
'51 Fleetline DeLuxe 2 DOOR SEDAN (Fathom Green)
'51 Styleline Special BUSINESS COUPE (Shadow Gray)
'53 6500 Dump Bed (Oxidized Red)
'50 Styleline DeLuxe 4 DOOR SEDAN (Mist Green)


 
52HardTop 
Frequent Contributor
Posts: 1708

Age: 67
Loc: North Haven, Connecticut
Reg: 05-09-04
11-23-21 01:40 PM - Post#2831337    
    In response to Kyle G.

If your running a 1960 235, look for a 2 carb intake. I've been running a Tattersfield intake since around 2004. It has 2 Carter WA 1s and it has been great for all those years. The Tatterfield is a a good flowing intake with the nice curved runners at each end. Three carbs may just be too much for the 235? I think carbking may have commented on this before.

2011 Camaro SS 426 HP, Red Jewel Tint. Killer!

52 Bel Air a traditional 50s Ride.

51 Convertible a 60s Ride.

51 1/2 Ton pickup soon to be a little of both..

1999 C-5 Corvette Convertible. Mid Life Fun..



 
Kyle G. 
Poster
Posts: 72

Age: 26
Loc: Delanco, New Jersey
Reg: 11-29-15
11-23-21 03:17 PM - Post#2831346    
    In response to Kyle G.

Thanks for the replies guys. I was looking at the clearance between my manifold and the firewall brace and I think I'm going to try the Offy triple manifold to see if it fits with no mods to the firewall. Obviously it is going to be a close fit, but I think it will be doable. I already have a 261 camshaft in the engine and carburetion shouldn't be an issue if I go with 3 Fish carbs.

According to the literature I have, small engines of 750cc to 1250cc ran pretty well on a single Fish carb. I believe I can make 3 fish carbs work due to their adjustability and unique pressure differential method of operation. Of course I'm not expecting much gain except maybe 1-2 mpg with a more even fuel distribution and maybe a little more acceleration at WOT.

Here's some pics of my current setup. I added an electric fuel pump on a timer that primes the carb for 10 seconds after the ignition is turned on or until 5 psi of fuel pressure has been achieved. Modified the oil filter canister to have both inlet and outlet on the bottom with check valve. I also adapted my own PCV system. Hydraulic lifters and a Pertronix ignition eliminate the annoying parts of engine maintenance. Still running 6v electrical system because why not?







1950 Chevy Styleline Deluxe w/ '60 235 engine and '58 torque tube 3-speed overdrive with 3:55 gears in the back

1946 Willys CJ-2A


Edited by Kyle G. on 11-23-21 03:21 PM. Reason for edit: No reason given.

 
rrausch 
"16th Year" Silver Supporting Member
Posts: 14711
rrausch
Loc: L.A, Cal. & St. Louis...
Reg: 04-07-03
11-24-21 08:03 AM - Post#2831385    
    In response to Kyle G.

That's what hot rodding is all about. Throw them three fishes on there and see what happens.

1953 210 Convertible, 261 with dual Carter YF 966S carbs, P.S., Remote Bendix P.B. Booster... shade-tree restoration about done.




 
rrausch 
"16th Year" Silver Supporting Member
Posts: 14711
rrausch
Loc: L.A, Cal. & St. Louis...
Reg: 04-07-03
11-24-21 08:04 AM - Post#2831386    
    In response to rrausch

Hey Kyle, love them horns.

And what is a "'58 torque tube 3-speed overdrive"?

1953 210 Convertible, 261 with dual Carter YF 966S carbs, P.S., Remote Bendix P.B. Booster... shade-tree restoration about done.




 
Kyle G. 
Poster
Posts: 72

Age: 26
Loc: Delanco, New Jersey
Reg: 11-29-15
11-24-21 05:31 PM - Post#2831411    
    In response to rrausch

Yeah, I found those horns in an antique store and just had to have them.

I modified a '58 overdrive transmission to accept the ball joint and universal joint from the original torque tube transmission. I also had to shorten the torque tube and drive shaft to accommodate the new transmision as its 6" longer than stock. It fit pretty well in my '50 Chevy and I only had to bend the shift rods a little bit to clear the new overdrive kickdown switch. I modified the position of the clutch fork in the new bellhousing to be in the same location as with the old bellhousing to minimize any alignment problems with the clutch.




1950 Chevy Styleline Deluxe w/ '60 235 engine and '58 torque tube 3-speed overdrive with 3:55 gears in the back

1946 Willys CJ-2A


Edited by Kyle G. on 11-24-21 05:45 PM. Reason for edit: No reason given.

 
carbking 
Senior Member
Posts: 1540
carbking
Loc: Missouri
Reg: 06-14-03
11-25-21 06:11 AM - Post#2831425    
    In response to Kyle G.

On a Chevy 6, due to the cylinder head configuration, performance from best to worst: 3 carbs, 1 carb, 2 carbs.

Eye candy from best to worst: no correct answer, up to the owner.

If one is going to run three carbs on say a 235, 3 from a Willys 134 4 cylinder would be about the correct size.

The fuel mileage quoted is good. Not at all surprised that the Fish is way down on performance.

Some 55 years ago, my mentor did an extended (1000 miles plus) comparison test with the M-1 Fish versus a Holley 1904 on a Ford 223 in his personal car. The Fish provided about 10 percent MORE fuel economy, and about 40 percent LESS power. The Fish was so bad on power, he had to alter the route of the test (which may have helped the Fish fuel economy - no hills).

While the 3 carb unit, done right, WILL improve both power and economy, the mileage increase will not pay for itself, and not sure you can beat what you have posted. The power output, compared to the Fish, or multiple Fish or a whole school of Fish, will be quite impressive.

Jon.

Good carburetion is fuelish hot air!

The most expensive carburetor you will ever buy.....is the incorrect one you attempt to modify!

If you truly believe "one size fits all", trying walking a mile in your spouse's shoes!


 
Kyle G. 
Poster
Posts: 72

Age: 26
Loc: Delanco, New Jersey
Reg: 11-29-15
11-25-21 02:51 PM - Post#2831434    
    In response to carbking

Thanks for the insight Jon. Just for reference I have 12,000 miles logged with the single barrel Fish carb setup, and most of that was on New Jersey roads with too many stoplights and too much traffic for my liking. My brakes sure get a workout which isn't conducive to good gas mileage, but anytime I used the interstate to travel my gas mileage averaged 20 mpg at 65 mph sometimes up to 22 mpg.

My most recent 20 mpg figure I quoted was achieved driving 150 miles west on I-76 then south on route 15 from Bristol PA to Gettysburg PA averaging 65 mph. I was doing 65 for pretty much the whole drive except for a quarter of it I was doing 70 mph.

As far as the Fish carb lacking power well, I don't have access to a chassis dyno but I can tell you that my amature 0-60 time is about 15 seconds at sea level. I believe a stock 1955 chevy with the same 235 3-speed overdrive powertrain ran a 0-60 time of 13.7 seconds? I don't think I'm that far off, haha.

Haha, I actually have several of those Carter W-O carbs already. They're sitting on the shelf from my Jeep, although they're not in the best of condition and I'm pretty sure there's no way they would match for a triple carb setup.

1950 Chevy Styleline Deluxe w/ '60 235 engine and '58 torque tube 3-speed overdrive with 3:55 gears in the back

1946 Willys CJ-2A


Edited by Kyle G. on 11-25-21 02:54 PM. Reason for edit: No reason given.

 


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