/6 Offy 4 bbl intake CFM carb?

[deek1965]

My buddy has a /6 in his mid 80s truck. He has purchased a Offy 4bbl intake. I told him to get a small CFM carb like a 450CFM probably a Edelbrock so it will have jets and rods for better fuel ecoonomy. His truck is stock with automatic and 3.23 gears 1/2 ton 2wd. He says one barrel is starving the motor I told him to get a 2x2bbl for better fuel distribution but he got a deal on the 4bbl intake. Anyhow has anyone done the 4bbl thing with good/bad results? His motor is stock with stock exhaust.

[mrdodg]

don't have an answer but I'm facing the same situation. have a '63 1/2t p/u short step side w/258(?) industrial /6 motor, granny 4 speed and 3.08 posi RamCharger rear. recently picked up an Offy 4bbl intake and tube headers so I need the carb size into, too. will watch for replies.

[goldduster]

ok, I'd use the 500cfm edelbrock. I'd also use some clifford headers, and a 2 1/4 dual exaust system. Your real problem is going to be the kickdown likage. Not sure if there's a kit for the offy intake or not. I would also mill the head for more compression

[Fluid]

The Mopar Performance book 'Six Cylinder Engines' has quite a bit of info on the /6. The book has drawings depicting mods to the 4-bbl intake manifold floor to improve fuel distribution. This book is a must-have for modding the /6.

Former 198cid Duster owner

[dschumers]

Personally, with an otherwise stock engine, I would stay in the 390-450 range. I also would not use a 4-bbl with a stock exhaust manifold. If ya can't get the exhaust out, there is limited success in trying to put more charge in.

[goldduster]

yeah, I guess that is a good idea, dennis...

[dschumers]

I know this isn't always a popular view, but to me, a set of headers is THE best bang-for-the-buck mod on a Slant.

[satman]

I have an Offy 4-bbl. myself. I plan on putting it in my wagon, since it needs headwork anyway. Original non-hardened seats are starting to show their weakness with unleaded.
For now, It'll be the intake, headers and better exhaust all the way back. It's already got the sure grip.

We'll see..........................good luck to you.

Tracy

[deek1965]

We ended up using a 1977 Pontiac 301 2bbl Rochester that looks like a 4bbl with out the back 2 bbl. Called a Twin Jet. I rebuilt it , there was not much inside. We used a Holley to QJet adaptor. The stock throttle linkage hooked up great. These carbs were used on Pontiac 301 and Buick 260 in Mid 70s. This carb powered my 77 Catalina 4 door demo derby car just fine. My buddy says the Slant 6 never ran better. The main trouble we had was with the Offy manifold. The bolt holes that hold the carb to the exhaust was a little small for the stock bolt and we had to force the two together. I would enlarge this before installation next time. We both swore off this project the next time. INstallation took 6 hours times two people.

[plumcrazy73]

I hada 73 Duster with a slant six I put the Offy intake,a Holley 390 CFM carb w/ electric choke,clifford headers the duel output version, an H pipe Dynomax Mufflers, and a Mopar Performance Ignition with a MSD Blaster 2 coil. The rest of the engine was basically stock. It ran great had Very good power. I took it to the track and got 11 flat in the 1/8 with it and could have had more out of it if i played with timing and carb settings but I never did. Several people thought it had a V-8 in it when they seen it run and when they heard it run. Yes Offey makes a linkage kit but i had to modify it a bit nothing to stress about it was not hard to do the modifictions. email me if you have anymore qusetions.
I averaged about 22 mpg on the highway, averaging 70 mph. It was definatly a conversation peice
plumcrazy

[SlantSix]

I would stay under a 500 cfm carb. I have a 225 slant six that is bored 30 over and the head is decked .75". The cam is reground, I have dual headers and a 4-barrell intake from cliffod. The headers are clifford as well. But the 500 Edelbrock is drowning the engine. I have 2.79 gears in the rear right now and I am changing it to 3.21 gears soon. I am going to see how it runs then with a bigger cam and the new rear, and if it is still choking I am going with a 390 cfm Holley. But for now anyways I am a slug off the line.

Jacob Gray
1970 Plymouth Duster
225 Hyper pack Slant Six