Inliners International Forums General Discussion Hi Performance Clifford vs Offenhauser Intake Manifolds

I can't find any comparisons for Clifford and Offy intakes. Does one out perform the other? I have a 1949 Chevy car, stock 250, hei,with a 3speed. I bought a set of clifford headers, also I may install a mild cam, and not sure the best way to go for the intake or cam. One last question, I was told by spliting the exhaust and then combining it into an expansion tube and using a 3" tail pipe will enhance performance. Is this true or only for sound effects? Regards

Bobber, I believe the offy is a better street mannered manifold, the cliffords big wide runners are for high rpms and really suck up the bottom end I was told,, the only reason I didn't use the offy was the flanges were significantly different thickness than the split irons I used for exuast, I could never fab up something that looked right,,though I wish I still had it now,, (Larry, do you still have it???)

The offey is better for a daily driver, better low end to mid range. over the clifford.
you want it back ? do i still have it? yes i do. A thin spacer
would work i do beleave.(at the head & intake)Or maybe mill you
steel clamp with a offset?

Thanks guys, I really appreciate the quick response, I'm glad this website was referred to me. Regards

Your Welcome.

HHmmmm, I would like to try it to judge a difference,,, I still have that set of flattops with the little ding in the top ring land,,(I think?),, Can you make the (well I know you can), spacers,, could they be positively attached to the manifold, maybe welded so I would only have to use one gasket,,???

fingersix give me a call when you get a chance. What?????? I can't have the valve cover back LOL jk jk

Has anyone added a 2 inch spacer between the carb and the Offy manifold?

If the manufactures claims are any good it will add torque and rpm.

Larry

I ran a 1-inch spacer with my Offy, and it didn't seem to make a huge difference. Couldn't go over 1 inch due to hood clearance.

63, That's about what I figured. I'm not going to run for any extra performance. I want the transition area for the Quadrajet. This is going to be in a truck so I don't have a problem with hood clearance. Thanks for the feedback.

Larry

I ran a 4 hole 2",4" & a 2",4" open spacer.

The 2" open spacer hurt low & mid range.
Best overall performance for the street was with a 1" 4 hole phenolic spacer.

The offy has sharp turns below the four holes.
I cut out the four holes and put nice radius's into each port (3 total)

MBHD

Thanks Hank, that's the info I was looking for. Sounds like the extra plenum hurt.

Hadn't looked that close at the Offy. The four holes are going to have to go, so I'll figure some additional work after they do.

Larry

If you cut out the built in 4 hole divider in the Offy,you can use a 2" 4 hole spacer.
This allows for the air/fuel mixture to have a smooth turn/transition into the runners.

MBHD

Hi Larry,, I had a q-jet set up on my offy,,what I found was with the carb transverse(secondaries toward valve cover), the type of throttle arm I had was slung real low, for the t.v. hookup,,and it came in contact with the manifold, if you have a earlier design for a detent cable, it should clear,,(the arms are different), I used the 1" phenolic spacer from Jegs, with the swirl design,,I really don't know if it does anything engine wise,,also with the standard gaskets that came with it,, the positive stops on the throttle blades hit the gasket,,some trimming was needed,,I ended with the carb inline for cable routing,, that created another thing,, my offy's bolt pattern was not square, so you couldn't rotate the carb plate, I made my own from a Mr Gasket, adapter,,,I've seen some different offys,, mine had a clover leaf for a square base built on the manifold,, I cut that out and re-shaped the hole to match the open plenum q-jet shape,,before I put the spacer on, the secondaries would not open becuase of it,,with the spacer there isn't a concern,,,

I've got the Mr. Gasket adapter for square bore to the Qjet and the Mr. Gasket 2" four hole spacer for the Qjet. The two Mr. Gasket parts do NOT match like I would think being from the same mfg they should. I'm going to have to smooth the transition from one to the other. I'm also going to have to drill some holes in the adapter to mount it to the Offy. Considering what MBHD has said I may want to get a shorter spacer than the 2", because with the adapter I'll have about 3" from carb to manifold.

It thought I'd make a bracket to mount a bell crank of the manifold studs and use bicycle cable to the Qjet throttle shaft.

fingesix which Qjet (number) did you use, any changes to get it to work right?

Larry

Larry, I could get you the number when I get back home, but yes changes were involved, the carb is a late seventies BOP (fuel inlet straight), with an APT, (adjustable part throttle), you want that, it controls the amount of fuel delivery just off throttle and cruising,,mostly enough can't be said about adjusting the opening rate of the secondary air flaps, likely that is where all "bogs" come from, it is usually a case of not enough fuel for the rate of the flaps opening, not over fuel as most bog guys think,,the flaps have a positive stop that limits the amount they open, controlling the "cfm" for which the carb could flow,, I was explained cfm was a unit of measure derived for comparisons of carbs and really shouldn't be use for q-jet determination,,,q-jets are metered to put fuel into the stream for the amount of air passing through it, you want to remove the positive stop or grind it down so the flaps open a full 90 degrees,, if you grind it off, you can tap the body and put a set screw for adjustment,,,the next thing is the spring, it controls the speed of the flap, if the flap just "pops" open during WOT it dumps to much air in to fast you need to adjust it to smoothly open, you shouldn't feel the "bog" as it goes into the secondaries,, the front choke pull off also makes sure the flap doesn't fly open under WOT,,, Cliff Ruggles q-jet book ia a wealth of info,, after struggling for a while, I sent the carb to him for work, he had to enlarge the idle air bleeds,I hate to cut into the internals of the carb,, the carb has been good since,,,his site is cliffs high performance.com,, I have also heard of people finding "q's" off of 4.3's and seem to be calibrated well,,

Thanks fingersix. I've got a Qjet from a 69 Olds 350 I'll try that. I've got Cliff Ruggles book and I'm going to send him a carb to zinc plate and setup for the 292. I've got to find time to do more work on the engine.

Larry