Inliners International Forums General Discussion Hi Performance 235 4bbl intake manifold

Hello,
I've been lurking here for years. This is a great site.
I have a '51 Chev Coupe with a 235 and a 5 speed S10 trans.

The engine is bored and decked. The head was milled to clean up. I've calculated the CR at about 9:1. It has a 254 cam and HEI Dizzy.

I drive the car nearly every day, so around town driveability is
very important.

I am going to install Fenton headers and I want to upgrade the intake. I want to use a single 2bbl carb, and eventually install a Throttle body EFI system.

I am not aware of any single 2bbl intakes, and am only aware of the Clifford intake and an earlier production of Offy intakes that are 4 bbl. I've heard that the offy has a smaller runner cross section and is better suited for lower rpm use. Is this correct, or are the two manifolds similar?

Thanks for any input.
Flatout

With the Clifford you can you have to use an adaptor plate so install a 2bbl. adaptor rather than using the more common 4bbl unit. Both are available with water heat to help with the streetability( is that a word?)

The recent dyno runs that were done on a 292, and in process on a 250 seem to indicate that the Clifford may be as streetable as the Offy at least for those two engines. In that you have a 235 the "streetability" of the Clifford may still be a question. The Offy 4bbl manifold, at least the ones I've seen, are cast with 4 holes for a 4bbl. I had the center of mine removed so I could run a Qjet. I don't see why you couldn't do the same, then put an adapter plate on for a 2bbl.

Larry

As I stated earlier,the Offy gives you better torque down low,stronger signal to the carb from idle & up to about 2000 RPM.

Sure the Clifford is a streetable intake manifold as long as you have about a minimum of 2200+ rpm stall converter.I would go w/a 2500 stall on my own vehicle. That's not that high of a stall fellows. Factory cars have higher stalls.
My parents 1998 Olds Intriege (SP) 3.8 Liter stalls to 2600 RPM.

I have used both intakes w/a wide range of carbs 2 bbls,4 bbls(I do mean a lot of carbs).
The Offy is the hands down winner from idle up to the 2000 RPM range.

You need to take into consideration the dyno tests are taken @ 2500 RPM.

My tests were all done on a 250 L6 & raced against my friends cars that wre very consistant street/track cars.

I also tested by timing my car in the 1/4 mile w/different combos. Try one,carb,tune it,run the 1/4, try another carb,tune it,,run the 1/4, & so-on.

I can't say for sure how the Clifford reacts on a 292 because all my testing were done on a 250.
But w/292 CI engine,I am pretty sure the results would be different than on a 250.
The 292 would most likely not mind the larger plemun & runners do to engine size & w/4.120" stroke that makes up for something that the 250 does not have much of,,,torque.

So w/that being said, I can say the 230 & 194 ci engine would suffer more low end loss from using a Clifford intake.

Just my two cents.

MBHD

X2 - the extra displacement overs a lot of lag due to slow air movement in the plenum. The smaller engines will not be as happy, pick your useful speed range before making a choice.

Good info. I must have heard correctly that the Offy has a smaller cross section area, therefore the air velocity is higher than the Clifford when used on the same cubic inch engine. Since my use is for the street, and with the overdrive highway speeds are 2500-2700 rpm, my smallish engine won't like a big intake.

Did anyone ever make a "high rise" intake for these engines? I've only seen the flat log style manifold. It seems that there would be a higher efficiency with an elevated carb and radius runners. The flat runners and 90* bends don't seem to be too efficient.
Any thoughts?

flatout

The manifold runners will all be nearly the same X-section at the port, but larger runners near the plenum lower the velocity and allow fuel droplet fall-out, especially when cold.
The entry angle to the port isn't practical to change without altering the port, but yes, a slight down-draft from the plenum is helpful - but it ruins hood clearance etc. There's no way to get around a 90° bend from the carburetor to the runner except much more height and width to ease the transition, or a side-draft carburetor.

Here are the pictures promised. This is only to give you an idea of what to do. The carb sits on a governor and has a spacer on top. If you look at the pic on the left you can see a support from the center of the air cleaner down to where the coil mounted. You will need to use two supports. I'll be working in the shop again tomorrow and try and get some more pictures.

With multiple carbs you will have think about a box/oval cylinder on top of the carbs with tube over the valve cover to an air cleaner. An oval air cleaner would probably work better for you.

http://www.flickr.com/photos/33950672@N08/

Larry

I've added photos of the air cleaner. The photos show all the pieces and how they fit together. Any questions please ask.

http://www.flickr.com/photos/33950672@N08/?deleted=4542243684

Larry