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Discussion Starter #1
i was curious as to what would be a better option for a chevy inline six: a triple 1 barrel by Offenhauser or a single 4 barrel by Offenhauser. One of them will be mine, but i wanted some input from other people who know more about stuff like this than i do.
 

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Hei Sicksix

The single 4 barrel system will definitely be easier to tune and more reliable.But the look of a few carbs lined up is more appealing.Is it an OHC Pontiac?
 

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Inline 6

You might also want to check out the stuff Clifford Performance has for 6 packs. That is their specialty.

cliffordperformance.com
 

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Discussion Starter #5
I'm pretty sure that it is the original engine for my car, an 1967 Chevelle. I don't know too much about, other than it isn't as fast as I would like it to be. My only concern about the single four barrel is the fuel consumption. Seeing as this car is my daily driver and I all ready spend about $30 a week on gas with a 1 bbl. carb, I want something that won't just dominate my gas gauge. I do like the appeal of a row of carbs, and I will check out Clifford. Thanks for the input
 

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inline 6

I take it you have either a 230 or 250 CID 6.
I would recommend that use a 390 CFM 4 bbl. Holley.
With a 250, and a peak RPM of 5000, your carburation requirements are only 362 CFM.
If you desire to turn it higher, You would still have plenty of carb to feed it.
The 390 would feed you adequately out to 5400 rpm and higher.

You may actually get better gas mileage with this carb than you do with the stock 1 bbl.

IF you go with multiple carbs, I would recommend going with 3 one barrels over 2. The reason being is that with 2, carbs, either your front three or rear three cylinders are going to get the better fuel air flow under normal operation. This could lead to over heating on the three that are getting starved. With the 3 carb setup, you will have the same flow as you have now under normal conditions, but with your foot in it, you will have equal fuel air distribution to all the cylinders.
 

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Discussion Starter #7
Max Keith-
thanks for the idea, i took a look at that carb and i think that's what i will get. now for the intake manifold itself.... i am between an offenhauser and a custom job from CLifford Performance. I like the one from clifford, but it is $120 more than the offenhauser... i guess i have until february to decide because thats when my car hits the shop anyways. Winters are not very nice to classics.
 

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inline 6

If its a consideration of $$$$$$$$, then I would opt for the Offenhouser. While its an older design intake and not up to the inth in power capabilities of the Clifford unit. When you consider spending $120 of your hard earned bucks for an extra 2-3 HP all through the power band and maybe 5-10 Hp on the top end power, I think my wallet would do my talking for me, and settle for a little bit less. Dont get me wrong. Clifford makes probably the best stuff you will find for an inline 6. But $$$$ are $$$$.

As the sign on an old friends speed shop used to have over the door.

Cubic $$$= HP linier; how fast do you want to go?
 

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Discussion Starter #9
Not that i do it often, but when i step on it, i want a car that can at least make a squeel. This car cannot even chirp the tires, and i want it to. The OEM exhaust makes the car sound stupid, not even hinting that it is different from any other car on the road, which it is. I plan on running true dualies with headers to solve that problem. The motor runs sooo smooth that i don't want to screw eith it. i have seen so many engine swaps go bad that i am frightened of them. i want to build this engine up because it only has 81,000 miles on it and i don't want too big of a headache because i depend on the car, but thats part of the charm.
 

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inline six

Are you running standard trans or automatic?
This can make a big difference if you are planning other mods like a cam etc. I do believe that you will find plenty of gains by just going with the small 4 bbl and a good exhaust system.
I would consider running headers, which are usually a dual collector set up. What I would do is to run a flowmaster Y-pipe and run the two back into a single exhaust, running a 2 1/2 inch exhaust system all the way back with a BIG turbo muffler. The reason I suggest staying with the single exhaust with large diameter tubing is that this will gain you a big amount of torque on your lower end with out sacreficing your top end.
There are some companies that actually make a 6 to 1 header, but I dont know if this is applicable to street use or not. That would be something you might want to look into as well. I would stay with headers that the primary tubes are the same size as your exhaust valves or slightly larger. There would be no gain for you to go to large diameter prlmaries on your engine.
If you are adamant about running dual exhausts. Have a balance tube installed between the two, as this will seriously improve your lower end torque as well, without hurting your top end. I am projecting that 4500-5000 is probably about as tight as you can turn it with the stock cam anyway. Having an exhaust system that builds lower end power will give you more benefits than you will lose on top end, compared to a large primary tube exhaust will hurt you more on the lower end than it would help you on the upper end.

As for the dual exhaust, I would run 2 inch pipe for that.

The reason I suggest turbo mufflers over glass or steel packs is that dyno tests have shown that they actually flow just as well as the other two, and last longer, not to mention, usually no more expensive.

I project that going with the 4 bbl and the headers will net you about 25-30 hp, minimum. The big key to your HP gains will be not so much the big increase in carburetion, as that will help a lot, but your stock exhaust system is what is killing you. You will also want to do some ignition retiming as well.
 

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Discussion Starter #11
Thanks a bunch for the info, as i basicaly stick to sbc's and i wanted a change of pace. I have all ready ordered the headers from clifford, but they won't be here till february. They are a 3:1 design and i also ordered this peice called and x pipe, which is an improved h pipe designed for inlines. It is running a powerglide tranny, and i will probably build that up too. Any ideas? i have heard that transmission coolers are a big plus, but are they worth the money?
 

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any ideas?

A tranny cooler would definately be a good idea. I would suggest going to a turbo 350 trans, rather than to build up the p-glide.
That will give you an extra gear and thus better gearing to get going with. In comparison to the powerglide, it will be like putting a 39% deeper gear in the rear end, (low gear comparison of 1.8 low with the p-glide vs approx. a 2.5 low with the 350 trans., exect you will have the same topend gearing as you have now, and 3 gears are always better than 2.
In my opinion, while p-glides are a good transmission in their own right, they are obsolete. The only place I see them now are on dirt tracks with direct drive couplers to eliminate the torque converter, and they are running rear end gears deeper than you will ever see normally on the street. In stock car racing, once you are in high gear, you leave it there, on the ovals, and you dont need the acceleration to get moving from a stop, or some guys run them in drag racing where they have such light cars and so much power that running the deeper rear gear multiplication of the 3 speed automatic would be to their detriment.
The dropping in a turbo 350, would for all practical purposes be a good hopup trick in itself, especially with your stock rear end. They arent that expensive and not hard to install. I wouldnt be surprised if you could even use your stock flex plate.

The X pipe is an excellent idea and far better than the conventional balance tube or H pipe. The X pipe may well help in mellowing out your exhaust as well, getting rid of that tinny sound of a 6 banger.

I used to race I-6's many years ago on dirt track (69-70), and we gave up nothing to the V-8's.
Something that most people dont realize.
Given a 6 cylinder and an 8 cylinder of the same displacement and state of tune, the 6 will put out 30-40% more torque, and its torque that gets things moving as well as keeps them moving. Horsepower is just a figment of imagination.

If you should decide to go to the turbo 350 trans, I would definately put a shift improver kit in it. Tests have shown that shift improvement kits not only make your trans shift faster, but also give you more transmission selectability, as well as longer life, due to the reduced wear caused by the slow and soft factory shift programs. The cooler will help with life as well. I would run the trans to the cooler directly and bypass the trans cooler in the radiator all together. Mount the trans cooler between the grill and radiator. While your car only weighs around 3500-3700 lbs, I would recommend a cooler for a 7000 gvw vehicle. They arent that much larger and the double cooling area will be to your benefit.
 

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Discussion Starter #13
I'll have a word with my neighbor about a turbo 350, as he has one under a tarp in his yard, and seeing as he doesnt own a vehicle to put it in, maybe he would part with it. If the swap isn't to dificult, and he would part with it for cheap, than i would definately swap it. I guess he bought it with what he thought was a 327, but through further investigation found out was a 307. He was thurouly displeased and it has sat there for like 5 months. If i remember correctly, it is rebuilt. Would i have to change anything along the lines of my coloum shifter or shift linkage or anything like that?
 

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Those little motors work good with a holley 4412 2bl. The circle track guys use them a lot so there are lots of them floatin around.(and they run em on 355 v-8s) Think about things that might lighten your car up. Its a lot of car for that motor to push...Not saying not to do it.. But lighter is faster + better gas milage. I run one of those carbs on and old 235 and love the 24+ miles to the gallon. I also use a 5 speed O/D which would help your car a bunch.
 

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Look at the pictures of what I did to my 230cuin 6 here. The Powerglide was beefed up with the following,

Steel clutch hub (replacing cast iron one)
shift kit
Stronger input shaft
machined clutch piston to accept 5 clutches
2200 stall speed converter

With this combo and the engine modifications as described in the other thread, we got 25mpg on regular unleaded, and the car ran cool even in 110F Bakersfield summers. All that in a heavy '36 Pontiac 4-dr sedan. Except for my custom intake manifold (use Offy or Clifford's), you can easily do all the mods yourself.
 

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inline six

I concur with the 4412 series 500 CFM 2 bbl. Thats what I had to run on my Limited Sportsman 240 cube Ford 6, back in 69-70, down in South Carolina. I didnt get that kind of gas mileage out of mine though. LOL. Mine was more like 6-7 if you wanted to figure it out in 3/8ths and 1/2 mile laps on dirt.
 

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Discussion Starter #17
willys36-

That looks really good. I have all ready ordered a set of headers, and in february i plan on getting an offy intake and probably the holley 4 bbl. i also plan on getting an electric fan and some other stuff.
 

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The 4412 2bbl and 390 4bbl will both give you the same top end performance. The 4bbl will actually be more economical since it will run on the primaries 99% of the time which are smaller than the barrels on the 2bbl.

It is really fun getting these grand old in-liners putting out serious power. And you will get twice the looks at a rod run than the ubiquitous and boring 305/350 drive trains.
 

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Discussion Starter #19
That is sooooo true. That's basicly why i wanted to build this engine up, because i'm sick of the sbc's dominating shows. I have 1964 Bel Air with a 327, and while that's fun and all, it's pretty boring. My dad thinks i'm nuts for doing this, but i want a six cylinder car that screams. I thought i was alone on this until i found this site. Thats for the help.
 

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inline six

I would definately agree with Willys36 on the gas mileage thing, between the two carbs. Guess its a tradeoff. The 500 2 bbl. is a lot cheaper to purchase, but the 390 will get the better mileage. Thats your call.

Back in high school, (early 60's) a buddy of mine had a 38 Chevy coupe. He dropped a 292 six in it with 3 speed. For mods, he did some hogging out of the top of the stock intake and put a 2 bbl on it off of a 389 Pontiac. It also had fenton Cast headers, and he had done a little work on the ports. Stock cam.
He embarrassed a lot of V-8's that were 100 cubes larger. Nothing wrong with 6 in a row, and they will go.
 
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