6 Motorcycle carbs on my Pontiac OHC 6... any ideas? - Page 3 - Hot Rod Forum : Hotrodders Bulletin Board
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  #31 (permalink)  
Old 02-12-2012, 02:04 PM
boatbob2
 
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Huh ??????????

Hi 4 barrels,gee were going to miss you,we really are hurting for members...NOT
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  #32 (permalink)  
Old 02-13-2012, 10:44 AM
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Quote:
Originally Posted by 52fatness
The latest (April '12) issue of Street Rodder has a collection of Steve Grimes cars in it. One has A Buick straight eight in it with 8 Honda side draft carbs! Check it out
do you have a link for the article? I googled it and couldn't find, the search motor of the mag's site can't find it,

I can't get the mag over here, it's a pity though I would love having it.

the looks of the I8 with 8 carbs must be wonderful.

Last edited by Augusto; 02-13-2012 at 10:50 AM.
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  #33 (permalink)  
Old 02-13-2012, 01:46 PM
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Quote:
Originally Posted by Augusto

you think only in the USA there are motorheads? well for what I know, most people in the states can't even drive a stick shift car, but that's not an issue, the thing is that at your age most people think they know everything, well let me tell you don't and you are wasting the chance to learn a bit more today,
Bwahahahahaha!!! I spit coffee all over my desk Augusto! Thank you sir!

My favorite is these 300 pound cows that fight over parking spaces closest to the fitness center...lazy
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  #34 (permalink)  
Old 02-13-2012, 03:15 PM
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6 Carburetor/1 quadrajet

Hey Chris, While I have to agree a six carburetor setup would be really cool looking, maybe you could take a different route equally as cool.

Not sure which Pontiac OHC six you've got, one barrel carburetor or a four barrel Sprint version. The 230 with a single barrel carburetor made about 165 HP on a good day versus the Sprint version that made up to 215 HP with a different cam, intake, split exhaust manifold and a Rochestor Quadrajet carburetor. I think they upped the last ones to 250 cubic inches.

You may want to consider the Sprint engine package if you can find the parts to upgrade yours. I had the opportunity to drive a Sprint equipped Firebird years ago and it was quite impressive for a straight six. They made fools of some guys in V8 cars from stoplight to stoplight, back in the day. olNolan
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  #35 (permalink)  
Old 02-13-2012, 04:58 PM
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If the OP gets on inliners.org he may be able to get info on cams and heads for one of those OHC pontiacs

Sam
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I have tried most all of it and now do what is known to work..
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  #36 (permalink)  
Old 02-13-2012, 05:05 PM
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Quote:
Originally Posted by AutoGear
Bwahahahahaha!!! I spit coffee all over my desk Augusto! Thank you sir!

My favorite is these 300 pound cows that fight over parking spaces closest to the fitness center...lazy
I hope your coffee didn't have lots of sugar, it will be a pain down there cleaning it up

300 pound cows..!! LOL, yea, I've seen them, they should walk to the gym...
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Old 02-13-2012, 05:11 PM
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Hey Augusto! Don't have a link but I think the car was at the Detroit autorama. It's rear engined and rear steer! The thing is wild!
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Old 02-13-2012, 05:24 PM
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Hey Augusto! Google Steve Grimes cars. That worked for me
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  #39 (permalink)  
Old 02-13-2012, 07:08 PM
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I think I found it:

http://2.bp.blogspot.com/-cZhscTwtTL...25281%2529.jpg

AWSOME..!!!

well those are not vaccum carbs, plain slide vintage bike carbs, just like the ones modern dirt and cheaper bikes use, harder to tune but I believe the effort is very well worth it.

AWSOME, again, I love it.

I wonder why I didn't find it in my first google search?

thanks.
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  #40 (permalink)  
Old 02-13-2012, 08:06 PM
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that looks good, you can not deny...
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  #41 (permalink)  
Old 02-13-2012, 08:18 PM
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Clarinet

Whoa, That is cool, looks like a horn or something to play music on.
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  #42 (permalink)  
Old 03-17-2012, 11:31 PM
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Hi Chris,

It sounds like we're doing about the same type of hot rod project, using a six cylinder and wanting to adapt 6 motorcycle carburetors or just 6 carbs. I'll tell you a little about what I've found out so far. Maybe we can help each other as we go along.

I always like a totally different type of hot rod, something that not everyone else is doing, just for the fun of doing it. My last T Bucket was powered by a 427 set on kill. This one now with the six, is something for a totally different reason ... just to see if I can do it and hope it turns out as well as I imagine it will.

I'm making my frame from round d.o.m. tubing, my own aluminium 23 T style body and a six banger with 6 Mikuni carbs. Everyone uses a V-8, but a Six in an old T hot rod seems to get more interest. Plus, if the combination of parts is all matched properly, there's nothing that sounds quite as cool as a hot six banger when at high rpm's.

The engine I'm using is a 200 cubic inch Ford inline six with the intake and exhaust cast as part of the head. That aspect of this engine seems to be one of its Achilles heels. To me it sounds like a fun challenge.
I'm a retired machinist and welder so the head-work needing to be done, I can do here in my garage. I don't know if your Pontiac has the intake and exhaust cast into the head like my Ford does.

I'll just mill cut and mill the intake runners down flat with anything else in that area. Then make my own intake manifold from about a 3/4" plate, then weld the same size tubes to match the Mikuni carburetor and attach the carbs to the new intake runners the similar to the way they were attached on the bike. I believe these carbs are about 36mm.
Then drill and tap the side of the engine making sure not to drill into a water jacket or anything, then use screw-in studs with some good adhesive on the threads for the intake plate to fasten to. That's the plan now but sometimes plans can be subject to change.

There's been allot of questions by others about doing this project or a very similar type of project. The main question they have is about how to properly keep the carbs all tuned. I'm learning as I go on this particular project and often times that's just the way we have to learn. But if the tuning of these multiple carbs is anything like the other multiple carbs on my other hot rods, a good vacuum gauge is the trick. I am thinking that I may even need to install six smaller vacuum gauges - one vacuum gauge per intake runner. Welding a bung up above the runners so the bungs don't interfere with the intake flow. On my other hot rods I've found the value of tuning an engine with a vacuum gauge works wonders!

On most of my cars I've installed a large faced vacuum gauge inside the car under the dash and I also mounted a smaller faced vacuum gauge under the hood into a threaded hole in the intake manifold. This has worked wonders on the tuning of a Holley 4-barrel 390 cfm on an Offenhauser intake and home made headers on my AMC Eagle with the inline 258 six cylinder. It's amazing how much closer I can put a good tune on an engine with the addition of a vacuum gauge or gauges.

A computer would be able to keep a modern system like this tuned constantly but when building an old school hot rod I just prefer to leave the computers in my newer cars, and keep a tool box handy, just my opinion. So to make the tuning last longer I'm going for the vacuum gauges to help me keep everything tuned and to tell me when something is starting to go out of tune so I can make the adjustment before it becomes a big problem.

I realize going into this project the complexity of using six motorcycle carburetors for this engine and I'm okay with it. I'm prepared to make adjustments more frequently than I would on something else. But I really like the coolness about using a hot six banger with six carbs in a 1,000 pound hot rod.

Let me know how your project is going. Like I said, maybe we can help each other as we go along.

Best wishes!

Quote:
Originally Posted by chrisinestes
I'm building a hot rod from the frame up. I'll be using a Pontiac OHC 6 for power. I thought it would look sweet having 6 MC carbs on it. I've done a ton of Googling on the subject and it's been done, but it's a tricky thing. Nobody I've talked to has actually done it themselves, they just have seen it done succesfully by somebody else. It seems the main problem is MC carbs don't have accelerater pumps and aren't designed to run with much fuel pressure at all. It's a budget build, so I can't just go buy 6 new Mikuni Harley Davidson carbs at $500 each.

Has anybody here done this, or know somebody who has? Any Ideas? They wouldn't have to be MC carbs, I'd just want 6 1 BBL carbs.

Thanks!
Chris

Quote:
Originally Posted by chrisinestes
I'm building a hot rod from the frame up. I'll be using a Pontiac OHC 6 for power. I thought it would look sweet having 6 MC carbs on it. I've done a ton of Googling on the subject and it's been done, but it's a tricky thing. Nobody I've talked to has actually done it themselves, they just have seen it done succesfully by somebody else. It seems the main problem is MC carbs don't have accelerater pumps and aren't designed to run with much fuel pressure at all. It's a budget build, so I can't just go buy 6 new Mikuni Harley Davidson carbs at $500 each.

Has anybody here done this, or know somebody who has? Any Ideas? They wouldn't have to be MC carbs, I'd just want 6 1 BBL carbs.

Thanks!
Chris
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  #43 (permalink)  
Old 03-17-2012, 11:46 PM
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My first thoughts are how much CFM does the engine require to operate? I suppose you could take the CFM required and divide by 6 therefore you have each single carb CFM requirement.

Did Pontiac use a variable CFM Q-jet on this engine? Sounds like a interesting project.

BT
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  #44 (permalink)  
Old 03-18-2012, 04:26 AM
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Quote:
Originally Posted by beertracker
My first thoughts are how much CFM does the engine require to operate? I suppose you could take the CFM required and divide by 6 therefore you have each single carb CFM requirement.

Did Pontiac use a variable CFM Q-jet on this engine? Sounds like a interesting project.

BT
The Sprint engine used a 750 CFM, side fuel inlet carb, much like what you'd expect to find on a SBC, except some Sprint Q-jets had the cutaway secondary air valve flaps seen on some (mainly Pontiac) V8 carbs. My original '68 Sprint had the the cut out flaps, I've seen other Sprint engines that had solid air valves- although I do not have any way of knowing if the other carbs were original or not.

Some carb number info:
1969- 7029260(AT), 7029261(MT)
1968- 7028260(AT), 7028261(MT), 17054906(?typo prolly?)
1967 (230cid) - 7027268(late, AT w/o AIR), 7027269(late, MT w/o AIR), 7037268(late, AT w/AIR), 7037269(late, MT w/AIR) [7027260 (early, AT w/o AIR), 7027261 (early, MT w/o AIR); 7037260(early, AT w/AIR; 7037261(early, MT, w/AIR)
1966- 7026260(AT), 7026261(MT)]
(info inside brackets from HPP magazine)

Besides the Q-jet carb and intake, the OHC Sprint engines had a bigger exhaust valve, higher compression and more cam lift and duration along w/dual valve springs and a split exhaust.

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  #45 (permalink)  
Old 03-18-2012, 07:46 AM
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slight subject change...

Hi,i was at Big Daddys (Don Garlits) anti-billet, rod show yesterday,just South of Ocala,fla,there was a car there with 8 SMALL TURBOS,turbos were mounted right in the header pipe,very close to the head,maybe 1 to 2 inches from head.,kinda neat,but i didnt have a chance to talk to the owner.nice engineering...
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