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Anyone convert 2 to 4 barrel carb? Is using an adaptor ok? Our do I need to but the 4 barrel manifold? Bj's off road makes an adaptor.
2 barrel to 4 barrel
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Most people stick with the 2barrells. But the people who switch to a 4bbl usually run the 390 Holley with a offenhauser intake , a header and most of the time they have a aftermarket camshaft also
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4,757 Posts
What Tom said.
I have the Offenhauser intake, and a 4bbl carb, but my motor is far from stock.
Most 4bbl carbs are too large in CFM for a 6cyl motor. I have the Holley 390CFM and even it is pushing the limits on my motor. Besides needing all the extras to go along with a 4bbl, it is much easier to do an MC2150 2bbl for a swap.
The adaptor plate is ok to use if you are dead set on putting a 4bbl on it, but you have to keep in mind that even though there is a ton of room in there now for clearance, there wont be once you switch to a 4bbl and an aftermarket air cleaner. Your stock air box system will no longer fit on the mouth of the 4bbl.
I have the Offenhauser intake, and a 4bbl carb, but my motor is far from stock.
Most 4bbl carbs are too large in CFM for a 6cyl motor. I have the Holley 390CFM and even it is pushing the limits on my motor. Besides needing all the extras to go along with a 4bbl, it is much easier to do an MC2150 2bbl for a swap.
The adaptor plate is ok to use if you are dead set on putting a 4bbl on it, but you have to keep in mind that even though there is a ton of room in there now for clearance, there wont be once you switch to a 4bbl and an aftermarket air cleaner. Your stock air box system will no longer fit on the mouth of the 4bbl.
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64 Posts
I have a webber carb on it now. A friend has a 4 barrel holly, he said he'd Give me. Today he said he also has the intake for it. I dont know the brand of intake. I Dont have my heart set...I just figured free 4 barrel. .. why not?
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4,757 Posts
The only 2 intakes that I have ever seen that are 4bbl for a 4.2L are either a Clifford or an Offenhauser. I went with the Offy because the mounting ears that share a bolt with the exhaust manifold are the same thickness as the exhaust ears, the Clifford does not. It requires shims to mount properly. I didn't like that idea, so I went with the more expensive intake.
I should've stayed with the 2bbl set up, because like I said above, even the little 390 CFM Holley is a bit much for the 4.2L. And after having to buy a fuel pressure regulator, and float springs so that it doesn't flood on a hill, and all the other linkage adapters, I have a pile of money into running a 4bbl carb. With the cost of the carb and intake and all the rest, I have close to $1000 into just the intake system.
I should've stayed with the 2bbl set up, because like I said above, even the little 390 CFM Holley is a bit much for the 4.2L. And after having to buy a fuel pressure regulator, and float springs so that it doesn't flood on a hill, and all the other linkage adapters, I have a pile of money into running a 4bbl carb. With the cost of the carb and intake and all the rest, I have close to $1000 into just the intake system.
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Hmmm. I think ill stick to the 2 bbl that I have. Maybe I'll just sell the 4 bbl then.
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Years ago I put a brand new Edelbrock 200cfm ( I believe) 4bbl carb on my CJ7 on the stock intake and it fit just fine. Actually got better fuel economy than my Weber because the front jets were smaller. But when you opened her up and the back jets came on she woke up fast. Also had to install a fuel pressure regulator for those off-camber situations so it didn't flood.
You would buy a 4 barrel to 2 barrel adapter and turn it upside down to make it a 2 barrel to 4 barrel adapter....... but, like Drednot said, why?
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1,020 Posts
We tried it on a buddies CJ 4.2 cause he had a 4bbl laying around..think was off a 327....motor would flood when the 4 bbl opened up...he is running a 2100 on that jeep now...it can be done but why?
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Probably flooded because it was a high CFM 4bbl. My 200CFM was perfect. Never flooded. The fuel pressure regulator helped.
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1,020 Posts
No probably about it that was the issue..we adjusted so all 4bbl never opened just the front 2...runs a lot better now with a 2100...we pieced that Jeep together with left over parts from 3 other Jeep rebuilds..lol..so we were experimenting with just about everything..
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92 Posts
Ain't it awesome how you can do that with Jeeps? Experience is the best teacher.
For those of you asking why I would want to put a 2bbl carb on an Offenhauser Intake manifold... My stock intake manifold on my 1989 jeep wrangler yj 4.2L is warped and has a massive vacuum leak. The only other manifold I found was the Offenhauser. I have read that the four barrel carbs are too big for the straight six and issues can arise, plus the motorcraft carb has been a great, reliable carb thus far and I don't want to get rid of it.
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