Inliners International Forums General Discussion Hi Performance Duel jet done!

I FIANILLY got the 2 bbl Dualjet 210 put on the car. Had to buy a new longer throttle cable, used 2 adapters, and the throttle bracket from a truck with a varajet carb. Ran a steel fuel line extension. I like steel fuel lines when possible. I used a 3/8 brake line and adapted it down to the stock 5/16 line. Because of the odd shape of the air horn a stock air cleaner base was used with good results. I am now out of hood clearance lol. The first adapter I used was a standard 2 to 1 sold at summitt racing for $14. That got me to a large base 2gc carb. The second one I had made out of me piece aluminum. A totally smooth transition to the first adapter. The carb I used was a reman off of e bay for a 267 or 305 Chevy. Bolted it up and adjusted the idle mixture screws. All I can say is WOW! The driveability difference is night and day. No more miss at idle no more cold engine stalls even the exhaust doesn't smell as bad. The pedal is at least an inch higher than with the old carb as soon as you touch it it goes! I may have to richen up a little, going to wait til I get my exhaust done first, then use the o2 and voltmeter trick to get it right. So..... I am going to "claim" 5 extra horsepower! This is simply the best carb swap that I have ever done. Jay

Oh yeah, I forgot you were using a Dualjet. Big bolt pattern there for little jets. Half a Q-jet.

Weird how 210cfm on a stock Monojet is so much more sluggish that 210cfm on a 2bbl?

i don't really know how much faster it is if at all. i went from 210 cfm to 287cfm. slightly morethan a small base 2gc which is rated at 278 cfm. Supposedly there is a small base 2gc with the same size venturi as my dueljet (7/32) that was rated at 311 cfm. I have never seen one but i am FAR from a rochester carb expert. I believe most of my driveability gains are from going from a wore out monojet to a reman dueljet. On the old carb you could shake the mixture screw by hand. The remaining other gain is from a little more cfm and the efficient triple venturi system. I expected it to be better, even i was surprised by how much better it runs. What i have is a little more than the front half of a 390 Holley. Jay

Oh, I thought you said it was a 210cfm Dualjet. 287cfm makes more sense. Yeah, my Monojet was rebuilt a few years ago when I bought the Camaro, so it probably is a lot more drivable than yours was.

I am sorry if I have confused anyone. There are two types of 2bbl Q-Jets made. The first one is the same size as a 4bbl Q-Jet but the secondaries are just blank no parts inside or fuel/air passages. The later model which I put on the car Is called a Dueljet 210. That's the model stamped on the carb. For those not fimiliar the carb has a smaller bolt patern than a 4 bbl but bigger than any 2bbl that I know of like a Holley 350/500. The air flow is exactly the same as an Autolite 2100 with a 1.08 Venturi but is more tunable with metering rods and "Adjustable part throttle" for even finer tuning. I like Autolite 2100/4100 carbs and have run them before with success. I just wanted to try something different and was very pleasantly surprised with the results so far. If a good one piece adapter could be made, this could be made to work better IMHO than a weber 32/ 36 conversion because it's easier to work on and flows more air. Jay

The 210 model number threw me off, I thought you were referring to the cfm.

What's the issue preventing a single adapter? Seems like an aluminum blank block could be drilled for the carb studs and manifold studs. Not just on the Varajet integrated head, but removing the 4bbl plate on the Offy and drilling the adapter out to fit the screws on that too. Maybe even the Monojet heads?

It seemed easier to me at the time to do it that way. The top adapter, which I had made, had a less of of a size drop top to bottom. The machine shop could also use a smaller block of metal to start with. So far no problems. If I had it to do over again, I would spend the extra $ and have done in one piece. The next adapter is going to adapt a Dueljet 210 to the Varajet 2bbl head and will be made in one piece. Another project I would like to try is to open up a 1bbl head as best as possible to see If any improvements can be made like has been done on a "Falcon 6 " head to accept a autolite 2100. Jay

this IS the Rochester book https://www.amazon.com/Rochester-Carbure...ster+carburetor from the ol' Model B to the electronic babies

Yes it is. I have both that new book and the old one that has a blue and green background. According to the above mentioned book the "big" 1-7/32 Venturi carb flows 287 CFM @3.0hg. After comparing other carbs, including the 50 CFM difference on Q-jets, I think that the real CFM should be around 300-305 @3.0 hg. Maybe I'm just splitting hairs and it really doesn't matter. One thing for sure the car runs a lot better and seems to have a little more power. When I get my exhaust done with the o2 sensor I can tune this the right way. I also took apart a junk 79 Dualjet and harvested the jets and metering rods. The rods in the junk carb are .051 with a .026 tip and the jets are #74 which is .074. I don't know yet what rods and jets are in the carb that I'm running on the car. It is a reman bought for me as a Christmas presant. Supposed to be for a 1979 267 or 305 V8. I should be pretty close. Jay
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with the emission cars, and carbs, a little fiddling with enriching the carb and advancing/quickening the timing, can really improve the response and general character of the vehicle. Even Monojets when treated to weaker power piston springs, plugging of the adj. part throttle circuit, and enrichment can really become nice carbs.
They are cheap at the swap meets--easier to find one of them without wornout throttle shafts than the old model "B"s so no rebushing is required (and they don't have that wheezing whistle at part throttle operation)
Old timers claim that when the four bbls came out, existing testing equipment could not "suck" hard enough to bring vacuum readings down to required 3.0 vacuum level, so to be able to use existing equipment, they starting using the now common 1.5 vacuum readings as a "standard" (for four bbls), thus the two different standards by which many are fooled/confused. Even some manufacturers stir that pot to their benefit.

I did a little more digging on the carbs that I have. The junk carb that I got the 74 jets and 51 metering rods from was for a 1979 Chevy pickup with a 305 and auto trans. The carb that is on the car (jets and rods unknown) is for a 1980 Chevy car with a 267 v8 and auto trans. Don't know for sure but it should be leaner than the 79 carb. We will find out when I get around to tuning it. I must be close because of the engine size and the car runs pretty good. I would like to try carb tuning with an O2 sensor, even a narrow band. I have bumped the static timing which helped a lot but I need to go ahead and recurve the dist. I have heard that model B carbs are getting somewhat hard to find. The last 2 swap meets that I went to there were no 1bbl carbs of any kind. Jay

Pictures thanks to my daughter

Finally get to see the Nova. Wow, that's impressive.....it must have take a long time to spray everything the same rusty oily black paint.

I didn't think about the fuel line have the big detour to get around the side like that. No real room to reverse it on the other side. Next is the adapter for the dual 2" manifold?

I have a dualjet off a 283. No tag on it, though. Have wondered if it would work on a lumped 292?

it should , but it mite ???? be a little small.

FWIW I'm using one on a 302 ci V8 and it pulls strong to around 5000 where it starts to nose over.

I didn't get notifications that you guys responded. I just added it to my watched thread list.

I may have to weigh my options when it comes to which carb to install. Recalibrated Q-jet, or the DualJet.