What carb is this?

[79blazer]

Hello I wanted to rebuild and tune my carb, but I don't even know what kind it is. It's on a 79 blazer I assume it is stock, but I am not a 100% sure it is. thankyou david Pictures:

[84 400]

i would be guessing so don't go by me but a rochester. hard to tell by the picks do you have any numbers off it? is it a 350? as fr stock i think the only options were rochesters and hollys. like i said with those pics i really can't tell

[lilpup69chevy]

looks like a rochester 2 bbl to me

[79blazer]

Brilliant! I went outside to take better pictures and look at it closer and it says Rochester Dual Jet 210. I am posting pictures anyway. This is all off my camera phone. So it looks like it is on some of v6 and 4 cylinder cars, and it’s like half of a quadrajet? I am getting 11mpg on a 2wd blazer 305 with spare and backseat removed to save weight. Any tuning/adjusting/rebuilding info out there? I’m looking too

[79blazer]

Found there is a Haynes book for this. http://www.shop.com/op/aprod-p365572...er?sourceid=13 i may get it, but is there anything online about this?

Update: Apparently, it is basically the primaries off a quadajet, with slightly larger diameter bores, maybe. CFM is around 225 and that’s measured at 3 vacuum, so it really flows a little more. It moves quite good for such a tiny carb. My caprice used to have a Q-jet with the lob cam on the secondarys broken, so it was effectively a dualjet. When we replaced it, it hardly made a difference, just used more gas. In stock form the 305 intake/heads/exhaust doesn’t flow anyway. So I will rebuild it with whatever autozone has for a rebuild kit. Does anybody get good mileage with this carb? I’ve read carbs are usually thrown together.

[MylilBowTie]

Look up Doug Roe for good info about Rochesters. ASIN: 0895863014

[jimfulco]

Model 2MC, I believe.

[84 400]

wow glad to see that u got it figured out. What is the rest of the truck look like? got any pics? what are your plans for t?
thanks and good luck with the rebuild

[cliffsta]

I have that same carb (i do believe), mine is a Rochester DualJet, stock on my '80 305 V8. As crappy as a carb as it may be, its like a cockroach. Done been rebuilt a few times, needs another rebuild, but it still gets the job done. Not very efficiently or effectively, but it works. Hoping it makes it this one more winter until I get a new motor next spring/summer.

[79blazer]

The doug roe book is on the mail now, there's a lot of good reviews for this book, so I got it. According to the Hanes book, The dualjet 210 has 1 7/32 venturi and 285 cfm. There's a 800 cfm quadrajet with 1-7/32 venturi primaries, and apearently, they're the same. Also it says when you lean out the jetting for better cruising and and light throttle, low speed and and medium to heavy acceleration are adversely affected. Anyway if I could be getting 14 mpg instead of 11 mpg i would save $40 a week in gas. I don't have a spare car at the moment so I don't have a lot of downtime to let the parts soak to clean them.
What can I use that will clean it faster? acetone?
CLIFFSTA, nice truck. what milage do you get?

[cliffsta]

Thanks I'm workin' on it.

At best, W/O air condition, I get about 12.5 city and 14.5 highway... with A/C we're talking 10-11 city / 13 highway. This is of course average... the most I have EVER gotten since I've driven the truck (about 2 and a half years) is 14.7. Worst is 10 flat.

[swervin ervin]

The Dualjet is basically a Quadrajet with the back barrels gone. It should get pretty decent mileage, although I've never had a vehicle with this carb so I can't say for sure. A Qjet will get the best mileage of any carb if properly tuned and driven right.

Believe me, rebuilding a carb is not brain surgery. I've rebuilt a ton of Qjets in my day and a few Rochester 2 bbls and Holleys. Rebuilding a Dualjet should be a piece of cake. Although not cheap, I prefer to use carb dip to clean my carbs when rebuilding. You buy it in gallon buckets with a dip basket. Although the basket isn't big enough to dip most throttle bodies. This stuff will take the skin off your bones and quickly cleans metal parts. You can brush the parts to make it clean quicker but don't even think about getting any on your hands. Rubber gloves don't help anything either.

The Doug Roe book is a Qjet owners bible. It offers a ton of advice and pointers for getting the most out of a Qjet, performance wise. It will surely help with stock rebuilds too. To do a stock rebuild of a Dualjet, a book isn't really needed. Just disassemble everything you can. Clean everything and put it back together. Check all measurements like float levels etc. Don't ever think about removing any of the throttle blades unless you want a mess on your hands. If it has the APT (adjustable part throttle screw below the power piston you don't need to remove it. There's nothing below the screw to clean anyway. If you do remove it, screw it in first and count the turns so you can get it back to stock settings. This will kill mileage if not set correctly. Oh, don't put any non metal parts in the dip or they will be history.

Check the throttle shaft for excessive loosness right off the bat. If the throttle body is worn around the shaft, it will never tune up right. You will need to rebush it to stock tolerance. Basically, check everything to make sure what you have is worth rebuilding. If it's been butchered by a previous gorilla and messed up, it's usually futile to even try to make it run right. Believe it or not, some people need to leave rebuilding carbs to others with a more gentle touch. With a little patience and kindness, rebuilding carbs is rather simple.

[cliffsta]

Ditto what Mike said. My dad rebuilt the DualJet at least four times. Granted he works on intricate copy machines all day long, but he's no Mr. Goodwrench. Usually takes him a good long while since he does it right, but I definately recall him doing it back in the day.

Only reason I'm not tackling a rebuild is because I know come next year I'm getting a new motor anyways.

[79blazer]

Was just going to get berryman's b12 Carb spray, but I got the dip bucket too $20 at Az. Popped off the carb and inside the intake is caked with carbon, I think? I've never seen one this dirty. Must be from the PVC valve? BTW, I am putting a new one in at the same time. It was buzzing at an idle. Also it idles fast but if you tap the gas petal lightly it will settle down to a good idle. 20" vacuum in the too-fast idle and about 17" lower idle, It will wander about an 1" Heres some pictures I took with my camera-phone and a flashlight. Going back outside to do the carb.

[79blazer]

My dad was telling me today my grandpa used to change the jets and other things and then test out the truck up a hill, to see if it got more powerful. This was at least 10 years ago. Gas wasn't an issue then. Now I know it's modified. He has alzheimer's now, and I wish he was well now, it would be so fun.

Well its all soaking now. Its pretty dirty. Lots of light brown something on the metering rods. The pictures show the holes where the oil is coming out of. ALso the space next to the barrels was were it was coming from. after I took the top section off and turned it over, around a teaspoon to a tablespoon came out of it, I would estimate. I am sure the combustion chamber is loaded with carbon. It smokes on start up, and I used to assume it was loose valve guides. The back bumper is oily by the exaust pipe, which exits a foot in front of it. It uses a quart of oil every 1000 to 2000 miles.

Any Idea what could be causing that fast idle? It's like the warm up fast trottle when its cold outside, but seems to be lean. If you shut it off with it like that, it will diesel. But if you lightly tap the trottle, it settles down. Drive with a little gas and it will come back, or drive in the nieghborhood with super low throttle, and that condition wont occur. I have read Low throttle is leaner than idle. thanks

[79blazer]

it went good. the hardest part was putting the top section onto the mainbody. Going back together it seemed very simple. Then I realised I for got the cup thingy and had to redo that. Then it wouldn't run untill i set the choke 180* (upside down) from what it was. And it took awhile to find several unconected vac lines. I need a vac diagram now. I knew I should have marked them, but it looked so obvious! It pings lightly at full throttle. If youre going 20 mph, hit the gas and it pings then it stops when it downshifts. It could be all the carbon in the engine. Well thanks for the help! David

Oh and I'll get pictures, when I clean it, its embarrising at the moment.

[MylilBowTie]

I would check the timing and see if that helps. Look to see how the spark plugs are burning. This will tell you more about what is going on.

[79blazer]

Topped off last night, then topped again today, I drove 109miles today, agressivly, and I was on the freeway at 75mph with windows down for several miles (lots of drag) The rest stop and go. I didn't drive like a grandma at all. Also I have a slowly leaking front tire thats 30PSI when I usally keep it 45PSI (looses 1/2 mpg) The mpg today was 13.366 a solid 2mpg increase 20%. The original tires were 235/75 and right now it has 31 X 10.5 may throw the speedo off 10% so it may be 14.8 mpg! The carb was modified a while back.. Now that is clean again, you can really feel more power at mid throttle, and it is addicting to hit the gas. I remember the markings on the metering rods were "T51" and the seat "75". Will check plugs today. how do you know if you need a new dizzy cap? Base timing is around 8 to 6* base

[81 rustruck]

I changed the dual jet to a Edelbrock 600 4 barrel ,then converted to a 700 r 4 tranny .

Now with 3.42 gears I get 250 miles out of 15 gallon tank at 70mph



If I drive at 60 mph I get about 20 mpg but who want to drive slow anyway