[zbhover]

Hello everyone, today between the rain drops I was messing around with our 350 donor engine, just trying to get it running as good as I can while its still in the truck, which is a 1977 Chevy C-20 Camper special.

The choke is always closed on the quadrajet carb so I figured I’d take a look at it and see what I could do. I got out my Haynes manual to look at a parts break down of the carb to check and see if all the linkages were there and correct, etc…. Maybe it’s the bimetal heater too???

Anyways that’s when I noticed that my carb didn’t match the drawings of the 4MC/4MV or M4MC/E4ME series quadrajet carbs in the manual. The main difference that I noticed was the fuel line was going straight into the front of the carb instead of into the side like the drawings. So I wrote down the numbers from the carb which were:

Rochester Quadrajet
17058263
0938 BBC

I jumped on the internet to see what I could find and it looks like this carb was originally on a 1978 Pontiac with a manual transmission. And built 93rd day of 1978, and I have no clue what the BBC means??? From what I could find it’s an 800cfm and the original carb on the truck may have been a 750cfm????

Does anyone know a link to a parts break down of this carb or have one they could email me??? Or maybe which series or model # this carb is???

I also have a couple other questions:

If this carb is actually a higher CFM carb could I get any performance advantage with it???

Also would this carb have mounted to the stock chevy intake??? Or is it likely that I also have different/ Pontiac intake.

As far as I and the p.o. know this was the stock engine for the truck (casting #3970010) he had the engine and heads reman’d but reused the intake and carb that was on it when he bought it.

[zbhover]

I found one on ebay that looks simular and the number on the carb is the same except it was on an automatic. the link is:

http://cgi.ebay.com/ebaymotors/Rocheste ... enameZWDVW

and if that doesn't work the auction # is 250292353819

Thanks

bye

[curtis73]

GM was very loose with their part stamping. It's quite possible it was from a 78 pontiac and someone put it on your 350, but more than likely it was what they had on the assembly line and it went on. The front-feed fuel line was more typical of Buick and Chevy. A quote from recarbco.com's website:

Keep in mind that just because the OEM numbers between two carbs may be different, it doesn't mean they are different carbs. It's very possible to have two carbs, their date is 2 years apart, one is for Buick and one is for Chevy Truck, and one is for automatic, the other for stick, and the carbs are identical in every single way, even down to the jets and metering rods. It's much more common than you might think.

If its an electric choke, check to see if you're getting 12v to the wire, and then also test continuity from the choke housing to ground. If its more than 1 ohm, run a dedicated ground from the choke housing to the manifold.

If its a mechanical choke, make sure the linkage is freely moving and bend the rod to adjust it.

[jb63vet]

that most likely came off a pontiac 455 Big Block cuz thats what the BBC is its big block casting and people now say it stands for big block chevy but it was originaly the abreviation for big block casting thats why is also is pushing more cfm

[jbvcw71]

Chances are that it's off of a 400-455 1978 49states Pontiac.
Vehicle could very well be a Trans Am.
Might be a better idea to sell the carb for restoration use & use the funds to buy a much healthier model.

It is DEFINATELY NOT a Chevy carb. They NEVER had front facing fuel inlets.
Peorid.

As far as the manual trans identification it is not set in stone so it could be from an auto trans donor car.

Adjust your choke setting to get the valve to open slightly in the current weather conditions at hand. (carbs are generally adjusted seasonally)

[JeffB]

Originally Posted by jbvcw71

Chances are that it's off of a 400-455 1978 49states Pontiac.
Vehicle could very well be a Trans Am.
Might be a better idea to sell the carb for restoration use & use the funds to buy a much healthier model.

It is DEFINATELY NOT a Chevy carb. They NEVER had front facing fuel inlets.
Peorid.

As far as the manual trans identification it is not set in stone so it could be from an auto trans donor car.

Adjust your choke setting to get the valve to open slightly in the current weather conditions at hand. (carbs are generally adjusted seasonally)

Strange! my next door neighbor had some carbs for sale I posted for him,His '78 one ton 454 dually had a rebuilt Quadrajet from Holley purchased from Summit, numbers crossed over to the correct year and model also shown as 650CFM and had a front inlet same as the original.

[jbvcw71]

Originally Posted by JeffB

Strange! my next door neighbor had some carbs for sale I posted for him,His '78 one ton 454 dually had a rebuilt Quadrajet from Holley purchased from Summit, numbers crossed over to the correct year and model also shown as 650CFM and had a front inlet same as the original.

Only a couple of red flags with your experience.

1. All Rochester Quadrajets were either 750CFM or 800CFM
They never made a 650cfm carb from the factory.

2. Not sure what you'd get back as far as mainbody casting #'s if you had Holley (not Rochester) & Summit (also not Rochester) "rework" a factory carb.
Sounds alot like a "Frankenstein" carb. Probably a mish-mash of aftermarket parts...

3. The front inlet for all Chevy carbs points toward the passenger's side.
Front inlets for BOPC (Buick,Olds,Pontiac,Caddilac) all point toward the radiator.

What did you get for the carbs? (*Bay I'm assuming)...

[zbhover]

Thanks for all the help and ideas guys...

After a few hours of searching I finally found the info and drawings I was looking for. I finally found one of these carbs on ebay and he had a model # with it so I searched for that model # and came up with the carb doctor http://www.carburetor.ca/carbs/tech/...jet-index.html

There is a BUNCH of drawings of all the rochester carbs on there along with a bunch of manuals, etc.

I found carb sheets for 75-79 pontiac carbs (104mb pdf 200 pages) and after searching it looks like the only car that this carb was put on was the 1978 pontiac firebird 400cid 4 speed manual and the carb model # is M4MC. The carb sheets show a few nice exploded views of the carb and list out the part# for various kits, gaskets and every part in the carb.

I also found an 79 page manual that covers that model carb, with lots of info

If anyone needs info on rochester carbs, I'd take a look at that link above..... Lots and lots of stuff

I think I'll keep this carb, it doesn't look like people are getting much from them off of ebay, I might go with a different intake, but I think I'll keep the q-jet.... But that will be another post.

Thanks again to everyone for the help..... Now if it ever stops raining here in central IL I'll be able to go back to working on it.... LOL



Talk to you all later

bye

[JeffB]

Originally Posted by jbvcw71

Only a couple of red flags with your experience.

1. All Rochester Quadrajets were either 750CFM or 800CFM
They never made a 650cfm carb from the factory.

2. Not sure what you'd get back as far as mainbody casting #'s if you had Holley (not Rochester) & Summit (also not Rochester) "rework" a factory carb.
Sounds alot like a "Frankenstein" carb. Probably a mish-mash of aftermarket parts...

3. The front inlet for all Chevy carbs points toward the passenger's side.
Front inlets for BOPC (Buick,Olds,Pontiac,Caddilac) all point toward the radiator.

What did you get for the carbs? (*Bay I'm assuming)...

The carb in question was sold on Phoenix craigslist for $85 it came from Summit @$249, the Holley rebuild tag was on the side,the 650CFM showed up when I googled the number I thought that was odd also as I had only heard of 750 and 800CFM Quadrajets.I can only imagine that the majority of rebuilt Quadrajets out there are a combination of mis-matched carbs and the casting numbers are probably worthless anyway,that being said for the Quadrajet lovers out there check out My Classifieds and find these a home so I can buy more Ford parts.

[curtis73]

Originally Posted by jbvcw71

It is DEFINATELY NOT a Chevy carb. They NEVER had front facing fuel inlets.
Peorid. The front inlet for all Chevy carbs points toward the passenger's side.
Front inlets for BOPC (Buick,Olds,Pontiac,Caddilac) all point toward the radiator

Sorry, gotta disagree on this one. There were trends, but no hard and fast rules. I've built three caddys, all had a side inlet. Almost all of the BBBuick engines I've seen have the front inlet. I've owned four Pontiacs and they all had side inlets. My 78 Chevy 1-ton truck with a 350 had a front inlet.

The front inlet is much less common than the side. What you would be suggesting is that about 75% of them should have front inlets and that is just not the case.

It was more dependent on the vehicle and where the accessory drives were (as well as what accessories were installed.)

I do agree, though. No such thing as a 650 Qjet... all 750 and 800, and it was a difference in the primaries. Take a look at these two comparisons. Notice the larger primaries on the 800. By the way; the 800 came off a Caddy 500 and the 750 came from a pontiac 400... both had side inlets. I'm not arguing, just presenting info.

[ScoTFrenzel]

Quadrajet cfm ratings are determined by the amount the secondary air valve opens.
301 TransAms the air valve only opened about 1/3. Had one.
Dad had a Buick with one that opened about 1/3.

So NO, they are all NOT 750 or 800 rated.

[badmystur]

i have a quadrajet that i got from a buddy thing is in mint shape , but i need to know what it originally came from, here is the numbers i have ,,,
17080202
0280 CPK
anyone know of a site that tells all about the carb numbers ,and what they mean,,,,,,,,,,,,,,,thanks very much,,,,,,,

[cobalt327]

Originally Posted by badmystur

i have a quadrajet that i got from a buddy thing is in mint shape , but i need to know what it originally came from, here is the numbers i have ,,,
17080202
0280 CPK
anyone know of a site that tells all about the carb numbers ,and what they mean,,,,,,,,,,,,,,,thanks very much,,,,,,,

1980, AT trans linkage hook up most likely.

Good carb to build for performance, unless it's a feedback-type carb w/electrical connections on the carb top for TPS and the mixture solenoid. These generally were used '81-up, but a carb made in '80 could be used on a '81.

More- http://www.cliffshighperformance.com...carb_ID_2.html

That site has a lot of good info, tech discussions, forum, etc.

Good luck.

[345 desoto]

17080202 = 1980, Non California (Federal), Chevrolet, automatic transmission...

[badmystur]

hey guys , very much appreciated this site has an amazing amount of info,thansk again,have a good