Re: Rochester 2GC info
 

Jeff, sent you a pm on some of the bigger 2bls.

Re: Rochester 2GC info
 

I to am interested in the 1.375" venturi carbs. Thanks.

Re: Rochester 2GC info
 

While researching some other carb's today i ran across the following. Carb's 7042118 and 7042838 (large 1.375 venturi's) were installed on all models of that year with the 400 motor.

Document used was the napa carburetor application and parts guide......then checked the nhra eng. Spec. Sheet and found 1.250
venturi listed..maybe typo???/ these carb's have never been machined as the parting line(s) in the venturi are still there....

Any suggestions?????

Re: Rochester 2GC info
 

Here's another one:
The 1969 full size Chevy 327 /235 used some form of the big base carb.
The 327 /210 used the small 1.09 carb .
That is the difference between the two engine options..
Yet the NHRA specs list both using the same (small ) carb and manifold.

Re: Rochester 2GC info
 

Mark & Norm -

When I was building the database for the ClassRacerInfo application, I had to physically enter about 90% of the engine data. That's why I have repeatedly asked for input for any discrepancies that are found since I know tat I make lots of mistakes. But that also means that I read every tech sheet in the book and know that NHRA office personnel have made mistakes, too. As you two have pointed out in your examples, there are "questionable" items in the specs (and the class guide, too!). I compiled an Excel spreadsheet for some of the tech specs and it is not a short list. Mostly the items are for engines that have never been raced so it's not like anybody is getting screwed on the deal. Engines that have been pounded on over the years have forced corrections (remember the 4-bbl 260 Olds?) and many times racers have worked with the tech department to get corrections done.

I wish there were an easy way to submit corrections and then some public feedback about to explain what makes acceptable documentation and what doesn't work. I know the tradition of "writing a letter to the tech department" works, but most racers don't even know it is available and that those processes are active now. The stumbling block for NHRA to manage the technical data is the cost of the time to do the tasks necessary and management decisions.

Norm, information from aftermarket sources is rarely accepted as evidence for spec accuracy. While it may be correct and the assumption is that it is pointing to factory specs, documentation from the OEM is the best source . . . most of the time.

Mark, if we have never had that conversation about the 327-235hp carburetor, I am in total agreement that the bigger carb was on that engine. I have parts books from that era that clearly shows the same intake manifold used as on the 350 250, and Rochester specs indicate that the components of the carbs listed are for the big series 2GC.

Finally, my goal for ClassRacerInfo is to be the most complete and accurate source of data for Stock & SS racers as well as representing the NHRA data. And having the data in a database where you can query for data is so cool and powerful.

I'm finished rambling.

Re: Rochester 2GC info
 

Dwight, remember a couple of Texas Jr Stock racers punching the inserts out of the boosters in 2bl Rochesters? Took me a while to find out how they made 2bls run that fast. One of one of those guys recently-ex-friend told me. I asked about it, so they showed me. Got through tech a long time that way. Only a mechanic that kind of specialized in carbs & tuning would likely have even noticed while looking at one.
A record or two was set like that. :-)

Re: Rochester 2GC info
 

Ed, I've found some Marine 2Gs that didn't have the inserts in them over the years. Especially on OMC 2.3 FFFord motors

Re: Rochester 2GC info
 

Never head about that! But it sure doesn't surprise me! LOL!


My very, very first race car was a '57 Chev 283-185 hp 150 business coupe and I found that I could use secondary boosters from certain 4GCs that didn't have the inserts and pick up a bunch. I never ran fast enough to be seriously inspected, but I doubt that it would have been caught.

Re: Rochester 2GC info
 

guy's that's an old trick from the 60's , but it reduced the booster signal . brad urban from the carburetor shop also tried it years ago but with limited success.

for our circle track customers that have to run a 2gc or a marine carb. we designed a
a cnc'd alum. insert that replaces the original restrictive insert. booster signal improved as did the total cfm.

the above may not be legal per your track rules. but some times it pay's to think outside the "box".......

Re: Rochester 2GC info
 

If I told you who it was (no longer racing) you would not be suprised at all. LOL
I will tell you at the track some time. Not ratting them out here.

As for booster signal, yes they need jetted differently. Both were stick cars.