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Discussion Starter #1
After a hundred or so easy street miles on the outer springs only, I finally put the inners in and was able to really see what the new carb was all about.

It is like an on/off switch.

One minute you're cruising around at 2000 rpm, the next minute the engine is on the 7k rpm limiter sideways at 50 mph.

Unbelieveable response! Awesome idle! Fantastic driveability on the street!

Gonna try it out at the track tonight, so I'll know exactly what the carb is worth over my old setup....

I am guessing a couple tenths in the 1/8.

I'd like to thank not only Bob Oliver at Competition Carburetion, but also Dave McLain for turning me on to him.

Later,

Greg
 

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Sounds cool Greg I can't wait to hear about your track results.

Bobby Oliver is a real stand up guy who builds some great carburetors. He builds all of them one at a time by hand and after seeing him in action I totally understand that in carburetion, the really good stuff has to be built that way. There is just so much detail work it's quite amazing.
 

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Discussion Starter #5
Well, the car ran awesome last night.

Right off the trailer it ran a 6.88 at a tic over 100 mph. Previous best was 6.97 at 98.5 mph. Upped the jets 2 numbers front and rear and the car went 6.85 at 100.5.

I think the mph increase speaks for itself, the ET was a little low due to poor 60 foot times. I think the car had an easy 6.80 in it if the traction was there.

Although we had the car torn down for the winter, the only engine change I made was to install the cam straight up (vs. 4 degrees advance) and have Bob rework the dommy.

Greg
 

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Discussion Starter #6
Jim W said:
Greg, Are you still at 1050 cfm? If so, what made you choose that over 1250?

Thanks!
Jim
I drive the car on the street, and didn't see the need for a gigantic carburetor. Hell, I was happy with the 850 DP!

Greg
 

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That is good!!! You got a tenth in the 1/8-mile. It shows what a good professionally dialed in carb can do; better times and better driveability.

Dave
 

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Try this link to a page on my website it'll give you some idea as to what Bobby can do with a carburetor core. He'll build new or rework used stuff and you can ask him, I've sent him some dandy cores! For instance there are some before and after pictures of a 4412 Holley. The same carburetor and then another one that's modified and not "tech legal".

http://misn.com/~frd460/compcarb.html

There are some prices on there which while not exactly current should be reasonably close for a given carburetor package.
 

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How does a carb guy build a carb for a known engine, when he doesn't have the engine to test it on? I saw he has a test stand/engine. but.

Are there formulas he/she works off of for air bleed settings, etc?
 

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I wondered the same thing till I went to Reno for a visit. Believe it or not what he has is a book with all of his carburetor recipes written down, various combinations of bleeds, jetting and metering block calibration all developed after many years of dyno and track testing etc. Sometimes what runs good on the dyno won't race or drive very effectively. Some of this stuff stays about the same and other stuff changes quite a bit over time. Bobby has a huge list with every carburetor listed by serial number, what calibration was used, what booster and what application.

A really good carburetor package will run very good on a variety of engine combinations and the better the package the better it will do this and the less engine specific it will be because the fuel curve is more controlled from conditions of very low, moderate or very high flow for a given design and it will only require some minor tweaking to be spot on with any given combination. He'll adjust the carburetor package a little one way or another, setting it up somewhat differently for drag, circle track or street to get it really really close out of the box for the intended application it is quite amazing.

Usually carburetor builders who play like their stuff is very engine specific and won't run well on something else, a Ford big block instead of a Chevy for instance really just don't have a very good package for a specific carburetor.

What the engine test does is verify that all the circuits are working, the float levels are correct, accelerator pumps work, no leaks etc.

While I was there we did two gas 4412 packages, one tech legal and another with a modified booster as per the rules. The difference on the test engine was quite astounding with the tech legal 4412 sounding good and crisp but the modified booster version sounding just that much better response wise.

Nothing about the carburetor build process is very high tech but it's very time consuming with an incredible amount of hand work. The metering package involves lots of careful compromises and precise work. Placing and sizing the restrictions in the emulsion well is both art and science when it comes to getting something that will run well at many throttle positions, rpm, engine loads etc.
 
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