Anybody got any experience or thoughts on the topic of carb porting? Is it worthwhile? are there significant improvements to be had? what is involved?

If your'e talking about Holley carbs, check out the Proform main bodies.

http://store.summitracing.com/defau...0+200405+304808

Unless you have a flow box and airflow experience, stay away, all you will do is destroy a good carb..

Porting a carburetor wrong can not only lead to poor performance, but can cause an engine to run lean enough to actually hurt itself. Unless you have the testing equipment, and money for trial and error you're generally better off getting a properly set up carburetor.

You guy's gotta start thinking outside the box.

Yes you can rework a carb for lot's of advantages as well as a few disadvantages but you gotta know what you are doing. You can do the same thing that C&S or BG or The Carb Shop or whoever does as long as you have a FULL understanding of fluid Dynamics and thermal transfer and chemical analysis.

For example...I worked over a 4412 two barrel carb two years ago for a circle track buddy in a IMCA Modified. While other people are spending $1200 on a carb this one cost 200 in part's and Misc. stuff. It has a bore large enough to drop a silver dollar straight thru the bottom. It flows (stock trim @480cfm) 635cfm at 3". The same as the popular street version four holer. Drivabilty was suffering but track packing was the biggest concern without loading up. 7000 RPM power peak was the goal. It takes time and patience but the average dude can do it with enough determination to really learn the carb functions. I must say though, it does take extensive research, more than what most are willing to put forth.

I appreciate the replies.
I seen a website about "home porting the holley carb" and was wondering if this is just somebody selling books or if it was a worthwhile venture.

I don't know what your definition of average is, but the majority of average guys I know find it a challange to just tune a Holley let alone redesign one.

More power to ya' but advising the average guy to have at it will in most cases lead to a tossed main body.

Holley (HP series), BG/Demon and others have already done the R&D. (To say nothing of the "tuner" shops.) If a guy wants such a carb........buy one.

I understand your concern,
but I am trying to get away from this mail order performance trend. I am a fairly experienced mechanic, and would like to further my studies into engine optimization, rather than just doing the bolt on stuff. Anybody with a bank balance can do that. You know, the stuff like intake manifold porting, head and possibly carb porting and tuning, balancing, deburring and polishing block surfaces the stuff that makes small gains, but adds up to be a superior engine to the off the shelf stuff. i think this crate engine craze is really okay for the kind of guy who is afraid to tear into an engine, but we really need to keep the hotrodding roots alive!

Good luck to ya' then. And keep us posted.

I appreciate the encouragement, and I encourage anyone else to forward any other links or info that may be of interest to this subject....What the hey, it may add some more depth to the knowledge base here.
ps great link to the proform stuff. I hate to say it but that's pretty cool, and you still get to monkey with the carb a bit!

The Holley 6425 two barrel, came stock at 650 CFMs. I paid $100 for the one I used to have.

Yea but.........could you drop a silver dollar straight thru the bottom?

David Vizard's carb & induction book has some info about things you can do to increase the flow of a carb.

I'll be looking into that one! A 4412 is the only legal carb by the sanction. The numbers had to be visable so the choke horn could not be machined flat and port entry had to remain "stock appearing", Whatever that means.

Thanks

just a little follow up on this subject.
I live in canada, so all prices quoted are $canadian.
A proform carb body is worth $179 (up here)
would have to purchase a new throttle plate to get the 750 cfm I am after, according the the guys at Mopac auto for $150
package deal was just under $400 cdn with taxes.
New holley avenger about $400 cdn 750 dbl pump mech sec
new street demon $600
used holley carb avg $200.
used demon avg $200-400
any thoughts on the best combination of parts given these variables? I am thinking used holley with proform carb body will equal about $400, or reworking a stock holley (used) for about $250.