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I'm considering going to the national level next year, either with my ITB Capri (F Prod)or ITB Rabbit (G Prod). The GCR mentions that the Capri 2000 can have dual sidedraft carbs with 30mm chokes. Those are awfully small and probably less carb than the 32/36 DGAV on my car right now.
Question, where are the production sites like this one for IT?
Anyone with experience with a 2 liter built to Prod trim with these small carbs?
Joe,
Check out http://www.coloradoscca.org/prodcar for the prod website.
As far as carb goes, the dual side draft has (4) throttle openings, w/ 30mm chokes. The area of the openings is approximately 28.26 sq. cm. The 32/36 has (2) openings w/ an area of 18.21 sq. cm.
Looks like the dual sidedrafts have a little more breathing than your 32/36 DGV! http://Forum.ImprovedTouring.com/it/biggrin.gif
Don't discount that Rabbit in GProd either. If you look at the two classes, you'll probably be more competitive with it in GProd than the Capri in FP. Plus there are a lot more VW guys racing in GP than Capri guys in FP, so you'll have a larger network of racers to rely on.
MC
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Mark Coffin
#14 GP BSI Racing/Airborn Coatings/The Shop VW
Scirocco
Zephyr Race Coaching and Consulting
http://pages.prodigy.net/Scirocco14gp
Mark, that is what I originally thought. A carb dealer told me that my motor needs at least 34mm chokes, 30mm will restrict power to under 5000rpm.
After thinking about it, the full capacity of the DGV is available to each cylinder since they draw through it one cylinder at a time through the common plenum of the stock intake manifold. In the IR manifold with 4 carb barrels, only one barrel is available to each cylinder. Plenunms for side drafts are explicitly against the rules.
The low cost and high reliability is the attraction of the Rabbit. I've found that my Capri is faster than the Rabbit in ITB, although I'm probably within a second of each other at most tracks. I have an incredibly amounts of spares for the Capri, 4 blocks, 11 heads, 3 carbs, 4 transmissions, 3 complete rear ends with limited slips, 3.22, 3.44, 3.89, 4.11, 4.66 rear end gear sets etc. I don't have many spares for the rabbit, nor has it really needed them - LOL.
Tough choice. Keep the Capri for ITB, Rabbit for GProd, maybe that is good way to go.
Thanks for the prod site link.
I ran a 2 liter Ford in the '70's with cam and side draft carbs of 40mm throttle bores. Seems to me I had 32mm venturi on them which I eventually opened to 36mm.
The Weber Catalogue recommended the following:
High performance would be venturi 90% of the throttle bore.
Street performance would be venturi 70% of throttle bore.
My engines would rev freely to 7500 RPM then starve for air, with the engine not exceeding that limit.
It was quite the Tiger up to that point. Smaller percentage venturi will give better signal strength to the emulsion tubes for mixture and response at lower speeds.
If there is any choice, I'd go with the Capri for handling (rear drive,using the 3.89 rear), and power. The 2.0 is bullit proof, and a lot of fun. Miss mine.
Incidentally, racer14itc may be misleading if his comparison is with the "32/36". Those numbers are actually Throttle bores, and the comparison should be with the Venturi sizes, which are actually 27/28mm. They are marked on the outside of the carb body, about where the venturi are.
His point is valid; Four 30mm chokes are greate than one 27 and one 28mm choke.
Go for the larger!
Good racing.
Bill
Thanks for clarifying that, Bill. I know NOTHING about carburetors, and just assumed the 32/36 stood for the throttle bores/chokes. I've only dealt with fuel injection my whole racing career, so carburetors and all their components are a mystery to me.Quote:
Originally posted by bill f:
Incidentally, racer14itc may be misleading if his comparison is with the "32/36". Those numbers are actually Throttle bores, and the comparison should be with the Venturi sizes, which are actually 27/28mm. They are marked on the outside of the carb body, about where the venturi are.
His point is valid; Four 30mm chokes are greate than one 27 and one 28mm choke.
Go for the larger!
Good racing.
Bill
My recommendation about the Capri in FProd vs. the Rabbit in GProd is that in FP the cars to beat are the Huffaker Midgets, and Steve Sargis' Spitfire, which are both as fast as 98% of the EProd cars! GP is a little more reasonable in terms of car potential and variety.
MC
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Mark Coffin
#14 GP BSI Racing/Airborn Coatings/The Shop VW
Scirocco
Zephyr Race Coaching and Consulting
http://pages.prodigy.net/Scirocco14gp
Thanks guys, I did look at the Valvoline runoff results and those FP cars are 2 secs/lap faster than GP. I don't think a Capri with 30mm venturis will be that much faster than a LP Rabbit.
I did some searching on the internet and this is what I've found out.
Pinto 2000 needs the following DCOE Weber choke sizes by rpm
5000rpm 32mm chokes
6000rpm 36mm chokes
7000rpm 41mm chokes
On another site, they list various recommendations for cars. Using a BMW 2002 and expected power output
120-130hp 40mm DCOE w/32mm chokes
130-140hp 40mm DCOE w/34mm chokes
150-160hp 45mm DCOE w/36mm chokes
BTW, my ITB 2000 is putting out between 130-140 flywheel hp. If I put on dual 40mm DCOE w/30 mm chokes, information indicates that I will probably lose hp. My motor with stock cam gets peak hp a bit over 6000rpm.
I just ordered a book, need to learn more about this.
Where did you find this info at? mike
Joe,
Try to get your hands on the original Weber Catalogue, the "master book" which explains theory of carboration and relationships of various circuits in the applications. I never understood the device until reading it, and the remainder of the book deals with applications.
You might find it with a search engine.
Good luck.
Bill
thanx...mike g http://Forum.ImprovedTouring.com/it/smile.gif
Here is the site with the Weber DCOE venturi size information
http://members.aol.com/dvandrews/webers.htm
I did other searches with Google to get different information.
BTW, it appears that the optimum carb will be the DCNF 40 with dual 34mm chokes on either the stock or aftermarket single carb manifold. I wonder how much power one can get with a Pinto 2l lump with stock valves and a single carb.
Joe,Quote:
Originally posted by Joe Craven:
Here is the site with the Weber DCOE venturi size information
http://members.aol.com/dvandrews/webers.htm
I did other searches with Google to get different information.
BTW, it appears that the optimum carb will be the DCNF 40 with dual 34mm chokes on either the stock or aftermarket single carb manifold. I wonder how much power one can get with a Pinto 2l lump with stock valves and a single carb.
In FP, you'll have to use the stock intake manifold with the single DCNF downdraft carb, w/ 34mm chokes. You can port it, etc., but the aftermarket intake manifold isn't permitted with the DCNF. At least that's what my 2004 GCR/PCS indicates.
MC
Unless I misunderstood Joe's intentions, he seems to want to go to FP, not neccessarily with an IT car, but normal level modifications (jump in here, Joe!).
My 2003 GCR lists:
"(1) 40 DCNF, IDF w/34mm choke(s), (2) Automotive type sidedraft w/30mm choke(s) on I.R. manifold, 32/36 DGV.DGAV,"
Assuming no changes in 2004 (a bad thing to do, I know), that would allow two sidedraft carbs of unrestricted throttle bore sizes with 30mm chokes on an independent runner syle of manifold, in addition to the other choices listed. At least that is the way that I read this section. Corrections?
Good racing.
Bill
That is correct. Joe thinks that the single downdraft with 34mm chokes will make more horsepower than the dual sidedrafts w/ 30mm chokes, and he may be right. Only way to find out for sure is to build it and try it!Quote:
Originally posted by bill f:
Unless I misunderstood Joe's intentions, he seems to want to go to FP, not neccessarily with an IT car, but normal level modifications (jump in here, Joe!).
My 2003 GCR lists:
"(1) 40 DCNF, IDF w/34mm choke(s), (2) Automotive type sidedraft w/30mm choke(s) on I.R. manifold, 32/36 DGV.DGAV,"
Assuming no changes in 2004 (a bad thing to do, I know), that would allow two sidedraft carbs of unrestricted throttle bore sizes with 30mm chokes on an independent runner syle of manifold, in addition to the other choices listed. At least that is the way that I read this section. Corrections?
Good racing.
Bill
MC
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Mark Coffin
#14 GP BSI Racing/Airborn Coatings/The Shop VW
Scirocco
Zephyr Race Coaching and Consulting
http://pages.prodigy.net/Scirocco14gp
Thanks guys for your advice, I missed some of the legalities the first time I read the rules.
Bill, you've got it right, if I go to Production I'll want to improve my cars performance. I read many of the messages on the Prod site and it was good to see a few names from this IT site.
My plans are to continue to research and decide on which car to convert. I plan to race ITA with my 72 V6 Capri next year, and build and test my Production car in preparation for the national event in 2006.
JOE!
You've missed the best idea. Leave the Capri alone and run vintage with it or run with the B-sedan racers or do both. You'd still have the VW to run in IT. Run B-sedan and you can run any size carbs you want as long as it adds up to 4 barrels total. The B-sedan group runs pro type races and I think they run for money too. Look at their web site at B-Sedan.com (I think)and their on the left coast too. What more could you ask for? Your Capri will never be "the killer car of F-P" but it could be a front runner in vintage or B-sedan (U/2.5 Trans-Am). If I still lived on the left coast, I know where my Pinto would run. Later, DICK
I was seriously considering B Sedan but I don't think they are running anymore. If someone knows different I'd love to hear more. I actually have another vintage race Capri in my garage which used to be raced in Nasport many years ago. I was planning to build it up for B-Sedan.It already has a fiberglass hood when the car was competing in GT3.
BTW, I just read Vizard's Hot Rod 2.0 book and he says the stock intake with Holley 500 2 barrel is good to 170hp. Perhaps the Weber 40DCNF is similar to the 500 in flow capacity.
Anyways, lots of options to spend lots of money and have fun.
I guess I'll list my cars (maybe I need a Pinto!)
71 ITB Capri (FP candidate)
72 ITA Capri
71 GT3 Capri (flares too big for FP)
83 ITB Rabbit
JOE!
Last time I was on B-Sedans web site, they were racing in 2004. Jerry (Racer) Walsh once told me that a 500 two barrel holly would make with-in 5 HP of any dual weber set up. The old IMSA sedans ran them. I have a 2.0L intake that I got from Jerry, thats machined out under the carb so you can run a 500 two barrel.Its not a simple bolt on because the adapter for the Holly is much bigger than the opening in the intake Let me know if you need it. DICK