Mill Choke Horn or Get New Proform Body

[Cobra 29]

I have a 650 CFM Holley (4777-3) that runs great with my FMS 351W crate engine but I need to remove the choke horn to provide better air flow into the carb. I can only run a 2" high air cleaner with a slight drop base (Ford Racing 13").

Should I take the carb body to a machine shop to have the choke horn milled off or purchase the Proform replacement carb body (67100C). My base plate bore is 1 11/16 which will fit the new Proform main body. The primary venturi diameter will increase by 2/16" and the secondary venturi diameter will increase by 1/16".

I really like the responsiveness of the 650 as it is now and fear that the venturi diameter increase will reduce the responsiveness. Most of my driving is between 2000 and 4500 RPMs.

Has anyone made this swap? What was the effect on mid RPM responsiveness? Milling the choke horn away would increase the air flow but the modification can not be reversed.. Thoughts on what direction to take?

[lovehamr]

I'd go with the Proform. If your throttle response suffers I'd be very surprised and the end result will be much neater.
Steve

[Cobra 29]

Has anyone converted to their 650 or 750 DP to Proform body?

[Rufus]

Cobra 29 -

I'll be interested in what you find. I'm contemplating doing that too to improve airflow. I read in an old Holley book that the correct jetting is very sensitive to things like booster design and placement within the main venturi. Therefore it would seem crucial to make sure the Proform assy matches the present carb body exactly or else you'd need to start over rejetting the new carb assy.

This made me stop and think that maybe it's better to bite the bullet and go for a complete new carb.....

[cleandan]

Cobra 29, exactly how close is the choke horn to the air cleaner lid?
Depending on the clearance, and the carb body, you can mill a good bit off the carb and still keep the choke working as normal.

[Ron61]

Cobra29,

I had my Holly 800 DP did by an outfit in Los Angles that builds them based on the BG carbs, complete with changing the metering blocks and everything and I am very happy with it. However it is a completely different carb than I had before, not even the same float bowls. Basically I traded my Holly for one of their race built type and it has worked great.

Ron

[Frank Messina]

Hsss427 just went through this with his 427SO and he had a heck of a time getting it to run. You already know your carb works great and you seem to be happy with it. Why complicate things? If it was me, I'd mill the air horn off and be done with it.
Frank

[cuda66273]

IMO you should forget you ever heard the word Proform, it's nothing more than a Chinese copy of an old BG Claw design.

In order to make the main body work you need to change the base plate and metering blocks by the time you get done you'll have a Chinese carb with Holley float bowls, no warranty from anyone and no tech support if you get into trouble.

Look into a Mighty Demon, designed without an air horn, better air entry, full tech support, American Made, you just can't beat them.

http://www.4secondsflat.com/mdemon.jpg

[kountzecobra]

I had very good luck with the Proform main body but others I know of have had major problems. Seems like Proform's QC is really inconsistent.

[CHRIS POTTER]

I agree with David, I have also had good luck with a Proform main body, but have heard of QC problems. I tried my son's 750 Speed Demon on my car, and it seemed to have a little more power, but the driveability isn' t as good. To be honest, however, I fine tuned my Holley, and I tried his carb out of the box. I couldn't get the Demon to idle down without kicking the gas at every stop. Tried extra springs, and there are no binds when the engine is off. It's not my carb, so I didn't get too involved, but it does the same thing on 3 similar engines, maybe their tech line would know why.

[cuda66273]

It's a simple adjustment call Mike at the tech line

[Cobra 29]

If I went with a Demon carb, which model? Mighty, Speed, etc. I have a FMS crate 351W (385HP). This present Holley 650 DP has a very good low RPM response. I like that. What model Demon would be the closest? Should I stay with a 650 DP or go with a 750 vaccum secondaries?

[SSSnake]

We started out by throwing the proform body on a holley 650 DP. THe car ran much better than before. After a few calls to Qwik-Fuel technologies we ended up with an entirely new carb with the anodized metering blocks and throttle plate. The car runs better than ever but man does it suck down the gas now. Oh well, its well worth it. I recommend giving Qwik Fuel a call.

Glenn

[cuda66273]

Your getting the quick throttle response from the small 650 venturi size which gives you high velocity. Our experience has shown us that the 351/385 in a light car like yours likes the 650 Mighty Demon for street application.

The Mighty 650 will give you even better throttle response over the Holley. It's designed to read the low vacuum signal from that engine and will flow more air at the top end of the power band than the Holley...all around just a better carb than the old Holley design. The comparitive Holley would be the HP carb at $639.00


(I'm sorry but that is a one ugly carb)

I have a customer who's the Top Diveability Tech for a large local Toyota Dealer and he's a very successful Drag Racer....he bolted down one of our 650 Mighty Demon's on his 395 HP 355, 55 Chebby Hard top Hot Rod last weekend....turned the key and it ran perfect with the exception of the idle speed, it ran at 1050 instead of the desired 950, 1/4 turn on the P side and 1/4 on the S side and it purred.
.......$499.00



He hooked it up to his 5 gas sensor at work....never took a screrwdriver out of his tool box, needed no adjusting.

I know this is a long way from a Cobra or Mighty Mopar, but it's just an example of how well these Mighty Demon carbs work right out of the box (with our baseline set up) even under the scrutiny of a tuning professional.

You just can't beat them for $499.00

I'm sure that Quick Fuel does a fine job of re-building and modifying Holley carbs. Obviously they have corrected allot of the issues on the Holley's but with a price ticket of $690.00



There's no less than 500 shops modifying, improving, rebuilding, replating and swapping out Chinese parts in Holley's and I'm sure that most of them do a pretty good job after all there's plenty of room for improvement.

Some of these guy's stay around for years and some just fade away. Most of them depend on their existance by the longevity of the owner...when old Bob retires the company goes into the history books along with the tech help and parts availability.

So why is it that there is virtually NO Company's anywhere that are modifying or "Improving" the Demon carbs???

Could it possibly be that there's nothing that can be done? How do you improve on the Demon air horn? The metering blocks are Billet so they don't leak, the float bowls are huge and don't leak, the base plates are billet....what would you change?

125 different Demon carbs for every conceivable application, good Factory tech support, excellent parts availability, easily tuned.

To my knowledge there's only us and one other company in NC that will modify a Demon carb and both of us are limited to setting them up specifically for Drag Racing, Road Racing or Off Road and we're both using parts right out of the BG catalog.

BG Inc. tech department and service parts will be around long after most of us are long forgotten.

Up untill about 4 years ago we would overhaul and repair Holley carbs, we stopped. The standard work order would read "Modified by XYZ Company" most of the time the company was gone or the individual couldn't be found. We found that in most cases it was cheaper to just replace the carb with the correct Demon for the application, the car would run better and the customer got away cheaper and happier. Chasing some unkown metering block and trying to figure out the circuitry was too time consuming. Time is money we're no different than any other shop and we have to charge whether we're hunting parts or assembling a carb.

When you invest in a $500-$800 carb for your pride and joy do you really want to gamble that the guy your buying from will be around in 3-5-10 years when you need help to rebuild or repair it?

IMO I doubt that Holley will be around in 5 years as we know it today. Remember where you heard this 1st, there's some major changes coming to Holleyworld. Might be next month or it might be 3-4 years but there's a shake up coming that will rock the performance industry. They've already closed the technical and service department for all pumps, so you racers out there that own a $500 Holley race pump be prepared if it looses a seal you'll writting a check for another $500, there is no parts available.

[PRO-SYSTEMS]

The reason builders don't work on the Demon carburetors is the design of the unit does not allow certain modifications that most builders like to perform to improve performance. The Demon carb line is designed with "shiny" appeal and its a great carb for the kids. They love shiny. But as far as being superior to off the shelf holley designs, testing by many customers have seen varying results.

Your post comes off like you work for BG or have something against the people at Holley (they're hard working people too). As far as your comment concerning Holley and their situation, there has been a rumor that Holley was going out of business since the 1930's. 75 years later....

Sorry if this comes off a little gruff, but Holley employees are proud of their products and probably like their jobs too and don't deserve a rumor starter or what appears to be an unfairly biased opinon.

Its a competitive market in America. You have to work your butt off to design products that work, so the product will sell. You have to support the customer after the sale and you have to be price competitive. The old saying "Price, Quality or Service" pick two no longer applies. People expect all three. I do when I buy something and I do when I sell something.

Thanks for reading.

Patrick James
PRO-SYSTEMS Worlds Fastest Carburetors

[RACER X #99]

Patrick,
I agree with you about shiny around here. My new 408 Dart made 530 HP with shiny carb, replaced it with old not shiny Holley with same jets removed from shiny carb both were 750 DP. Engine now made 580 HP. This was done within 1 hr while engine was on dyno.Later same day installed 800cfm DP Holley and made 615 HP. Shiny carb occupies place on shelf in garage.
BTW, not a kid.

[cuda66273]

"The reason builders don't work on the Demon carburetors is the design of the unit does not allow certain modifications that most builders like to perform to improve performance."
Exactly, they don't need it for 90% of the intended applications.

"with "shiny" appeal"
When you use modern casting methods and superior materials the finished product is smooth and somewhat shiny and doesn't require any brown flat coating to seal it.

"carb for the kids"
We're all kids at heart, our toy cars just get bigger....:-))

"against the people at Holley"
Not at all, but I do have a grudge against Federal Mongrel and the way they treat their employee's and their Customers. Their attempt at controlling the performance aftermarket isn't working out that well for any of us.

I snuck over to your website, very impressive looking stuff! And…. probably every bit as good or better in allot of cases than a box stock Demon. But in your own immortal words:
" Listen to him, because sometimes a voice of experience is more valuable than a voice of theory based assumption."

You have obviously found a very exclusive niche in the market and are probably successful due to your research, development and ability to take a raw product and refine it to a very high level of performance and market it to a relatively elite group.

Your pricing on what I looked at, is very competitive, many so called "Carb Modifiers" who basically just add a bunch of Chinese parts to a Holley and sell it for (or try to at least) to an unsuspecting customer base with little or no knowledge of what they're actually getting for their money. Your Company seems far beyond that level.

Holley is a Division of Federal Mogul, which is a publicly traded company, if you review their annual report and the profitability expectations of FM divisions you'll see that Holley is one of the companies that is struggling to keep with those parameters. It's no secret that Holley is for sale and has been for at least 3 years now and a few suitors have looked at it closely, but no offers have been made public that I'm aware of anyhow.

If you study the FM balance sheet you'll see they had a net loss per share of $1.39 in 2003 and a net loss of $3.07 per share in 2004. Some pretty competant people run FM and they will turn it around, we just don't know what things may change to accomplish that.

Will Holley go away? I don't honestly think so, will they possibly change Leadership, maybe and hopefully it'll be a great improvement at the product AND employee level.

"I doubt that Holley will be around in 5 years as we know it today. "

Read every word "As we know it today", hopefully it will get better, with more design changes, modern casting methods, new machining processes, more product diversity, better customer support.

Do I work for BG? No, but we've also found our niche, take the best "Corporate Carb" on the Market, add top customer service and technical assistance to this largest sector of the Market....The Street and occasional Bracketeer group who are not professional racers, tuners or mechanics. Get them going for under $500 with a carb that will perform to 90% of the engines capability and be trouble free.

Your customers may have had "Varying results" we race, drive and tune Demons everyday and have for 11 years our results are not varied, the new Demon line of carburetors are by our hands on experience the best bang for the buck when correctly selected and tuned, without any modifications.

If I was a Stock Eliminator racer or out to set a Land Speed Record I would have no issues at all with bolting one of your units on my car and I have no doubt that between the two us we could accomplish some very impressive results.

But, like almost everyone else here I'm a bracket racer, I change my dial-in as the day goes on, not my jets and tune-up. Setting a speed record is not a priority, I want dependability and consistancy and be able to relax when I go to the track, not tune the car in the staging lanes.

Thank You for reading... and I respect your opinions as well as what you've accomplished. I've Bookmarked your site and no doubt I'll be referring customers to you for your special applications.

Everyone have a nice weekend, our track opens in 6 hours for testing I'm going out to load up.

[cuda66273]

Cranky
Did you attempt to tune it ? There's more to a carb than jets?

Was it the right series for the engine specs? Right size?

Tell us more

If it's just collecting dust I'll take the shiny POS off your hands, you claim it has no value so what's the appropriate price?

[PRO-SYSTEMS]

Like Racer X stated, "mixed results".

Obviously as a builder, mixed results are not acceptable. So you can see the pressure it puts on the builders.

Great response Cuda. Quoting stock prices as well. Now thats intellectual banter. I am always impressed by factual info from the obviously well educated or naturally sharp.

Patrick James

[bigmike]

After fighting Holley tuning problems for years, I switched to a Mighty Demon 750 on my 428, and I am very pleased with the results........my $.02
BigMike