Currently running a Holly 750 DP.
Comsidering replacing it with a Demon 850.
Those with Demons, what do you think of the Demon Vs the Holly ?
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Jim,
fyi, food for thought, the ramblings of a senior mind...
The 850 Demon would be equivalent to a 950 Holley. Demon & Holley measure their carburetor's flow performance differently, so the numbers are not directly comparable. Holley's are "dry flowed", Demons are "wet flowed". So Demons numbers are approx 100 cfm lower for an equivalently sized carburetor. Your Holley 750 would be rated as a 650 by Demon. So you are contemplating a carburetor that is 25% to 30% larger.
In the opinion of this old mechanic & hot rodder, for the state of tune your motor is in, it does not need a larger carb. For instance, going up to an 850 Holley "may" gain you 10 bhp and a few hundred extra rpm on top, but the trade off would be the loss of some throttle response on the bottom. I see this as a bad trade off on a street motor or a track motor. Accelerating from a stop light, or coming out of a turn, is more important than gaining power on the top end.
The acid test would be to test the car with each carburetor installed, on the same track, the same day, being driven by the same driver. I admit I could be wrong. However, in the absence of such testing, I would rather err on the conservative side.
Finally, also consider what you think is your motor's weakest link. Increasing carb size will accomplish little if the exhaust system is too restrictive. If a Pantera is running a factory exhaust system, including the GTS exhaust system, I can summarily say the exhaust system is too restrictive. Panteras need headers that dump into 3" collectors of reasonable length, connected to free flowing mufflers with 2 1/2" tubing.
An investment in the motor would be best spent on the motor's weakest link.
your bro, the cowboy from hell
fyi, food for thought, the ramblings of a senior mind...
The 850 Demon would be equivalent to a 950 Holley. Demon & Holley measure their carburetor's flow performance differently, so the numbers are not directly comparable. Holley's are "dry flowed", Demons are "wet flowed". So Demons numbers are approx 100 cfm lower for an equivalently sized carburetor. Your Holley 750 would be rated as a 650 by Demon. So you are contemplating a carburetor that is 25% to 30% larger.
In the opinion of this old mechanic & hot rodder, for the state of tune your motor is in, it does not need a larger carb. For instance, going up to an 850 Holley "may" gain you 10 bhp and a few hundred extra rpm on top, but the trade off would be the loss of some throttle response on the bottom. I see this as a bad trade off on a street motor or a track motor. Accelerating from a stop light, or coming out of a turn, is more important than gaining power on the top end.
The acid test would be to test the car with each carburetor installed, on the same track, the same day, being driven by the same driver. I admit I could be wrong. However, in the absence of such testing, I would rather err on the conservative side.
Finally, also consider what you think is your motor's weakest link. Increasing carb size will accomplish little if the exhaust system is too restrictive. If a Pantera is running a factory exhaust system, including the GTS exhaust system, I can summarily say the exhaust system is too restrictive. Panteras need headers that dump into 3" collectors of reasonable length, connected to free flowing mufflers with 2 1/2" tubing.
An investment in the motor would be best spent on the motor's weakest link.
your bro, the cowboy from hell
Coz you can change bleeds and feeds in a Demon without drilling and tapping. In a holley you have to drill and tap them:
Holley didn't want anyone messing with them. Demon figured out car guys want more then a ride. They want to figure it out too. When my brother changes from summer gas to winter gas his airbleeds have to go up 20 high speed and 10 low speed. Can't do that with a holley unless you drill and tap like I did mine:
http://www.rc-tech.net/cars/panttransam/1905/bleeds.jpg
http://www.rc-tech.net/cars/panttransam/1905/feeds.jpg
Gary
Holley didn't want anyone messing with them. Demon figured out car guys want more then a ride. They want to figure it out too. When my brother changes from summer gas to winter gas his airbleeds have to go up 20 high speed and 10 low speed. Can't do that with a holley unless you drill and tap like I did mine:
http://www.rc-tech.net/cars/panttransam/1905/bleeds.jpg
http://www.rc-tech.net/cars/panttransam/1905/feeds.jpg
Gary
Jim, While the Demon 850 may be a little to large for your car, I have found them to be a great carb! Much easier to dial in, and they have a great variety of types. I am running a Mighty Demon 750 on my car, and you remember Todds car, which had a fairly radical engine was running a Speed Demon 650. They usually say if you are stock to a mild cam go with a Road Demon, medium cam go with a Speed Demon, and with a radical cam go with a Mighty Demon. There are other parameters of course, but if you call Barry Grant tech number (706-864-8544), you will find them very helpful in selecting the correct carb that you will be happy with. Also for many of us we have to consider if it will pass the smog tests and often that larger carb can cause problems.
Thanks Kevin. I've been online reading about the various series on the Demon website.
You & George are right on the mark. For my current set up, the Speed Demon 650 would appear to be the best choice.
I think I'm going to go with the Speed Demon 650 with Mechanical Secondaries. Will call Demon to discuss it with them first.
Thanks brother !
You & George are right on the mark. For my current set up, the Speed Demon 650 would appear to be the best choice.
I think I'm going to go with the Speed Demon 650 with Mechanical Secondaries. Will call Demon to discuss it with them first.
Thanks brother !
You know they also have a submission form on their website. You put in a load of date from your engine parameters to your car type and driving goals. They will recommend a carb for your application.
Haven't found that area yet, looking for it.
quote:Originally posted by comp2:
You know they also have a submission form on their website. You put in a load of date from your engine parameters to your car type and driving goals. They will recommend a carb for your application.
Coz, I don't think it's on there anymore. When I got the demon for the 434 they had a link where you filled out a questionair and they got back to you in a day or so with their recommendation. I guess you just have to write or call now. I would guess they would be good about getting back if you e-mail them. They will need to know as much info as you can give them; even things like the weight of the car, tire size and how you intend on driving it.
http://www.rc-tech.net/cars/panttransam/1905/434pd2.jpg
http://www.rc-tech.net/cars/panttransam/1905/434pd2.jpg
Thanks brother. Going to call them this morning...
quote:Originally posted by comp2:
Coz, I don't think it's on there anymore. When I got the demon for the 434 they had a link where you filled out a questionair and they got back to you in a day or so with their recommendation. I guess you just have to write or call now. I would guess they would be good about getting back if you e-mail them. They will need to know as much info as you can give them; even things like the weight of the car, tire size and how you intend on driving it.
http://www.rc-tech.net/cars/panttransam/1905/434pd2.jpg
I replaced the old and tired OEM carb/manifold with an Edelbrock Perf. and a Speed demon 650.
My engine is close to stock (dual pts) with Mind Train headers and pipes. The car starts right up and runs very strong.
Barry Grant's tech support is outstanding. Call and ask for Eric Nickonivich.
My engine is close to stock (dual pts) with Mind Train headers and pipes. The car starts right up and runs very strong.
Barry Grant's tech support is outstanding. Call and ask for Eric Nickonivich.
I think you will get better results calling them, the last time I emailed them a question it took them 2-3 days to respond. Since then, I call them and get the answer right away. I guess that I am not very patient.
Just called and talked to Eric. Spend about 20 minutes on the phone with him. Went over everything and he recommended the 650 Mighty Demon. He also told me after I get it to call him back and he'll take me through the set up and fine tuning of it.
Great guy. Thanks much for the contact !
That's the way I'm going to go.
Great guy. Thanks much for the contact !
That's the way I'm going to go.
quote:Barry Grant's tech support is outstanding. Call and ask for Eric Nickonivich.
I'll make a real long story short.
I have a 750 Speed Demon and wish I had went with a Holley HP.
Demon has great tech support but if I ever get some spare time, I'll try to get my second replacement Demon to run decent.
Alot of people have had good luck with Demon. I haven't.
BTW, does anyone know of someone who can tune a carb in the Toronto area?
Will (hoping for EFI soon)
I have a 750 Speed Demon and wish I had went with a Holley HP.
Demon has great tech support but if I ever get some spare time, I'll try to get my second replacement Demon to run decent.
Alot of people have had good luck with Demon. I haven't.
BTW, does anyone know of someone who can tune a carb in the Toronto area?
Will (hoping for EFI soon)
Will,
I would not give up on the Demon. Give Eric a call. He will stay with you until the carb is right.
I live in Atlanta just south of their facility. Eric even came by to set up my carb, that I probably screwed up. And he would not take a dime for all the time he spent. He may even know someone in Toronto to refer you to.
Jeff
I would not give up on the Demon. Give Eric a call. He will stay with you until the carb is right.
I live in Atlanta just south of their facility. Eric even came by to set up my carb, that I probably screwed up. And he would not take a dime for all the time he spent. He may even know someone in Toronto to refer you to.
Jeff