MotorHead

Slapped the ol' 825 Race Demon on and it works fine right out of the box, which is kinda cool because it is the drag race version and I thought there was going to be some major tuning to get it work at all but it seems to work very good already. It has no vacuum ports at all so I had to tap the Vic Jr. intake for the power brakes.

I think is carb is going to be plenty enough for my motor. I have an LM-1 O2 sensor hooked up and it is running around 11 A/F at idle and cruise but it doesn't go up to 14 A/f at WOT like the Holley did.

It really pulls nice above 3000RPM when the cam and heads start to work, seat of the pants tells me alot more power up top. How much ? I guess I'll have to put it on the dyno, anyway it will need some tuning but I am happy with it so far.

The_Dude

Nice.

Eddie 70

I like the look of the Demons. Glad to hear it is working out better. Maybe this one will tune in easier.

zwede

Does it have a power valve? If not you will have about the mixture at WOT as you have when cruising. It will work but may foul plugs in traffic.

MotorHead

I was just playing ound with the idle mixture screws and got it up to about 12.5 A/F so if it stays around there at cruise then it should not foul the plugs. This carb is a full blown race carb I am suprised it runs so well at idle and cruise but we will wait to see if it fouls the pugs or anything else.

To tell you the truth I know nothing about this carb inside, pretty sure the jets are the same in primary and secondary but I will not know untill I tear it open. I got it for a song on ebay brand new, like I said it is the drag race version and it has no vacuum ports and internally if I need to put in or take out a power valve or swap a few parts in from a general competition model I am still ahead.

norvalwilhelm

I would be concerned about running rich all the time. New cars cruise at about 15-1 and that adds to longevity of the motor. The plugs don't bother me as much as washing the cylinders and shortening ring life.
I run 15-1 on cruise and 13-1 under power and plugs last forever and mileage is good. That tells me my rings are not taking a beating with gas wash.
Being a race carb it would be rich like the holley double pumpers.

MotorHead

It is true Holley DP's run about 12:1 at idle and cruise out of the box and this is no mistake, Holley does this to be on the safe side, that is the way I look at too, much rather run rich than lean. That being said I am going to keep at it and try and get this race demon a bit leaner at idle and cruise.

Anyway just had it out for about an hour and it runs pretty near perfect and the motor pulls harder with the Demon than the Holley at least that is the way it feels

Matt Gruber

send back the LM-1 for a refund.

C3 Stroker

Good luck with the new Demon. I just purchased a new 825 Mighty Demon for my 383, and though I haven't "fine tuned" it yet on the dyno, I am very impressed with its throttle response. FYI...the stock specs on the DR version 825 are the same as the Mighty 825, but yours has jet extensions and screw in boosters. Jets are 76 pri. and 84 sec. Power valve is 6.5 hg. ....I have talked with the tech dept. at Barry Grant, and they informed me that the 825 actually flows 980 cfm WET FLOW ! All of their carbs flow more than the stated number, so it's wise to talk to them if you're switching brands to get a comparison for your engine.

Schmucker

???

Matt Gruber

it appears to be defective

zwede

12:1 from an out of the box race carb sounds right on the money. If you're going to make statements like that you need to back it up. What makes you think the reading is incorrect?

73C34me

I have a mighty demon 825 on my 383. I had to replace the idle feed restrictors with a smaller orfice to get a leaner idle and low speed air fuel ratio. I believe the stock i.f.r. is .037" and I went to a .032". This cleaned up the low speed dramatically.

MotorHead

Are the idle feed restrictors removable or something on the Demon carbs ? I know the Holleys you gotta put a piece of wire in there to make them smaller

red79vette454

I love my Demon Race carb. I'll never buy another Holley Period..
This 975 RS carb is making about 615 RWHP on my 454.
Best time (on motor - No spray) 10.62 ET at 128.25 MPH.