[TWC]

I know this isn't a chevelle but please allow me some liberty. I have a 70 1/2ton PU we use for running parts etc..It has a 350 crate motor from Sallee chevrolet in it. The motor is rated @ 380 [email protected] 5200 RPM Torque 424 @ 4200 RPM. It has votec heads, air gap manifold, with a Comp 12-242-2 hyd. cam; .477 Intake/.480 exhaust @ .50 224 Degrees Intake / 230 degrees Exhaust. It has a 700 R4 trans. Neat little pickup.
The motor came w/ a 625 CFM road demon which I have never gotten to run properly and I've tried hard. I want to try something else. I'm tired of messing with it. ( I only have so much time and I want to spend it on my chevelle!!)

I'm looking @ the Holley street avenger 670CFM w/ electric choke or the Edelbrock Thunder series AVS 650 CFM w/ electric choke.
Which do you think will be the best choice for a hassel free carb , esp. cold starts etc. I don't have any experience with the new generation of carbs.
Thanks for your opinions.

 

[greg_moreira]

Ive tried both and have no big complaints. The most rescent was the holley 670 on a mildly built pontislack 350 engine. After some mild ajustments it seemed to be a nice addition. Nothing major...not even a jet change...just simple mixture screw adjustments and experimenting with the adjustable vac secondaries and it ran well enough not to dig into. However, this carb never did see a lot of miles and Ive heard others speak that they dont hold up good for the long haul. Others have said that they are put together with cheap guts and start having issues after lots of use. I cant comment on that.

The eddy proves to be a good carb for a reliable driver. Never used the thunder series ones...just the regular performer series ones...the 600 and 750 manual choke carbs. In the case of a good driver that your not looking for absolute max performance...they are nice for sure. Id prefer the tuning options of a good holley for something more race bred. Id probably go with the eddy myself.

Dont have much experience with demons though. I have been in friends cars that have good running demons, but never myself had to "get to know" one of these carbs good. Since you have it..its worth going to another source that does know a thing or two about em. As long as nothing is wrong with it and you get it set up right....I cant see one good reason to say it would be worth spending your money anywhere else.....cause none of the others you mentioned are gonna be worth much of anything over your demon with a good tuneup. Post the kind of issues you are having with your carb and maybe you will get some good suggestions that will help you save your money!

 

[TWC]

I have three major complaints w/ the Dmon. First is that I can't get the choke to operate properly, which is strange as it is the same as a holley. If it stays on long enough for the truck to warm alittle it is so rich it doesn't want to run. If is on for a short time it won't run as it is too cold.
I can't get it to idle properly w/o using too much idle stop screw which makes the transfer slots too big and then it is way to rich on idle.
Lastly I've tried different springs in the vac secondary and also tried different squirters to eliminate a bog as it opens the secondaries. best combo has been 2 sizes up on the squirter and a medium spring. Better but still not great.
So that is why rather than spend two hundred bucks to have someone mess with it,I'm thinking I'd try a different carb that I could get to work. I'm concerned about the quality of the new carbs as you suggest. Anyone else have experience w/ these new carbs???

 

[vrooom3440]

Have you validated your ignition setup? What is your initial set at? Vacuum advance on ported or manifold (should be manifold)? What is your idle vacuum? (these things all greatly affect idle and can cause your type of problem)

The rub is that all of these carbs work off of the same theory, just in some cases using slightly different techniques. For idle/transition circuits and choke they do not even vary in technique. Further since you are talking about general street machine carbs, they probably even have the same target operating parameters. So replacing the carb may fix your problem but it is taking a bit of a random shot in the semi-darkness.

The other factor against you is the RPM Air Gap manifold. I have one on my 402 and these things are notorious for being very cold blooded. Your regular dual plane heated manifold setup relies on manifold heat to complete fuel atomization. Thus the carb does not need to, nor does it, provide full fuel atomization. Now throw in an Air Gap without that heat and your fuel atomization takes a dive. No engine runs very well on liquid fuel.

If you really want to replace the carb, you should consider stepping up to something with annular boosters. These provide better vacuum signal and fuel atomization than you plain boosters. They would work better with the Air Gap manifold.

 

[TWC]

Thanks Steve good points. I'm running 14 initial, 36 total advance. Been told that Vortec's don't like alot of advance. I'm not using a vacume advance. Can't remember my vacume @ idle, I need to record it one more time. good point on Airgap.
I guess you caught me being a typical American wanting a quick fix. I spend alot of time on my racecar researching and trying different things but I was looking for a quick fix for the PU. I'm going to call Barry Grant again and ask some specfic questions and take one more shot @ removing the demons from the demon.

 

[JimChevy]

I also have a 70' Chevy truck with a Road Demon and love it. I drove it today and after sitting 3 months fired right up. I had an Edelbrock on it before that was very reliable but no where near the power of the Demon. My Demon was fair at best before until I finally had a hard core racer make a few adjustments for me. BIG difference. I would stick with the Demon and get it tuned properly. My 2 cents.

 

[bowtiepower00]

Is the Demon in good shape? I've never run one, but I've never heard anyone complain about 'em. I too would give tuning it one more shot. Maybe someone with a similar setup can give you a baseline to start with. I've run both Holley's and Edelbrocks, and in my opinion (just thought I'd throw that out there because I'm sure someone is going to disagree with me) I prefer the Edelbrock on a mild engine. Both will do the job just fine however. Again, I would keep fiddling with that Demon.

 

[Bob West]

Performance=Holley, mild performance,fuel economy=Edelbrock, I think BG's are alot better than they used to be, but I'd have to try one out before I'd ever think of buying one, too many horror stories. I know Bill Burke loves his BG carb.

 

[vrooom3440]

Thanks Steve good points. I'm running 14 initial, 36 total advance. Been told that Vortec's don't like alot of advance. I'm not using a vacume advance. Can't remember my vacume @ idle, I need to record it one more time. good point on Airgap.
I guess you caught me being a typical American wanting a quick fix. I spend alot of time on my racecar researching and trying different things but I was looking for a quick fix for the PU. I'm going to call Barry Grant again and ask some specfic questions and take one more shot @ removing the demons from the demon.

Nothing wrong with wanting a quick fix so long as it does not mean throwing good $$$ away.

Why no vacuum advance? Your timing sounds about right except for the lack of vacuum advance. On my 402 with Crane HR296 I run something close to that but with vacuum advance. I had it setup wrong for a long time and had problems getting it to idle right. Switched to manifold vacuum instead of ported and limited vacuum advance to 12*. Huge difference. Much happier motor. Picked up a couple inches of vacuum at idle.

You want a vacuum can with around 6* distributor advance total at 1-2" less vacuum than you have at idle.