My tale of carb woe started off w/Holly 3310 from Jet perf done by "Shawn" who I wouldn't let pump gas. He promised me I would like this better than the 750 dp I ordered. Money has since been refunded. This 750 VS wouldn't idle properly. Next is the 750VS Demon. After much tuning it was OK. Then the idle circut broke and it had to go back to factory. The Tech Rep gave me a lecture fit for a 5 yr old about their carbs flow more than advertised and the 750 was too big. I sent him a detailed build sheet for my engine as requested. In between I used a cheap Edl 600VS that works OK but is too small. I can feel the difference. The carb came back WORSE that out of the box! After again more time/money it was barely adaquate. Again it malfunctioned internally and this time flooded the oil w/fuel. This has caused "according to my mech" the valvesprings to sack and a valve job was done! The Demon is on its way back. I will not buy any Demon product ever again. Next up is a Holly 750 VS off my mech's boat. W/O any tuning it is so far the best of the four. I can't spend any more time/money on this. Any advice out there? I need help!
360 sb, 10.25 cr, TFS heads pocket ported& backcut valves, Air Gap port matched "it was way off, CC hr 270-276 (218-224) w/1.6 rrs, stk ex man dual ex for now. Headers after next smog. I want to stay w/VS, this is a daily driver.

 

650 Speed Demon is the best carb I have run so far...Comparing with a Quadrajet ,Holley 750, and edelbrock performer 600(before mods)

 

Given your engine specs. from your sig. I would recomend a Holley 650 Mechanical secondary carb. I too think that the 750 vacuum secondary carb is a bit too much. I had a Holley 750 vacuum secondary on my engine and could never get the low speed tuning issues straightened out. Changing to a 670 Street Avenger solved the problem but I can feel the differance on the top end.

 

:iagree:

I would go with the Holley 650 dp mech or the 670 Street Avenger.

 

Why do you people like being tortured with all these crap aftermarket carbs?
Use your stock Q-jet and ask Lars how to tune it and you will have a smile ear to ear!

 

:rolleyes: Ask Lars how he ranks the Demon vs the Quadrajet for a modified engine :yesnod: .You may be suprised at the answer

 

Well, I can help you with the Edelbrock carb. but don't know much about the others.

The Edelbrock is good to over 400hp with proper jetting, sense you already have it you might want to rejet it and try it again. Typically the Edelbrock kind of fall off over 4500 RPM, but rejetting them makes all the difference.

I would recommend leaving the front jets the same and installing 104 in the sec. with your set up that should let it rev past 6000 RPM.

If that works there is a lot more tuning we can do for it. You can get or have a parts store order them for a few $.



[Modified by Tominator, 12:06 PM 2/17/2003]

 

Last summer I bought a new Edelbrock 750 replacement carb and it works perfectly. It took about a half hour to replace and a few trips to set the timing and idle once the gaskets set. I have a stock SB in my 70 vert and it starts, idles and accelerates without hesitation. Don't know if this helps but it was absolutely no hassle.
:steering:

 

I don't think the 750 is to big of carb. The reason is most carbs flow less (yes I said less) then advertised as they are dry flow tested (to get there rating) not wet flow tested which is a much more accurate reading. The wet flow test is much more like when the carb is running on the motor not just attempting to run air threw it, as fluid takes up space and will bring the flow rating down in most cases by atleast 10%. Also, the rating is usually done on one venture and then x by 4 to get the rating instead of rating all 4 at the same time. A 780 vaccum (factory holley) to me is a very tunable carb. For me it has been very easy for a backyard mechanic like myself to get dialed in and make respond to your personal liking...


[Modified by ragingbull, 5:36 AM 2/21/2003]

 

I am talking to Lars at the moment and he and his buddies all runs Demons. :yesnod: My order is in for one! :D :cheers:

 

Lars has been heling me (via email) in getting a crab selected and installed properly. I went with the Speed Demon 650 (actually it's the Crate Demon but according to Demon it's the same as the Speed Demon). So far it seems to be a great carburetor. :thumbs:

 

After talking w/Demon rep, he recomends the 650 VS Speed Demon not the Road Demon. I wonder if Demon rates their carbs on "wet flow"? That would explain how they say their carbs flow more. Despite my problems they will not refund my money. I will keep the forum posted on how this works out! I was very happy w/Q jet reworked by The Carb Shop. I hope the Demon can do as well.