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Old 04-20-2006, 08:15 PM
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Barry Grant Blues

I have read a few road demon problems and solutions, but I have one that is still lingering. I have a vortec head 355 c.i. with hi-po cam(?), stock ignition, new plugs and wires, dual plane edelbrock with a 725 road demon. All of this is backed by a rebuilt 700r4 in a 1952 chevrolet panel. After many calls to the tech line(very helpful and informative) and many readings online I am still experiencing rich eye burning smells. It finally idles without the black smoke(larger air bleeds), but now it runs rich afterwards. My next option is to change the jets from #76 to #74. Before I do this is there something I am overlooking?
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Last edited by blackchevy777; 04-21-2006 at 07:19 AM.
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Old 04-20-2006, 10:06 PM
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BlackChevy
I wish I sould give you a good answer to your question. If the techs on the phone are as good as our own BGtech on this site seems to be, I suspect they have the answers. The real reason for this post is to tell you that that is one *****in' looking truck. Really, really nice looking.

Pat
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Old 04-21-2006, 12:46 AM
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i had the 725 road demon and got rid of it. the tech's told me that the 725 road demon is made for a stock 454 big block and stock cam thats it.

i had it on a 383 small block with a 224 degree cam (which they also said was to big for the carb). i was very rich at idle, the idle screws had no effect at all. the carb was sent back to my engine builder. i now have a 750 double pumper and get twice the gas milage of the demon and runs better. the holley needs tuning to but i have dyno time set up for that. latter down the road i might try a 650 speed or a pro built holley, and if those dont give what i want then i will go Fi.
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Old 04-21-2006, 07:26 AM
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When I ordered the carb, this particular carb was said to be the one that I needed. The Barry Grant website even states this carb for hi-perf small block and big blocks. I even read an article where this carb was put on the same engine as what I am running and the same trans and rear in an el camino and it worked great. The tech that I normally speak with hasn't said anything about this model being too big. I have ran a performance Q-jet(750 cfm) on this engine before and it ran great. I wanted to run the demon because I have heard so many great things about them.
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Old 04-21-2006, 07:58 AM
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blackchevy777,

Without knowing more information about your combination it would be hard to say if is the proper carburetor or not, but we should be able to get it to perform better.

How far did you open the idle air bleeds?

Other than the rich at idle, how well is the carburetor performing.
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Old 04-21-2006, 08:12 AM
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I opened the air bleeds the amount the tech specified(can't remember exact #). The vehicle actually runs fairly decent except for the rich gas smell. I think it should do a little better as for performance. But there is no hesitation when I accelerate quickly. Is it possible this 725 carb is really bigger than a 750 Q-jet? Again, I refer back to the el camino(hot rod magazine?) with basically the same running gear as what I am running (without knowing exact # on cam) and it ran 13 something in the 1/4 and had decent gas mileage.
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Old 04-21-2006, 08:16 AM
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carb

I know you have been through alll this before but i need to ask again.

What is the initial and total timing??? Is the vaccum advanced hooked up??? if so to ported or manifold???

Is there fuel dripping from the boosters at idle???

What heat range plug are you running??? and are you changing them after you make changes to the carb????

What is the cranking PSI and the idle vacuum????

Do you have the correct fuel pressure??? and float settings???

Are the carb mounting gaskets soaked with fuel????

Have you had the carb apart and checked for debris????


Keith
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Old 04-21-2006, 08:53 AM
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The timing is advanced as far as it can go without the "wah wah" cranking. The vaccum advance is hooked up on the ported fitting, but I have tried both(no noticable diff.). There is no fuel dripping from boosters at idle. The plugs are new NGKs for the vortec heads(not sure of the heat range). The cranking psi is approx. 120 on all cylinders(it has been a while since I measured it). The idle vaccum I haven't checked yet(next on list). No fuel on gaskets, but I have noticed a little fuel under the throttle shaft on the driver's side. I have checked the carb for debris(I am used to Q-floods, I mean Q-jets). Thanks for all help.
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Old 04-21-2006, 09:46 AM
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carb

A few observations...

You really need numbers for the timing for us to help... The wah,wah start can happen for many reasons... The entire problem could be because of the timing being retarded....You may spend alot of time and money on other isseus and this could be the problem. The timing is the first place to go....

Then, If you really only have 120psi this engine will never idle clean. You have to big of a cam, not enough static compression or the cam is installed incorrect.... This will neeed addressed... What are the duration @.050 of your cam??????

Gas on the throttle shafts mean you have a issue inside the carb that also needs fixed. they should be dry..

Keith
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Old 04-21-2006, 10:05 AM
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blackchevy777,

Without knowing the specifics on your engine it's hard to say if this carburetor is going to work optimally or not. If the only issue you're having right now is the richness at idle we should be able to help with that. However we're going to need more specific information.

Really need to know:
What size you drilled the air bleeds to?
How much timing you're running at idle?
Where the settings are on the carburetor (Float levels, butterfly position, mixture screws)?

Now if you have fuel at the throttle shaft most likely your float levels are too high. There aren't any fuel passages around the shafts, so if fuel is at the shaft it has most likely dripped onto the butterfly. Try lowering the float level a little further.
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Old 04-21-2006, 10:22 AM
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now tech at bg why are you trying to help him when i had the same carb on a 383 and told me my cam is too big. you are not asking him how big his cam is, how come? you told me i might be able to get it to work but the carb wouldnt run right. my engine was a 383. you are now helping him but wasnt willing to help me.
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Old 04-21-2006, 10:31 AM
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Quote:
Originally Posted by airraptor
now tech at bg why are you trying to help him when i had the same carb on a 383 and told me my cam is too big. you are not asking him how big his cam is, how come? you told me i might be able to get it to work but the carb wouldnt run right. my engine was a 383. you are now helping him but wasnt willing to help me.
As you said we were willing to help you, but prefaced that given all of your information it was not the carburetor we would have recommended for your application, and that the proper carburetor would have worked better. At this point he is happy with everything other than one small issue, which as stated we may be able to make better. Without knowing his engine specifications we can't say how well the carburetor will or won't work, and we've asked for this information.
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Old 04-21-2006, 12:07 PM
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ok thanks......

i added the dots because i had to put atleast ten letters in here lol
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Old 04-21-2006, 01:50 PM
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I have not got the vaccum or timing #s yet(broke foot). The carb does fine at idle(now), but runs rich afterwards. I had a mechanic put a timing light on it a while back and I think he said he had it at 14 BTDC. It is probably still close. Another reason I am trying to stay with this carb is because the Barry Grant website states
"The Road Demon™ 725 is perfect for stock V8 engines from 350 to 500 cubic inches. This makes them ideal for daily drivers as well as weekend cruising for a wide range of vehicles".
Until I can get the other information(vaccum # and definite timing #), thanks alot for all the replies. You guys are very helpful.
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Old 04-21-2006, 01:55 PM
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Also is there a way to check the cam specs without pulling the cam since I do not know the exact specs? I do have a dial indicator.
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