edelbrock off-road needle and seat assembly - Hot Rod Forum : Hotrodders Bulletin Board
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Old 07-28-2004, 01:29 AM
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edelbrock off-road needle and seat assembly

I replaced the needles and seats with this kit and readjusted the floats to 7/16" just like I have done for years on other 750 edelbrock carbs.....1407 carb number.....

the trouble I have is the blazer runs out of gas at full throttle and gets steady worse or, at less throtle as I increase my altitude.

When going up this one road that is form 3500feet to 6000 feet I notice the problem more than at sea level. and when I reach 6000 the motor just runs at idle, and a little bit of pedal.

I have changed full pumps, put a holley 750 on it, and tried rochester quadradjunk . they all worked fine and the pump change made no difference.

I put the carb on another blazer with another 454 and it does the exact same thing on the exact same stretch of road.

From the internet , I found a section on vapor forming from temp,weird angles in the fuel lines ,low atm. pressure and other things. But if this is the case ,why this carb only and only after I changed to this kit?

The Question I have is: does this kit of spring loaded needles make the needles seat harder and could it be causing all of this problem?

I am betting that others have had the same problem.
The kit works fine at sea level ,and does what it claims with the angle range they mention.......BUT UHMMMM!

Well you see the problem.....I have to stay at idle or somewhat less than wide open for the motor to stay running correctly.

Anyone else have an answer that lets me keep the angles, but with a bit more user friendly street driving?


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Old 07-28-2004, 07:24 AM
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Have you verified fuel pressure? How about Bad fuel filter? How steep are the angles exactly? Have you considerd a collapsing float?
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Old 07-28-2004, 10:45 PM
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fuel pressure is 7 at idle and about 5 under power.
The weird thing to me was, when I reached 6000 feet I pulled the new oversized filter loose from the fuel line to check it and the gas sprayed across the front of the blazer. My people suggested a fuel return line to the tank, but again, only this carb. and two different motors, and all other carbs work perfectlyon this set up on the mountains.

The stretch of road that I always notice it on is inclined, but nothing rediculous. I would guess around 5 -10degrees incline.

what are the floats , or better yet where do I get them?

could the step up springs be causing the problem?
I changed them to get better throttle response before I put the kit in and never bothered to mess with them after.

My guess is the new spring loaded needles are held tighter in their seats and the carb is running out of gas , but with the fuel pressure at normal presure it seems the gas pressure would overcome the force of the springs.

Anyway, I am willing to try new floats or whatever ,if it will help.

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Old 07-28-2004, 11:56 PM
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Is it possible that the "off road" needle and seat have a smaller inlet hole compared to the ones you took out? That would explain the fuel starvation all of a sudden. If you still have the old needles and seats, find a drill bit that fits the hole in the seat, then see if it fits the "off road" seat. Chances are they are different. I know that Edelbrock makes a "high flow" needle and seat too. Might be worth a try.

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Old 08-20-2004, 02:53 AM
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Thank you for the info.
I will try this and get back to you.

If there is no return line will the presure steadily build up in the lines??????
I know , stupid question, but,,,,,
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Old 08-23-2004, 05:22 PM
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I drove another suburban with a 350 and a quadrajunk up the same mountain pass the other day to see a 4x4 race and on the way the carb cut out just like the edelbrock on my other cars.

This must have something to do with altitude, heat , and angle of attack.

the motor cut out and I had to feather it in idle to keep it running, until the rpms slowly shut down and then it died.
I started it back up and drove slowly as I could with as little gas pedal as possible and with as much air over the radiator untiil it finally started acting right again.
The head temp. never passed 180 but the cooler air and lower rpms helped it get back on track.

sounds like vapor bubbles in the lines from heated fuel lines to me now , I guess????

I will try another car soon with a completely different set up and see what happens.
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