Backfires through carb

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Jun 18, 2001 | 08:29 PM

bufordt

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Backfires through carb

I have a 400 with a peformer intake, 750 edelbrock carb, and a Comp cams 270H Magnum Series cam. The problem is that it backfires through the carb right off idle. I thought it was the carb so i took it of and rebuilt it, but its still shoots a flame out the carb right of idle. If you hold it open about 1500 rpm and goose it doesnt do it near as bad. Could it be my timing its set at about 14 degrees BTDC. Im thinking maybe my vacuum advance went out.

Jun 18, 2001 | 09:27 PM

FE427TP

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From: yes

Backfires through carb

have you tried adjusting the accelerator pump shot? I think it's the hole closest to the carb body that gives the strongest shot.

Jun 18, 2001 | 11:16 PM

bufordt

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Backfires through carb

I tinkered with it some and did what the instructions said but i do wonder if i set it right now that you mention it. I'll look at it again, but i think its something else. When i tried to set the idle mixture it seemed to make little difference in the way it ran. Maybe its just me but i think that its running to rich at idle.

Jun 19, 2001 | 07:34 AM

Nathan

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Backfires through carb

I had the exact same problem. Finally rebuilt the carb, adjusted the acc. pump as per rebuild instructions (it wasnt even close from the factory) and put the biggest primary jets in, the next biggest in the secondary side. No more "burps".

If that doesnt work, buy a Holley!

Nathan

Jun 19, 2001 | 07:50 PM

73supercamperspecial

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From: Overland Park, KS

Backfires through carb

Check the vac advance...make sure the E-clip is holding on the vac advance arm within the distributor. If the clip pops off...bad things...

Jun 21, 2001 | 10:49 AM

bufordt

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Backfires through carb

Thinks for the tip on the vacuum advance. I pulled out the distributor and the eclip was on there but the diaphragm was shot. It runs good now, but I think it still needs some fine tuning. Any ideas on what to do to the edelbrock to make it run a little better, far as I know it still has stock everything in it. Dont suggest a holley, your vehicle would run better if you had a gallon milk jug full of gas sitting on the intake than one of those damn things.

Jun 21, 2001 | 11:06 AM

heavymetal

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Backfires through carb

Let's line them up...
Bet my Holley will take that edel. I like Edelbrock , but can develop more horses with my holley. Use the vacuum method to line out that carb.
disconnect vacuum advance
hookup vacuum guage
set each side of carb mixture for highest steady vacuum
HeavyMetal (Rod)
1977 F100 429CJ bored 30 over, Heads milled 30, edelbrock performer cam, intake, lifters, valve springs, Flat top forged pistons, polished and ported, Holley 750 Legacy, Hooker Super Comp. headers with dual Hooker Comp. exhaust and Hooker dual resonators, B&M C-6 racing tranny, with a TCI Breakaway 2600 flash stall converter, 9" rear with 2-72 gears.

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Jun 21, 2001 | 06:55 PM

bufordt

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Backfires through carb

[font size="1" color="#FF0000"]LAST EDITED ON 21-Jun-01 AT 07:59 PM (EST)[/font][p] I agree a holley is better than an edelbrock for performance, but for driveability I feel edelbrock is better. I have had holley's and they perform better than an AFB but you got to mess with them to much. I've also had promblems with them cutting out in rough terrain even with the springs on them. That and there good at starting fires. I did adjust the acc. pump on it, and it runs a lot better.

Jun 22, 2001 | 06:41 AM

#10

73supercamperspecial

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From: Overland Park, KS

Backfires through carb

Call Edelbrock customer service. They can give you some tips. There are some internal screens that can be cleaned that might help. Adjusting the mixture screws on the front can certainly help as well. Procedure is set out in the manual with the carb.