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Odd thing happens under full throttle=can heard almost like a backfire noise

1271 Views 6 Replies 3 Participants Last post by  BobEhud
Okay this is not your everyday Burban.It's a 91' with a 98/99 454 but its been converted to carb.Now the guy had spent some money on the engine and then slapped a leaky,shot Q-jet on it .I replaced that with a Barry Grant Street demon 750cfm Vac sec..even though the carb looks new i still went thru it and he had the jets all wrong so prior to installed i set it up.Adjusted the electric choke,one pump on s cold start and bang she fires right had ti fiddle with the fast idle speed a bit but now when warm you can reach in and turn the key and it starts.

Now all the above wasn't bragging it was to show im an old dude that has played with alot of carbs and never ran into this.When you are accelerating hard and the secondary's come open you can feel the truck pick up speed but once or twice when they opened i felt as much as heard a BG's from the factory are like 74's in the front and 83's in the back which is a big set of jets.

I checked for vacuum leaks and ended up replacing 90% of the hoses under the hood.

Any feedback,suggestions,thoughts to steer me in right direction would be great.


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Yeap...i was afraid someone was going to say that im glad in sprung for the blue gaskets,you reuse them a few times..secondary fuel circuit on the BG mimic's the Holley so i will move to 85's and have a set of 86's as well..funny thing is it doesn't happen every-time but i have been dealing with cars since i worked at Western Auto..ok guys under 30 wont get it but guys about my age
Western Auto was always owned by Sears and Sears one day just pulled the plug on them they then were turned into PartsAmerica,which was just a RedWhite and Blue AZ..then Advanced did a hostile take over and all of what was Western Auto just Vanished.We had catalogs under the counter and if while you were waiting on your car you need a Couch or a Frig we would just order it and it would come in on the next stock order which was every Thursday.

Okay enough memory lane i raised to float level just a tad,really about an 1/8 of a turn and it seems to have cleared it up.Thanks for the complamints on the Burban.Wife named it Chubs',just kinda fits.

No lift kit all 1 ton running gear.Full floater 14 bolt in the back with Auburn locker and a 4 bolt Dana 60 in the front. 454 with a HD 400-205 TC-it truly is a monster.I have that BG dialed in im going to double check the timing and drive it.Barry Grant did a good carb sucks they shut the doors earlier this year.

OH yeah it pulls like a bear once it gets rolling on any open stretch and no traffic i ran for about a mile at to check the balance on those new i know better when there is other cars around you arent going to haul that train down in to big a hurry.
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