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57 willys 04-13-2013 11:57 AM

backfire
 
Built 302 Ford 670 Holley Truck Avenger. Off Idle stumble, and backfires through the carb sometimes. Why? 700 RPM, 6 degrees BTDC.

vinniekq2 04-13-2013 12:42 PM

try more static timing

33Willys77 04-13-2013 02:44 PM

What do you mean by built? Give your cam specs, trans type, stall speed if auto and so on. I am sure off the top you will need more intial timing as Vinniekq2 stated.

57 willys 04-13-2013 04:13 PM

30 over 2 valve relief pistons, 160 150 on the valves, 262 512 comp cam roller tip rockers, weiand intake shorty headers, stock converter, c6 automatic, 456 gears, 4-wheel drive. Seems to pull down flat spot until you nail the throttle but when crawling that's when I get the burp out of it. Not really sure where valve adjustment is now it's been a long time.

57 willys 04-13-2013 04:14 PM

How high does it need to be?

33Willys77 04-13-2013 05:03 PM

Is that 262 advertised duration with 512 lift? Solid, hydraulic, roller, flat tappet? Do you have a grind number so we can see the specs? What is your compression ratio? Wieand intake... but dual or single plane? So far, it may just be a simple lean tip in. Is the pump set correctly too? I can't tell you much for intial timing yet, but I would think 12-14 would do much better. How do you have your curve set on the distributor? Using vacuum advance or mechanical?

There, answer these any we may have a little better picture of what you have.

bondo 04-14-2013 08:21 AM

Quote:

Originally Posted by 57 willys (Post 1666010)
Built 302 Ford 670 Holley Truck Avenger. Off Idle stumble, and backfires through the carb sometimes. Why? 700 RPM, 6 degrees BTDC.

Ayuh,.... Sounds like it's goin' Lean,....

Richen up the fuel abit...

57 willys 04-14-2013 02:18 PM

Quote:

Originally Posted by 33Willys77 (Post 1666100)
Is that 262 advertised duration with 512 lift? Solid, hydraulic, roller, flat tappet? Do you have a grind number so we can see the specs? What is your compression ratio? Wieand intake... but dual or single plane? So far, it may just be a simple lean tip in. Is the pump set correctly too? I can't tell you much for intial timing yet, but I would think 12-14 would do much better. How do you have your curve set on the distributor? Using vacuum advance or mechanical?

There, answer these any we may have a little better picture of what you have.

xtreme 4 x 4 flat tappet hydraulic cams
INT. 262 EXH. 270 INT. 218 EXH. 226 Lift INT. .493 EXH. .512 lobe sep. 111 degrees Roller lifters compression ratio 10 if I remember right. Weiand intake dual plane Set from Holley probably should check I'll try 12 -14 on timing and to fatten up the carb that would mean to turn the screws in? And not really sure how to adjust the rockers. I never had rollers before. Thanks for the help. It is in a 57 Willys Wagon with 456 gears and an automatic. Pertronics distributor vacuum advance

vinniekq2 04-14-2013 02:44 PM

mixture screws out will fatten idle only. do you know how to change jets?

57 willys 04-14-2013 03:04 PM

Quote:

Originally Posted by vinniekq2 (Post 1666369)
mixture screws out will fatten idle only. do you know how to change jets?

will that make idle go up

vinniekq2 04-14-2013 04:25 PM

everytime you change something in the carb,tweek the mixture screws


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