'57 213 Y Block Backfire Holley 4 BBL

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Proidgy68

New member
I have a 57 312 Y block in a 58 F-100 that has a backfiring issue. Once the engine is warmed up it will backfire every 10-20 seconds, some are louder than others. I attributed that to too rich of fuel, so I adjusted the jet ports on the Holley 4 BBL carb, it did not help. I've used my vaccum gauge to adjust the jets to maximize the vaccum, but I can screw the jets in and out as much as I want and it does not affect the vaccum. I've even replaced the carb (thinking maybe I have a warped fuel block) and the problem still exists with the new card. Am I wrong in thinking too much fuel? Can you help me confirm my carb is on correct?

Any help would be appreciated.
 
More info is needed to try and help you. Is the backfiring in the exhaust system or is it coming from the carburetor ? If from the carb, then it means there is a lean condition, or the accelerator pump on the carb that could not be working or mis-adjusted. Could be a lot of things combined too. If backfiring in the exhaust, that is caused by unburned fuel accumulating in the exhaust system and then igniting.
Another possibility could be a cracked distributor cap making a cylinder firing when a valve is open (out of time). An easy check to remove the dist cap and look carefully for a crack or carbon tracking going from post to post.
Like I said, it could be a lot of things. Hope I was of some help.
 
Have not done a compression check yet, dont have the equipment for that yet...

The backfire is from the exhaust. It even happes while driving, not just idleing. I will check the distrib cap later today.
 
Upon further review, could I have a problem with my distributor?

I ran the engine for about 5 minutes (with the backfires) and noticed that two of my header pipes were cooler than the others? Could those cylinders be firing intermitantly and when they miss that un-burnt fuel is causing my backfire?

It does have a rough idle too...

So what do I do from here? I have been thinking about electronic ignition for a while rather that the vaccum advance but that is beyond my scope of skills. Any advice?

Still does not explain why my vaccum does not change when I adjust the jets on my fuel block?
 
I have heard engines sound like they are backfiring or spitting through the carb and it was a sticking valve. Easy to check if it is a valve problem, just lift the the rocker cover on that side.
In your case you say that two header pipes are cool to touch, I would check to make sure you haven't got the plug leads crossed. Those cylinders are not firing. Simple mistake - simple fix.
Regards
 
Make sure the plugs are firing - if not replace with a good plug to see if ok. There is such a thing as a bad plug, even if new.
 
Has the truck been sitting for a while or have you done any work to it that may have caused the concern? Sometimes when working on your vehicle you may have crossed up something. Like Streetdreams mentioned what is the vacuum reading? Is it just low or does the needle bounce when its running. A low vacumn reading w/a bouncing needle may point to a valve concern.
 
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