Hey guys, so I recently picked up a 63 fairlane with a 302 swap. Yesterday I wanted to see just how much power this motor had. Well I punched it and it backfired before it took off. The backfire sounded like it came from the carb. What does this mean? Am I running too rich? Any wisdom would be awesome. Thanks George
so, what do you know about motor? likely timing issue but, have you checked plugs & wires, etc? post pic of motor.
Too lean, maybe you need to make sure that the accelerator pump is working. If its an older holley you may not experience good running now if it happened to pop the power valve.
I don't know what year it is. I haven't researched the block numbers yet. I do know it was rebuilt 8,000 miles ago and it was a complete rebuild. I have the paper work so I know the guy was full of ****. I'll check the plugs today Thanks
Ok ill check it out later, we took it on a 30-40 min drive and seemed to run fine after the backfire. Thanks
Before you start throwing money at it try making sure that what you have is working properly, maybe the squirter needs cleaned they do get plugged, also make sure that the pump you have is not shot. Good goobldy goop does anyone on here actually practice mechanics any more or are you all just parts replacers.
Too many variables , however is the va***e advance hooked up and properly functioning? The accelerator pump is a visual thing that can be checked by looking at how much fuel is injected while depressing the accelerator .The va***e advance can only be properly checked with a good timing light .
How can I tell if the shot needs cleaning? Would you reccomend using a carb cleaner gas additive? And by pump you do mean fuel pump? How can I tell if that is bad or going bad? Ok perfect, well I plan on doing a tune up so I'll have a mechanic check the timing. Thanks!
I'd start by checking the timing and If that's ok, then increase pump shot volume and/or different pump cams.
Alot of varaibles for sure. I had a pretty bad lean spot just off idle trying to use the specified accelerator pump setting and tried everything to make it work like that but then just said **** it and set it to have the biggest stroke and now it accelerates smoothly. Still not right, but it's my daily and unwarped carbs are scarce, so I'm making it work. It's a slant six btw, totally different animal but you get the idea. With me a backfire from the carb has always been ignition or a lean drop. A timing light is not hard to use and a good old one can be had for about 5-10 bucks at any swap meet even new from harbor freight. Goodluck with it and nice Fairlane.
Backfire thru carb,,,As stated, usually means it's too lean off idle. Holley, and Ford (Motorcraft) carbs have a vacuum operated power valve,..and a backfire usually damages it's diaphram. A low float level can make things too lean, and that's easy to check and adjust without taking the carb apart. Happy Roddin' 4TTRUK
Don't take this wrong, but your engine was completely rebuilt 8000 miles ago and looks like that? Heres a picture of a engine I built for a Engineer friend of mine about 8000 miles ago. I hope you get things dialed in sir.
How do I adjust it? The same way as any other carb by using the vacc***e gauge and adjusting the air has ratios?
Well granted yours is painted and has shiny parts on it but that doesn't mean the internals are not rebuilt on mine = ) I do have the paper work to show what has been done to the "internals" though. Thanks I appreciate it.
I found this cool video about holly carbs and the squirters. My car doesn't always backfire it just did once yesterday when I put the peddle to the floor. I'll have to try it again today. http://www.youtube.com/watch?v=k-Nx5HEzvlY&feature=youtube_gdata_player
Take the cover ( air cleaner) off of the carburetor, with the engine not turned on look down the throat of the carb and open the throttle all the way up with your hand. If the nozzle or squirter is plugged it will do one of two things it will either dribble fuel or no fuel at all will get sprayed down the throat of the carb. Sometimes on a 2 or 4 bbl carb it will squirt down on throat and not down the other. Depending on what kind of carb it is the quirter is pretty east to remove, you remove it and take a little strand of wire and push through the holes. If it is a hoilly carb or holley type of carb it will have a needle valve under the squirter, it may be that the needle valve is stuck or gummed up. See if you can wiggle or remove it. or maybe just hold your finger over the hole and work the linkage and see if gas suirts up through the hole if so thne it was just your nozzle plugged, if no gas squirts up it is either then the needle or check valve is stuck or that the pump (acceperator pump) is bad. They can be replaced or sometimes it is just as easy to put a carb kit in the carberator. That is really not much more than dismantling the carb and giving it a good cleaning. Or after all that is said and done if you are taking your car to a "mechanic" for a tune up maybe he can check that for you.
Consider this: A backfire through the carburetor will occur when a cylinder attempts to fire, and an intake valve is open. So how can this happen: (A) sticky or burned intake valve (B) timing not properly adjusted (C) advance mechanism not working correctly (D) timing chain (belt, gear, whatever) slipped (E) crossfire from defective plug wires, etc. (F) carbon gap acting like a capacitor in a radio suppression spark plug wire. Good luck. Jon.
DId you wash the car/engine before it backfired? I've washed off engines numerous times only to have them start running like **** shortly after. Moisture gets into the distributor and causes misfires. Take off the cap and make sure there is no condensation there. I just had this happen to me last week in a 46 Buick. It kept backfiring through the carb. I thought it was a stuck intake valve until I found the moisture under the cap.
Had a truck that would backfire from the carb like that - bad fuel pump. It would give enough to drive normally but acceleration would cause the float bowl to run low and the accel pump shot would suffer.
Its rare but ive had engines backfire because of weak valve springs. Most times it is caused by a lean fuel problem.
Time to learn for yourself, take the carb off, get a 'kit', 2 cans of carb cleaner and spend next sunday afternoon going thru the carb. You'll make a lot of mistakes, you probably won't fix anything but you got this big empty spot called experience that you need to fill. Don't even think you will do it right, all the guys giving advice did it wrong the first time too - thats called learnin. When you get it back together you'll know a squirter from an accelerator pump and you'll be talkin from experience so taht when somebody shows you a picture of thier engine with 8k miles you can tell them to piss off, the engine you got is the one you are working with and thats taht. Hes a good guy and will understand.
Funny you said that, the day before I wash my car an pressure wash the motor. I didn't take it out for a spin till the next day. I've been driving it lately and it hasn't been back firing and I've punched it a few times. Maybe there was just water like you said.
I would be all for that and would love too, but this is my daily driver and if I ruin it I'll be screwed waiting for a rebuilt carb to be shipped. I appreciate it and normally I do things like that but I also just moved to be cal with my wife and do not know another soul out here so finding rides to work is nearly impossible.
Ok so I did a little more research and found the mechanic that did the work on the motor in my car. The motor is a crate remanufactured 302 from ATK motors. Anyways I think the back fire might have just been because of the moister from the previous day when I spray the motor down. I haven't been able to reproduce the backfire since then. I'm having the timing checked and the carb looked at on Monday just to make sure. I'll let you all know what happens from that. Thanks!
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