Backfiring and popping...
Thread Starter
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Senior User
Joined: Jun 2005
Posts: 174
Likes: 0
From: Palo Alto, CA
Backfiring and popping...
So I just installed a new intake mainfold and carb on to my 75 F250 with a 360. When I first started it up i got a huge fireball that came out of the carb. After that I stardted it up and it was fine, then when I reved it it popped through the carb. Any ideas what could be causeing this? Also when I shut it off after running it for a while and testing for leaks it backfired so loud through the mufflers? I'm thinking that thats not normal...any idea on that? any help would be apreciated! Thanks
Freshman User
Joined: Jul 2004
Posts: 46
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is the intake tourqed to specs it souds like it could possibly be leaking . while the engine is running you can spray some w-d 40 around the intake and see if the engine speeds up. Also i would check the timing.
Cargo Master
Joined: Apr 2004
Posts: 2,574
Likes: 4
From: Golden, CO
Backfire through carb: most likely suspect is timing. After that, lean A/F ratio (overheating, preignition), entire valve train.
Backfire through tailpipe: Leaky exhaust valves, valve timing off.
Check ignition timing/total advance: easy
Dry/wet compression test: easy
Index the motor, leak-down test: time consuming
Keep us posted, Mike
Backfire through tailpipe: Leaky exhaust valves, valve timing off.
Check ignition timing/total advance: easy
Dry/wet compression test: easy
Index the motor, leak-down test: time consuming
Keep us posted, Mike
Elder User
Joined: Jan 2004
Posts: 867
Likes: 0
From: Eastern Pa
Easy stuff first. For the backfire out the exhaust is could be wires crossed. Especially if it gets worse when it gets hotter. Seems to make crossed wire problem worse when its hot. Don't know why that is.
Thread Starter
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Senior User
Joined: Jun 2005
Posts: 174
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From: Palo Alto, CA
The fire ball was huge!!! Almost took all my hair off, it was pretty awesome, I have to admit! Thanks for all the help though. I'll keep you guys posted! Looks like I got a lot of work to do! But it will be well worth it in the end! Thanks again,
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Freshman User
Joined: Sep 2002
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From: grafton usa
I agree with the firing order issue. Check it, check it again, then have someone else check it. I've been bit by that one more than once. Oh, by the way....Hair grows back. (I'm living proof!)
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Laughing Gas
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Originally Posted by greybullit
When you guys say crossed wire, you mean spark plug wires?
yep yep thats it.
you just cant post a simple yes.
The message you have entered is too short. Please lengthen your message to at least 10 characters.
Thread Starter
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Senior User
Joined: Jun 2005
Posts: 174
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From: Palo Alto, CA
Well, I did my best with what you guys told me but I had to take it in to the shop. So my guy is looking at it and says its running way better now but whenever he tries to put any sort of power into the motor it bogs down and such. So it's still yet to be determend. Now, I haven't checked the intake itself yet for leaks, could that make it run REALLY rough like it is, even if the timing is dead on?
Lead Driver
Joined: Sep 2003
Posts: 5,844
Likes: 6
From: Albuquerque
What intake and carb did you install? Did you install a spacer between the carb and the intake?
Can you give a better idea...of what "bog down" means? Like no power at higher rpm's?
Thanks...hope we can help get this resolved...
Oh ya, if you manifold is leaking, then yes you would loose power due to loss of vacuum...and run rough.
Can you give a better idea...of what "bog down" means? Like no power at higher rpm's?
Thanks...hope we can help get this resolved...
Oh ya, if you manifold is leaking, then yes you would loose power due to loss of vacuum...and run rough.
Lead Driver
Joined: Oct 2004
Posts: 8,062
Likes: 35
From: Central Oregon
Maybe when it backfired it jumped the timing chain. You said that you changed the intake, did you change anything else? I have had a timing chain jump a tooth and still run "ok" but no power.