78 backfiring 460
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78 backfiring 460
Just added a new truck on ford rd but having a few problems. Don't know much about the truck just picked it up this afternoon. It's hard to start and idle, and backfires they card. It's a rebuilt holly with new fuel tank, lines, pump, and filter. Idle is low and doesn't improve when it warms up. Thinking it might be a vacuum problem for the booster is not much help when it comes to stopping the ol girl. I was wanting to verify all vacuum hoses are in the right place. This is my first big block in this series of ford and have been looking forward to the power, but it's not there.
It will not stay running without giving it gas and then it runs like a five cylinder. Once the truck is at a high enough rpm it smooths out but still revs up and down slitely. The transmission doesn't want to shift and jumps straight to third.
It will not stay running without giving it gas and then it runs like a five cylinder. Once the truck is at a high enough rpm it smooths out but still revs up and down slitely. The transmission doesn't want to shift and jumps straight to third.
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Freshman User
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Yes I was going to check the timing tomorrow after I get home. Not sure what the timing is on this truck, but I know there is a numbers guy that floats around here that has that info. I am thinking that maybe it's a combination of wrong location of vacuum hoses and timing. Or it might just be a timing issue all together.
Tuned
Joined: Nov 2016
Posts: 269
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From: Shelbyville
I got my 79 f150 460 for cheap because it was backfiring through the carb, didn't idle cold or warm, and if unplugged the vacuum advance it would die.
Turns out the ignition timing was majorly retarded.
It's running happy at about 10*BTC now.
I'd definitely start there.
Turns out the ignition timing was majorly retarded.
It's running happy at about 10*BTC now.
I'd definitely start there.
Thread Starter
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Freshman User
Joined: Aug 2017
Posts: 26
Likes: 0
I got my 79 f150 460 for cheap because it was backfiring through the carb, didn't idle cold or warm, and if unplugged the vacuum advance it would die.
Turns out the ignition timing was majorly retarded.
It's running happy at about 10*BTC now.
I'd definitely start there.
Turns out the ignition timing was majorly retarded.
It's running happy at about 10*BTC now.
I'd definitely start there.
Tuned
Joined: Nov 2016
Posts: 269
Likes: 14
From: Shelbyville
that is exactly what it turned out to be. The distributor was turned as far as it would go and was hitting the thermostat housing keeping it from timing in. Pulled the distributor and turned it back another tooth and set the timing and solved the backfiring. The trans is another problem in it self. Something is wrong inside tranny. reverse locks in and grabs and moves well. First thru third the truck is slipping thru them all and does shift from first to third, but only if I manually shift it down to first every time.
It's a C6 tranny right?
If I left it in D it would only shift up to 2nd.
Reverse worked just fine.
And I could manually shift between 1-2 just fine.
And sometimes I could get it up to 3rd if I kept moving it between 2nd and D.
If it sounds like my experience then try replacing the vacuum modulator. That fixed my issue.
Mine had a retaining bolt and a vacuum line hooked up, once disconnected it slid right out with a little tranny fluid too. And I mean little. Their pretty cheap too. I think some screwed in and out though? Not really sure on that.
It's on the passenger side of the transmission.
Oh and there's a little metal pin/rod inside of it. Don't lose it you'll need it for the next one.
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