300 cu incher
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Senior User
Joined: Dec 2001
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300 cu incher
Guys,
today a friend gave me an 85 ford F250 for free. He says the motor is toast but im not so sure. It has a 300 in in. when he cranked it, it cranks unevenly--fast then slow then fast again--like there are cylinders that have screwed up compression. Funny thing is, once he gets it to run, it makes this horrific backfiring out of the carb on a regular basis as it runs. What the heck could cause this and where do I start first? I am only used to working on those ole FE's is a 6 any good? If i wanted to sawp it out for a V8, what would be a direct bolt in? The truck has a 4 speed in it now and the truck is a 2wd!
thanks again
regards
~~NUT~~
today a friend gave me an 85 ford F250 for free. He says the motor is toast but im not so sure. It has a 300 in in. when he cranked it, it cranks unevenly--fast then slow then fast again--like there are cylinders that have screwed up compression. Funny thing is, once he gets it to run, it makes this horrific backfiring out of the carb on a regular basis as it runs. What the heck could cause this and where do I start first? I am only used to working on those ole FE's is a 6 any good? If i wanted to sawp it out for a V8, what would be a direct bolt in? The truck has a 4 speed in it now and the truck is a 2wd!
thanks again
regards
~~NUT~~
Elder User
Joined: Oct 2002
Posts: 516
Likes: 1
From: La Crosse, WI
300 cu incher
>Guys,
>today a friend gave me an 85 ford F250 for free. He says the motor >is toast but im not so sure. It has a 300 in in. when he cranked >it, it cranks unevenly--fast then slow then fast again--like there >are cylinders that have screwed up compression. Funny thing is, >once he gets it to run, it makes this horrific backfiring out of >the carb on a regular basis as it runs. What the heck could cause >this and where do I start first? I am only used to working on those >ole FE's is a 6 any good? If i wanted to sawp it out for a V8, what >would be a direct bolt in? The truck has a 4 speed in it now and >the truck is a 2wd!
Sounds to me like your spark plug wires may be switched around in the wrong firing order, possible loose plugs as well. The inline six is a very good motor, they run forever if you take care of them. I have on in my 78' 2wd. As far as swapping one out, any of the ford small blocks will bolt right in, the 302, 351c/m, and the 400. You would need a bigger radiator and new engine mounts though, let us know what you find out.
Mike
>today a friend gave me an 85 ford F250 for free. He says the motor >is toast but im not so sure. It has a 300 in in. when he cranked >it, it cranks unevenly--fast then slow then fast again--like there >are cylinders that have screwed up compression. Funny thing is, >once he gets it to run, it makes this horrific backfiring out of >the carb on a regular basis as it runs. What the heck could cause >this and where do I start first? I am only used to working on those >ole FE's is a 6 any good? If i wanted to sawp it out for a V8, what >would be a direct bolt in? The truck has a 4 speed in it now and >the truck is a 2wd!
Sounds to me like your spark plug wires may be switched around in the wrong firing order, possible loose plugs as well. The inline six is a very good motor, they run forever if you take care of them. I have on in my 78' 2wd. As far as swapping one out, any of the ford small blocks will bolt right in, the 302, 351c/m, and the 400. You would need a bigger radiator and new engine mounts though, let us know what you find out.
Mike
Senior User
Joined: Aug 1999
Posts: 166
Likes: 0
300 cu incher
Back firing through the carb can be caused by a defective vacuum advance unit on the distributor. Check the unit with a vacuum guage/pump like the mighty mite or similar unit. Most parts stores can check this for you as well. Replacement cost is about $10.00.
Posting Guru
Joined: Jun 2001
Posts: 1,208
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From: Conyers
300 cu incher
Also, go invest in a good compression tester before you get into replacing everything. Good readings are around 160 psi, if any of the readings are below 135 psi then I'd say rebuild it or swap it for something.
Senior User
Joined: Jul 2001
Posts: 423
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300 cu incher
My motor did that once when the valve adjustment was too tight. The valves were hung open and the motor would spin really fast.
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Elder User
Joined: Nov 1999
Posts: 796
Likes: 3
From: Anderson Northern Ca
300 cu incher
Sounds like the same noise my 300 made with a blown head gasket between #1 and #2 cylinder.A rebuilt motor fixed my problems!
"bowties in the rearview mirror"
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