300 problems
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Posting Guru
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From: townsend DE
300 problems
need your thoughts here guys
i bout a 79 f250 a few weeks ago with the head already pulled off it. the PO said "it started smoking", not very helpful
so i took a gamble and cleaned the head up and checked for visible damage oh which i found none. put a straight edge on it and didnt see any warpage with the naked eye.
i then bought a gasket kit and put the motor back together. i got it to light off and well lets say the exhaust could extinguish a small brush fire, its pumping out tons of water from exhaust, it was actually quite comical.
unless i over looked a major crack in the head, the only thing i can think is that the block is cracked some where letting water in one of the chambers. would i be correct to assume this or am i possibly overlooking something?
should also note that this motor has been bored at some point as on the top of the pistons have a ".040" stamped on top.
thanks for any input, Dave
i bout a 79 f250 a few weeks ago with the head already pulled off it. the PO said "it started smoking", not very helpful
so i took a gamble and cleaned the head up and checked for visible damage oh which i found none. put a straight edge on it and didnt see any warpage with the naked eye.
i then bought a gasket kit and put the motor back together. i got it to light off and well lets say the exhaust could extinguish a small brush fire, its pumping out tons of water from exhaust, it was actually quite comical.
unless i over looked a major crack in the head, the only thing i can think is that the block is cracked some where letting water in one of the chambers. would i be correct to assume this or am i possibly overlooking something?
should also note that this motor has been bored at some point as on the top of the pistons have a ".040" stamped on top.
thanks for any input, Dave
Posting Guru
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From: Riverview, FL
It could be a cracked block, there could even be a crack in the head that you couldn't see. The only way to find it would be magnafluxing it. You could puull the head off and rotate the engine to get each piston all the way down and check for cracks. If the cylinder wall is cracked you might be able to put sleeves in it.
Lead Driver
Joined: Mar 2008
Posts: 7,182
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From: Near Los Angeles
I would also post in the Inline forum. That's where you'll find the inline experts.
First I'd pull the head again and ck the cylinders as the other member said. Ck oil for water. If they look good, then pull the head and have it checked, magnafluxed.
If it were mine, I'd rather pull a block from the boneyard and have it machined than put a sleeve in a cylinder. But thats just me.
Good luck.
First I'd pull the head again and ck the cylinders as the other member said. Ck oil for water. If they look good, then pull the head and have it checked, magnafluxed.
If it were mine, I'd rather pull a block from the boneyard and have it machined than put a sleeve in a cylinder. But thats just me.
Good luck.
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Posting Guru
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From: townsend DE
well i found the problem, definitely over looked a major problem
it was on the front side of cylinder 5 so if you are looking under the hood at the motor its pretty hard to see. im kinda mad i didnt look at it closer but oh well, im only out a few bucks for gaskets and im pretty good at working on 300s now
im pretty sure this is because of the over bore. the wall looks extremely thin where it broke. also the piston can rock on the wrist pin about 10* in either direction so the skirt must have went away lol
found a guy on CL with a motor for 450 that is still in a running truck so im going tomorrow to pick it up
it was on the front side of cylinder 5 so if you are looking under the hood at the motor its pretty hard to see. im kinda mad i didnt look at it closer but oh well, im only out a few bucks for gaskets and im pretty good at working on 300s now
im pretty sure this is because of the over bore. the wall looks extremely thin where it broke. also the piston can rock on the wrist pin about 10* in either direction so the skirt must have went away lol
found a guy on CL with a motor for 450 that is still in a running truck so im going tomorrow to pick it up
Lead Driver
Joined: Mar 2008
Posts: 7,182
Likes: 380
From: Near Los Angeles
It is pretty common to bore these blocks .050 and .060". Some guys do so and install pistons from 352's, 360's, even sbc's. Of course it is always a good idea to have the block tested first. I'm wondering about the quality of the machine work, etc.
Good luck.
Good luck.
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Posting Guru
Joined: Oct 2010
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From: townsend DE
who knows, all i know is its toast. picking up the running motor tomorrow or thursday maybe have it in by the weekend
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