400m head cracked
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Senior User
Joined: Jan 2001
Posts: 199
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From: Valley, NE
400m head cracked
Hello, I have a 1977 f250 with a 400m, with extremely low miles. 13,000. The truck was used by our Fire Dept. as a weed fire truck.
The truck was getting anti freeze into the oil when I bought it, and I had my mechanic check it out and he found a cracked head. I bought a pair of heads and we had one magnafluxed and reconditioned and it is running very smooth. Now I changed the oil recently and there is antifreeze in the oil again, a few ounces this time.
So here are my Questions, was it wise to only change one head? Could it have had both heads cracked all along? Are these engines prone to head cracks? Could there be residual antifreeze in the block that we didn't get all out before?
It is possible that the truck may have been overheated in its life, weed trucks are run pretty hard sometimes.
Thanks, Greg58
The truck was getting anti freeze into the oil when I bought it, and I had my mechanic check it out and he found a cracked head. I bought a pair of heads and we had one magnafluxed and reconditioned and it is running very smooth. Now I changed the oil recently and there is antifreeze in the oil again, a few ounces this time.
So here are my Questions, was it wise to only change one head? Could it have had both heads cracked all along? Are these engines prone to head cracks? Could there be residual antifreeze in the block that we didn't get all out before?
It is possible that the truck may have been overheated in its life, weed trucks are run pretty hard sometimes.
Thanks, Greg58
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Joined: Feb 2002
Posts: 6
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400m head cracked
Your first and easiest check will be to wait until the engine is cold, pop the rad cap, then start it up. Look into the top of the radiator, if you see bubbles rising to the top in the antifreeze, then you know somethings cracked. If your worried about residue antifreeze in the oil try changing it again.
I plan to live forever... So far so good....
I plan to live forever... So far so good....
Senior User
Joined: Jan 2002
Posts: 237
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400m head cracked
Those 400's were famous for the block cracking in the lifter valley, about 1 1/2 inches down from the deck. I've seen several and they always have a crack about 2 to 3 inches long, horizontal, right in the center of the engine below the head. You can see this with the intake off.
There will be rust or discoloration in that area.
tom
There will be rust or discoloration in that area.
tom
New User
Joined: Mar 2002
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From: US
400m head cracked
[updated:LAST EDITED ON 12-Mar-02 AT 11:33 PM (EST)]It could be the top of the block is warped (causing a head to crack), so if you have the head off again it might be wise to check it with a straight edge. A curious note: I had to have 3 sets of heads checked before I got a good set. The machine shop said they were all cracked along the exhaust ports although I couldn't see anything myself.
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400m head cracked
If a head has a crack in it, even a small one, is it common policy to just junk it? I mean, how big a problem is it? I know there are products out there (chemi-weld forex) that are designed to fill up cracks in older motors. say, for example, there is a crack but water and oil arent mixing etc.... would the crack itself be a reason to junk the head?
Elder User
Joined: Nov 1999
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400m head cracked
A good machine shop will put your cracked head back in service, and save you a lot of junk-yard time, mis-matched components, etc. A lot of the time a machinist knows little tricks that will return your head in better shape than it was in the day it left the factory. If the head is indeed too shot to fix, the machinist will know it better than anyone else.
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Senior User
Joined: Mar 2001
Posts: 296
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From: Maryland
400m head cracked
Hey, I have 2 heads off my 351m that I am not using. I have no use for them. I think they are the same as the 400. If anyone wants them they are for FREE. please contact me at agillings(No Email Addresses In Posts!). Thanks Art
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Elder User
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From: Porterfield
400m head cracked
Here's one thing most people don't know about old fire trucks. Fire Trucks sit in the Station for months at a time with very little run time, guys do there maint. on them but they really don't get up to operating temp. Then the fire call comes in and the truck get started and are for the most part run wide open to the fire, And then they will be left running during the whole fire then returned to the station.Levels will be refilled and it sits untill the next alarm.
OK these trucks don't have many miles on them but they may have 100's of hours of running on the motors, most of this is ideling.
So buyer be were on them ..
Former Fire Fighter
ShaZam
OK these trucks don't have many miles on them but they may have 100's of hours of running on the motors, most of this is ideling.
So buyer be were on them ..
Former Fire Fighter
ShaZam
Lead Driver
Joined: Nov 2000
Posts: 6,625
Likes: 342
From: Albuquerque
400m head cracked
I think what usually kills the heads on these engines is heat. If they run hot they will crack around the valve seats and blue the rods. The cracks are usually too long to fix with new valve seats.
If you buy an old engine for a builder check it for rusted/frozen out freeze plugs.
Bear
If you buy an old engine for a builder check it for rusted/frozen out freeze plugs.
Bear
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