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Discussion Starter #1
Took the 4BT head to a machine shop for valve job, nine cracks in the seats, some into the injector bore so its now a good boat anchor. New loaded head $750. This engine came out of P30 van. Oh well, these projects always end up costing me more than planned. So factor that possibility into your budget.
 

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Ignorance is not bliss

If it is any relief...... imagine putting money in the whole motor to have the head ruin everything. By doing it right the first time, you avoided much time, money, headache, and heartache down the road. Still is a bummer though.
 

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You never know what your going to find, but for sure the cost skyrockets. I have a 4BTA I am going to tear down soon. Have no idea what to expect as it was a non runnig engine when I got her. I pulled the pan and do know the Thrust Bearing is shot.....one side of it was down in the pan. She is probably a little out of spec on end play LOL !

Paul
 

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Discussion Starter #5
I might be able to find u a better price on a head . Should i try ?
Thanks, but I've already committed to this price from the machine shop and they waived the magnaflux fee, it seemed to be in line with what I found elsewhere, Cummins wanted $750 for a recon plus my old head. I saw 6bt heads on the net for $450 plus shipping but the 4BT's seem to be more expensive. Thanks anyway! I could visually see a few of the cracks in the exhaust seats. It probably overheated.
 

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Where would this head be located and would you get rid of it. I need a head (bad head will do) for a future jig.
Thanks, Carl
 

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Discussion Starter #7
Where would this head be located and would you get rid of it. I need a head (bad head will do) for a future jig.
Thanks, Carl
Carl - I'm going to hang onto it. I was looking it over today and I'm not totally convinced that it could not be a serviceable head with four intake valve seat inserts and a couple new valves. I'm near Buffalo,NY, if you're close you could borrow it to get some measurements if you want.

Steve
 

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Thanks for the offer Steve. I would normally trot right over with my tape measure but Im in northeast TX. Not in any big hurry right now but when I get tooled up I think it will help these engines.
Carl
 

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Discussion Starter #10

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Discussion Starter #12
save yourself alot of grief get another head
I already got one. I may order some of the tools and stitching bolts from locknstitch, put the old head on my mill and try the repair to it. Doesn't look that difficult.
 

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The early 9mm injector 4B 6B heads always crack. You never know it untill you do a gasket or pull the head. The later 7mm 91 and on don't crack.
 

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Why is that so? Bad metal? Poor cooling? Weak design?

The reason I ask is that my NOS engine is an '88 and would like to avoid head cracking issues.
 

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Took the 4BT head to a machine shop for valve job, nine cracks in the seats, some into the injector bore so its now a good boat anchor. New loaded head $750. This engine came out of P30 van. Oh well, these projects always end up costing me more than planned. So factor that possibility into your budget.
I went through the same thing with my rebuild. What's interesting is I did not observe any performance issues with the engine while it was on the engine dyno prior to tear down. I did 33 dyno runs all the while adjusting power up and down. I was wondering if the cracks truly are leaking or are they just surface?
 

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Discussion Starter #18
The 9 mm heads have less metal between the injector port and the valve seats. The later heads with the 7 mm injectors have an extra mm of metal between the injector port and each valve seat so are less prone to cracking. A crack in a head doesn't automatically make it junk, as noted by the previous poster. In fact the shop manual says cracks between the injector port and the valve seat are OK but a valve seat insert must be installed if the crack extends thru the seat. Cracks between the valve seats are not acceptable and the head must be replaced. I needed several seat inserts installed plus new valves so decided just to go with a new loaded head. One thing to keep in mind if you a scrapping a 9 mm head, go with a new 7 mm head. Then you must also replace the injectors.
 
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