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Cracked head, need advice.
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Author:  87D100 [ Wed Sep 07, 2016 6:56 pm ]
Post subject:  Cracked head, need advice.
Pulled the head off my 87 D100 on Monday to address a burnt exhaust valve causing a dead miss in cylinder 6 at idle. I tore it down and cleaned it up at work today. When I got it home I noticed a crack running between the two valve seats in cylinder 5.
Now I'm not sure what to do........ Fix the burnt valve as planned and put it back together and forget about the crack (was not using any coolant or overheating) or search for a head or more preferably a whole engine ( this one is quite worn and uses a ton of oil). My instinct tells me to find a motor but they seem to be like hens teeth around here, nothing on Craig's list and nothing in the local junk yards. Plus money is very tight right now to the point that the plan for the head was to replace the burnt valve and hand lap the seat and all the rest of the valves and put it back together. 🙁

Anyone in my area that might have something they could throw my way for reasonable money it would be much appreciated.
Author:  87D100 [ Wed Sep 07, 2016 8:00 pm ]
Post subject: 
Well I just emailed a guy on Craig's list that supposedly has a head free for the taking, we will see what happens there. Fingers crossed.
Author:  DusterIdiot [ Wed Sep 07, 2016 8:10 pm ]
Post subject:  Make sure...
See what he also has with that head....if it's a pre-1981 head, it will need a different valve cover than the 1981-1987 heads... FYI. If it's a Pre-1975 head, you will be changing spark plug styles and need seals for the spark plug tubes if they are intact....
Author:  87D100 [ Thu Sep 08, 2016 5:43 am ]
Post subject: 
The head is a 1968........ Will my hydraulic valve train work in this head? I'm gonna ft t anyway cause it's free.
Author:  coconuteater64 [ Thu Sep 08, 2016 12:56 pm ]
Post subject: 
Quote:
The head is a 1968........ Will my hydraulic valve train work in this head? I'm gonna ft t anyway cause it's free.
Yes, that head will fit, but you will need to swap over your hydraulic valvetrain. The rocker shaft will swap over like it was made for it, but make sure you put the bolts in the replacement head exactly where you removed them from the cracked head. The reason is, one of the bolts is a special bolt that allows the pushrods to get enough oil to pump up the hydraulic lifters.

While you have this replacement head off, you might as well swing by a machine shop and have them make sure it's not cracked too, and check to see that it's perfectly flat on the deck surface. No sense changing one cracked head for a cracked or warped head.
Author:  Reed [ Thu Sep 08, 2016 12:58 pm ]
Post subject: 
Quote:
Quote:
The head is a 1968........ Will my hydraulic valve train work in this head? I'm gonna ft t anyway cause it's free.
Yes, that head will fit, but you will need to swap over your hydraulic valvetrain. The rocker shaft will swap over like it was made for it, but make sure you put the bolts in the replacement head exactly where you removed them from the cracked head. The reason is, one of the bolts is a special bolt that allows the pushrods to get enough oil to pump up the hydraulic lifters.
This is mostly corect. See HERE. You use the rocker shaft bolts for the head you are using, but you may or may not need to drill out the lower rearmost rocker shaft bolt hole in the hydraulic rocker arm shaft.

The stepped rearmost rocker arm shaft bolt is not a function of oil feed for hydraulic lifters. It is a design change made in the late 70s, prior to the mass production of the hydraulic lifter slant six, to all slant six heads to prevent the rocker arm shaft being installed upside down and causing oil feed problems to the rocker arms.
Author:  87D100 [ Thu Sep 08, 2016 4:23 pm ]
Post subject: 
So I just got the head home. Looks a little crusty lol. The guy said it was removed from a van in the mid 70's!!!!!! And been in his garage since. It came with the mech rocker shaft and the valve cover so that's good. How can I rig up a PCV system to this valve cover? It has two "stacks" sticking up one longer than the other. Will get pics when I get a second to get to the garage.
Author:  Reed [ Thu Sep 08, 2016 4:59 pm ]
Post subject: 
Quote:
How can I rig up a PCV system to this valve cover? It has two "stacks" sticking up one longer than the other. Will get pics when I get a second to get to the garage.
Sounds like someone pulled the head off of an old A100 van. Grab a 1970s era slant six valve cover and you should be fine.
Author:  87D100 [ Thu Sep 08, 2016 7:26 pm ]
Post subject: 
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Some pictures...... I have it all torn down, no signs of cracks yet, will throw it in the solvent tank at work tomorrow. Fingers crossed again. Seems in pretty good shape though. Just gotta get this valve cover thing figured out. Anyone wanna sell me something that will work with this head and a
PCV system?
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