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I got a call just now from my head shop. They are well respected here in LA, so I take their advice seriously.
They say the heads are warped, and they want to know what I want to do. They read up on the IDI heads, and their literature says not to resurface. They said they can resurface them if I want, but it will lead to other problems. Also, they found cracks in the pre-chamber, which they say other diesels sometimes have, but they do not like the look of them. They also said that my heads had been worked on before. They are making a lot of suggestions (like installing guides due to valve issues) and that I'm already at the bare minimum according to tolerances when it comes to machining the head surface, assuming I elect to have them mill the surface.
This is my first Head job so I'm not sure what to ask or what to do. Is there a supplier that can ship out replacement 7.3 IDI heads?
Some cracks in precups seem to be normal depending on severity. I reused mine with small cracks on them. I had new guides installed in mine also along with the seats ground/lapped which ever the shop done. Heres my cracked head fiasco
My shop doesn't seem too happy with the cracks they found in the precups. They must be bordering on large then. Thanks for the link.
I found this company that makes American-made aftermarket heads. Called them, and they said they could have them done in 3 days for $660 per head. Anyone heard of them and if they are a good replacement part: New Heads - Diesel Cast Welding
Seems like I heard mention of them on Oilburners. You mught search over there. I may be remembering incorrectly though. Also seems like justin posted somewhere that a lot of precups have cracks in them.
I bought a complete motor for $400. So not counting spare parts and bottom end setting in my way, I had $650 in a set after machine shop ( machine shop friend hooked me up with good price).
Ive sold off a few items from the motor and recouped some cash which has helped and I still have bottom end, IP, steel lines and other do-dads.
I recall seeing a document that had head specs for machine work. There was a range for thickness as measured from valve cover rail. People have resurfaced them. It is critical to get the valve recession from gasket surface distance correct though. Valve seats must be cut to maintain that distance as there is very little piston to valve clearance. I believe around .060", and I've read of shops doing the heads improperly and pistons hitting valves. Find that document and it'll have all the specs. Your machine shop should be able to figure if your heads can end up within those measurements after surfacing.
Precups I've heard can be run if the cracks don't extend past the fire rings... But of course we don't have anything available in the aftermarket. If yours are bad you may want to buy up some heads and pick the best of the precups or use those heads if they are better than yours.
I'm not a machinist and my experience is building small block and 385 series engines, so my thoughts are worth exactly what you paid for them.
I found the "cannot be resurfaced" warning in my Ford Service Manual. I missed it before, because it was in a side-box. It says:
IMPORTANT: Replace cylinder head if any one of the inspection criteria does not meet specifications. Cylinder Heads cannot be resurfaced, because removal of bottom deck material will result in piston to valve contact.
I found the "cannot be resurfaced" warning in my Ford Service Manual. I missed it before, because it was in a side-box. It says:
IMPORTANT: Replace cylinder head if any one of the inspection criteria does not meet specifications. Cylinder Heads cannot be resurfaced, because removal of bottom deck material will result in piston to valve contact.
Hmm.
They said the same about my old Duramax heads, i just ran a type C head gasket that was like .004" thicker. I think my machinist took off 002. and 0.003. Its been 50k since then with no issues.Do they make different thickness head gaskets for the IDIs? I don't know anything about precups though.
I decided to have Diesel Cast Welding out of Oregon do up a new set of heads for me. $660 per head ain't too bad considering it will come fully dressed and calibrated with new valves and springs.
here are the pics of the old heads if anyone is interested. The camera was my phone, so it really doesn't show the cracks and pits well. The warping was in the middle, and the shop thinks that was where I was getting my oil in the coolant.
when I sent my 6.9 heads in they did not resurface. Did do a valve grind and valve seals which came in the head set. they said one head was cracked beyond usable. I did not compare for myself but my understanding was small cracks are acceptable. I called a wrecking yard right down the road from the machine shop and they had a pair of heads. I paid them $150 to send one over to the machine shop. They said if the machine shop deemed it unusable they would refund my money. Machine shop said it was good and we went forward with it. It has ran great in the 2 years since. If you've already bought the new cast heads then you're set. If you have the engine out its probably worth a re ring if you need it. I wish I would have done it but I did my heads with the engine in truck.
I recall seeing a document that had head specs for machine work. There was a range for thickness as measured from valve cover rail. People have resurfaced them. It is critical to get the valve recession from gasket surface distance correct though. Valve seats must be cut to maintain that distance as there is very little piston to valve clearance. I believe around .060", and I've read of shops doing the heads improperly and pistons hitting valves. Find that document and it'll have all the specs. Your machine shop should be able to figure if your heads can end up within those measurements after surfacing.
Precups I've heard can be run if the cracks don't extend past the fire rings... But of course we don't have anything available in the aftermarket. If yours are bad you may want to buy up some heads and pick the best of the precups or use those heads if they are better than yours.
I'm not a machinist and my experience is building small block and 385 series engines, so my thoughts are worth exactly what you paid for them.
This. I just had my heads decked. Then again my shop has done hundereds if not thousands of IDIs (bus / truck fleets in boise and surrounding area)
04-19-2016, 04:03 PM
