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vortec heads cracking?

49K views 13 replies 7 participants last post by  cobalt327 
#1 · (Edited)
Hi, just going to fit my vortec heads(906) ready for the new season,have been reading that they are prone to cracking! Do they crack in a certain place? if so where do I need to look, if they are can I weld them up and what rods do I need to use?,thanks in advance Dave
 
#2 ·
These heads usually crack from the center exhaust seats to the nearest cooling crossover or center head bolt hole. Minor head bolt hole cracking can be fixed by drilling and reaming the hole oversize (usually 5/8") past the end of crack, about 1 1/8" deep. Then pressing a repair locktite coated sleeve ( I use a farm tractor cast iron guide) into the oversized hole. Then drill the ID. of the sleeve to std bolt hole size. Trim length. Mill head. Never had a return.

Seat cracks cannot be welded by a novice. The insert type seats, if equipped, must be removed. Heads heated to red hot in a kiln. Welded while red and very slowly cooled. Then heads cut for inserts and seats cut. Finally chambers shaped and heads milled flat.

Lots of labor and cheaper to buy aftermkt heads..
 
#5 ·
I definitely wouldn't buy an intake until you have them checked, I've been junkyarding 4 times over the past 2 weeks trying to find 1 good head to finish a set. In all I'm out a couple tanks of gas, 10hrs of my life and about 125 dollars in heads for the 3 bad ones I've picked up.
 
#10 ·
would some one here show me the picture where the crack on vortec crack because i had set #906,i want find crack before i install on my block thanks
Red lines show where to look for the more common cracks (this is an end chamber, you're much more likely to find the center chambers cracked). I have no info on them cracking between the valves on the center chambers because they lack a heat crossover like the earlier heads, but I'd still check there.

Best bet is to haul them in to the machine shop and have them checked. You need to know if they're flat or not, and you should CC the chambers so you know what the compression ratio will be.

 
#12 ·
Ballpark $50-$75 should get you a thorough inspection including deck flatness. I would clean it real well before taking them in, or plan to have them tank or cook them before inspecting. Hopefully that'll be deducted from the cost to rebuild them if you have them done at the same shop.

There are good machinists here (BOBCRMAN has posted to this thread already) that can tell you what they do, I'm going by what my shop does and that might not be what they all do.
 
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