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That sounds about right. Just make sure they use intake and exhaust seats made from the correct material, so the seats do not wear rapidly. I used to purchase factory oversize seats and furnish them to my machinist, but he did not like those seats and now furnishes his own when we need to replace seats.
I can't see into the ports. Is the aluminum eroded under the valve seats enough that they need to weld there, too?
That sounds about right. Just make sure they use intake and exhaust seats made from the correct material, so the seats do not wear rapidly. I used to purchase factory oversize seats and furnish them to my machinist, but he did not like those seats and now furnishes his own when we need to replace seats.
I can't see into the ports. Is the aluminum eroded under the valve seats enough that they need to weld there, too?
I think I've heard several times that welding up aluminum, after it's been glass beaded, makes for a major PITA... something about microscopic glass embedded into the surface... but I'm not a welder... Ken
I think I've heard several times that welding up aluminum, after it's been glass beaded, makes for a major PITA... something about microscopic glass embedded into the surface... but I'm not a welder... Ken
You are correct. The proper way is to thoroughly clean the surface by washing in a hot chemical solution, cut out the damaged aluminum to the base metal, then weld it up, for resurfacing. Porosity, surface cracking, or any cracking, is not acceptable. Glass bead is for the outside surface area, keeps it looking pretty. After welding and machining. I do use it on my Harley engine cases, their two piece, easy to clean, then I use Rustoleum Orange primer to seal the cases internal surface. Harleys are dry sump engines, but their cases are very porous. We've welded broken cooling fins on heads, intake runners, broken cases, etc. Clean and weld first then machine, then glass bead the exterior.
Back 50 plus years ago carbon tetrachloride, was the best solvent for cleaning aluminum, it's banned. Today it's acetone and alcohol. You gotta prehead the hell out of aluminum. Welding aluminum is a skill, just takes patience and time to learn to do it correctly. I have a purge box, and use helium as a backing gas.
That corrosion isn't bad, it actually looks fairly normal for a 928 head. Most that look worse than that are saved, especially the 89+ heads that aren't prone to cracking.
Just have your machinist pop in a new set of seats, have them cut, do some welding, deck the heads to the correct RA and away you go.
Now would be the time to port match the intake to the heads as well
That corrosion isn't bad, it actually looks fairly normal for a 928 head. Most that look worse than that are saved, especially the 89+ heads that aren't prone to cracking.
Just have your machinist pop in a new set of seats, have them cut, do some welding, deck the heads to the correct RA and away you go.
Now would be the time to port match the intake to the heads as well
Those heads are destined for my stroker project. That's why they are getting properly repaired.
02-13-2019, 12:50 PM
89 heads after sitting intercooler and coolant fluid for 10 years
