Cracked Head? In Need of an Experts Opinion!

[awolfe]

I recently removed the head from my '77 280z because of a leaking head gasket. After reading the post "Check head for cracks" http://atlanticz.ca/zclub/techtips/h...head/index.htm, i decided to further inspect the head and found two cracks on cylinder 3 & 4.

Basically, what i'm asking is...What are my options with this issue? Time to replace the head?

Thanks in advance for any advice!

[240260280z]

Yikes.... it is those darn exhaust liners that are the cause. They expand and contract at a different rate from the aluminum that surrounds them. They probably conduct heat faster as they are thin and less of a heat sink than the surrounding aluminum.

Time to get a new head. You can use that one for porting experiments.

A Maxima N47 would work nicely but you have those pesky liners again.

Mine cracked in exactly the same spot:

btw this follows my question last week as to why Nissan placed the two exhaust runners for 3 and 4 side-by-side in the head? So much heat in one area is unwise.

Edited August 7, 2011 by Blue

[robftw]

I've got a replacement head if you want it, 62k miles. came off a 77 280z.

I will be keeping the rockers and cam-shaft for my re-grind you can have everything else 50$ obo + shipping, i have no idea what these sell for

[Walter Moore]

these are questions, not a statements: Is it possible to repair the crack? Is it possible to remove the liners?

Since steel expands and contracts much less than aluminum, and aluminum conducts heat much faster than steel, I can see how the head might crack as it cooled.

Of course even if it could be repaired it might be cheaper today to find a good replacement. I am just wondering from the long term perspective if years from now when there are fewer sources for used parts for the S30, if a repair is possible.

The #6 cylinder on my cylinder head was severely eroded, apparently by a leaking head gasket. The damage was so severe that the exhaust valve seat was partially unsupported. The shop that repaired it re-welded the chamber and re-machined it to where it works great. The guy who did the work claimed that any aluminum head can be repaired, but of course he didn't say that it would always be cost effective to do so...

[240260280z]

This is #6 in the E31 I am restoring. Looks like water but maybe detonation?

Sure it can be ground and welded up then machined back to shape like a racing head plus new seats but I went for a Maxima N47 with custom cam from BMC in Arizona.... and probably saved $.

Unfortunately, I am now reassembling and noted the corresponding piston top from #6 is peppered with small holes and it is 5grams less that the others. I may need that tended to with a welder and surface grind.

Edited August 8, 2011 by Blue

[Phred]

Blue,

Your head looks like electrolosis erosion to me. The main reason I reply, is to try to convince you not to weld a piston dome. The piston dome is not that thick, and the welding will likely distort the top ring groove. The top ring groove is probabbly worn out anyway. To check, lightly glass bead the piston top groove, install a new ring and check the ring land clearence with a feeler gauge. New pistons will have a land clr. of .001 - .0015. At around .004 clr. the groove will not support the ring properly and it will lead to compression loss. My 2cents, and FWIW, and I've been there many times.

Phred

[240260280z]

Thanks a million Phred! I appreciate your intervention

[awolfe]

I've got a replacement head if you want it, 62k miles. came off a 77 280z.

I will be keeping the rockers and cam-shaft for my re-grind you can have everything else 50$ obo + shipping, i have no idea what these sell for

I have an entire spare engine that came with my '78 280z that I'm gonna check the condition of the head on wednesday. If it is not worth using i will definitely be interested in buying yours. If you could, in the mean time, check the shipping rates to 30547 and let me know.

Thanks

[awolfe]

BTW, Thanks for all the help Guys! I really appreciate all the advice and help everyone has givin me since I've join this forum. And many thanks to you Philip, for taking the time to share all your great Knowledge about the Z cars. It has been most helpful to a newcomer like me.

[az240z]

if you want an mn47 head I have one that's been rebuilt.