Might get new heads for my 90 NA...need advice please

[es.biggs]

I probably need to replace the heads on my 1990 NA eventually because of a machining flaw that affected the early 1990 models...Nissan has a TSB about it and my VIN matches the ones affected, and it also has the exact symptoms described in the bulletin. I have one more step to confirm this problem; my ignition timing won't stay at 15 degrees before TDC, so I need to check to see if the "spindle" on the CAS is damaged.

I am pretty sure this is my problem though...so I can either continuously replace and destroy CAS's or I can put a pair of different heads on and be done with it.

What years will fit my engine? Are there any differences in the heads from year to year?

Also, will I have to rebuild the heads before I put them on my block? Stupid question I guess, but money is tight, and I was just wondering if that would be asking for problems.

I wish I had the paper for a TT swap

Just to let you guys know, here is a photocopy of the TSB I found:


Modified by es.biggs at 11:58 AM 4/9/2010

[evildky]

I call BS but even if the mounting points for the cas plate were off kilter you could shim it up and if you really wanted to replace that head the passanger head has nothing to do with the cas

[es.biggs]

I've attached a copy of the TSB to my original post, just so you guys can understand the problem.

How could I shim it up? I'm all for not doing the heads on the car if I don't have to...but I think if I do end up doing the left one, I will do the right one as well. Do you think it's ok to just replace one side?

[Zwicked]

My '90 tt is in the same time frame of manufacture, lots of miles, and never had an issue. I have all the service records from the original owner and the head nor CAS have ever been replaced. Had the CAS off many times and no evidence of abnormal wear. When I first got it I wondered as well, but I think there must have been very few that actually got out the door that way as it's rare that I have seen anyone over the years post they personally have had this issue.

Just pull the CAS off and inspect it before jumping to conclusions.

[es.biggs]

Will do, there is hope after all!

[es.biggs]

I removed my CAS a few minutes ago...inspected it best I could and it seems to be alright, it does look a little dirty though around the index pegs. Nothing looks chewed up from what I can see, but I've never seen one of these before so I'm not exactly sure what to look for, damage-wise. Can I get some opinions from those of you who are familiar with the way this CAS and camshaft are supposed to look? I took plenty of pictures of it:

EDIT - I just looked at it again before I put it back on, and I cleaned it off a little...noticed a lot of scratches, and there was acutally what looked like a whole section on the CAS shaft that was worn down, like it was slowly grinded down. Looks like that TSB is the problem. The good news is the camshaft "index peg" doesn't appear to be damaged at all. I think if I can swap a good CAS into it we will be good. Hopefully this was the stock CAS on the car now; if so, I will be good for another 90k miles

my CAS

the end of my cam/index peg
Modified by es.biggs at 4:52 PM 4/13/2010