Rebuild a head or no?
07-25-20, 09:41 PM
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Rebuild a head or no?
I have to pull the head off my 94 SC3 NAT w/ 85k miles. The engine started misfiring and it looks like the #6 cylinder has an intake valve problem, according to the leakdown test. My end goal is 500-600whp and I want to rebuild the head. 2 questions.... if the head is safe to reuse would a full OEM rebuild be good enough? And lastly, where is a good source for OEM parts other than the dealer? Seems a lot of place want you to buy 1 valve at a time, or if they have a valve kit it's for people with big lift cams and they want A LOT. If anyone has suggestions on finding head parts in 2020, I'd appreciate it cause I'm striking out. Thanks in advance!
07-25-20, 11:59 PM
#2
I would rebuild the cylinder head. OEM parts to replace what is necessary and worn out is best unless you want to go with a much more exotic build capable of running higher than the factory 6800 RPM redline. Even between 500-600whp a fresh stock rebuild of the head will do just fine.
As for where to get all the parts... what do you mean you are "striking out"?
I recommend using partsouq to look up all the exploded parts diagrams to note all the part numbers you will need and check the shipped prices between McGeorge Toyota's online parts portal and Amayama Japan (due to COVID19 they have recently suspended their reasonably priced EMS Japan shipping option and if this is still the case I only recommend their Fedex shipping option as an alternative... which will be more expensive). You can also try Lexus of Pembroke Pines' online parts portal, Elmore TRD Toyota Parts and mylparts.com using the code "CL5". Also Driftmotion will carry all the relevant rebuild parts but I'd stick to OEM for the most part.
When I had my GTE head rebuilt I did not replace every valve, just the couple that were too out of spec to clean up and re-use. Replacing every single thing can get expensive fast. The buckets need to be evaluated, the shims may need to be replaced as needed by the rebuilder. The valve springs, retainers and valve stem seals should all be replaced with new ones.
....
After the head rebuild is complete buy a new set of 2JZ ARP head studs (or maybe re-use your current ones? Not sure if they are meant to be re-used), a set of new OEM 2JZ head bolt washers (it is better to use new OEM washers over ARP's supplied washers) and a new OEM Toyota 2JZ-GTE 1.6mm MLS head gasket.
As for where to get all the parts... what do you mean you are "striking out"?
I recommend using partsouq to look up all the exploded parts diagrams to note all the part numbers you will need and check the shipped prices between McGeorge Toyota's online parts portal and Amayama Japan (due to COVID19 they have recently suspended their reasonably priced EMS Japan shipping option and if this is still the case I only recommend their Fedex shipping option as an alternative... which will be more expensive). You can also try Lexus of Pembroke Pines' online parts portal, Elmore TRD Toyota Parts and mylparts.com using the code "CL5". Also Driftmotion will carry all the relevant rebuild parts but I'd stick to OEM for the most part.
When I had my GTE head rebuilt I did not replace every valve, just the couple that were too out of spec to clean up and re-use. Replacing every single thing can get expensive fast. The buckets need to be evaluated, the shims may need to be replaced as needed by the rebuilder. The valve springs, retainers and valve stem seals should all be replaced with new ones.
....
After the head rebuild is complete buy a new set of 2JZ ARP head studs (or maybe re-use your current ones? Not sure if they are meant to be re-used), a set of new OEM 2JZ head bolt washers (it is better to use new OEM washers over ARP's supplied washers) and a new OEM Toyota 2JZ-GTE 1.6mm MLS head gasket.
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RudysSC (07-29-20)
07-26-20, 12:22 PM
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Really appreciate the input. I've never worked on a 2JZ internals so this is new territory. I priced out the head parts and yeah, crazy expensive to do all ne valves, springs, retainers, guides etc. But if I'm taking the head off with 85k miles I have that "you shoulda did it!" thought bouncing around my head knowing I could have addressed all the valves. So I think like you said, tear it all down and try to clean the valves and see if I can reuse any of them. If they're square, the new seals and springs should make it a lot better.
Also thanks for the OEM links, never used them before but will see what I can find.
Also thanks for the OEM links, never used them before but will see what I can find.
07-26-20, 08:31 PM
#4
You’re welcome!
Your intuition is definitely spot on. Especially if you have a cylinder #6 issue now you should just have the head rebuilt.
Valve stem seals are good to replace on the head during a rebuild even at 85k just because of the age of the engine. Springs and retainers and guides definitely replace with new OEM.
The buckets should be evaluated and the shims will need to be evaluated. But you shouldn’t need to automatically replace all of those
Now valves... as I mentioned on my own head rebuild I re-used most of the original valves (they were all cleaned up though) and only had to replace the specific ones which were no longer good with new OEM parts.
The recommendation I have is to source all the OEM parts that you know you will need anyway including the couple of intake and exhaust valves you know are problem parts to begin with.
But from there, let your cylinder head rebuilder come back to tell you what additional parts you will need.
There should be no reason to replace ALL of those factory valves, just the offending ones. Some of the other parts such as valve stem seals, springs retainers and guides, yes replace with new OEM.
Exotic aftermarket valvetrain parts are not needed unless you want to do some extra special head work for higher than stock redline use (which is more $$$).
Try those sites for your parts! They’re a big help to keep your build within some semblance of a budget
Your intuition is definitely spot on. Especially if you have a cylinder #6 issue now you should just have the head rebuilt.
Valve stem seals are good to replace on the head during a rebuild even at 85k just because of the age of the engine. Springs and retainers and guides definitely replace with new OEM.
The buckets should be evaluated and the shims will need to be evaluated. But you shouldn’t need to automatically replace all of those
Now valves... as I mentioned on my own head rebuild I re-used most of the original valves (they were all cleaned up though) and only had to replace the specific ones which were no longer good with new OEM parts.
The recommendation I have is to source all the OEM parts that you know you will need anyway including the couple of intake and exhaust valves you know are problem parts to begin with.
But from there, let your cylinder head rebuilder come back to tell you what additional parts you will need.
There should be no reason to replace ALL of those factory valves, just the offending ones. Some of the other parts such as valve stem seals, springs retainers and guides, yes replace with new OEM.
Exotic aftermarket valvetrain parts are not needed unless you want to do some extra special head work for higher than stock redline use (which is more $$$).
Try those sites for your parts! They’re a big help to keep your build within some semblance of a budget
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