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Uber - since you last asked I learned a bit more about dropped seats. Here's a link to an article from Len Hoffman wrote that speaks a bit about it. On a similar note, I was talking with my neighbor who owned his own shop for years and holds multiple SCCA AutoX records in Datsun 510s and he said it's usually from not cooling the car down adequately (especially after track runs) and can also be caused by bad injectors where the mix gets too lean.
Thanks for the update! Being the owner of a (late) 03 I guess I just add this one to the list of worries....
The great thing is, after frequenting this and other forums I am always pleasantly surprised every time the car starts up perfectly.
Yep, valve seat failure is what killed my '02 C4. According to Jake on my thread it seems to be one of the more common failures in 2002 M96s.
Hey Shawn - yeah, Len Hoffman just said he was seeing more and more of these. Maybe I should get out of the SEO business and start a machining shop. LOL
Interestingly, my 02 996 engine with ~108,000 miles was rebuilt by the PO because of a valve seat failure. I am not sure which cylinder had the failed valve seat. The motor went the full rebuild route with nickies on all 6 cylinders.
Interestingly, my 02 996 engine with ~108,000 miles was rebuilt by the PO because of a valve seat failure. I am not sure which cylinder had the failed valve seat. The motor went the full rebuild route with nickies on all 6 cylinders.
I'll let one of the pros here chime in, but it seems this can be caused by a faulty/worn out injector. As I understand it if it's not performing correctly it can either lean out the engine or cause hot spots. I looked all through the invoices I was provided and while there was a complete rebuild, there is no mention of the injectors being replaced. I know Jake recommends replacing them with new ones whenever replacing the engine.
Same deal with documentation that came with my car.... I have the receipt for the engine rebuild. It mentions new chains and tensioners, bearings, pistons, rod bolts, and "rebuilt block," and re-cut valves and seats. There is no mention of coils, plugs, motor mounts, injectors, or even whether the alternator belt was replaced.
UPDATE: I connected with Len Hoffman about my heads and Charles Navarro of LN Engineering about the cylinder cases and IMS shaft/bearing. How refreshing to get quick responses from both guys who I can only imagine are incredibly busy.
Len thinks the damaged head can be repaired. Now I just have to get an estimate on the cost of the repair. Does anyone have any opinions on paying to have the existing head repaired as opposed to buying an already refreshed head or getting a used head and sending it in to get refreshed? Is there any sort of advantage to keeping the original head becuase it mates up better to the cyliner or ????
Charles was very encouraging as well regarding being able to save the bad case half with re-sleaving. I'm going to send in both to get inspected and possibly honed. He recommended going with new pistons as well as they have been updated to newer designs. I'll also send in my IMS shaft to be updated to the IMS solution.
Next up is the final disassembly of the crankshaft and cradle.
So it's been years since I tore an engine apart and dealt with camshafts (might have even been high school autoshop 30 years ago...). So can I get some opinions on what I have here? The two exhaust cams look like new, but both intake cams seem to have odd wear points on each lobe. Do I need new ones, can they be machined? Do I just get them polished?
UPDATE: I connected with Len Hoffman about my heads and Charles Navarro of LN Engineering about the cylinder cases and IMS shaft/bearing. How refreshing to get quick responses from both guys who I can only imagine are incredibly busy.
Len thinks the damaged head can be repaired. Now I just have to get an estimate on the cost of the repair. Does anyone have any opinions on paying to have the existing head repaired as opposed to buying an already refreshed head or getting a used head and sending it in to get refreshed? Is there any sort of advantage to keeping the original head becuase it mates up better to the cyliner or ????
Charles was very encouraging as well regarding being able to save the bad case half with re-sleaving. I'm going to send in both to get inspected and possibly honed. He recommended going with new pistons as well as they have been updated to newer designs. I'll also send in my IMS shaft to be updated to the IMS solution.
I would suggest sending your heads to Len for repair. There is no advantage in going with other heads, unless yours can't be repaired. Mating up better to the block is not really a factor. As long as the heads and block are from the same version engine, it shouldn't matter. But why introduce more chances of mix-up by going with an "already refreshed" set of heads? In the end, the costs will be about the same.
LN is probably the best choice for block repair (Nickies). There's a thread around here somewhere... Where a guy did a recent engine build using both Hamheads and LN engineering to build a solid foundation for his engine. Look around for something like: the 133,333 mile engine rebuild thread. From what I understand, there's some good information there - as long as you are able to wade through all the off topic business.
Oh - do not attempt to build this engine without the Jake Raby video series on the M9X Engine Assembly.
Thanks for the update! Being the owner of a (late) 03 I guess I just add this one to the list of worries....
The great thing is, after frequenting this and other forums I am always pleasantly surprised every time the car starts up perfectly.
Don't worry but do be aware. Should your motor ever stall while driving, do not try and restart it! A mistake seen over and over here, causing more ($$) damage.
As I was packing up the heads this evening I discovered a strange wear mark on the inside of the valve cover just opposite the #5 cylinder valves. Can anyone explain how this could have happened? (In case you are just tuning in, I dropped a valve seat on #5).
Do you know if that valve cover is original to the engine? Bc they are machined as a set to the heads from the factory. If they were swapped out you can have that clearance issue happen.
06-14-2020, 10:10 PM
