MIRROR FINISH ON PISTON WALLS

[Captain Obvious]

11 hours ago, siteunseen said:

This might be it? Enjoy your Holiday. Just a few more days for me.

https://forums.hybridz.org/topic/95316-braaps-l6-efi-induction-advice-and-tips/

Thanks for the link. Good info in that. 

[EuroDat]

5 hours ago, Captain Obvious said:

Thanks for the link. Good info in that. 

Yeah, That is the thread alright. I remember first reading it about ten years ago and made a copy for my own use, just can't seem to find it

I have not found anything serious dating before this thread. It looks like this might be the first seriously thought out explanation.

@siteunseen Thanks for posting the link.

[zKars]

Back to the original topic (harumph….). I’ve a L24/N42 combo in a 72 with crap for compression. 100-20-20-20-50-90. Oh oh…. This was an engine free spinning but not run for 10 or 20 years, cold with 10cc of oil added through plug holes, cranked until engine got oil pressure, which was almost immediately. 

Not number matching block, so something someone stuffed in. Block number is 90xxx, chassis has 160xxx mi. What’s left of it…

So why the poor or absent compression? Did someone not notch the L24 block for the N42 exhaust valves? Bent valves? Not likely, #1,5,6 has SOME compression. 

Pulled the N42 head, its been rebuilt at some point, clean, all new exhaust valves some new intake valves, AND!!!

the SHINIEST smoothest almost 99% no more hatching on the cylinder walls that I have ever seen. Stock 83.00 bore.  This thing must have 500,000 miles on the short block. No matter what block I’ve seen (not rebuilt) the stock hatching is plain for all to see., Not this thing.

Good new might be, fresh hone, fresh rings, and it might just drive away happy.

Oh, and bores had been notched. Someone new enough to do that when this N42 head was put on, but didn’t bother to check the state of the bottom end. I suppose that’s why I’m parting out a rusty 72 now…..

[Pilgrim]

My thought was stuck rings.

[dutchzcarguy]

13 hours ago, zKars said:

AND!!!

the SHINIEST smoothest almost 99% no more hatching on the cylinder walls that I have ever seen.

If thats so uncommon, you must have made a pic of it?  I  (we?)  want to see a poor cylinder.. how does it look? 😮

And another question.. maybe i'm stupid.. but what do you guys mean with a short block or a long block..??  to me they are all lóóóóngg  blocks! 😟

[zKars]

2 hours ago, dutchzcarguy said:

If thats so uncommon, you must have made a pic of it?  I  (we?)  want to see a poor cylinder.. how does it look? 😮

And another question.. maybe i'm stupid.. but what do you guys mean with a short block or a long block..??  to me they are all lóóóóngg  blocks! 😟

Yes pictures are definitely in order here. Will comply shortly, I hope they convey the smoothness.

Long block is block/pistons + head, short block is block/pistons only.  

[dutchzcarguy]

2 minutes ago, zKars said:

Long block is block/pistons + head, short block is block/pistons only.  

Ah..  so it should be a high or low block...  😂   we call a short block  a "under-block" (an engine without the head.)

[dutchzcarguy]

9 minutes ago, zKars said:

I hope they convey the smoothness.

Put your camera / phone  on Macro first. use flash and no flash.. and look whats best.. 👍

[zKars]

Not sure this is helpful.  

Under just the right conditions of light and angles, I can see remnants of home marks, but overall they are remarkably smooth.

First four are all cylinder 1.  Last two are the notches cut in #1, and 3td last is cylinder 6

[dutchzcarguy]

19 hours ago, zKars said:

Not sure this is helpful.  

I find it very iteresting..  lots of vertical scratches is a bad sign.. also those pistons were not the originals.. so the engine was taken already once apart.

Anyway, good pics Zkars!

[280zdude]

So where should I get my head checked on. I live in Southern California. 

[dutchzcarguy]

11 hours ago, 280zdude said:

So where should I get my head checked on.

At  58k miles it just needs a good clean and after these 40+ years some new gaskets and new oil seals on the valves that would be all..

Clean it up, get yourself some tools and take a good look in the serv.manual.. and take your time. you'll get there!

Some pics are always nice and maybe also helpful!   We can help you do it the right way...