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Good news and bad
https://www.slantsix.org/forum/viewtopic.php?t=22950		 Page 1 of 1
Author:  CStryker [ Sun Apr 29, 2007 7:58 pm ]
Post subject:  Good news and bad
Well, the poor gas mileage I've been getting for the past few months wasn't the blown power valve that I thought it was. As I was speeding (far faster than I should have been) to my grandmother's burial ceremony yesterday, I was introduced to exactly what a blown head gasket acts like. A compression test revealed zero compression on cylinders 1 and 2, 150 psi on 3, 4 and 5, and 120 psi on 6. That's the bad news.

The good news is that I discovered I can test the compression, pull the head off, and completely strip it down in four hours.

Before I found the blown head gasket, I had originally thought the valves were at fault: when my uncle installed the oversize valves, he just ground the existing seats instead of installing new ones. Since I already had the head off, I decided to take the valves out and make sure I wasn't having problems there either.

I didn't find any valves visibly burned (thought they're a bit dirty so I won't know for sure till I get them all cleaned up), but I did find several seats that have this ring partially around them:

Image

It's definetly a flat spot, and doesn't follow the same contour as the valve seat. I couldn't really get a photo that showed the contours very well.

I didn't look at it that closely as I was putting it together the first time, because I trusted my uncle to have done it right, but I'm pretty sure the rings weren't there. The fact that they're shiny also leads me to believe that it's something I should be worried about. Am I being paranoid here, or do I have receding valve seats?
Author:  steponmebbbboom [ Sun Apr 29, 2007 8:15 pm ]
Post subject: 
sorry about your grandmother.
Author:  SlantSixDan [ Sun Apr 29, 2007 8:18 pm ]
Post subject: 
I don't see recession *per se*, but I am concerned about that bright shiny ring, 'cause from your picture, it looks to me as if that is the only point of actual seating contact between the exhaust valve and the cylinder head. See how the bevelled ring of what should be the seat area is blackened? That looks to me like there's no good contact being made there. This would result if the valves were ground at a significantly different angle from the seats. A slight difference is sometimes specified, but this looks like it might be excessive and in the wrong direction. It might be worthwhile to smear a little machinist's dye on the valves, install them, spin them, and see where the dye rubs off to get a good visual impression of where contact is being made. Remember, the valve-to-seat interface is the exhaust valve head's only real chance to cool down...if the seat contact area is too small, the valve will run hot and fail early.
Author:  CStryker [ Sun Apr 29, 2007 8:20 pm ]
Post subject: 
Quote:
sorry about your grandmother.
Eh, it was merciful; she'd had Alzheimer's for several years now, and it finally reached the point that she forgot how to swallow. :shock: The ceremony was actually rather nice, as it gave me the chance to catch up with several relatives I hadn't seen in years and remember the good times.
Author:  steponmebbbboom [ Sun Apr 29, 2007 8:42 pm ]
Post subject: 
Quote:
Quote:
sorry about your grandmother.
Eh, it was merciful; she'd had Alzheimer's for several years now, and it finally reached the point that she forgot how to swallow. :shock: The ceremony was actually rather nice, as it gave me the chance to catch up with several relatives I hadn't seen in years and remember the good times.
that is exactly where my family and i are at with my grandmother, only she hasnt passed away yet. another constant in my life slipping away. there is much to learn from such an experience, the trick is to recognise those opportunities and seize them while you can.

good luck with the car
Author:  Doc [ Mon Apr 30, 2007 9:14 am ]
Post subject: 
Quote:
It might be worthwhile to smear a little machinist's dye on the valves, install them, spin them, and see where the dye rubs off to get a good visual impression of where contact is being made...
I would dye the area then use some lapping compound to see where the contact is being made.
From the looks of things, the seat angles are not correct.
Also spend the money to have the head resurfaced and spend time getting the block's deck surface as flat as possible. (pull the dowel pins and "long board" sand the surface)
DD
Author:  CStryker [ Mon Apr 30, 2007 9:37 am ]
Post subject:  And more bad
Image

Image

The valve question has become rhetorical. :cry: Closer examination and some cleaning with some emery cloth has revealed these nice little cracks in both the head and block. I've got a spare head on the way down here tomorrow, but I just don't have time to pull the block and have it resurfaced before I have to head up to IA for my summer internship.

I've got a spare short block, but it's all in pieces and needs a little bit of work. The plan is to get the replacement head and put it on for now, then cross my fingers that everything holds together long enough to get a new engine put together (2-3 months).

I'm still trying to figure out exactly what caused this: there were less than 15k miles on this rebuild. I didn't have the head magnafluxed the first time, so I'm thinking there may have been a hairline crack that got progressively worse, and then as the gasket blew out, the heat started cracking the block as well?
Author:  Doctor Dodge [ Mon Apr 30, 2007 9:03 pm ]
Post subject: 
Use a long board to sand on the deck surface to get an idea on how deep the cracking is. Looks like those cracks would clean-up with a cut to the block's deck and some head resurfacing.
DD
Author:  CStryker [ Mon May 07, 2007 1:18 pm ]
Post subject: 
Got it all put back together, and it runs ok, but still needs a final valve lash adjustment. I think I can limp it to at least KC, where I'll probably pick up my parents spare vehicle and tow it the rest of the way to IA, where I'll rebuild it properly. Depending on how lucky I feel, I may just drive it all the way there; not sure yet.

I have noticed that it's running hotter than it used to, right around 180 (it used to be around 160). It's the same 180* stat that I took out of the old head. That being said, I always thought it was running too cold before, so maybe this is an improvement?
Author:  sethmcneil [ Mon May 07, 2007 4:50 pm ]
Post subject: 
Quote:
long board
Ah Haa !
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