shaun65Polara
New Member
i have discovered all 8 exhaust valve stem seal boots have lifted up from their seats & #5 cyl has a failed piston ring, evidenced by damage to cylinder wall. most of oil loss, however, was coming from passenger bank.
tailpipe puking fresh oil update
- Thread starter shaun65Polara
- Start date
That sucks. What was the reason for the stem seal boots to have lifted?
volksworld
Active Member
and I thought I was having a bad day...if those are stock "umbrella seals " they don't attach to the head, they just slide up the valve stem and attempt to deflect the majority of oil splash from the guide...machine shops may or may not cut the top of the valve guide boss to use aftermarket seals that actually attach to the head and seal the stem like most new cars...
On the exhaust side of things, some engines in the middle 1970s did not use exhaust valve stem seals. Why? There is more positive pressure in the exhaust port than negative pressure. On the intake side, most usually vacuum. If you saw a puff of oil smoke on initial start-up, but then cleared up, that was most probably an engine without exhaust valve stem oil seals . . . after the engine got some miles and valve guide wear on it.
Then there were the "Studebaker" seals (as my late machine shop operative termed them) which had a band around their mid-section to stay put on the guide boss, so as the valve went up and down, it just wallered-out the center hole. Some later ones had a ribbed plastic insert that the valve stem operated in.
If using the white scraper seals, ALSO understand that they can keep the guide too dry, so there is a fine line of what it needed vs what is too much. Most oils have been ashless for over 50 years, so they would burn cleaner, for whatever was burned. That was one of the first changes to motor oils due to exhaust emissions, back in the later 1960s.
I highly suspect that modern engines obtain MORE oil control from their "MM" (thin) piston rings (which also help power and mpg via friction decreases) and "plateau honing" techniques. Oil scraper rings with better geometry and designs. One reason to consider Mahle pistons (which come with rings) rather than the normal brands, if Mahle has a piston for your application.
Enjoy!
CBODY67
Then there were the "Studebaker" seals (as my late machine shop operative termed them) which had a band around their mid-section to stay put on the guide boss, so as the valve went up and down, it just wallered-out the center hole. Some later ones had a ribbed plastic insert that the valve stem operated in.
If using the white scraper seals, ALSO understand that they can keep the guide too dry, so there is a fine line of what it needed vs what is too much. Most oils have been ashless for over 50 years, so they would burn cleaner, for whatever was burned. That was one of the first changes to motor oils due to exhaust emissions, back in the later 1960s.
I highly suspect that modern engines obtain MORE oil control from their "MM" (thin) piston rings (which also help power and mpg via friction decreases) and "plateau honing" techniques. Oil scraper rings with better geometry and designs. One reason to consider Mahle pistons (which come with rings) rather than the normal brands, if Mahle has a piston for your application.
Enjoy!
CBODY67
shaun65Polara
New Member
repair & re-install. But, i'm having difficulty locating a machine shop that still does heads.
I found one remaining in my area, but he doesn't knurl. So, i think i'll get the knurling tool & some progressive reamers & do that myself, after i verify wear clearances are within knurling range. But, i still need magnafluxing done to check for cracks first.
As for the rings, i'm going to pull all of the pistons & check 'em
I found one remaining in my area, but he doesn't knurl. So, i think i'll get the knurling tool & some progressive reamers & do that myself, after i verify wear clearances are within knurling range. But, i still need magnafluxing done to check for cracks first.
As for the rings, i'm going to pull all of the pistons & check 'em
If you look at the knurled surface, when done to spec, it is really quite jagged. The other option is a "bronze heli-coil guide insert". Once the seats are done, then the guide is drilled and grooved for the insert of a bronze heli-coil. The insert is screwed in, then snipped on the ends, and a tool driven into the insert to fully seat and size it. Bronze is supposed to be an excellent wear interface with a chrome valve stem. Not hard to do. Knurling is quite "sub-optimal", although it was "the norm" 60 years ago. Also much less labor that doing "knock-in" guides.
Just some thoughts and observations,
CBODY67
Just some thoughts and observations,
CBODY67
1970FuryConv
Old Man with a Hat
Ditto: Bronze Valve Guides!
Knurl is cheap short term inefficient fix,
Knurl is cheap short term inefficient fix,
shaun65Polara
New Member
thanks ... the guy i found, he offers service for bronze, at 6-700 bucks compared to knurling, which sure, is short term, but a 59 year old engine which is driven less than a thousand miles/year ... do i really need bronze inserts ?
shaun65Polara
New Member
th
there's a machine shop in Texas that reccommends knurling above guide replacement, if wear tolerances is within .001"
shaun65Polara
New Member
THAT, i have not yet determined
1970FuryConv
Old Man with a Hat
I have never had heads knurled. Our cars don't get driven many miles, so maybe it will work.
OTOH, I have been reading Mopar mags for 30 years. Every article on the subject opposes knurling and endorses new valve guides.
The engine builders I've known over the years have always recommended against valve guide knurling. Their reasoning was twofold. First was that oil still would go past the knurling and second was that the knurling didn't last very long.
You didn't say which engine.... If the shop's saying that they only do that with .001" wear, the guides, especially the exhaust, will probably be more like .010" wear if they have never been touched. That's been my experience with big block heads.
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