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#1
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Anecdotal info on failed bottom ends after top end rebuilds/upgrades.
In another amusing, now closed post this "wive's tale" was brought up. I'm in my '70's and can attest to how this wive's tale grew legs ... because it happened, a lot.
The fact is increasing the valve sealing via a valve job along with guide rebuilding on a car with excessively worn rings usually emphasized the failing compression by increasing blow-by and oil consumption and a wive's tale "My motor never smoked or used oil before I had the heads done" was born. Yeah, it did, but they just never paid attention to it until they re-did the top end and just couldn't admit they wasted their money on a worn-out engine because that would be stupid. As if that wasn't bad enough, inexperienced backyard builders would combine the cylinder head work (surface seats/valves and replace or knurl the guides) with an opportunity to install a performance camshaft and matching springs along with a four barrel intake upgrade on their 2 Bbl low compression, worn-out econo-motor. The old, worn motor was RPM limited (protected) by it's original 2 barrel carb that ran out of juice and old valve springs that floated the valves just north of 4,000 rpm. With the upgrades, the motor would rev past what was a safe upper RPM limit for its condition and well-worn crappy cast pistons with excessive clearance would rock in their bores, rod and main bearings became oil-starved at high rpm due to excessively worn clearances and of course crappy low-performance cast rods would get stressed as the bearings got hot. The continued abuses eventually would cause some combination of spun bearings, cracked piston skirts and broken rods. Motors got grenaded and the old wive's-tale was perpetuated.
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Triple Black 1971 GTO Last edited by NeighborsComplaint; 02-13-2024 at 12:58 AM. |
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#2
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#3
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Yes sir. Then head to the junk yard.
Lather. Rinse. Repeat. |
#4
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The high mileage 2 bbl motor conversion and down fall.
Install bigger cam and many times with more lift then there’s either enough retainer to guide clearance for or too much lift for the coil bind spec of the factory springs. Install 4 bbl man and carb, IE , call upon the worn rings to seat up the added cylinder pressure . Leave in the 40 psi pimp with its 5/8” pickup tube. Along with not enough oil pressure leave in the factory Moraine 200 series bearings where as the factory 4 bbl motors had the far better 400 series bearings. Now let’s float the valves at only 4500 and introduce the valves to the pistons , This I am guilty of 45 years or so ago. It’s a win win for the junk yard !
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! Last edited by steve25; 02-13-2024 at 09:46 AM. |
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#5
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But the engine in question wasnt a 2bbl, it was a HO (insert year, cid & code here) that had good oil psi etc etc. The main thing with that example was that the engine was never really driven after that or abused at high rpms, it started knocking in the driveway after the heads were rebuilt. Compression wasnt raised to cause detonation, if anything they might have had a .003 clean up that wont change the comp anywhere near enough to do damage. Highly unlikely the rebuilt heads caused the bottom end to fail on that engine.
I do agree the bottom end was fubar'd & on its last leg to begin with, and that 2 gallons of ATF, 2 different times probably didnt help the situation, but the rebuilt heads didnt "cause" the bottom failure. |
#6
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Then tears it down for a head rebuild and claims it killed the short block because a knock suddenly appeared? Yeah ok lol |
#7
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#8
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Oh yeah, the discourse on it was quite comical.
Not “sure” if Lou had an opinion on USING transmission fluid, purchased at Walmart on sale the prior week when it was raining, or he stayed on the periphery taking pictures of the sunset. Man I’m gonna miss those posts. LOL
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costs too much |
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#9
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Yep and was adamant that it was ok. According to him he's done that a couple times even after a bunch of us told him that was not a great idea
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#10
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Oh boy, live and learn I guess
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#11
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Triple Black 1971 GTO Last edited by NeighborsComplaint; 02-14-2024 at 06:04 PM. |
#12
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I put that Facebook marketplace add up, only because Mike thinks his motor is worth allot of money, just kind of showing him, kind of what they go for. The one thats for sale is about 1/2 hour from me.
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#13
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Subarus are famous for using oil. Everyone I know with one says that.
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#14
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I'm specifically talking about cleaning gasket surfaces with "surface conditioning discs" which--where I worked--were called "cookies". Basically a scotch-brite pad on a mandrel, spun by a die-grinder. GM service manuals have warned against using surface conditioning discs for decades. Man, they leave a beautiful, polished surface where the gasket and sealer used to be. 'Course, they also abrade the metal in the process--aluminum worse than iron, but even iron isn't immune. Load those parts into a surface-grinder, and you'll have visual evidence of the valleys they abrade into the gasket surfaces. The invisible damage is all the microscopic silicon dioxide particles that enter the internal (oil-wetted) surfaces of the block and heads. Worse still--all those microscopic particles entering your lungs, and entering the shop stall next to whoever is using the "cookie", so that all the work in the shop gets contaminated to greater or lesser degrees. Approximately the same can be said for hardened carbon deposits dislodged but not fully cleaned-up. All that "charcoal" dropped or washed into the oil pan, then run through the bearings and hydraulic lifters. Yet another facet is a failing engine makes half or less of it's supposed horsepower rating. The worn-out, clogged, restricted radiator can handle the heat inherent in occasional half-power. Engine gets repaired, now makes full power. Operator is so happy, he spends more time whacking the throttle open and feeling the newfound surge. Faulty radiator can't deal with the additional heat. Subarus should ship from the factory with a spare head gasket set in the trunk. Last edited by Schurkey; 02-14-2024 at 09:52 PM. |
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#15
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Don’t you guys know the bottom end failed because the truck was at Mount Everest elevation!!! Sheez !
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LIFT HEAVY, LIFE IS TOO SHORT TO BE SMALL! |
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#16
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I am still trying to find out how you get a "following" when you have done nothing in the Pontiac world besides endlessly babble and screw up PMD engines.
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#17
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I've had a number of Subarus. I've had the head gaskets done on 3, as new as a 2016. On EVERY one, they used oil after a top end rebuild.
The 2016 had 76k miles, popped HG due to oil leak on the top of pass cylinder head. At 83k miles, it was using 2 quarts of oil between oil changes after the HG replacement. |
#18
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Overheating a Subaru couldn't possibly
have a detrimental effect on ring seal. |
#19
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Here’s one for sale on Facebook marketplace $6500 .00 forged pistons .030
Over with forged H beam rods. Same code numbers as Mike’s 428. https://www.facebook.com/share/WKPuX...ibextid=79PoIi
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Last edited by Gach; 02-14-2024 at 04:36 PM. |
#20
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A shot of the block and for sale add, including crank
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