motor started as an olds 65 400, but has a 455 crank. Car is a 65 442 so its a stick. Motor rebuilt about 2500 miles ago, has .007 thrust from machine shop according to records........lost oil pressure on day out of the blue.....no signs leading up to this besides that daybthe pressure dropping slowly through the drive...... Cut filter found brass, pulled motor back to shop, now thrust is .015 with other bearing showing damage too, but they are blaming the trust. Clutch set is nothing more than a slightly upgraded over stk.....car has been owned for more the 30years by same guy, nothing else in the driveline was changed......he didn't beat on it, it just a cruise car he had 67 with stick also. So he knows how to drive stick. What could be some causes to wipe out the thrust so fast.....??????......the previous motor has in there for more than 20 years....with no issues
With manual transmission, starting the car with clutch pedal depressed can result in greater wear to the thrust bearing, as can extended sitting with clutch pedal depressed such as sitting at a stoplight, train crossing and such. Once the clutch pedal is released, there should be very little pressure of crank journal against the thrust bearing. I was taught to start on neutral with clutch engaged, and to shift to neutral if sitting for more than a few seconds. (but keep the shifter ready to push in first, foot ready). If release bearing adjustment is wrong and no airgap, likely bearing failure or damage to pressure plate fingers would be evident as well as the thrust issue.
No wear on pressure plate csn be seen as extra amount..........and seeing not more more than slightly stronger pressure plate, I cant see that being the issue. Seeing the kast motor lived 20years and it was a ring issue not a bearing issue that prompted a rebuild i can't see it being a driving habit issue???
Im guessing slippage in the oil pump drive gear (brass gear with debris in the filter??) or a sheared gear roll pin , still driving the gear but slipping. Brass showing up will narrow it down. Copper on the other hand is from the bearing shell plating process. Not much brass inside; is there a brass thrust button for the cam thrust? ws
Steel gear, cam doesn't require any form of cam bumper, Machine shop has pull engine down and its for sure the mains....... I just need to figure out how/why the thrust got ate so it doesnt do it again on him?
Whoever does the machining and final work to crank and main saddles needs to be sure to properly address the thrust surfaces and correctly polish the thrust side of the crank and main.
Still dont get the brass in the filter. Does it have brass valve guides? That wont affect the oil pressure. How about a brass end plug (freeze plug) on the cam back end? Yes, the grinder needs to pay special attention to the journal radius. Maybe provide him with the new bearing(s) for correct measurement. A few other issues could be a tweaked rod (were they resized AND checked for straightness?) Was a piston installed facing backwards? Was rod to piston thrust checked? How many cubic inches was derived from the 400/455 crank set up? Just curious... ws
Fowler machine in Columbus built it, they have a good reputation and bud alot of motors much bigger and badder than this..........so I'm goingbto sssume all was done right......i didn't pull it apart they did......i hated not getting peak mysrlf but if they were going to fix it maybe on them they didn't want me in there first.... The brass colored metal is from all the mains bearing eating themself. Stroke went from 3.975 to 4.250 and I think the early block have alot of meat in the walls the went like .100ish over when the built the custom pistons
Hi, Was the crank properly machined for the pilot bearing as most Olds cranks aren't drilled from the factory, maybe the depth was off causing the issue? Also check the crank straightness? May want to post on classic Oldsmobile as lots of special things on oil systems and lessons learned. Many good builders who might have better insight on your issues and root causes. Good luck,
It would be much easier to guess if you had pulled the pan. Obviously there is a chance the trans/clutch pressure ruined the thrust. A constant pressure from the back would damaged the rear facing side of the thrust more.d There is some chance the crank was not machined properly and the thrust surface had some sort of defect that spoiled the bearing quick- a bur, not polished, wrong angle etc.. Also, .015 of lateral movement of the crank wouldn't cause a drastic drop in oil pressure. I think you have more issues.
I realize that your engine is not a Nailhead, but stick Nails were notorious for having a lot of crank endplay after some miles. It never caused an oil pressure problem. I agree with those who say that the problems go deeper then the thrust surface of the bearing.
Ok after giving the shop some time to look things over more. ....even though the trust has almost double the clearance as when it was built.......he doesn't feel there was anything wrong thst cause it beside the wearing of the components...........all rod bearings were wore down through the backers.....and they said the engine and oil had a large amount of fuel mixed in......that the diluted oil cause all the wear issues. Now to find where the fuel came from from.......plugs look very good and car never stunk from fuel when running.....so not a tune up issue....... they vacuum check the fuel pump no issue found.......????? This motor had from new a strange issue that when the rpms would be increased to running rpms, oil drops would be flung up the breather/oil filler tube......to the point the breather cap would leak oil all over the front of the motor......we could tell if the oil was being flung up......or blown up........they made a stepped plate that slid down the tube to basically deflect the drops b4 they could blow out the top........i wonder if there was a major blow by issue that could had caused the fuel issue too
The condition of the cylinder walls would be an indicator of fuel dumping. Also check inside the headers and tailpipes for excessive soot.
