Ok so, my car had been having low oil pressure readings. But had been unable to tell if it was the guage or if the car was really having low oil pressure. Been having a lot of oil leak issues with it and decided to take it to a local performance shop to get it checked.

After letting it run (after hot), we noticed that it would idle low and buckle and eventually turn off... shop guy said it was low oil pressure and that the crank bearings are probably spun.

Motor was pulled and taken to the machine shop. Confirmed crank bearings are burned out and the cam bearings are shot too!

This motor was rebuilt by the previous owner with .40 over pistons and new oil pump. Machine work was done by the same machine shop where I have the block at now but the previous owner and a friend assembled it after the machine work. All done less than 1000 miles ago.

I guess my biggest question is, what could cause the bearings to give out soooo soon, and what can i do to make sure it doesnt happen again?
Can balancing the rotating assembly make a difference?

Sorry for the long story guys, I'm in need of help here. Thanks

 

yes, balancing can make a diff. But 1000 miles.....sounds like the machining wasnt check when the assembled it. Thats my best guess.

 

It could have been put together incorrectly, if the oil pump is high volume high pressure it could have been sucking the pan dry.

 

the shop machined it... but they took everything and assembled it in their garage. and the oil pump is melling high volume...

you think the oil pump would pump that much to do that? im not sure how that could happen

 

Name of the machine shop?? that did the work? I woudn't take it back to where they messed it up the first time..

 

I would say when the previous owner assembled it they did about everything wrong, cam bearings toast in 1000miles sounds pretty bad.

For the pressure to be that low with a HV pump sounds pretty bad, then again the fact the previous owner put a HV pump in it is a bad sign in and of itself.

I must say it a couple times a week, CHEAP "rebuilds" are a step backwards from stock and I think you are the second person this week here to find out the hard way just how cheap and badly a previous owner "rebuilt" stuff.

HV pumps can cavitate too that is not any good for bearings.


IMO find another stock shortblock and either run it as is or spend good money going it right, don't repeat the mistakes already made to the car.

 

^^^^ eeeehhhhhpp!

 

If this guy built this engine at home u have no idea if he checked all the clearences or how he put it together torque values...how clean his area was is VERY important putting a motor together. Berring clearences and a HV pump would be my guess.

 

High volume oil pump is a bad thing? what's cavitate?

The machine shop is charging me $900 to completely inspect the block and check the bore, balance rotating assembly, new piston rings, crank and cam bearings, polish and cut crank and polish cam. That's assembled short block to spec. That's $900 for parts and labor. Sound about right?

 

HV pump = fail without large enough sump,if there is not enough oil the pump will lose prime and begin to cavitate sending low/no oil to bearings at times.The bearing clearance needs to be set up properly as well when using a HV pump. What does the cam look like? How are they going to polish it? I would bet there was a problem with the cam bearings,dont ask me how I know.Been there ,done that.If you are in need of help,listen to this advice,find another machine shop,make sure to use a stock pump,and get it balanced.

 

I don't think the machine shop knew what oil pump/other parts the previous owner was gonna use.

So if you use a high volume pump u need a bigger oil pan for more oil?

The machine shop already did most of the work to the block. I'm not sure how they will be polishing the cam/crank. I will ask. The cam looks fine, just has some usual wear on it. The performance shop that's putting my car back together recommended I have the machine shop polish the cam incase it was off from the burnt out bearings

 

I just took my block yesterday to line bore /bore/turn crank/re size rods and check the block for cranks he est. Me 165 to bore 175 to line bore turn the crank 114 and re-size rods 12.50 a piece yes a little high for around my area But they back there stuff up and warranty it so maybe go that route and have them put the whole bottom end together to check clearance and def have it balnced if your planning on turning high rpms

 

Theres your problem, high volume pump with a stock pan will not work. Use the melling select high pressure standard volume pump with a new LT1 pick up on the stock pan and be done with it. You CAN NOT run a high volume pump with a stock oil pan. You need at least 8 quart pan to run a high volume pump.

http://www.jegs.com/i/Melling/689/10...oductId=751586

This pump will run a little higher pressure than stock.

 

actually, you want a high volume, standard pressure... or just an over all standard pump, unless your motor has the correct tolerances for the higher pressure it is just putting extra stress on everything and is unnecessary.


I beg to differ but a HV pump can be used with the stock pan.

 

All this talk of the evils of high volume oil pumps has me concerned...my new 383 has one and will soon be done. Mine's got a 7 qt Moroso pan however...is that sufficient?

Melling M155HV Oil Pump w/ Milodon Pump Bracket, hardened drive shaft, ARP Pump Stud
Moroso 7qt Kicked out Zinc Finish Pan with Matching bolt-on pick-up

 

So which one is it yes u do was a hv or no u don't with stock oil pan? I'm in the same boat I'm doing a rebuild and thought about getting a hv one ???

 

High volume pumps are usually unnecessary for most builds. They increase the strain on the oil pump drive gear and have the capacity to suck the stock pan dry.

It should be the choice of your engine builder on whether you should use one or not. Unless you have unusually loose bearing clearances a standard volume/high pressure pump is all you need. If that's the case I'd recommend the Melling SELECT series of pumps (10554), NOT the M155 series which have a weaker casing.

 

you can run a HV with the stock pan, just keep in mind you probably dont want to spin it to 6000 rpm for very long as it will eventually suck the pan dry at high rpm. to aid in the drain back there are little tricks that you can do to the block like enlarging the drain holes in the lifter valley.

 

The only reason to run a HV pump is if you run looser bearing tolerances than stock. If the clearances are w/in the stock tolerances then run a a standard volume, high pressure setup. Flow is far more important than pressure.

 

That is a good price.