Getting ready to drop $20,000 on engine overhaul

93097004xx · 05:50 AM

I live in Indy wondering what advise you guys all might have for me. My mechanic of 22 years tells me that there are a lot of problems with replacement bottom end bearings not being in spec NEW. Also there are a lot of inferior parts out there. He said he can completely overhaul for $15,000 but I'm budgeting $20,000.

Any comments or advise greatly appreciated.

By the way my car is a 79 RoW with 51,000 miles believed to be pretty darn accurate as this mechanic has maintained this 930 since the late 80s.

Edit got home a realized this car only has 51,000 miles lol.

OldSpool87 · 03-13-2017, 11:03 AM

The bottom end is in question after only 54k? Am I reading this wrong. In any event, 54K on the clock seems awfully low for rebuild time. What else is problematic?

T77911S · 03-13-2017, 11:07 AM

agree 54k?

reuses old bearings if good.
coat them?

read this thread, first half or so.

http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/900557-another-930-teardown.html

93097004xx · 03-13-2017, 11:08 AM

Nothing really just a 37 year old car that really has only ever had the headstuds replaced, trans rebuild. I probably have $20,000 plus in receipts but the engine has never been overhauled. Headstuds done and transmission rebuilt clutch ect. But the engine has never been done.

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Jeff NJ · 03-13-2017, 11:14 AM

I'm certainly no expert, but I can tell you that I am not rebuilding the bottom end until I have to. I am figuring on top end in the next couple years and hoping the bottom lasts much longer than that.

Rawknees'Turbo · 11:37 AM

Quote:

Originally Posted by 93097004xx

Nothing really just a 37 year old car that really has only ever had the headstuds replaced, trans rebuild. I probably have $20,000 plus in receipts but the engine has never been overhauled. Headstuds done and transmission rebuilt clutch ect. But the engine has never been done.

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So you want to have the engine re-built just for the heck of it?

None of the components typically age out except for rubber seals - if not pouring oil out, they aren't a problem.

Only high wear bearing in the bottom end is the intermediate shaft bearing, and that will be good for quite a bit over 54K miles if the engine has not been run super low on oil.

The valve guides are a high wear item with these engine, but again, talking much higher mileage than 54K.

kevin930t · 03-13-2017, 11:30 AM

I totally agree with you,i would chance inferior parts over org parts and even more so hoping the bearing were manufactured in CHINA just so i could rest easy knowing i would have to rebuild her again.

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willtel · 03-13-2017, 12:23 PM

Some bearing info:

http://forums.pelicanparts.com/911-engine-rebuilding-forum/856995-glyco-vs-clevite-rod-bearings-data.html

icemann427 · 03-13-2017, 12:53 PM

I agree with the consensus. No need for a bottom end. If you are burning a little oil and if you do a compression test/leak down showing some leakage or lower compression, you can refresh the top end, the rings, and rod bearings without separating the crankcase. While its out, replace the clutch and all its parts...

RDG · 03-13-2017, 01:00 PM

Wow, That price seems really low for a complete rebuild. I just had a top end rebuild done and i wanted to cap it at 20k, well couple performance parts later and using a top notch shop ended up at about 33.5 k when all was done. Moral of the story allways double what you think you want to spend and you will be much closer to actual cost.

93097004xx · 03-13-2017, 01:05 PM

Quote:

Originally Posted by RDG

Wow, That price seems really low for a complete rebuild. I just had a top end rebuild done and i wanted to cap it at 20k, well couple performance parts later and using a top notch shop ended up at about 33.5 k when all was done. Moral of the story allways double what you think you want to spend and you will be much closer to actual cost.

That scares me. But the mechanic I use does his work from his home. He is porsche factory trained. One of the reasons I've stuck with him for 22 years +.

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boosted79 · 03-13-2017, 01:06 PM

If it's really 54 and not 154 why do you want to touch the bottom end? If the seam is not leaking why go looking for trouble? How much oil pressure does it have when warm at idle?

93097004xx · 03-13-2017, 01:10 PM

I'm doing a complete overhaul because a top end is $8,000 or more why not spend $15,000 and get the whole engine done?

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bpu699 · 03-13-2017, 01:15 PM

To the op...what kind of oil pressure do you have? That may guide you...

Having owned several 911s, I have yet to see one with more than 4 bar warm... Though I keep hearing about the mythical 5 bar warm...

93097004xx · 04:38 AM

It's bar 4.5 at cold idle settles to bar 2 if the engine is extremely warm on a 90 degree day I can see bar 1.5

I'm using Castrol 20w50

I change the oil every 100 miles.. yes I've put 1700 miles in 20 years!! Lol

JFairman · 03-13-2017, 01:24 PM

Quote:

Originally Posted by 93097004xx

I'm doing a complete overhaul because a top end is $8,000 or more why not spend $15,000 and get the whole engine done?

Because it's very likely it does not need it and the new parts these days are not as good as the original parts. Even an old generic American made lazy V8 can easily go 100,000 to 150,000 miles without being rebuilt.
Engines (Like Porsche, BMW, and Mercedes) with a crankshaft main bearing on each side of a connecting rod throw are so strong and stable the bottom end will last almost forever as long as relatively clean motor oil is in them.

93097004xx · 03-13-2017, 01:38 PM

Quote:

Originally Posted by JFairman

Because it's very likely it does not need it and the new parts these days are not as good as the original parts. Even an old generic American made lazy V8 can easily go 100,000 to 150,000 miles without being rebuilt.
Engines (Like Porsche, BMW, and Mercedes) with a crankshaft main bearing on each side of a connecting rod throw are so strong and stable the bottom end will last almost forever as long as relatively clean motor oil is in them.

Even under hard boost? I thought turbos had higher stress the NA 911s. I know SCs can last forever but they are not blown.

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Rawknees'Turbo · 02:05 PM

Quote:

Originally Posted by 93097004xx

Even under hard boost? I thought turbos had higher stress the NA 911s. I know SCs can last forever but they are not blown.

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Boost in these cars has no real effect on the crank and rods (or their bearings) unless you've been getting a lot of detonation, but with detonation, the piston rings and ring lands go long before the crank or rods. The crank assembly is capable of withstanding more than double the horsepower that a stock 930 has (very "overbuilt" for the original application, in other words), and last a very long time with a measly 300hp passing through them.

The 930 put more stress on the top end (pistons, valve guides, etc) than NA 911 engines, but that is primarily due to the increased heat of the boosted engine (not the boost pressure itself).

kevin930t · 03-13-2017, 04:44 PM

I agree 100%,find a good charity if u want to blow 20g..

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RarlyL8 · RarlyL8's Garage

+19
The only reason to rebuild this engine is to say it was rebuilt. If the car is a low mile garage queen it doesn't even need an engine that runs let alone one that is freshly rebuilt. Best thing you could do for this engine is drive the car.