Bottom-end Questions

[gregwils]

I definately need to do a top end this coming winter and am struggling with the question of of doing my bottom end too. I am on a pretty tight budget and am wondering about the machine work required for the bottom.

Assuming that the crank bearings are good and the intermediate are beginning to show copper (nothing really serious), can I just replace both sets of bearings and seal it up with minor machine shop work? My thought was to have the crank measured, possibly polished and have the #8 bearing reconditioned. After that, am I good to go? I could probably swing $1,500 for the bottom end, but more dollars will be painful.

Thanks.

[Flat6pac]

Doing the top end and bottom row of studs, you ll be to the short block, just a couple hrs from holding the crank.
The intermediate bearings will be showing brass and need replacing but if you currently have good oil pressure just reseal it, you ll still have good oil pressure and you will know your crank.
#8 bearing is constantly under oil so there is nothing but changing the seals and re use it
In the bottom, the rod bearings are more delicate than the mains but if you open the rods, you need to replace the bolts
Bruce

[Steve@Rennsport]

Good advice & counsel from Bruce,....

The only thing I'd add is that the rods should be resized when the new bolts are installed. Big ends don't stay perfectly round during operation over time and this should be corrected. You may also need small end bushings, as well.

The other issue is that Porsche rods are not always the exact same length and I've seen variations in the same sets up to .020". Imagine what that does to deck height measurements and a good reason why its important to check this on every piston & cylinder.

JMHO, of course...............

[gregwils]

Originally Posted by Flat6pac

(1) - The intermediate bearings will be showing brass and need replacing but if you currently have good oil pressure just reseal it, you ll still have good oil pressure and you will know your crank.

(2) - #8 bearing is constantly under oil so there is nothing but changing the seals and re use it

(3a) - In the bottom, the rod bearings are more delicate than the mains but if you open the rods, you need to replace the bolts

(3b) - Steve's comment -The only thing I'd add is that the rods should be resized when the new bolts are installed. Big ends don't stay perfectly round during operation over time and this should be corrected. You may also need small end bushings, as well.

Bruce and Steve - Thank you. I run Brad Penn 20/50 and my oil pressure gauge displays very high. A few follow-up questions.

(1) - Are you suggesting not to replace the main bearings, just the intermediates?

(2) - Are #8 seals available separately? I didn't see them in the catalog.

(3a) - My motor is and will be a stock 3.2 (90k miles). If I do the bottom, I will probably use ARP rod bolts. I never thought about not removing the rods, interesting thought however.

(3b) - Steve - Are you suggesting using oversize rod bearings and have the rods machined to correct out of round?

After thinking about it, I can understand why people recommend doing the bottom. It's just a mental struggle when you hear people with 300k on their bottoms.

Thanks.

[Steve@Rennsport]

Greg,

I would not use factory rod bolts: ARP's are FAR better in every way.

The rods don't get oversize bearings unless the crankshaft gets machined; you simply use standard size rod bearings after the big end's have been restored to concentricity.

[304065]

I had my rods done with ARP bolts by a well-known Porsche Guru in Oregon who is known for his excellent work, free advice and occasional stories of clients letting it ALL hang out at the Rose Cup. A pleasure to deal with beginning, middle and end.

[gregwils]

Those rods are works of art. It's safe to assume I could send my rods to the same Oregon expert for a similar result.

Steve - Thanks for the clarification on the maching question.

Is the #8 seal 99970728541? It definately fits in vicinity of the #8 bearing, but not sure it is the seal you are referencing?

[Flat6pac]

#8 SEAL IS 999 113 290 41
Bruce

[boyt911sc]

Originally Posted by Steve@Rennsport

Greg,

I would not use factory rod bolts: ARP's are FAR better in every way.

The rods don't get oversize bearings unless the crankshaft gets machined; you simply use standard size rod bearings after the big end's have been restored to concentricity.

Steve,

I just completed my engine teardown for top and bottom rebuild. And now completing a long list of things to order for the project. One of the items on top of the list is the 'set of connecting rod bolts'. Should I stay away from using the factory rod bolts for my rebuild? What are the problems with these factory conrod bolts? Thanks.

Tony

[Steve@Rennsport]

Tony,

Factory rod bolts run about $210/set. ARP bolts, which are FAR better, run about $260/set.

For me and my customers, this is an easy decision.

[boyt911sc]

Originally Posted by Steve@Rennsport

Tony,

Factory rod bolts run about $210/set. ARP bolts, which are FAR better, run about $260/set.

For me and my customers, this is an easy decision.

Steve,

Since I'm totally new to DIY engine rebuilding projects, I had the impression that ARP products are outrageously very expensive compared to OEM bolts. But in this case, I agree with your recommendation. Thanks a lot for sharing your expertise and experience with us (DIY'ers).

Tony

[gregwils]

I am resurrecting an old thread because I am almost ready to start the project. I did a compression and leak down yesterday for a baseline and got the following results.

#1 170/6%
#2 170/7%
#3 170/6%
#4 150/50% Yikes!
#5 170/6%
#6 170/7%

I am not going to spend the time to diagnose this further, because the car uses a quart of oil every 300-350 so it's time. I could hear air coming out of the exhaust so I assume it is either carbon or a hosed exhaust valve. The car has 90k, mostly street and has great oil pressure. I am replacing the bottom studs with steel, sending the heads out, going to split the case to replace the rod bolts with ARPs and intermediate bearings. I am going to send my rods out to get them done too.

Here are my questions. Should I still replace the rings since compression appears good? If someone says you can check the crank and re-seal, do you do the same amount of cleaning? I assume that I leave the mains intact and just clean the edges of the case to reseal. Is this correct? Also, can I use new rod bearings without machine work to the crank?

That's all I can think of...for now. Thanks.

[Flat6pac]

If I take out the mains to be reused after cleaning, I wipe the bearing shell and label it #x right or left and group them together but separately because you dont need them mixed and running where they dont belong.
Bruce