Replace those items? Opinions varie, please help.

[farleyd]

Ok, me again. Ive had different source from at least two rebuilding books about those item:

- nose bearing (#8) is it that part?


- valve springs
- rods small-end bearings

One says to replace, the other not. What i am trying to do is NOT ruin my rebuild, but be the smartest possible vs the cheapest possible.

Id say that money is a matter for me, good thing its not for some others.

Can i go with IF:
- replace the #8 bearing seal
- check the springs specs
- check the small-end diameter

Thanks to all.

2.7
RS Mahle p/cīs
Webers
E-cams
Headers

[TimT]

Replace it.... It costs about $80, will you take a chance on your rebuild for that little dinero? You will be replacing all the other bearings during your rebuild. What makes this one any different?

[Wayne 962]

Spec it out and measure it according to the Porsche specs. If it's still in spec, then reuse it, if not, then replace it. The specs are located on page 204 of the new Engine Rebuilding Book...

-Wayne

[TimT]

hmmmmmmm I sometimes wonders about Waynes advice.
If in doubt replace it. The cost of that bearing compared to the total cost of a DYI rebuild is small.

When you rebuild a 911 engine you replace all the bearings except this one, yet it has seen the same amount of use as the others..

what does this part cost from Pelican?

[farleyd]

I am the one who started that topic. And this topic is about the ŦBetter to be safe than sorryŧ approach. In an ideal world, where everything would be free, we?d replace everything. In fact, we?d buy a new engine! My approach is: what is OK is OK. No matter the cost, $1 or $1000.

I had no hesitation plundging 1K into new Mahle RS p/cīs and i am glad that i did. They look great and make me feel safe. Does that make buying a $80 part mandatory???? Something to think about.

Rebuilding my engine reminds me when i builded my house. I am not a carpenter, i am a graphic designer. But ive read a lot, asked a lot of questions and in the end build it myself and saved $100K. And it wasnt that hard!

You want to know what was that hard? Having so much opposite opinions! The same applies to the rebuild of an engine. I am reading alot, i am asking a lot of questions, then decide.

Now, if someone could point me toward the DEFINITE source, id be a happy guy.

I am not taking risks, i am evaluating them
- Socrate

[TimT]

I wonder why this is so hard to digest? The engine has 8 bearings. Why on earth will you replace 7 of them during a rebuild. Replace all 8

[jgparker]

The # 8 main bearing is not adjacent to a rod so it does not get nearly the load of 1 through 7. I've heard they are often within spec when the others are worn out. I'm with Farleyd on this one, why replace parts that are in spec. This is especially true if you plan to go through your engine every season or two.

[snowman]

You are being penny wise and dollar foolish. The main cost in engine rebuilds is LABOR, in your case this is "FREE". Parts that are not likely to be replaced, but sometimes must, are the case, rods, crankshaft, heads, cams. All bearings, nuts and bolts, especially rod bolts and nuts, as well as crank shaft bolts MUST be replaced. There is no way to justify not doing so, even with free labor. TO have an engine failure for anything that costs as little as $80 is just plain stupid. To have an engine problen, not fatal, just aproblem is ABSURD after having put in the $ and labor for the rest of it.

The answer is clear, save your pennies, wait another few days, weeks or whatever and do it right. Its kind of like reusing gaskets, it ain't fatal, but its a real waste of a rebuild if you have to put up with leaks from day one.

[Wayne 962]

The number eight bearing is not really a load carrying bearing, and as a result doesn't experience the same amount of wear as the main bearings. In fact, calling it a 'bearing' is somewhat misleading. Just about everyone who knows anything about these motors agrees that the number eight bearing can be reused almost all of the time. I specifically asked Bruce Anderson and Jerry Woods this question at the rebuilding class two month ago. I spoke with many, many people when writing this engine book, and this was one area where everyone agreed.

I don't get it - people complain to me when I tell them to buy the correct engine stand to hold the case. This is a no brainer to me. Yet, here is an instance where a part can be reused, and people are still complaining!

The number eight bearing is $60. You can replace it if you want to. Theoretically, you can reuse the main bearings too, if they are in spec. However, since they take a majority of the load, you really wouldn't want to do that.

-Wayne

[jcbear]

Farleyd- Your evaluation seems sound - read, ask and then make your own independant decision - there are few absolutes but lots of options. I'm going to go with Wayne's advice. I spent alot for a rebuild, only put 9K miles on the engine before I (unfortunately) let it sit idle for 10 years. The parts are hardly worn but I am doing my rebuild to clean out any gum - blocked oil passages, replace deteriorated seals, etc and do a bunch of update / performance modifications. I am NOT PLANNING TO REPLACE PARTS I DON'T HAVE TO - if they are in spec - hopefully many shouldn't have to be with only 9,000 on them.

I think there are a good number of rebuilds that are being done to resurrect stored, previously unused Porsches as well as those rebuilding high milage, broken or worn out engines. Each engine, each situation has different factors to evaluate. I would agree with you that if money was not a factor -then heck just buy a 2003 boxster instead of putting it in a 914 - but for me money is a factor and I'm rather attached to both my money and my 911 ( I had to wait 3 months for the factory to make mine.)

Good luck

[911pcars]

Here's one. If a $2000 set of pistons were in spec in all respects, would you replace them? Would you replace the crankshaft even though it is within specs? Would you replace the connecting rods or crankcase, valves, camshafts ..... etc. , etc. etc.? How about the threaded fasteners? Replace them all?

Is your answer driven by the relatively low cost of the replacement part or by a legitimate need to replace it? It'd be nice to replace everything with a new part. However, there may not be a budget for this approach nor is it really necessary in many cases.

Sherwood Lee
http://members.rennlist.org/911pcars

[farleyd]

I am this topic initiator. I have my answer regarding #8 bearing. Sherwood cannot be more in the right
Quote: Is your answer driven by the relatively low cost of the replacement part or by a legitimate need to replace it?
Now, about the second item i mentionned, valve springs. SHould they be renewed or not if in specs? Some source says that it doesnt have to, that they have yet to see one that has broke due to extreme fatigue AND other source says that you have to, that microscopic cracks could be there, leading to spring failure.

How many of you have reused them with or without success?

Thanks for helping.

[snowman]

Valve springs have a finite lifetime. They are good for a certain number of cycles before they fatigue and eventually break. Sort of like bending a wire back and forth until it breaks. After their expected lifetime they will randomlly start to break, an odd one or two will break either very early, say at 20,000 miles or very late, say 1,000,000 miles, no way to say for certain. For highhly stressed springs like in a 911 engine one would expect to replace the springs at engine rebuild time, ie about 125,000 miles to 160,000 miles. The same springs may work for another 100,000 or not. The problem with NOT is if one does break it also takes the entire engine with it, ie piston, cylinder, or worst case, the crank, and case as well, or if you are very lucky and the thing is just idleing, no more than the spring itself.

Valve springs should always be replaced at major engine rebuilds, otherwise it is a potential time bomb, just waiting to go off.

I will make an additional rash statement here, I know many rebuilders, especially home ones, do not replace the valve springs. Thats probably one big reason why we see engine failures at the autocross and other track events. Not replacing valve springs gives some rebuilders a bad name. \

By the way valve springs only cost about a buck each (for a rebuilder) so there is no reason not to replace them.

[farleyd]

Quote: By the way valve springs only cost about a buck each (for a rebuilder) so there is no reason not to replace them.

Why then am i charged 110US$ for a 12 spring kit??? Mark-up i guess?

[snowman]

Thate right, a whole lot of markup, esp with a porsche. For example
I pay $22 for a full set of rod bearings, $40 for a full set of rings, $5ea for valves.

I know what you pay. Parts feel a lot more important when they are expensive, what can I say we all got to make a living. PS I am retired and not a rebuilder, just an avid hobbist.

[snowman]

Reflecting on the whole situation of cost I have came to the following conclusions:
If you consider cost rather than performance when you rebuild, you are building a chevy, not a porsche.

I am cheeper than cheep, but first I consider performance, and then performance again. If I need a part, because its needed or should be replaced, then I get the very best price I can. This is what real Porsche people do, cause we are all cheepskates. The only ones who pay list price really have to much money and should be releaved of it by paying list. But they are the ones who keep the light lit and the fancy stuff polished. For the ones who consider status with the car they drive, they set the standard that we are all measured to. They are fortunate and I do envy them. But like most Porsche fanatics I do have to account to the wife once in a while.

The whole automotive aftermarket has large markups, always has , and likely always will. If you don't like it start your own parts company, you can you know.

Its really the same for a whole lot of other products. What you are paying for is service, advertizing, profit, handling, warrenty.

The only auto product I personally think is overpriced is oil filters. This product can use some selling competition. The real price on a genuine, replacement oil filter for an early Porsche 911, $1.86 and the guy that sold it to me probably only paid half that. YOU pay $10 to $15 for the same filter. No wonder stations often changed oil and filter for parts only.

[Wayne 962]

Snowman (Jack), you're talking about things that you have no idea about. I have a dual monitor setup here on my computer. On the left side I am typing this message. On the right side, I have the costs of all my parts directly from my suppliers for rebuilding the engines. I can tell you my costs on a set of valve springs is *not* a buck. That's complete BS, and if you can get me springs at that price, then I will take 1,000 of them today. Placing such false information on this BBS gives out the false impression that we are gouging our customers (which we are not).

As for having large markups, you're completely full of BS! This industry has some of the lowest markups around! I work on websites for a clothing company, and their typical markup is about 400%. At Pelican, our markups range from -10% to 50% on some products. Markups over 40% or so are only on certain boutique-type items, not hard parts.

As for oil filters, if you can provide me with qty 2,000 at $1.86, I will write you a check this afternoon.

I hate it when people dispense blatantly false information.

-Wayne

[Wayne 962]

Back to the topic of valve springs...

Valve springs indeed can be checked to make sure that they are within their spec range (this range is shown in Appendix A in the new book).

However, springs suffer from fatigue and age, and there is no clear method of knowing how long they will last until they fail. Some points though:

- Springs can be replaced relatively easily with the engine in the car. All you need is the proper tool (which we have) to remove the spring from the valve with the cam tower attached

- Springs can be tested to assure that they are still within their spring-back range

- A broken spring may or may not cause severe engine damage. I believe that on the CIS cars with the domed pistons, a loose valve will have a tendency to become bent. On engines with pistons with flat tops (valve pockets) you can probably have a broken valve spring, and it will do minimal or no damage.

- I do recommend replacing springs because you cannot accurately measure the life remaining in them. Manufacturing conditions always have some degree of variance. One spring may be weaker than another, and ready to break, even thought it tests fine on the tester. The same can be said about new springs, although they almost never break (I haven't heard of a new one breaking).

It's one of those things. I recommend replacing them. If you're *super* cheap, then don't replace them. I think that there are lots of mediocre engine rebuilders out there that don't replace the chains or springs...

-Wayne

[farleyd]

Ok, i am *super cheap* but will replace them anyway. Your arguments are clear and convincing and my rebuilder said the same thing. So to resume, i asked three questions:
1) #8 bearing > i am keeping
2) valve springs > i am replacing

That leaves us with the small-end rod bearings. Apart some micrometering them, how can i tell if they are OK. I mean, how HARD should the fit of the piston wrist be?

- - -

About the mark-up Wayne is right. Clothing mark-up is up to 400%!!! How the hell do you think they can discount their stuff 80%? That one-buck-a-spring surprised me.

- - -

We are progressing, that the ONLY sure thing. Thanks for your patience.

[Wayne 962]

Hold on a sec - replace your number eight bearing if it is not in spec. This means that YOU HAVE TO MEASURE IT FIRST! Only then can you be assured that it can be reused. Most are all in spec, unless the oil was dirty, or there was some other catastrophic problem.

It's standard procedure to replace the rod-end bushings. They wear asymetrically, so they are probably oblong. You really need a dial bore gauge to measure it (also needed for the number eight bearing), and a dial bore gauge can be an expensive tool (not found in most households!). Have your machine shop measure them for you...

-Wayne