Bottom End Re-build Question 72 2.4T

I have around 130K on my 1972 911T. The top end of the engine was re-build at 100k. The top end included new pistons/cylinders and valves, etc.

What can I expect the lifespan for the bottom end of the engine?

Thoughts?

Sounds to me like you had the bottom end rebuilt also if you had new p@c's installed. On another note, my 72t broke a chain ramp and bent 3 valves at 136,000. Old chain ramps can get very brittle, can break and end up getting wedged between the cam cover and intermediate shaft. Thus, bending valves like in my case.

I definitely have receipts for pistons and cylinders but don't see any bearings. Thoughts?

Tensioners were replaced as well. Thoughts?

In my case, I got a new intermediate shaft with gears. In order to do this you have to split the case. If the case is split, a person usually changes the bearings and all other little goodies involved. I bought my bearings seperate. Some bottom end (kits) come with all gaskets and bearings. Is there anything stated in your receipt about this. A full rebuild done by a shop can run up to $8,000 for the engine you have. A somewhat good indication would be how much you spent. Call the shop and ask exactley what they did if they remember.

About 200K for the bottom end is reasonable if the oil was changed religiously. The top end on these usually go about 120K.

The 911 engine is different in regard to top/bottom end references. You can do the P/Cs without removing the connecting rods or splitting the case so it can be included in a top-end O-haul. On a 911, when people refer to a bottom end overhaul, it usually means the things that require splitting the case.

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Tyson Schmidt
72 911 Cabriolet

Hello

Well 100 000 mls is average for an top end rebuild. P&C are then mostly worn and out of spec some remount them some remount others some stock ones.

Bottom end will last much longer depending on driving conditions and how much fuel is in the oil.

Especially the last cases ( 7R ) have no problems for long durations. 2,7 is an other story.

Well i also did rebuilds and reused the old main berings as they had been good and those magnesiumcases are not normal engines. They get oval after the time. If you don´t bore them back round new bearings will not work smoth and wear out very fast. So you win nothing but have to redo it again.

This is something i have to discus with the costumer. It is there money and there choice.

Grüsse

I don't see any evidence that the case was split when they re-built the motor.

Are there any warning signs before the bottom end fails?

Is there anything that might clue me in on how much life is left? Noise, drips, etc?

There are 130K on the car. Top end was re-done at 100K.

Do people tend to agree that 200k is about right for the lifespan of a 72 2.4T bottom end?

Thanks.