Top End or Total Rebuild
 

I'm kind of torn in the middle on whether to do a top end only on my 1987 3.2 or do a total rebuild. The engine has about 110,000 miles and smokes a little during idle. What do you folks think?

What kind of oil pressure do you have cold (and hot), and at what RPMs?

By the time you tear down the top end (which in my opinion is the most difficult to set up and assemble) you're 70% the way there.

Also rod bolt failures are common place. You should go in there and upgrade. Better do it then and be safe.

True, the cost of going all the way isn't all that much more than the top end alone, but you can always pull the rods off and inspect the journals and have the bolts replaced on the rods still without pulling the bottom end apart.

I have pretty decent oil pressure throughout the entire RPM range. I am also pretty sure that my guides are worn (thus the top end rebiuld). What I don't know is the condition of the P&C's and rings on this motor.

In fact I will have an expert listen / feel / ride my 1989 3.2 with 145.000 mls on it tomorrow.
Oilconsumption and occasional smoke indicate that valve guides and piston rings are worn; so I am going through the same thinking process.

General opinion of my specialist is to do a top-end, and also inspect the rods and rod bearings; as they are subject to asymetrical loads causing the bearings to wear out-of-round / ablong. If required he machines them back to spec and replaces the rod bearings for new ones. These are must-do's when you pull the engine.

The crankshaft and main bearings are heavily overdimensioned for the 3.2 application and are said to last much much longer than the top-end parts. Unless you have problems/damage/leaks down there, my specialist will keep the case closed when the first top-end is due.
My concern is that opening a solid and non-leaking case, may have the risk of creating problems (like leaks) upon re-assembly.

I'm not the most experienced or knowledgable person on this board by a long shot, but I have been in this position before so here is my experience.

I decided to go all the way down to splitting the case because I wanted to KNOW that I was setting up my engine to last a long time. I am glad I did split the case. As it turned out that the large gear on the intermediate shaft had taken a beating from a jumped chain, I'm guessing it was a jumped chain, but regardless of how it happened the large gear had the edges of some of the teeth knocked off. And also the bearings for the intermediate shaft were showing some wear. The main bearings all looked good though. So in my case it paid off to tear it all the way down. Maybe you could take it as far down as removing the pistons and then use a light and small mirror to look around inside the case to check for any metal flakes, ect. ON the carrera engines we did not have the removable sump plate so if there are metal specs in the bottom of the case that don't come out with an oil change you'll never see them. Just if you do only do a top end be very careful to keep everything out of the case, from dust to washers! I can't tell you which route you should go but there is my experience. Good Luck

Cheers
Rich

I am glad I broke my case open rather than just a top end, I found the intermediate shaft bearings were about shot, it also made changing the rod bolts much smoother..my 86 had about 110k also.. oh the guides were also very shot, much more than I expected..

What was the condition of your P&C's?

I never had the p&c's checked because I was going up to 98mm anyhow, but there were several rings broken so I would guess the pistons were not that good, I still have the pistons, I went with j&e's to replace them and had the cylinders bored..

These examples following my previous posting, examples with no extremely high mileages (110k is not much) would make the decision easÿ: pull it......my goodness....

60K and my intermediate shaft bearings were showing wear - no brainer, full rebuild - rod bolts - make it count.

Drive the car while you save up for a complete overhaul.

It should be good for a few more miles and when it comes apart you will want to do it right.

New Ps & Cs and rod bearing are a must.
Although it is possible to replace the rod bearing without splitting the case, we never will.

Don't forget to replace the studs with a quality replacement.

Has anyone ever seen intermediate shaft bearings one of these motors that wasn't showing copper? They seem to wear much faster than anything else in the motor.
-Chris

I have seen cooper showing in race motors with no other sign of wear after 12 hrs.
I have always attributed this wear to the harmonics in the chains and the extream pressures created by the helical cut timing gears.

At the higher RPMs race engines operate at I assume the harmonics a exacerbated.

I wonder if straight cut gears might eliviate this problem?
JB Racing offers straight cut gears, I wonder if he has insight as to the bearing wear issue ?

Check out some of these cool parts!!

http://jbracing.com/eng_porsche.php

I did the rebuild myself with the help of John (Camgrinder) who did my cams, performance springs and rockers, Henry did the heads and purchased P&C's to go to 3.4. A local race builder to redo the rods and polish the crank. A Steve Wong custom chip (yet to be dyno'd and tuned). The bill with a new clutch, the clutch update, ARP rod bolts and all the above was around $6700 to $7000 to do. Here are a couple of pictures and yes the intermediate shaft bearings were showing copper with 88,000 miles. For the difference between a partial and full rebuild, I would drive it until you can do a full reuild. JMHO
http://forums.pelicanparts.com/uploa...1158371450.jpg
http://forums.pelicanparts.com/uploa...1158371503.jpg
http://forums.pelicanparts.com/uploa...1158371716.jpg

Your engine looks great Michael! Good job.

One thing that hasn't been mentioned is headstuds. It would be a good idea to replace the bottom row with steel studs. Stock or ARP or Supertec, etc. Anything but Dilivar. To do this without splitting the case might be kind of hard. You'd need to be careful to not let anything get into the case while doing the work.

My opinion is you'll be able to keep your old pistons and cylinders. In fact your rings are probably still within spec but of course you should measure them.

-Andy

VERY VERY NICE!

If you do your own work:

Take heads off, send out for machining, put them back - done. You will have 50k miles + left.

If you plan on keeping the car for only a few years:
See above

If you pay for the work and if you will keep the car for a long time:
Compete rebuild. Labor is expensive and you do not want to pay for it twice.

That's my two cents. Unless I had evidence (low compression, pressure in crank case) that my rings were bad, I'd leave it all alone. I am a DIYer and of course would not mind going in again after only a few years.

George