Engine Rebuild or Engine Swap?

amirpc · 02-09-2009, 09:15 PM

I've got an 86 951 with a spun bearing.

I've been leaning towards doing a rebuild (I'd be doing all of the work myself), because I think in the end it'll give me a better motor - and I really want the car to be in good shape for a while. I figure the cost on this to be $1500+ depending on how bad things are on the bottom end.

However, there is the possibility I can get an 80k motor in good shape. I'd probably have to do minimal work to get it back in shape. I figure the cost on this to be $1500-$2k for the motor (maybe more, dunno) - plus probably another $500+ in random costs to get it installed.

I'm not concerned with the amount of work involved I enjoy this sort of thing, especially since I learn so much. I'm not SUPER concerned with cost either, assuming they are within about $1k of each other. I'm more concerned about getting a "final solution" and having a low chance of failure.

Can I get some opinions here?

bjd34 · 02-10-2009, 03:06 AM

If it were me i would rebuild your motor that way you know how many miles you have on it. I have bought 2 motors and both companys i bought from clearly lied about the mileage.

TJFORGUE · 02-10-2009, 03:30 AM

Rebuilding my 968 engine was one of the best experiences of my life (I am 62)and you know exactly what you have when your done!!

2Tight · 02-10-2009, 03:46 AM

I did a little of both. My 86 spun a #2 RB also. I had a spare take out motor with 91K. After disassembling the spare 91K motor I found old valve scars on the pistons and nominal ridging at the the top of the bores. I decided to see if the blown motor was a better candidate for rebuild. It not only had a spun #2 rb, the rod bent, the crank was toast, and the #3 bore got torn up in the process. Needless to say it was back to the other motor. I'm about 1/2 through with the rebuild and the experience has been great. This was my first Porsche engine and there are so many techniques, procedures, and tricks I've learned during the work. I'm 60 so this has been a good project...except the going back and forth from under the car.

Go for it but have a back up motor in mind if yours has suffered terminal damage.

924RACR · 02-10-2009, 04:19 AM

With a spun bearing, you'll be needing a bit more than just a refresh of the motor. You may be better off rebuilding a replacement. That said, I'd rather rebuild than just swap in... at least that way you know what you're starting with! Though with a good core, you can just pop in fresh bearings, rings, etc, do a valve job, and be in good shape... may be cheaper than having to get all that machine work done on your block. I know when I've spun bearings, it's trashed cranks... but YMMV, that was on the track at high revs.

amirpc · 02-10-2009, 05:21 AM

So right now what I'm leaning towards is taking the thing out and having this shop I know near by do the bottom end. That way I won't mess anything up, and I don't really have all the tools to make sure everything is perfect down there.

I can then take the rebuilt bottom end and finish up the job myself, which is pretty easy from there. What do you guys think about that?

amirpc · 02-10-2009, 07:02 AM

Holy hell, The Porsche Workshop in Austin wants $6k to do a rebuild on the motor. I'm definitely doing it myself.

I figure I can send the block off to Lindsey to get the cylinders done, its not too expensive. I think I can handle most of the rest locally as far as machining goes.

The only problem I see now is that I'm not exactly sure what all I'll need to do. I've been reading as much as I can trying to get a handle on what exact needs to be checked and replaced before I dive right in. Does anyone have any good resources for this?

krystar · 02-10-2009, 07:04 AM

get yourself a copy of the workshop manual. everything u need is pretty much in there.

i'd say take the engine out and assess the damages first. then u can make a better decision whether or not to rebuild.

amirpc · 02-10-2009, 10:42 AM

This is my list of things I'll probably need:

Rod Bearing set
Connecting rod nuts (8)
Main Bearing set
Balance Shaft Bearings (4)
Timing Belt and rollers
Balance Shaft belt and rollers
Lower Crankcase gasket set
Cylinder head gasket set
Oil pump drive sleeve
Camshaft and balance shaft drive sleeves
Loctite 574
Piston Rings
Replace any cam followers that need it
Oil Cooler Gasket Kit
Motor Mounts
Waterpump
Assembly Lube
Spark Plugs
Cap if needed
Rotor if needed
Plug wires if needed
Break in oil

Can anyone see anything else?

krystar · 02-10-2009, 10:55 AM

that's..prob alot more than needed...but none of those would hurt

u gotta take the bearings off and use plastigage to measure clearance. then u'll know if u have to get oversize bearings or not.

are u doing top end rebuild too? if so, might as well do top end gaskets and seals if yer doing cam followers.

amirpc · 02-10-2009, 10:56 AM

Quote:

Originally Posted by krystar

that's..prob alot more than needed...but none of those would hurt

u gotta take the bearings off and use plastigage to measure clearance. then u'll know if u have to get oversize bearings or not.

are u doing top end rebuild too? if so, might as well do top end gaskets and seals if yer doing cam followers.

Yeah I'm doing top end but I already have a gasket kit for the top end...although I might need to do some lifters while I'm in there I think a few are squishy.

krystar · 02-10-2009, 11:01 AM

valve stem seals might be in order too...