Help needed assessing mystery motor rebuild.

[ibmiked]

I realize that this will be a shot in the dark, but some of the engine guys here might be able to help me sleuth this out.

I have a '68 aluminum case motor in my car from a Euro 911T that was rebuilt about 10 years ago. I have the receipts, but they aren't specific about certain things and I'm convinced the car makes additional power above the 110hp that Porsche published. I realize a dyno or the previous owner would tell me more, but there are sufficient details that I believe an educated guess could be made. Here's what I know;

Stock the car should have cast iron cylinders and 8.5:1 compression and a Marelli dizzy. Here's what the receipts reveal;

Rebuild occurred in 2002 with an indicated 63,074 miles (could have been 163,000 though).
R&L Timing Chain Covers
Carb kits
30mm chokes
125 main jets
55 idle jets
180 air correction jets
F26 emulsion tubes
chain tensioner update (leads me to believe this was therefore the first rebuild)
Rod bolts
Rod nuts
#8 main bearing
Machine work case:
6 resurface cylinder heads: $240
12 rebuild rocker arms: $240
2 repair cam carriers: $104
6 reconditioned rods: $438
1 R&R case oil galley, plugs, chain box modification, install case squirters: $859
911E distributor w/ 7,100 rpm limiter
MSD 5 ignition
MSD Blaster coil
Plus a lot of little assorted stuff like gaskets, nuts & bolts, etc.

Total rebuild cost in 2002: $9,197.37

Any thoughts on what the previous owner or repair shop was trying to accomplish? Simple straightforward rebuild, or were they going for more power somewhere? I don't see cams or valves anywhere, but I'd swear this motor is stronger than stock.

Thanks for any input,
Mike

[Mr9146]

I realize that this will be a shot in the dark, but some of the engine guys here might be able to help me sleuth this out.

I have a '68 aluminum case motor in my car from a Euro 911T that was rebuilt about 10 years ago. I have the receipts, but they aren't specific about certain things and I'm convinced the car makes additional power above the 110hp that Porsche published. I realize a dyno or the previous owner would tell me more, but there are sufficient details that I believe an educated guess could be made. Here's what I know;

Stock the car should have cast iron heads and 8.5:1 compression and a Marelli dizzy. Here's what the receipts reveal;

Rebuild occurred in 2002 with an indicated 63,074 miles (could have been 163,000 though).
R&L Timing Chain Covers
Carb kits
30mm chokes
125 main jets
55 idle jets
180 air correction jets
F26 emulsion tubes
chain tensioner update (leads me to believe this was therefore the first rebuild)
Rod bolts
Rod nuts
#8 main bearing
Machine work case:
6 resurface cylinder heads: $240
12 rebuild rocker arms: $240
2 repair cam carriers: $104
6 reconditioned rods: $438
1 R&R case oil galley, plugs, chain box modification, install case squirters: $859
911E distributor w/ 7,100 rpm limiter
MSD 5 ignition
MSD Blaster coil
Plus a lot of little assorted stuff like gaskets, nuts & bolts, etc.

Total rebuild cost in 2002: $9,197.37

Any thoughts on what the previous owner or repair shop was trying to accomplish? Simple straightforward rebuild, or were they going for more power somewhere? I don't see cams or valves anywhere, but I'd swear this motor is stronger than stock.

Thanks for any input,
Mike

Sounds like a pretty straight-forward rebuild ... nothing fancy. You can always check cam timing at the next service interval to see what cams are in there which might help a bit, and the heads may have been cut for compression or a shim left out to squeeze the motor and bump compression a bit. But those jets and venturis seem small for an HP motor.

Keep in mind that just doing a rebuild and sealing the cylinders/heads up tight will help with power.

[304065]

Happy New Year Mike!

Look at those carb specs
30mm/ 125 mains/ 55 idles/ 180 air correctors/ F26 e-tubes

Clearly that is not T spec. That is L spec, or 67 Normal spec, for 130 HP. So I agree with Marco, someone was trying for a mild improvement, not a screamer.

No main bearing set? Why replace the #8 and not the mains? I also don't see rings. Why are the cam boxes being fixed? What the hell breaks a cam box anyway? A chain tensioner failure maybe? Why drill the holes in the cam spraybar, that mod was done by the factory in 1967. I assume you have aluminum cam boxes to match the aluminum case.

Normally one wouldn't tear down a 63,000 mile motor-- especially one that doesn't show evidence of valve guides being replaced. (I can easily see an early 2,0 liter smoking and needing guides at that mileage and after many years). But if you had a tensioner failure, wouldn't you see new rockers, not rebuilt rockers, being installed? Why rebuild the rockers after 63,000 miles? Maybe the tensioners failed and snapped a few rockers and the PO bought replacement rockers and had THEM rebuilt and put them in. If you pull a rocker and look that is easy to find-- it won't be forged (those went out in 67) but by 68 they were not using the bronze bushing-- you should have an early style with nitrided shaft and plain cast iron running surface. If you have the later (post-1970) or the really later 930 type with the bronze bushing, that is your smoking gun.

Now I know you mean "stock the car should have cast iron cylinders" and not heads. . . unless this is a Model T! (us New Yorkers show affection by breaking each others chops) Quite right, it should have cast iron barrels and aluminum heads. I would be curious as to when the heads were resurfaced, how much material was removed, and what is the new combustion chamber volume. You might want to CC the heads if you ever take it apart-- this could result in you having slightly more compression than stock (along with reduced piston-to-valve and piston-to-head clearance as well)

A fun mystery for sure! How about some detailed photos and then the experts here can really dig in and tell you what you've got.

[ibmiked]

Thanks Marco and John, that is precisely the type of considered opinion I was seeking. I will do a compression test as a quick attempt to see how much pressure the cylinders generate.

[ibmiked]

An interesting turn of events has occurred. I was able to get in contact with the owner who had the motor rebuilt (!). He claims that he bought the motor in pieces as the previous owner had started to rebuild the motor himself and then stalled in his efforts.

He received the motor and approximately $5,000 in parts and receipts. He took everything to a Porsche specialist, who ultimately had the case work done, purchased the parts I listed, and did the reassembly. The bill for $9k was over and above the $5,000 in parts. Those receipts don't exist anymore, but the owner remembers that the car has 'S' pistons (from the now missing receipts).

What else could $5,000 have bought? Cylinders? Heads? I'm open to further speculation.

Mike

[Mr9146]

Like I said, check the cam timing.

An interesting turn of events has occurred. I was able to get in contact with the owner who had the motor rebuilt (!). He claims that he bought the motor in pieces as the previous owner had started to rebuild the motor himself and then stalled in his efforts.

He received the motor and approximately $5,000 in parts and receipts. He took everything to a Porsche specialist, who ultimately had the case work done, purchased the parts I listed, and did the reassembly. The bill for $9k was over and above the $5,000 in parts. Those receipts don't exist anymore, but the owner remembers that the car has 'S' pistons (from the now missing receipts).

What else could $5,000 have bought? Cylinders? Heads? I'm open to further speculation.

Mike

[ibmiked]

Marco, is it worthwhile to try and get cam timing with the motor still in the car, or should I wait for my next motor drop? I read Wayne's tech article and he encourages a motor drop for that.

BTW, after sufficiently warming up the motor I did a compression check and got these numbers;

90
90
91
90
98
90

Was I wrong to expect higher numbers?

-Mike

[Mr9146]

Marco, is it worthwhile to try and get cam timing with the motor still in the car, or should I wait for my next motor drop? I read Wayne's tech article and he encourages a motor drop for that.

BTW, after sufficiently warming up the motor I did a compression check and got these numbers;

90
90
91
90
98
90

Was I wrong to expect higher numbers?

-Mike

I would have expected 150s-160s based on your previous posts. I'm calling user error on this one and suggest you try again.

Checking cam timing with the motor in the car is no more difficult than checking it with the motor on an engine stand. SETTING cam timing with the motor in the car presents more of a challenge. Next time you have the intake valve covers off I would suggest spending the exta time to find out what you can about the motor.

[haycait911]

make sure you do the compression check with the accelerator wide open. I like to take all the plugs out so the engine can spin up well. I bought a semi-cheapie boroscope a while back. I've been able to read cam numbers from the sides of the cams, in place. and gone up though the sump hole to get numbers from inside the pistons. you can also go through the plug holes to look at the piston tops to get an idea of what they are.

[ibmiked]

I did remove all plugs prior to the test but neglected to hold WOT. Great idea on the boroscope, I'm going to see if I can borrow one.

Thanks guys.