O/H thinking

OldTee · 11-29-2007, 07:15 AM

I have a 79SC with 148K miles. Was topped at 110K. Alusil. The cams are toast, but it still runs OK except for some oil burning issues. It is a DE/road car without modifications except lowered to euro specs, RA1s, new shocks and bushings, SSIs, Cat by-pass.

I know at this mileage I will have to split the case. I could stand a little boost in performance but without sacrificing much dirveabilty. Here are my thoughts and questions.

I want to keep the cr to 8.5 to be able to use regular (read that as cheap)pump gas on the street. Thinking about going to 3.2 using one of the kits (without changing rods).

Thinking about a 964 Cam grind but wonder how this will affect drive-ability?

Will go new valves (etc), new springs.

Cost within reason is always an issue. Will disassemble and reassemble myself.

OldTee · 11-30-2007, 03:46 AM

da bumpee

surely somebody of note and experience can tell about the driveability with 964 cams in an older SC. Is bigger bore better for this cam?

cstreit · cstreit's Garage

964 cams will actually improve your power curve a bit. I understand there is a slight gain of lower end torque and a nice gain in top-end HP.

If your pistons and cylinders are shot, the displacement increase is a great idea. You'll probably have to reset your CIS but that's normal during a rebuild anyway.

ZOA NOM · ZOA NOM's Garage

Quote:

I know at this mileage I will have to split the case.

I disagree. I just took apart a 170k motor for the sole reason of putting ARP rod bolts in it for racing. It showed absolutely minimal wear. I was amazed. I would spend your time on the top end. My daily driver has passed 200k with no issues as well. I won't touch it until it asks me to.

Steve@Rennsport · 12-02-2007, 12:18 AM

JMHO, but if you intend to run regular (87) octane fuel, you should stick to the 95mm (stock) P/C's since these are more detonation resistant than the 98mm ones.

OldTee · 12-02-2007, 06:09 AM

Quote:

Originally Posted by ZOANAS

I disagree. I just took apart a 170k motor for the sole reason of putting ARP rod bolts in it for racing. It showed absolutely minimal wear. I was amazed. I would spend your time on the top end. My daily driver has passed 200k with no issues as well. I won't touch it until it asks me to.

Is this conventional wisdom? Would love to hear from some of the rebuilders about this. We are talking about a 79 3.0 engine with 150K miles.

Tha advice about 98 vs 95 mm cylinders has merit. Thanks

ZOA NOM · ZOA NOM's Garage

I would acknowledge that mine is a 3.2, but I know the SC rod bolts are 10mm, whereas mine were 9mm, which was the reason for my tear-down. If you have confidence in the history of maintenance and oil changes on the motor, I would not expect to find much wrong inside the case. I only have experience with the two motors I own, and I've only opened one of them, but I was stunned by the lack of wear when I did.

Eagledriver · 12-02-2007, 05:55 PM

It's rare to split a case of a factory built engine and find significant wear. There are many SC motors with 200k or more without even doing the top end. The things that seem to wear in the bottom end are of course the bearings, as well as the aluminum intermediate shaft gear. If you have good oil pressure the bearings are not likely to be worn. I'm not sure there is an upper limit to how far a bottom end on an SC motor will go.

-Andy