Knife Edgeing a 993 Crank?

[tocobill]

Looking at engines to buy. Found on that might have spun a bearing. 95 993 NA. While rebuilding is it worth getting the crank knife edged and cross drilled. Any other worthwhile upgrades that can be done while its opened?

Engine would be used in backdated 911 to a 73 RSR. Trans would be a 915 Mag based with additional upgrades. Induction would be PMO 50 Carbs. Thanks!

[BURN-BROS]

Cross drill yes.

Knife edged, no. Our cranks do not have enough counterweights as it is AND there is no performance advantage.

[tocobill]

Knife edged, no. Our cranks do not have enough counterweights as it is AND there is no performance advantage.

Doesn't help to lighten up the rotating assembly mass at all? Would have thought it would help it to rev a little faster especially with lighter rods and an rsr fly wheel.

[KTL]

Cross drill is 2 & 5 journals, correct?

[tocobill]

Thats what Ive read. Wont be a "race" motor but since its open it seems to be a good idea to get done especially if it has wipe a bearing IMHO. Little extra piece of mind.

The stock oil pump should be up to snuff. I dont really care to buy a GT3 pump just to say I have one. Would rather get better rods instead.

Not sure about shuffle pinning. Looked like ~$300 to get done. Worth it?

Anything else I should do for the experts out there?

[BURN-BROS]

Originally Posted by tocobill

Doesn't help to lighten up the rotating assembly mass at all? Would have thought it would help it to rev a little faster especially with lighter rods and an rsr fly wheel.

It's much more effective to use lighter rods or a lighter flywheel. There is not enough counterweight mass to do anything.

Originally Posted by KTL

Cross drill is 2 & 5 journals, correct?

You would be crossdrilling the Main journal #4, which bisects 2 and 5 rod journals

Originally Posted by tocobill

The stock oil pump should be up to snuff. I dont really care to buy a GT3 pump just to say I have one. Would rather get better rods instead.

The stock pump is fine, but because they are magnesium you must check that they spin freely with no binding. The turbo and GT3 pumps are aluminum and have much more long term stability.

Originally Posted by tocobill

Not sure about shuffle pinning. Looked like ~$300 to get done. Worth it?

Anything else I should do for the experts out there?

Save your money.

The 993 crank is a stout piece, but it takes away crucial rod bearing surface in order get said strength. Cross drilling is added insurance that you will have adequate oil to the rods. If you feel that your build will require better rods, A nice h beam set will remove some weight and provide you with a better rod bolt. Clearancing the oil pump I believe is mandatory if aftermarket rods are used.

[tocobill]

Thanks Aaron!

[BURN-BROS]

You are welcome!

[KTL]

Thanks for the clarification on the cross-drilling Aaron. I should have been more clear that I was referring to #2 and #5 rod journals.

Good point about rod clearance to the pump. The longer stroke on the 3.6 cranks puts the big end closer to the pump. The aftermarket rods typically have their bolt heads facing the piston side of the rod. The bolt heads stick out a bit more than the nuts do on the stock rod bolts. Do a search and you'll see how the pump has been clearanced. I think Aaron posted a picture of a 930 vs. 964 Turbo pump and how the factory relieved the pump case?

[BURN-BROS]

oil pump clearance

[KTL]

Originally Posted by BURN-BROS

oil pump clearance

From the horse's mouth! Thanks Aaron. Saved that in my tech info collection