bebbetufs

I just changed rod bearings, pickup, main seal one DE ago, but I currently have the engine on a stand due to a leaking oil pump. The clear view of the internals made me consider the need to x-drill the crank given that I will be tracking the car quite a lot, no racing though. There is one longish left turn on my track.

Given the cost involved in splitting the block: flywheel bolts, RMS, rod nuts, and the stress placed on rod bolts from multiple torque cycles I'm inclined to leave it. If I could reuse the rod bolts and BE studs the cost would be more reasonable. The BE studs have two torques on them in addition to the factory torque, the rod bolts have one, as far as I can remember. What would you do?

Mike C.

I think anything you do to improve oiling (especially for that #2 rod bearing) is well worthwhile for a DE car. I never had any problems re-using the flywheel bolts though. I don't believe the studs are torque to yield; as such, I can't believe fatigue life would be debited from 4 cycles vs. 1 (one cycle being 0 load up to spec torque and back to 0 again). As I recall, rod nuts should always be replaced, not sure about rod bolts. I never replaced them but I wasn't dealing with a turbo either.

dirtyTurbo

The chances of you losing a rod bearing are wayyyyyyyy higher than everything else you just worried about

M758

Replace all the seals and bearings. Re- use all the hard ware except rod nuts. I have done many rebuilts and only replaced rod nuts. Never any issues.

bebbetufs

Ok. Thanks. I'll order some nuts and the seals. Do I really need to replace bearings after only 1k miles?
What is the best way to cross drill the crank? I've read that all that is needed is to open a second oiling hole on the journal oposite the direction of rotation. Is this really enough?

(Yes I know....I'll search, but some subjects yield such overwelming results.)

M758

I would not normally replace main and rod bearings in this short time, but if the crank is out I don't believe I would ever re-use main and rod bearings either. Rod bearings are not that much money, but main bearings are. Personally I would hate to spend the money, but feel worred about putting the same bearings back it. Too many potential issues in my mind.

As for cross drilling. Last time I had it done I did it on #2 and #3 journals only in a attempt to balance the flow between all 4 more equally and just had them put in the same hole 180 degrees from the existing hole.

bebbetufs

Thanks for replying
I'm really going to run out of money. I wish I had started wiith a wreck of a car rather than the perfect example I have. it. It just feels plain wrong replacing one perfectly good part after another. I've spent thousands on preventive maintenance already. I'd much rather pull the engine in another 20K and replace the bearings then to take some more life out of them. Still, better safe than sorry I guess!

What do you guys think of the nascar bearings mentioned in post #22 here

I've been reading up on the cross drilling procedures and I'm slightly confused. What exactly does cross drilling refer to? For some it seems it simply implies drilling a second hole in the journal to make better use of the centrifugal force to help the oil exit. For others it implies drilling a second channel to a different main bearing journal to effectively double the flow potential to the journal being treated. Which one of this is it, or is it both?

M758

This

Main bearings have two holes in the journal. Rods only have 1 hold. Dillling the crank add a second hole to the rod journal.

bebbetufs

Forgive me for being so slow, but do you simply mean drilling a second exit hole into the existing galley effectively just relocating it?

M758

As for cross drilling. Last time I had it done I did it on #2 and #3 journals only in a attempt to balance the flow between all 4 more equally and just had them put in the same size hole 180 degrees from the existing hole.

harveyf

The factory shop manual is pretty good about mentioning parts that need to be replaced every time, etc. Regarding the rods, it specifically recommends that new connecting rod nuts be used every time the engine is repaired. Conversely, there is no mention of replacing the studs.

I got my shop manual for $20 on a CD from an internet based book retailer. I don't know how you would attempt to do any engine work without one.

bebbetufs

Thanks for pointing that out as it is important info to any newcomers and an important remainder to me that no matter how many times I have read it I should still consult it.

Still, the information in the manual is not intended for tracked or overboosted cars and cannot be trusted to provide safe advice when factory specs are exceeded. Mine will be both tracked and sometimes overboosted, so I've been trying to build in some extra margins of safety when I can, and can afford it, both by replacing parts and by consulting the forums.

harveyf

I don't want to get into an argument with Joe P, as he has a lot more experience than I do but...

Porsche did cross drill cranks on early cars, just like Joe states, a single hole from one side of the journal to the other side. They did this on all 4 rod bearing journals. I had one of these cranks on my track car. Mine spun a #2 rod bearing. Since I got the engine used from a wrecking yard I cannot rule out other mitigating circumstances but the rod bearings were newly replaced and only had about 10 hours on them when the failure occurred.

As far as I can tell, Porsche quit building their cranks this way. Looking at how the centrifugal forces work the single hole on later cranks (I have one from an early 85 car) lets the oil flow in the same direction as the centrifugal force. An additional hole 180 deg opposite requires the oil to flow against the centrifugal force. Not saying it doesn't help but I don't think by itself it is a "silver bullet" solution.

I also believe that some recommend drilling the hole at 90 deg to the existing hole. From a machining standpoint this is slightly more complicated but I do like the engineering in that at least the oil flow is going in a more "neutral" direction versus the centrifugal force.

harveyf

Well, Bebbetufs, if you are going to overboost your car than yes, you most go the extra mile. My car is N/A.

For what it's worth, the rod end studs see their highest stress due to the inertia of the piston at top dead center. Boost increases the compression load on the rod, bearing, crank etc but probably is relatively benign with respect to the rod bolt studs, the subject of your original post. So I agree with Joe P that there seems to be little value in replacing them as a precaution, unless you are planning on raising your rev limit, in which case all bets are off.

bebbetufs

Thanks for your well put advice. I won't be raising the revs. I just asked Rogue to keep the limiter stock on my recently ordered M-tune. Better safe than sorry.

I am curious about the 90 degree hole. Seems like the logical solution.