300guy

As I undestand there are three ways to combat the common #2 and #3 rod bearing failures.
1. Cross drill journals
2. Perp Drill rod journals
3. Just drill the existing oil journals a bit bigger

What are peoples opinions on what to do? I plan to use the engine mostly on the street... but if I get into racing - I dont want to spin a rod bearing!

ALSO - what are peoples opinions on just doing this modification to #2 and #3 instead of all four?

thanks guys...

alordofchaos

Bump, because I'm curious...

M758

Last I heard from good source was cross drill #2 & #3 only. This came from the only guy I know who has flowed the crank. Said doing just those 2 balanced the flow accross all 4 rods. I did this on the crank in my spare engine. I have not run the engine so I can't say how well it works. My currnet race motor has all 4 cross drilled. This seems to have work quite well over the many years of racing it has seen. I do however do other things (long list) as well to reduce my chances of a spun bearing.

I don't thing number #3 would work well and I am not certain that where you drill them makes and difference.

300guy

Thanks for the info... actually - in the research that I've done, I have read about your spare race motor.

Why did you choose to cross drill and not perp drill?

M758

why perp instead of regular cross drill? I was never happy with Huntley's reasoning behind "perp" part of it. Seemed to me just a way to say... Mine is better than yours".

300guy

hmm... as I understand it the idea is that the centripetal force of the rotating crank helps flow the oil.

My crankshaft is at the machining shop right now, and they are waiting for instruction on how to proceed.

Joe - do you suggest that I stick with the cross drilling instead of trying the perp drilling?

Just so that I know the process - does the machine shop drill, then ream, then polish - is that the process?

thanks,
Colin

xsboost90

i had my rods crossdrilled while my n/a motor was apart due to spinning #2. Also added lindsey pan baffle and crank scraper, and kept oil levels up. Worked great up until selling the car- still no problems from what i understand.

MichelleJD

Mine is perp drilled as well, but I don't have significant enough mileage to be of much help.



(So why the hell did I post?)

Skip

Much good discussion on this over on the 944-spec forum (http://www.nasaforums.com/viewforum.php?f=40). Worth reading. I have the Fordahl crank. [does that sounds weird?]

Here's one: http://www.nasaforums.com/viewtopic.php?t=4398

There are more.

300guy

Thanks for all of the info guys. I've decided to perp drill #2 and #3 rod bearing journal with a 3/16" hole.

Thanks again,
Colin

Smudo

Old thread but covers a subject relevant for me. I am doing engine rebuild and together with additional oil cooler and pick up tune modification, I plan to do the crank perpendicular drill on #2 and#3. Does it matter on which side the additional whole is drilled? I also read that to even out the oil flow between all four rod journals (i.e. increase # 2 and #3) cross drilling #2 and #3 rod bearing journals to 3/16" should be done. Is it relevant also in a situation when aftermarket rods are used?