Joe's Engine Update

[944-Spec#94]

Well,

Saturday we checked the engine on my race car. We started the car. It sounded fine, but had slight low end knock. Drained the oil and found not much.

 

We pull the oil pan in the car and found a spun number 2 rod bearing.

 

It was not real bad, but the crank will need a little machining to clean-up the bearing. Good thing is I caught it early and presereved the block.

We pulled the engine out of the car and we have spare block so will be building that up and should be back and running soon.

 

Still not clear as to why it failed. This evening we plan on pulling the head and cam housing to install on the other block. Maybe we will see something. Maybe not.

 

Well.... the only good news is that doing you own labor is a life and budget saver.

 

[Chris Benbow]

Joe,

When had the rod bearings been changed on the engine? What was the oil level, engine temp at the time of the incident?

You're pretty good about maintaining your engines from what I can tell. That's somewhat discouraging if yours just up and spun a bearing without any apparent reason.

[944-Spec#94]

Chris,

I had just done rod and main bearings in the fall. I had 5-6 days on the motor.

 

Oil level was good.

 

Oil pressure and temp are a little suspect. I was having issues with the pressure gauge and might have been running the engine too cool.

 

As stated in my previous post this was an 88 block that I got from an 88 924s parts car I got for practically nothing over the summer. (PS this motor made no more power than my 84 block with the same head and cam)

 

My guess is that the failure is from either a build error or something wrong in that particular motor. It was way too soon for wear out.

[Spec-944#70]

Sorry to hear about this Joe. How did you know this motor made no more HP than your other one? Dyno? If it made just a few more HP you wouldn't be able to tell just by driving. Was the oil pick up tube O.K? You said the motor may have been too cool? How can this be? Even when I ran my car in the cold air (less than 50') it still ran at just a hair over the first line on the temp gauge. I think you may be right as to something else wrong with the motor as I doubt you and you dad did something wrong. You guys know what your doing and you diagnosis of my failure at PIR was dead on.

Are you thinking about any preventive measures? Cross drill crank? Air/Oil seperator?

Good luck and keep us informed,

[944-Spec#94]

I could tell the power form the motor by accleration from turn 9 at PIR. Where I got in to 5th gear was key. Back last febuary I could tell I was hitting that point earlier in cool morning air. With this motor I hit that spot in the same place I did last febuary. No change in hp (at least nothig noticeable) that would give me any advantage vs the old motor.

 

The car ran cool. I had turbo oil cooler and had to run without fans just to keep the temp at the first white line.

 

Oil pickup was just fine with no issues there.

[Spec-944#70]

Good man!! Keep us informed as you have lots of eyes on you!!! We all want to know.

[Tim Comeau]

You guys are making me feel terrible. I'm going to go out to the garage and bust a hole through the side of my engine block....................on both cars.

[Spec-944#70]

Anything to slow you down!!

[greg f]

Just a tip, if your engine is apart and the crank needs clean-up, consider this: We had a whole bunch of #2 bearing failures on all different year engines. After researching this problem on the Web I decided that no one person actually knew the cause of this. We could debate oil level, temp, phase of the moon, etc. but instead let me tell you what I have found. I dissasembled an engine (85.5MY) and made a fixture that allowed me to supply 90psi water to the pressure side of the oil pump. I then observed the flow with no crank installed, then with a crank and bearings installed.

The oil supply to #1 is outstanding, ( big suprise, it is 3" from the oil pump) #4 was pretty good, but #2 and #3 were barely dribbling compared to the other two. I first installed a flow restrictor of around 30% to #1 and the flow was more balanced. I then installed a crossdrilled crank and did not see a big change in the flow distribution. I then had a crank crossdrilled but only the #2,3 rod journals. Big change! Now the ditribution of pressure and flow is much more equal to the bearings. I have not had a bearing failure in any of these engines yet, ( knock on wood) and your crank guy will only bitch you out if he tries to drill it before grinding the surface hardening in the hole area. BTW we also have been increasing the #2,3 oil hole size to 3/16" with good results. I do not install the flow restrictors any longer, as crossdrilling the two affected journals seems to be enough.

Everyone has their pet theories regarding this common failure. Joe S. from Phoenix told me that he updates the anti-drainback valve in the heads and has no bearing problems, but your 88 motor should already have that valve. Plus I remember that the valve was to stop noisy lifters on start-up and is not much more than a residual pressure valve ( ball and spring) Hope this was helpful, I am just doing my part to preserve the dwindling supply of std/std 944 crankshafts in the world! Greg F

[944-Spec#94]

Well intersting update and might fit in to your observations Greg.

 

I was doing rod bearings on my 84 motor preparing it to go back in my race car. This was the one I ran from Jan 2003 to Feb 2004. Lots of sucessfull races and tight rod bearing clearances. (Plastigagued to .038 on 2,3,4 and .051 on #1 (Spec is .034 to .092) Guess what? The #2 & #3 rod journals had been crossdrilled! Looks like I never noticed it when I had rebuild it in Dec 2002 and I know I never had it done. I noticed it after I had done the #1 and #4 rod bearings and assumed it was all the rods, but did not verify. I can check them again.

 

This 88 motor had not been cross drilled.

 

I do have plans to clean-up the 88 crank and will probably go for the #2 & #3 cross drill to 3/16" your observations with pressure drilling seems as valid as any as I have heard!

 

[PeanutinCA]

Can you drill the crank without removing it? I hear it's a big(ger) job removing the crank than just doing the rod bearings themselves. I'm about to do the rod bearings. I'm wondering what makes the differences on an engine that has been working, the rod bearings are changed and soon thereafter they fail?

 

P.Dilly.

[944-Spec#94]

Nope to drill the crank properly you need to remove it from the engine and of course remove the engine from the car.

[PeanutinCA]

Thanks Joe.