What a great month! Racecar and engine porn!

[cstreit]

What started out as a real bummer has turned into some great opportunties! I took a voluntary severance from my "real" job in April. Who knew it would be so much fun? I've been able to concentrate full-time on the new business and all things Porsche!

** Attended Autobahn Country Club opener, met Hurley Haywood and watched the Carrera GT's!
** Ran my first ROval course (the Milwaukee Mile). Gained some respect for the left turners.
** Worked on two cars that have run at 24 hours of LeMans!
** Did some fun fabrication and got my wrenches on some great racecars!

The pictures, Oh yeah, just some super stuff!

...engine shots! I've posted pictures of this 60's era Can-Am special before. The owner is a super guy and better yet, the car is Porsche powered! The motor is a 906 spec 2.0L putting out some astounding horsepower. It runs all day at 8500RPM. Unfortunately a missed shift resulted in something over 9300 RPM. Suprisingly besides some bent valves, a broken rocker and stretched rod-bolts, there was very little damage.

The motor arrived 7 days ago, and I'm under the gun to deliver it turnkey in 3 weeks. Full rebuild but man it's worth every minute!

The owner and I giving Burt Levy (author of "The Last Open Road") a shove at Grattan




Super high compression J&E's



Is the flywheel/clutch light enough for you?



Pauter Rods in a boattailed case



...and one ouchie!



We did some work on this 2.0L super well prepared racecar and our first inaugural track-support day.





We did a fair amount of custom suspension work and a trans swap on this beautifully prepared lighweight IROC replica with a 3.2L.
The ATV jack made this a lot easier!





..and finally one of MotoDelta's best customers. He owns 4 p-cars including this RSR with all the goodies!

[Jeff Alton]

Sounds likie somebody is having too much fun!!

Cheers, Jeff

[jluetjen]

Congratulations. It's great to hear that the "career change" has worked out so well.

[304065]

Hah! Ol' "BS" Levy talked you into a push! I've met him a couple times at Gingerman, he's awesome.

Chris, that 906-spec 2,0 has an interesting feature, the AN fitting sticking out of the top of the case adjacent to the oil thermostat. Now, I think that's where the oil pressure sender normally goes, but is it possible the owner connected an accusump there? I have been thinking that's a good place to supply pressure to the oil galleries-- it's one of the only places to tap into the "pressure" side of the oil system, no?

[cstreit]

John,

I didn't get any of the ancillaries with the motor, however I bet you probably could do that. I'd have to look at the oil-flow diagram to be sure that circuit is correct. For whatever reason the question popped into my head, what about the thermostat next to it... ...but I doubt the therm. would impact the functioning of this switch and hence interfere with the accusump.

[Grady Clay]

John,

That is exactly where to put an Accusump. I am surprised that engine doesn’t have the 906 oil filter.

Chris, nice looking rods. Where is the oil sump tank located? Original 906 location? I remember seeing that car raced.

What caused the over-rev? Missed shift, wrong gear, other? Does it have an electronic rev-limiter? How are the gear dogs and sliding sleeve? Anything wrong in the shift linkage?

I’m sure you know the places to look; upstream and downstream from the broken rocker.

Good luck with your new venture. I’m sure you will have success. Make it fun.

Best,
Grady
gradyclay@hotmail.com

[cstreit]

Grady,

I'm not really about the setup of the oil-sump. Unfortunately I've never seen the car fully naked. The motor was dropped off to me. It's got a pretty nifty hand-made baffle and seperator with a lexan window to verify operation.

The whole engine is being torn down and cleaned, although I've examined the broken rocker piece and there doesn't appear to be any bit missing, better safe than sorry at this point. A missed shift resulted in this overrev. There was no rev-limiter at the time, though you can bet one is going in now!

The owners team is checking the gearbox. It's a custom Hewland setup. THe oil filter is located where the engine oil-cooler was. Not sure what the 906 filter was all about, can you elaborate?

[Grady Clay]

Chris,

The 906 (and 911R) came out with a screen filter assembly in
place of the engine mounted oil cooler. The filter is a series of
fine mesh screens that are serviceable and can be easily
inspected. It is very similar to what originally was used on the
4-cam Carreras. It continued use through 935 and later.

The real advantage is that it is in the pressure circuit just before
the bearings and cams. This prevents any debris that finds its
way to the sump tank from damaging an engine part. The
normal 911 spin-on filter is in the dry-sump circuit just prior to
the sump tank. It can bypass, allowing engine failure debris to
contaminate the tank.

There is also a part necessary to replace the engine thermostat.
This forces all the oil to go through the 906 filter. It appears
that this engine has a standard engine thermostat so I assumed
it had a regular engine mounted oil cooler.

What and where are the baffle, separator, and window?


It looks like the engine had a mechanical rev limiter – cast rocker
arms. For most this is a savior when the engine gets buzzed.
The valves float, the head of the valve contacts the piston, the
rocker brakes, and it drops some cylinders. Sort of like hitting
the driver over the head. The downside is the necessity to use
stronger valve springs.

When the valves hit the piston there is very high shock stress in
the valve train from the crank gear to jackshaft, chains,
tensioners, idlers, sprockets, cams, retainers, keepers, springs,
etc. All those parts become suspect. There is also the possibility
of damage to the cam housing, rocker shaft, valve guide, head,
piston, wrist pin, and rod. Even with a light flywheel/clutch
assembly, the sudden angular acceleration can loosen the
flywheel bolts on a 6-bolt crankshaft.

How much of the valve perimeter contacted the piston?
Any sign that the piston contacted the head?

Here are some of those parts:
Filter assembly - upper right.
Bypass piece in place of thermostat - right center.
IMAGE: my9146eng03



You are sure correct about being safe, the sorry part is devastating.

Best,
Grady

[cstreit]

Grady,

Interesting. I'll check the engine thermostat when I replace the o-ring. I guesss if it doesn't have it, there is no filtering untill the engine warms up, probably not a good thing.

You learn something new every day!

The funny thing is, there is no evidence of valve to piston contact at all, nor head contact!

[Grady Clay]

Chris,

I have seen the cast rockers break with no sign on contact in a (very) few cases. I have no proof but speculate that the valve can float on some engines and not contact the piston. The valve and rocker reconnect with the cam at some point with each going opposite directions – so to speak. This could break a rocker from the sharp contact.

The usual case, particularly with large valve cutouts in the pistons, is for the valve to hit the piston squarely and snap the rocker. If there isn’t much carbon on the valve and piston, it might be possible to not see any signs of the contact.

Keep the pictures coming. Let us know what you find.

Best,
Grady

[cstreit]

Grady,

I have been thinking the same myself. When the valve head leaves the rocker, then slams back onto it with such high-force springs, it could very well snap that thin end of the rocker right off without even touching the piston... I'm testing all the spring pressures and wonder if the one that is broken might be the weakest spring, and therefore was the first to allow float?

[cstreit]

Okay so I'm doing a rebuild on this 2.0L race motor. The engine was over-revved to somewhere past 9300 RPM (Not typo, 9300+). A number of rockers were broken but it appears there was no piston to valve contact.

When I split the case I found that some of the main bearings are showing copper along the edge, maybe 2mm worth on the #4, #5, and #6 bearing. THe picture shows two of them. The wear is towards the #8 bearing end of the case.

Any ideas why?

My only theory so far is that when the crank was ground (it's .25mm undersize) the edges near the counterweights were left a little thick.

[Grady Clay]

Chris,

How do the rod bearings look? How long on the engine prior to the over-rev? The obvious first thing would be to measure the crank and torque the case back together and measure it. Clearly something is out of alignment. In the earlier image, the crank appears to be a stock 901. Is that so?

Was there data acquisition on the oil pressure?

Perhaps in my travels today I can have some others offer opinions. Guys that used to work for me at Rennenhaus and still build these engines all the time.

Best,
Grady

[304065]

Chris,

Might that be the results of a longevity-enhancing trick? Could the builder have ground the crank undersize and left larger fillets at the edges for strength, but then not put enough chamfer into the bearings for clearance? Or could a subsequent rebuilder not have known about the fillets and used standard oversize main bearings?

[cstreit]

I'm going to measure the crank across the main bearing contact area today... I'll post what I find.... The rod bearings were perfect. No significant wear.

The guy who had the crank ground also built the motor, and he was a very reputable builder.

I'm also going to check for crank "end play"because I wonder if this might also cause it.

[cstreit]

Hey I started a thread in engine rebuilding forum to continue this bearing discussion. Strange main bearing wear. Any ideas WHY?

Crank measurements in there...