revolve40

Motor is being picked up Thursday at a cost of $475. This includes residential pick up, no stacking, and ~4-day transport to Phoenix. Patrick Motorsports helped arrange pick up through a freight broker, so I'm not sure who the transporter is yet.

revolve40

Tear down pics coming in. Bearings look pretty good (except the intermediate shaft bearings which are clearly shot). Hopefully more to report tomorrow.

jeff33702

What was ultimately found as the reason for the poor leakdown?

revolve40

I had suspected that this ‘90 motor was updated for the cylinder/head sealing ring back when the top end was done around 2010, but it was not. There were indications of combustion leaking from around the weaker cylinders as shown below:











Also, it turns out the valve springs were installed too high, which allowed the assembly to rattle around (eventually leading to failure) and damage the seating area of the head. Fortunately, it was repairable.



More clean up and machining.

Ecosse911

I am sure your wallet is taking a hit but at least you will have piece of mind that everything was down right this time around.

Keep the updates coming as there is nothing more exciting than revealing what went wrong and seeing things done right

revolve40

Patrick will walk me through the details, but curious for Rennlister's feedback on this one. Before I dropped my motor, I drained the oil while cool. Obviously, this means a good bit of "old oil" is still in the system sitting in the lines and cooler. Is there a procedure to evacuate the rest of the oil before installing the new motor?

revolve40

Making good progress. Case is closed and heads are in process. Also picked up a new oil tank and cooler. Thermostat on order.

revolve40

For those curious, here are a few notes of what they found:

• Poor leakdown on cylinders 2 and 4
• Lots of JB Weld used to address leaks
• Broken intake valve springs on cylinders 1, 2, and 6
• Broken springs were due to prior rebuild; installed height was 33.4mm vs. 34.5mm, resulting in too much spring pressure
• One of the head studs stripped the case threads upon removal
• 3 false case thru bolt holes were found

gpallem

Hey Revolve40,
Interesting thread. Looks like you will have a new motor when done. I was wondering what "3 false case thru bolt holes were found" means. Can you elaborate?
Thanks,
Geert

revolve40

Good question! Until I speak with PMS again, I can only provide what the work order states below:

"We found 3 false case thru bolt holes that needed to be plugged for the o-ring groove to properly seal. The case had to be machined to an exact size so a plug could be made to be pressed in."

darylbowden

IIRC there was a TSB for certain 1990 964 engines where the through-bolt holes were machined improperly and so to fix it you need to either a) machine it properly or b) use two o-rings (Less desirable obv), maybe that was a previous owners attempt at fixing that themselves?

revolve40

So, to follow up on the false case through-bolt holes: evidently early 964 motors had two false through-bolt holes that were machined from the factory but not all the way through and they did not accept through bolts. When machining my cylinders for a larger bore and the RSR-style o-ring, it would have opened up into the false through-bolt hole. Therefore, they had to be precisely plugged before machining the o-ring groove to add material and prevent a hole from appearing. Hopefully that makes sense.

revolve40

Exhaust seats finished. Intake seats need to be finished before further assembly. Getting close.

revolve40

For anyone following along, the motor is essentially complete. Assembling the ancillary bits and getting it on the dyno next.

Ecosse911

It’s looking very pretty! How many hours are estimated in the motor build?