Leakdown numbers and have questions.

gab997 · 01-19-2013, 05:29 PM

I purchased the car a little over four years ago and is an 84 Euro Widebody. The previous owner said he rebuilt the motor approximately 15k miles prior to me purchasing the car. He stated that he installed 964 cams and ported/ polished heads, new P&C's arp bolts etc, etc. So long story short I have no idea what is in this motor.

I have been tracking the car since I purchased and have been having a small issue with oil getting into the catch can I installed on the oil tank breather with the pcv disconnected. I started to look into this and had a friend who has worked on these cars stop by and complete a leakdown. The first words out of his mouth is that he would guess that I have blow by with a couple cylinders. This is not what I wanted to hear!!
OK so the numbers on the leakdown.

1-100% (no leakage!)
2-100% (same)
3-100% (still looking good!)
4-50% (CRAP!)
5-100% (OK good recovery)
6-54% (Double CRAP!)

Air is coming through oil reservoir on 4&6.

OK so engine is coming out and this is what I know.

Heads will be sent to extreme for inspection and refurb as needed and possibly twin plug.
Cams will be sent to Elgin for inspection and to see what I actually have and what kind of shape they are in.
Will find out what the issue is with cyl 4 & 6 when we open the engine up. I have two train of thoughts.
#1 if it is the rings then this is best case, install new rings and send off cylinders to have them inspected.
#2 if the its the cylinders then I need to think about what I want to replace the P&C's with once I get the information back from Elgin and Extreme.

I have two main concerns.
Concern #1 Due to the blow by on 4&6 could I have caused any damage to the bottom end of the motor with the positive crank case pressure? Due to not know what is in the motor should I open the case and inspect? What would the increase cost of doing this?
Concern #2 is budget. I am at a point that I realize that the car is going to be out of commission for awhile and do not want to be penny wise and pound foolish. With this I am going to install shorter gears, diff, bearing retaining plate and cooler to the 915. I feel that this is overlooked when people are rebuilding and upgrading motor with more hp/tq if your outside of the power band then your not taking full advantage of the new motor.

Wont be able to pull the motor for a couple of weeks to see what's inside of 4&6.

So another rebuild starts...

Greg

burgermeister · burgermeister's Garage

Did you "pop" the offending valves, or go for a drive & re-measure just to make sure you don't have some carbon bits keeping the valves open? Valve adjustment is OK (not too tight)?

Pretty close to what my car did after my rebuild. Issue turned out to be valve guides - all somewhat worn, one was completely gone and due to valve seat wear, horrid leakdown on that cylinder - still not sure what exactly caused the guide to go south. If yours ends up valve guide related, I'd love to know what brand valves and what the finish of the valve stems looks like.
Here's mine:
Valve stem finish & valve guide wear

Seems if this was cylinder/piston related, you'd be burning insane amounts of oil...

gab997 · 01-20-2013, 05:48 AM

Quote:

Originally Posted by burgermeister

Did you "pop" the offending valves, or go for a drive & re-measure just to make sure you don't have some carbon bits keeping the valves open? Valve adjustment is OK (not too tight)?

Pretty close to what my car did after my rebuild. Issue turned out to be valve guides - all somewhat worn, one was completely gone and due to valve seat wear, horrid leakdown on that cylinder - still not sure what exactly caused the guide to go south. If yours ends up valve guide related, I'd love to know what brand valves and what the finish of the valve stems looks like.
Here's mine:
Valve stem finish & valve guide wear

Seems if this was cylinder/piston related, you'd be burning insane amounts of oil...

We measured the leakdown from tdc and thought that if it was valves the pressure would be coming through the air intake or exhaust and not the oil tank.

Will let you know what I find once we open the engine up and start diagnosing.

drmatera · 01-20-2013, 06:01 AM

100%? I didn't know that was possible

gab997 · 01-20-2013, 06:04 AM

Quote:

Originally Posted by drmatera

100%? I didn't know that was possible

Ok you got me, within 2% is pretty close to 100%. Major difference to 50 & 54.

Jcslocum · 01-20-2013, 07:38 AM

you did them all at TDC or you rotated each to their own TDC?

If the only air sounds were from the oil fill then you have bad rings. No other suggestions will work until the P&C are pulled for a closer look. Cylinders can be replated to fix many imperfections, depending on severity. Millenium in MI can do them for you.

Good luck!

gab997 · 01-20-2013, 07:46 AM

Quote:

Originally Posted by Jcslocum

you did them all at TDC or you rotated each to their own TDC?

If the only air sounds were from the oil fill then you have bad rings. No other suggestions will work until the P&C are pulled for a closer look. Cylinders can be replated to fix many imperfections, depending on severity. Millenium in MI can do them for you.

Good luck!

Rotated each of them to tdc which led me to rings or cylinders. Should I be concerned with any issue in the lower end or is it a bit premature until I get the motor apart?

Thanks,
Greg

E Sully · E Sully's Garage

If you want to get an idea about the lower end, I would cut open the oil filter and see what is in the element. Also see if there is debris on the oil drain plugs. Have you also tried a compression test to back up the leak down test results? How do the spark plugs from the low cylinders look?
I would think it is possible that the rings might have been broken during the rebuild. Do you know if the cylinders are Alusil or Nikisil?