[Fot] Oil Blow-by Cause? More Data but nothing obvious

[Scott Janzen]

OK, I re-ran the comp and leakdown tests.  Replaced a gauge that was reading low on the leakdown tester, so I now trust the results. With the exception of #3, leakdown was almost all piston ring leak-by.  #3 had exhaust noise too.

1 - cold leak 4%, hot leak 4%, hot comp 195, prior cold comp 200
2 - cold leak 9%, hot leak 12%, hot comp 175, pcc 180
3 - cold leak 15%, hot leak 16%, hot comp 170, pcc 180
4- cold leak 3%, hot leak 3%, hot comp 195, pcc 195
5- cold leak 4%, hot leak 4%, hot comp 172, pcc 190
6 - cold leak 3%, hot leak 5%,  hot comp 170, pcc 185

The leakdown results look good to me and are probably valve related.  I’m used to seeing higher numbers on a season-old motor.
Compression - I don’t know if the drop on 5 and 6 is normal for cold to hot testing.  What would cause this relative to cylinders with almost no change?
Plugs - Kas asked about the plugs - When I pulled them the first time, the insulators were very light tan, almost white, with tan electrodes - plugs looked the way they usually look in this motor.  After warm-up, they got darker, but not surprising since it was mostly idle time and nothing under load.  No oil on the plugs.  No visible oil coming out the tailpipe, same color back there as usual.
BTW, my lap times on the last session were a second off the weekend best, but so were most of my competitors, so the engine still seems strong.

At this point, unless anyone has more suggestions short of tear-down I guess I’ll run it again as-is.  The oil venting points (two valve cover hoses) have not changed, so there was nothing that would have dumped more oil than usual.  I have no block vent, so nothing to blame there. 

I could have had a mind fart and run with the accusump valve closed (it’s manual) but when I pulled the car off the trailer there was oil and pressure in the accusump, so I must have shut it off full.  Thus, there should not have been excess oil in the pan.

> -----Original Message-----
> From: Fot <fot-bounces at autox.team.net> On Behalf Of Scott Janzen via Fot
> Sent: Tuesday, May 21, 2019 10:32 PM
> To: 'Friends of Triumph' Triumph <fot at autox.team.net>
> Subject: [Fot] Oil Blow-by Cause?
> 
> I just had a great weekend at Summit Point, perfect weather, four days and
> lots of track time, some quick laps and good racing.
> After my last session, I noticed some dripping oil as I put the car in the trailer.
> Got it home to find a half full catch can (1 pint?), and evidence of oil blowing
> out of the valve cover cap vent hole.
> Tonight I ran a compression test and leakdown test.  Cold engine results:
> 
> 1 - 200 and 2%
> 2- 180 and 6%
> 3 - 180 and 9%
> 4 - 195 and 0%
> 5 - 190 and 0%
> 6 - 185 and 0%
> 
> Note - I suspect my longacre leakdown gauge may not be reading quite right,
> as when i have the air side set to 100, the leakdown % on the last three is
> slightly below zero.  So, perhaps the leakdown on the first three is higher.
> There was no excess oil until the last session.  Oil pressure is about 50 hot at
> idle and 65 - 75 at speed, depending on RPM.
> EGT readings remained in the 1200 - 1250 range across three monitored
> cylinders at top speed What do i have - failing rings?
> Any diagnosis or tests you recommend before I start pulling the thing apart
> would be appreciated.
> 
> Triumphs racing - I’m sure I’m missing a few but this is who I remember.
> TR3 - John Hasty, Henry Frye, John Styduhar
> GT6 - me, Paul King, Jason Sukey, Jay De Pol until his diff case broke Spitfire -
> Russ Moore, Marty Sukey, Jeff Govert, Kent Bain, others
> Tr4 - Mark Wheatley, Allen Goode, I’m missing at least another one
> 
> Scott Janzen


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