Holiday ride of shame

[Dan Epperly]

It's been running o.k. for 9K miles and then something went wrong. Has it been run under similar circumstances: heat, altitude and uphill climbs without incidents? Keep us posted.
A
Mike

I've driven it on hot days, it's been up the mountains, grades, etc. never a hint of a problem. Granted we had driven 6 hours at 97 degree temps and it was a hellish climb from sea level to 4K but a healthy engine should have had no issue. I'm still banking on a part failing vs poor timing or compression set too high. I'm pretty sure I would have had indications of a problem long before this.

[Mike Horton]

Dan, recheck the distributor timing before disassembly, when you have it apart, re confirm the compression ratio, and have the distributor total timing confirmed in a distributor machine. Also, remove the fuel pump, and slowly turning the engine, view, and inspect the brass distributor drive gear, for damage. Was this gear an original Porsche part, or aftermarket?

Glen, of note, in your description, are;
a) 9:1 C/R
b) a switch to "Premium" fuel
c) Confirm your timing, as above

" The climb might have caused detonation and the rings may be stuck in the piston grooves. "
Note C.J.'s comment, and other council. Check ring side clearances, and end gap, and let us know.

These failures sound like the detonation damage to which C.J. refers. Some of the causes, historically, have been;
a) too much timing, especially for the octane of the fuel, to adequately support
b) too much compression ratio, for the fuel octane used, and ignition timing, as well
c) a "too lean" fuel to air mixture. Per David Jones, if you run the 10% ethanol, you MUST install richer jets, for your conditions
d) too high engine loading, in too high a gear, "The climb might have caused detonation"

The heat observed, is a hint... same with increasing oil consumption, these engines will let you know,

Forged pistons, are tougher, under higher stresses, but in my aviation days, I worked with both cast, & forged pistons, various manufacturers, and had both fail, due to detonation. I usually found the root cause, to be in some combination of the causes mentioned. One of the most dependable combinations, was the Lycoming, with parallel valves, the C/R of 8.5:1, and 100 octane leaded avgas. The closer an engine combination is built, to the "detonation margin", the less tolerance it will have for deviations, in these state of tune settings, and situations. These are just my 5 decades of observations. I have put many miles on cast pistons, and was it Vic, or Jacques, who said that only the competition 4 cam engines came from the factory, with other than cast pistons?

This deserves close scrutiny, and good post mortem inspection, and we will all benefit, from the result.
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[Mike Horton]

...in all examples, were the heads properly reconditioned?

In the B head engine, were the pistons made for the 22* angle, or, heads, or pistons reconfigured, for those head angles? … inquiring minds,

[C J Murray]

If it is popping compression out at the top of the cylinder you may have a head where the sealing surfaces of the two cylinders is not the same depth. I have also seen brand new p&c sets with cylinders not all the same height. If the case has been machined the sealing surface must be true.

[Mike Wilson]

So since the engine was running o.k. after 9K miles, would the long drive with heat and grade finally manifest a problem like cylinder to head fit?

Mike

[Dick Weiss]

Dan and others:

I've said several times that torquing the heads should be done alternately by flipping over the engine
each time starting w/7, 15, 22, and 28 ft.lbs. and twice more w/the final 28 figure.
This stresses the case evenly which (RIP) Ray Litz of the early Competition Engineering shop found during
the racing events way back in the late '50s-'60s. Fully torquing the 1st head--then the 2nd head, the 1st won't be correct which can loose some compression and oil leaks; This is always noted on the area between the combustion chamber faces due to the cold fuel intake passing thru the inlet valves and the hot exhaust end faces--You'd think it would be the other way around w/expansion rates. (MHI)

Also, I might disagree w/piston ring gaps moving around in their grooves but I never disassembled an engine w/low? mileage to check that; I do chart gaps after the cylinders are removed for reference,
and I do orient new rings showing on my P/C chart during inspection of piston and cylinder clearances making sure the oil ring gaps are UP!

BTW, Running the engine--What RPMs when climbing hills?
Dick

[Dan Epperly]

Dick,
I've always flipped the engine and built up torque values across..a practice from building so many VW engines, and using the maestros advice, check the final torque three times.
Rpms on the climb where in the 4ks.
I would imagine an uneven height situation would have manifested earlier unless again it was marginal and over time through hot cold cycles something changed?
A friend is coming over today with a dial in timing gun to check my real timing. I will report back.

[George Hussey]

I would leak it down first and see where all of the compression is going. If brass flakes from the valve guide coming loose then the valve clearance would have changed and the engine would have made noise

[Al Zim]

My first guess is that the depth between the bottom of the cylinder head and the ledge where the piston sets was too great and the hot gasses have worn a channel between the two. You still have to take it completely apart!!!!! The metal is everywhere in the engine. Tear everything apart for a thorough cleaning and measurement including cleaning the oil cooler. al zim

[C J Murray]

I would take it apart without running it any further, not even down the block.

[Wes Bender]

+1 Don't turn a $200 problem into a $2000 one.

[Mike Horton]

My first guess is that the depth between the bottom of the cylinder head and the ledge where the piston sets was too great and the hot gasses have worn a channel between the two. You still have to take it completely apart!!!!! The metal is everywhere in the engine and tearing everything apart for a thorough cleaning including the oil cooler. al zim

+1

[Mike Horton]

I would take it apart without running it any further, not even down the block.

+1

[Mike Horton]

+1 Don't turn a $200 problem into a $2000 one.

+1

[Dan Epperly]

Yeah it's sitting in the driveway looking forlorn. I have another project t in the garage so it's gotta wait, but expect an update with los of pictures in a few weeks.
Thanks for all the input. Gives me an idea of what to look for.