Tom---Looks like you rounded up all of 'the usual suspects' for the cause of
excessive pinging. One thing you didn't mention I will suggest -- that being
the real possibility that whoever shaved the head did not break the corners
after doing so. Unfortunately, unless you can get confirmation that this was
done, you'll have to pull the head to check this. Sharpness at the edges of the
combustion chambers and the sparkplug holes can get super hot if not stoned or
polished down.
IF---your timing marks on the damper pulley have shifted due to a breakdown in
the rubber, you can get a feel for its accuracy, by noting where the pointer is
when the key on the crankshaft is at TDC. Should be at "0". There is a more
precise method for checking this, that being a tool for finding TDC without
engine dismantling. All that's required is removal of #1 sparkplug and
inserting this (extended) plug. More info on this if you wish.
Dick
-----Original Message-----
From: Tomislav Marincic
Sent: Monday, April 9, 2012 11:45 AM
To: 6pack@autox.team.net
Subject: [6pack] Pinging Engine
My TR6 is pinging after a high performance rebuild, and I can't stop it.
I've done lots of things (high octane via xylene, retarded ignition, colder
plugs, richer mix) but it's starting to look that either the machinist
screwed up the head, or I've just built a monster.
I had a few specific questions:
1. Cranking compression. The engine was built to 9.5:1 specs,
45.6cc/chamber. My cranking compression hot is 195 +/-5 psi with a Goodparts
GP-2 cam, which strikes me as 10-15 psi high. Anyone else have a comparison
of nominal CR vs. compression with a similar cam?
2. Timing. Jeff at Advanced Distributors does great work, but he
refuses to tell me what specs he built my distributor to, which is not
helpful. Does anyone have experience with the 123 Distributor, which allows
the timing curve to be manipulated? Is that distributor compatible with the
MSD 6 series ignition?
Thanks for your help. If I hadn't used forged pistons, I'm sure I'd have
blown a ring land by now.
Cheers, Tom
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