[6pack] Pinging Engine

[Alex & Janet Thomson]

I used the GP-2 cam in our TR-6 when the previous cam lost a couple of
lobes. I had the head milled to bump compression up to approximately 8.8 or
8.75:1. No indication of any pre-ignition but I generally do use 93 octane
fuel.

Alex Thomson

-----Original Message-----
From: 6pack-bounces at autox.team.net [mailto:6pack-bounces at autox.team.net] On
Behalf Of Tomislav Marincic
Sent: Monday, April 09, 2012 2:45 PM
To: 6pack at 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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