John:
Hepolites are a very solid piston, so don't worry about the
quality.
As far as the compression ratio, it depends on the cylinder
head, not the piston. The pistons are interchangeable for all years.
Triumph machined more metal off the head for the high compression UK
motors (9.5:1) and less metal off the head for the very low compression
US smog motors (7.75:1).
They will perform just fine for 10:1 compression naturally
aspirated applications and beyond *IF* you stay out of detonation. Run
them with detonation (pinging) and they will quickly fail. Since pinging
is more likely with higher compression ratios, most people like to go
with forged above roughly 10:1 compression. For pump gas and cast
pistons, 10:1 is a reasonable upper limit, with most people aiming for
about 9.5:1. I run 9.6:1 with no issues. I machined 0.120" off my later
7.75:1 smog head and 0.010" from my block deck to get to 9.6:1.
If possible, have your block zero decked (machined to make the
pistons flush with the top of the engine block) and then machine the
head to make up the difference to reach your desired compression ratio.
This will make more power and get you better detonation resistance than
if you machine the head only. This typically means taking about 0.015"
off the block, according to Kas Kastner in the TR6 racing prep handbook.
Cheers,
Vance
-----Original Message-----
From: owner-6pack@Autox.Team.Net [mailto:owner-6pack@Autox.Team.Net] On
Behalf Of John North
Sent: Saturday, January 27, 2007 2:26 PM
To: Triumph 6 Pack
Subject: AE Pistons
Anyone know anything about AE pistons?
I have seen several places selling AE pistons. TRF sells these, I
believe and I also see them at Advanced performance Technology and on
eBay. Rimmers sells AE Hepolites, not sure if these are the same.
Some places give a CR for example, 7.7-1 or 8.5-1. Not sure what
this indicates... Are they adequate only for up to these CRs or does
this indicate the usual application and I could expect them to be
adequate for higher CRs? I am putting together and engine and
shooting for 9.5-1.
Any help appreciated.
John North
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