Terry:
The PI systems all used wide port spacing cylinder heads. The
head was milled for a 9.5:1 compression ratio. Early PI units used the
280 degree PI cam. Later PI engines used the 254 degree cam that was
used in the later carbureted North America motors. The PI motors also
used a higher ratio rocker arm, and used a special assembly to drive the
fuel distributor off the ignition distributor. PI motors came stock with
cold air induction, and a slightly taller rear end ratio. All PI cars
also had the dual exhaust found on the later North American Cars.
Get John Williams book on restoring the TR6. There is a detailed
section on PI motors and how to restore them.
Simply put, the PI motors got all the factory hot rod stuff that
North America did not get. As emissions requirements sapped the engine
output, the factory started adding the better parts to the motor to make
up the difference including the higher performance cylinder head, a
hotter cam, and the dual exhaust system. One thing the PI cars did NOT
get was the later, better flowing intake manifold for the carb models
(for obvious reasons).
The thing that was killing the north American motors was the
dismal compression ratio, which got as low as 7.5:1. Surprisingly, the
carburetors are not a limiter to power until you reach about 140HP or
so, then Webers or a third Zenith start to pay off.
Cheers,
Vance
-----Original Message-----
From: owner-6pack@Autox.Team.Net [mailto:owner-6pack@Autox.Team.Net] On
Behalf Of Terry Geiger
Sent: November 29, 2007 6:52 AM
To: 6pack@autox.team.net
Subject: [6pack] TR6 Cylinder Heads and Lucas Petrol Injection
The recent discussion of TR6 cylinder heads brings up a subject for
which I
anticipate to come up next year.
A friend and myself both have TR6's and my friend has family in
Australia. A
recent visit from one of the Australians (he is a car guy) brought up
the
subject of Lucas PI systems as used on the six cylinder TR engines. Our
Australian friend is going to check on getting two complete PI systems
shipped
back to us for possible installation on our TR6's. They are basically
throw
away items in Australia at this point so we probably will have more in
the
shipping cost than in the actual components.
The web site www.lucasinjection.com has been somewhat helpful but I'd
love to
hear from someone with first hand experience with converting a
carburated 2.5
Triumph engine to Lucas PI.
What cylinder head is needed for use with the Lucas PI system? My car
has the
later (wide port spacing) cylinder head. My friend's car has the
earlier
(narrow port spacing) cylinder head. Rimmer Brothers shows two
injection
systems early (to commission # CP5000) and late (from commission #
CP50001).
Is the differences for spacing of the cylinder head ports?
Are the ignition distributors different?
I realize they are more modern alternatives for fuel injection (Rick
Patton's
electronic injection, etc) and from a purely performance/reliability
standpoint the modern electronic system is probably a better choice.
I'm
trying to gather some input to try to determine which way to go. I'm
actually
leaning toward the modern system electronic system but my friend wants
to go
the Lucas PI route.
Terry Geiger
'74 Triumph TR6 | '63 Triumph Herald | '70 MGBGT | '84 Mercedes 300D
Diesel
|