[6pack] Connecting Rods with Relief Holes

[Robert M. Lang]

On Thu, 20 Dec 2012, Andrew Uprichard wrote:

> I may be talking out of turn, but my understanding is that factory rods will
> not withstand significant increases in horse power in these 6-cylinder
> engines.  When I rebuilt my 250, I went for upgraded rods as a hedge against
> this.  I also installed cam bearings but I did stay with the original crank.

There's no "out of turn" here. So, no worries.

Kastner built his 12.3:1 motors with factory rods. Granted, they were 
prepped to a high level, but they were factory rods. The prep included 
lightening and polishing, end-to-end balancing.

But they got 165-ish HP on those motors which is def. borderline 
"significant increase in power".

Part of the discussion should always address the "why" aspects. In his 
case, Kastner was restricted by rules. Our situations may be different, 
but still constrained by factors such as money or availability of parts.

>From a cost / price perspective, getting a set of alternate rods is 
probably cheaper than paying for all the prep referred to above. Unless 
you do all your own work and you charge $0 / hr for your labor in which 
case the stock rods are the way to go (because you have them).

I agree on cam bearings. It's worth the cost. Period.

The original crank is fine unless you plan to turn stupid RPMs in which 
case you pretty much have to look at billet cranks and learn to write 
REALLY BIG CHECKS without flinching. Of course, if you're trying to get 
stupid big power from a TR6 engine, common sense and affinity for your 
cash are long gone from the picture.

> Andrew Uprichard

regards,
rml
---------------------------------------------------------------------------
Bob Lang              Triumph TR6!!            |  This space for rent
Former NER Solo Chair                          |
Voice:617-253-7438                             |  Cell: 339-927-4489
---------------------------------------------------------------------------