Subject: Re: [6pack] Connecting Rods with Relief Holes

From: "Robert M. Lang" <[email-masked]>
Date: Thu, 20 Dec 2012 11:20:12 -0500 (EST)

Hi,

There are two rod styles for TR6, early and late. The late rods appear 
with the change to CF / CR comm. numbers.

The early rods are "better" if you're building a race engine. This is 
according to a reliable source with credentials in materials science.

All TR6 cranks are forged. EN40, if I recall.

If your motor has three early rads and three late rods, there's probably a 
story there unless you have an early CF / CR block in which case you have 
"the luck of the draw"...

Also, if you have different rods types, I'd make sure the dynamic balance 
of the motor is good - there's a difference in the weight of the early and 
late rods. ;-)

regards,
rml
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Bob Lang              Triumph TR6!!            |  This space for rent
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From: "Andrew Uprichard" <[email-masked]>
Date: Thu, 20 Dec 2012 11:29:31 -0500

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.

Andrew Uprichard

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of Robert M. Lang
Sent: Thursday, December 20, 2012 11:20 AM
To: Brian J. Alwin
Cc: [email-masked]
Subject: Re: [6pack] Connecting Rods with Relief Holes

Hi,

There are two rod styles for TR6, early and late. The late rods appear with
the change to CF / CR comm. numbers.

Also, if you have different rods types, I'd make sure the dynamic balance of
the motor is good - there's a difference in the weight of the early and late
rods. ;-)

regards,
rml

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From: Richard Seaton <[email-masked]>
Date: Thu, 20 Dec 2012 10:40:46 -0600

I'd suggest,If not going over 150hp, then the stock rods will be fine.

I thought I read the late rods were better??? I must be mistaken.

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From: "Robert M. Lang" <[email-masked]>
Date: Thu, 20 Dec 2012 11:52:43 -0500 (EST)

> 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.

regards,
rml

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From: "Robert M. Lang" <[email-masked]>
Date: Thu, 20 Dec 2012 11:58:12 -0500 (EST)

> I'd suggest,If not going over 150hp, then the stock rods will be fine.

Don't forget the factory CP cars were 150 HP in stock form.

> I thought I read the late rods were better??? I must be mistaken.

I've had some lengthy discussions with JK Jackson about this and he was, 
adamant that early rods are the better choice.

I believe the reason that the early rods are better is that they don't 
start out with a huge stress riser drilled into the rod at the spot where 
the stresses all converge.

But I've been wrong before.

;-)

rml

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From: "Chuck Arnold and/or Kathleen Kelley" <[email-masked]>
Date: Thu, 20 Dec 2012 11:35:34 -0800

Added FOT to this string -- sorry for those it is a duplicate.  Wanted to
try to equate the hp number I just got of by car from a DynoJet chassis
dyno with the numbers from "back in the day".

Found a great article at :
http://www.hardtail.com/techtips/hpexplained.html

to net it out, as it were:
HP before 1972 in US was a gross figure -- engine dyno, no accessories.
After 72 SAE HP is engine with accessories -- about a 20% parasitic loss
(net SAE)
When you factor in rear wheel through drive train with a standard tranny
you lose 15% more.

My racing TR6 was measured at 172 on the dyno [and running rich] with PI,
hottest cam I can get, lots of head work and a Pacesetter exhaust maifold
to 2.5" pipe with racing muffler [am putting in  a Goodparts header before
racing next year].  Using .15 for parasitic loss instead of .2, I get about
202 SAE Net HP and a wopping 238 using 1970 gross SAE values.  I seem to
recall in one of KAS books they were getting around 240 HP on the engines
-- and there gross versus net were probably the same as thee were no
"accessories" on the race engine.  That seems about right also -- I should
pick up some HP with the header and leaning it out and I run about 12.5:1
compression.  Think Kas was around 14:1.

On Thu, Dec 20, 2012 at 8:58 AM, Robert M. Lang <[email-masked]> wrote:

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-- 
Chuck Arnold and Kathleen Kelley

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