There is usually a lot of "bench racing" associated with building a Triumph engine.
Which pistons, what camshafts, etc... However there has always been an ongoing debate over the weight of internal parts and how much that matters.
Pushrod material and weight have been the subject of much speculation over the years, mainly steel versus aluminum. Finally the verdict is in, and now the answer is...BOTH!
I know that seems ridiculous, but studies of engines on dynos have convinced even the most stubborn engine guy that weight is not as important as how stiff and straight the pushrod is. Performance builders usually hate adding weight to parts, as the added mass increases the spring pressure needed to control the valvetrain. However, the stability of a stout pushrod is a welcome improvement to any Triumph engine, and a small amount of added weight will not limit rpm or hurt performance in any way.
My favorite pushrods have always been the Kibblewhite tubular alloy type for Triumph, and I have used them in every type of 650 engine, street, race, and restoration. Compared to the spindly, small diameter Triumph pushrods it seems like an obvious upgrade. The stock pushrods are solid aluminum with steel ends, and are almost guaranteed to flex at low and moderate RPM. ( The pressed on ends have also been known to come loose...yuck. ) Pushrod flex reduces valve lift and can also lead to cam and tappet damage.
Some of my friends have touted the benefits of Chromium Molybdenum steel (aka Chrome Moly or Chromoly) pushrods and I would usually point out how heavy steel pushrods usually are. (I have seen custom steel pushrods that one weighed as much as an entire set of four stock Triumph OEM). Most of these custom pushrods are made by automotive manufacturers so what is lightweight to them is heavy to us. Now I can fully endorse the ChroMoly, as the engineers at Kibblewhite have thoughtfully solved this problem.
A real solution
Newly available are Chrome Moly pushrods for 650 and 750 Triumph twins. These were designed with light weight in mind, and are made to the same exacting standards as their popular aluminum racing pushrods.
||WEIGHT (each)||PART NUMBER|
|Triumph 650 OEM alloy||24.6 grams||70-2620 or E2620|
|Kibblewhite 650 alloy||17.4 grams||70-0301 aluminum|
|Kibblewhite 650 Chrome Moly||34.2 grams||70-0301 chrome moly|
|Smith Bros 650 Chrome Moly||52.5 grams||(custom)|
Now even those who have an aversion to Chrome Moly pushrods can now choose one that is incredibly strong, while still maintaining light weight.
If you prefer the tubular aluminum ultra light pushrods, get them while you can as they are being phased out and stock is limited.
Many races have been won, and countless land speed records were set using the aluminum Kibblewhite pushrods. They have become the standard of performance worldwide. Now that standard of excellence has been improved and these light Chrome Moly pushrods will soon be the choice of restorers, racers, and builders everywhere.