Briggs valve train question

[Knots]

Does anyone know why Briggs Intek engines use one steel pushrod and one aluminum one? Is it to keep the valve train balanced? The aluminum pushrod is paired with the larger (intake) valve. Or does it have to do with thermal issues?
Just wondering. Seems strange.
Thanks,
Knots

 

[Scrubcadet10]

Stealing this from Bertsmobile1

In theory, the alloy rod will expand at the same rate as the alloy block so the valve lash remains constant.
2nd reason is to reduce the inertia but that should not be a problem sub 4000rpm, sort of becomes important at 9000 rpm.
More of the mowers I service have used exhaust pushrods from old dead engines on the inlets than the original alloy ones.

Using steel lift rods instead of aluminum

Hey all, I have a broken intake pushrod with my Intek/Briggs&Stratton 331777. About 2 years ago I blew the head gasket. I fixed it and all was well until about 2 weeks ago when aluminum intake rod broke in half. I took off the head and pull the pushrod out, which had broken right in half...

www.lawnmowerforum.com

 

[rgrottk]

Does anyone know why Briggs Intek engines use one steel pushrod and one aluminum one? Is it to keep the valve train balanced? The aluminum pushrod is paired with the larger (intake) valve. Or does it have to do with thermal issues?
Just wondering. Seems strange.
Thanks,
Knots

To the best of my knowledge this is do to HEAT. The aluminum is always intake no heat and the exhaust is Steel lots of heat.

 

[VRR.DYNDNS>BIZ]

To the best of my knowledge this is do to HEAT. The aluminum is always intake no heat and the exhaust is Steel lots of heat.

rate of growth due to heat causes valve lash settings changes. Exhaust is hotter, steel expands less than aluminum.

 

[7394]

yep