Using steel lift rods instead of aluminum

Michael_Gee · Jul 4, 2017

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. Everything looks good and value seats are fine so I was just going to order another lift rod BUT then I watched this (https://youtu.be/NM28FSoUGLQ?t=8m36s). He replaced the intake aluminum rod with a exhaust steel rod for added strength. I also thought this might be a good idea since maybe the steel would only bend next time (and you know there will probably be a next time with these engines) and not break in half like the aluminum. When it broke in half I was a bit worried that a piece might end up in the crankcase where with the steel, this chances of this happening might be lessened.
Other than maybe added cost, I can't see why Briggs & Stratton would not go with all steel pushrods but this also seems to be the norm with everything I've seen.

Anyone have any insite into this metal choice as well as any concerns with me doing this?

Thanks in advance,
Michael

Tinkerer200 · Jul 4, 2017

There has been a lot of discussion about the aluminum push rod. B&S uses aluminum push rods on the rocker arm which is operating the valve involved in compression release. This is NOT for cost reasons. The Intake valve on Intek and the Exhaust valve on V twin Vanguards. Several have used steel as replacement with no apparent problem. HOWEVER, if you broke a push rod in the middle then the problem was not strength. Most likely you will find that the valve guide has moved up and is hitting the valve spring keeper. IF the pushrod didn't break, something else would, usually the rocker arm.

The cause of this is usually a cooling problem, plugged cooling fins and or cooling shroud. The guide should not extend more than 1/8" above the head casting. B&S says the only fix for that condition is a new head. I have a fix however which has been used by dozens over the last several years.

Walt Conner
wconner5 at frontier dot com

bertsmobile1 · Jul 4, 2017

Michael_Gee said:
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. Everything looks good and value seats are fine so I was just going to order another lift rod BUT then I watched this (https://youtu.be/NM28FSoUGLQ?t=8m36s). He replaced the intake aluminum rod with a exhaust steel rod for added strength. I also thought this might be a good idea since maybe the steel would only bend next time (and you know there will probably be a next time with these engines) and not break in half like the aluminum. When it broke in half I was a bit worried that a piece might end up in the crankcase where with the steel, this chances of this happening might be lessened.
Other than maybe added cost, I can't see why Briggs & Stratton would not go with all steel pushrods but this also seems to be the norm with everything I've seen.

Anyone have any insite into this metal choice as well as any concerns with me doing this?

Thanks in advance,
Michael

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.

Michael_Gee · Jul 4, 2017

Really good info. So, follow up.

Cost: Good to know. Just an assumption. I've seen too many little cost saving measures.
Heat: Fins were pretty clean and engine had the right amount of oil.
Guide height: So, from what I found online, which I can't say is definitive, looking inside the valve chamber the valve guides aren't sunken. I have calipers so I can measure that but I figured an image might show more (See attached images)
I have a fix: What's the fix? I saw that you can pin the valve guide but I also here that's a temporary solution.

Tinkerer200 · Jul 5, 2017

First, my fix is permanent.
Second, if your valve guide hasn't moved, you don't need it.
Third, fix is too long to post here, my address was in previous post.

Walt Conner

Michael_Gee · Jul 6, 2017

Tinkerer200 said:
First, my fix is permanent.
Second, if your valve guide hasn't moved, you don't need it.
Third, fix is too long to post here, my address was in previous post.

Walt Conner

So, from the looks for the image I supplied, does it look like it's moved? The only reference I have is that video I provided a link to.

ILENGINE · Jul 7, 2017

Your valve guide position is fine. Most that I see you can't compress the valve spring enough to get the keepers off the valve without pressing the valve and guide back down into the head. Normally seen on twins more than singles. Usually it will bend the pushrod not break it. Most of the broken aluminum push rods I see that break are due to the rod guide plate wearing a groove into the pushrod on the single cylinder engines.

Michael_Gee · Jul 7, 2017

ILENGINE said:
Your valve guide position is fine. Most that I see you can't compress the valve spring enough to get the keepers off the valve without pressing the valve and guide back down into the head. Normally seen on twins more than singles. Usually it will bend the pushrod not break it. Most of the broken aluminum push rods I see that break are due to the rod guide plate wearing a groove into the pushrod on the single cylinder engines.

Great and thanks for verifying that. You just saved me a whole bunch of money. ?
I'll get those parts ordered right away. It'll be nice not to have to use my backup walk behind anymore.

CaptFerd · Jul 21, 2018

On some models they get rubbed and worn by a plastic bushing or guide they go through and break. Also wear from the cam, lifters, rockers, valves and so on will increase the tappet gap causing the push rods fall out then break or bend and sometimes fall down into the motor. Most engines recommend adjusting them ever so often because of this. My personal opinion is it saves the manufacturer millions to do this and that's the only logical reason for it. I put steel back in and have never had an issue or a return because of it.

Tinkerer200 said:
First, my fix is permanent.
Second, if your valve guide hasn't moved, you don't need it.
Third, fix is too long to post here, my address was in previous post.

Walt Conner

Walt conner is a cocky one with a fix for anything posting his bs on multiple sites. Never a solution you gots to email him. Whats up with that. collecting mail addresses are we?

bertsmobile1 said:
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.

bertsmobile1 - What lawnmower engine revs at 4000 and 9000 RPMs. Dang thats a serious high revving motor. I want one

Tinkerer200 · Jul 21, 2018

"Walt conner is a cocky one with a fix for anything posting his bs on multiple sites. Never a solution you gots to email him. Whats up with that. collecting mail addresses are we? "

I sure have no use for your email address or any ones and don't ask me for any of my fixes which do work. Ask bert or any of the people with some knowledge whether they work or not. If you don't know what you are talking about save the space for someone who does.

The reason I ask to contact me directly is clearly stated plus it keeps know nothings from interrupting things, ring a bell?

Walt Conner

Using steel lift rods instead of aluminum

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