Valve guide Inserts

[eestatic]

Starting the rebuild process on my '74 318:

What is preference of materials of choice for valve guides & why, please, for a mild 318 rebuild.

The machine shop says they use a "steel/alloy"? guide and I've read where "bronze" guides are used by people on this forum.

Am I misreading something?

The shop mentioned something like..."The harder ones were easier to work with"..?

Are they talking about using bronze guides?


Thanks













;

 

[txstang84]

Unless I've misunderstood things told to me in the past, steel guides are easier to install/finish machine because they're harder material than bronze. They're also more wear resistant and cost less to install. Bronze is popular because they require less direct lubrication...perhaps it was only urban legend, but I have heard tale of machinists ganking up bronze guides during installation because it's a softer material...probably just a tall tale though.

 

[eestatic]

The machine shop expressed hesitancy and the word "bronze/brass" and said they preferred the steel/alloy ones for ease of install/quality of workmanship.

 

[txstang84]

That would be the deal then...they probably don't want to risk damaging the guides during install.

 

[moper]

It's more a question of performance. It's not brass - it's bronze. Bronze guides wear similarly, but run a tighter valve to guide clearance which means a truer motion of the valve, a more stable closing action (less bounce), and a more immediate sealing of the cylinder. The valve closing is like dropping a ball into a funnel. If you were to drop it perfectly centered, it wouldhit and stick in place, sealing the funnel. If you drop it off-center it will bounce around until gravity pulls it down tight. The more guide clearance, the more the valve is "off center" when it goes to open and close. So you lose a tiny amount of lift, and when it closes it doesn't seal immediately. So - it's always bronze for me. Honestly and in my opinion - if your machinist is worried about screwing up a bronze guide - move on. He's not worth your time and can't do quality performance work.

 

[txstang84]

Thanks for the elaboration moper

 

[skrews]

Honestly and in my opinion - if your machinist is worried about screwing up a bronze guide - move on. He's not worth your time and can't do quality performance work.

Quoted for the truth.

 

[eestatic]

It's more a question of performance. It's not brass - it's bronze. Bronze guides wear similarly, but run a tighter valve to guide clearance which means a truer motion of the valve, a more stable closing action (less bounce), and a more immediate sealing of the cylinder. The valve closing is like dropping a ball into a funnel. If you were to drop it perfectly centered, it wouldhit and stick in place, sealing the funnel. If you drop it off-center it will bounce around until gravity pulls it down tight. The more guide clearance, the more the valve is "off center" when it goes to open and close. So you lose a tiny amount of lift, and when it closes it doesn't seal immediately. So - it's always bronze for me. Honestly and in my opinion - if your machinist is worried about screwing up a bronze guide - move on. He's not worth your time and can't do quality performance work.

On "todays" modern engines, what type of valve guide is used?

 

[RustyRatRod]

I agree 100% on moper's post, it is a good one too. There is one drawback though that's not been touched on with bronze guides and here it is. Their only drawback, if there is one is, they cannot stand any oil starvation whatsoever. They are totally non forgiving. If you have an oil shortage upstairs, or even if the engine overheats in some cases, bronze guides or liners can seize to the valves and ruin your day. So, again I'll reiterate moper's point. If your machinist seems skeered of bronze guides or liners, it might be time to run the other way.

Lastly, I will say this. Most street engines will probably never see a benefit from bronze guides or liners. But, even so, they still an improvement over stock ones. That said, stock guides are all I will probably ever run, unless one day I am lucky enough to be able to afford some aluminum heads.

 

[perfacar]

hi, if you run sst valves, you will need bronze liners or guides. bronze guides are the best way to prolong wear. we've ran bronze liners in a motor 12 years, had very little wear. running tighter clearances are the key.seats were still good.