Exhaust valve rotators

Propane, Butane, LPG, GPL, C3H8, C4H10
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Exhaust valve rotators

Post by Oddy » Wed Feb 07, 2018 1:40 pm

Should I keep or remove the exhaust valve rotators on my chevy 350 heads for propane? They are stainless valves with stock hardened seats.

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Re: Exhaust valve rotators

Post by C3H8 » Thu Feb 08, 2018 2:59 pm

Keep them. Back in the pre-unleaded days it was controversial. Ford said disable them and did so on all the 429 F700 and F800 trucks. I believe they continued to do this even after unleaded came to market. Chrysler and GM said keep them. After unleaded our company went right to the source and asked all the manufacturers which of their engines would be compatible with LPG without any modifications. GM said the 350 among others was compatible straight from the factory for LPG and NG. They emphasized the 350 as being the most compatible. They even stated that there was no difference between the factory LPG unit they produced in 1984 and the gasoline engine. The 350 was one of the few engines we were very confident in converting without recommending any mods. Disabling the rotators will lead to valve guide wear. If there is any wear on the valve at all it will begin applying pressure sideways on the guide. Keeping the rotators will give even uniform wear. Although no one can guarantee long life it was common to see 350's go 300,000 to 500,000 and never be opened. We successfully converted 350's up until 1997 when it began to be replaced with the 5.3 and 6.0L engines which began to give us intake valve problems at first. later on these engines gave erratic results with the flex fuel engine having the best success.

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Re: Exhaust valve rotators

Post by storm » Thu Feb 08, 2018 9:30 pm

Just to add to what C3H8 has said I'll say "keep them" as well.

Why? well simply because during normal engine operation valves, especially exhaust valves, go through a continuous process of "mini" welds between the valve and valve seat. Each time the "weld" occurs it is broken by the valve reopening but if the valve does not rotate the "weld" has a much greater chance of landing back in its original position which makes the next "weld" event easier. This can, and eventually does, lead to valve and valve seat deterioration. Anything that can help keep the valve from landing in the same spot helps limit deterioration and therefore prolongs valve and valve seat life.
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