Is valve seat recession fact or fiction?

[dibbons]

According did this short article, the writer/mechanic valve seat recession in classic and antique vehicles it is not common in the real world. Here is the link:

Unleaded gasoline and classic cars: A mechanic's viewpoint

 

[dibbons]

Hera's another article (from Great Britain, perhaps, we better take note of the mention of research octane numbers). Here is the link:

www.classiccars4sale.net/classic-car-how-to-guides/restoration/a-guide-to-unleaded-additives

 

[RustyRatRod]

It is solid fact. What's myth is what causes it. Valve seat and valve face recession is not caused by unleaded fuel. It is caused by dust and dirt being sucked into the engine and acting like a grinding agent on the valves and seats.

 

[brian6pac]

Old head with out hardened seat get the valves worn into heads mostly exhaust because lead is a lubricant and kept the head from wearing, with out lead they need hardened set to stay alive.

 

[pishta]

Here is another theory. The intense heat of the exhaust valve actually causes small bits of the seat to be welded to the valve, lifted out of the seat and blown out by the near supersonic escape velocity of the hot exhaust past the valve and this constant action digs the seat out like millions of tiny shovels...imagine that. The lead oxide produced by the leaded gas burning would coat the valve and seat, preventing this adhesion. Who cares....install hardened seats at $2.30 a piece next valve job.

 

[brian6pac]

I had a 340 W/X heads I put 10000 miles on and when I pulled it down for inspection the seats looked new. My theory on this is that I put a lead additive in every spring on the first tank, once the lead is pounded into the seat it takes a while to wear off. I put anywhere between 1000 to 3000 miles a year on it. In Ohio we don't have that many nice days to cruise.

 

[RustyRatRod]

The lead argument is funny to me, because valve seat recession has been around long before the elimination of lead from fuel. I have some OLD literature from the 1940s that tells all about it, its causes and its cures.

 

[MOPAROFFICIAL]

When I was 15 and built my first engine, which was a 225 slant 6 , New .030 pistons, deck milled, std crank polished....I had a good low mile head off a '69 motor and just ported it a lil and set up springs for the .460 lift purple cam I got for it as well as lapping the valves and milled .040 ...'no hard seats'....about 70k and 6 yrs later I pulled the head after numerous losenings of the exh rocker arms and later on, in general "poor running" , to not only address what I knew it was... but, also upgrade to bigger valves and more porting...as I expected the exhaust valves were all sunk a 1/4 of an inch.
I run hard seats , int & exh.
Lead additives did not work btw....
fuel changed, iron burns away...

 

[dibbons]

I guess from what I have read so far, a bracket car doesn't have to run hardened exhaust seats if the car is just driven to and from the track. Or let's just say they would be optional, not a bad idea but not a requirement.

 

[4spdragtop]

I asked my machinist about hardened exhaust seats in the 273 when the heads were off. He said dont bother if you are under 5000 miles a year.

 

[moper]

It's not fiction. It's also not an "every engine will have it" problem. I put unleaded exhaust seats in every time a valve job is done because it can be a big issue, and heavier springs and harder driving can exasperate it. Once those exhaust seats are in, there's no more worry or continued purchase of additives or special fuel. So the extra $50-$100 is well worth it at that time.

 

[Abodybomber]

The lead argument is funny to me, because valve seat recession has been around long before the elimination of lead from fuel. I have some OLD literature from the 1940s that tells all about it, its causes and its cures.

I remember posting those ,to someone...
A damn, good read...(maybe you_,I don't remember...) It's all about the suddenly'70's EPA reduction on leaded fuel" And Detroit's lazy ***,to respond....
I waa pumping leaded gas ,deep into '88 .in Cali.. It was, ****... The batch of unleaded premium was purple-reddish...,it had a RON rating,of 93 octane.. Of course,the liberals killed it.

 

[oldkimmer]

.............For very light duty driving u can get away with " unleaded " exhaust seats.......maybe...............kim.........