I read a couple of comments on this forum the other day that surprised me. A discussion came up about hardening valve seats during the engine rebuild process. Several members commented that it was unneccessary and potentially a problem maker. I always understood that this process was essentially required during the rebuild of an older engine to accomadate the lack of lead in current gasoline.

Having just had this process done during a recent engine rebuild, I am now concerned that I did the wrong thing. Can someone please enlighten me?

Randy

 

There will be better people than me reply to this but at one time I thought as you did. I feel like this is a matter of what you will use the engine for. If it is a weekend cruiser you will never hurt them. I had several well named engine builders say it is a wast of money and not worth the risk to change them if that is the only reason. If you will drive it daily long distances it may be another story but not many of these engines are used like that any more.

I know there are threads on this but would like to hear more recent thoughts on this also.

 

I have heard the same thing. If it's just a cruiser, not necessary, if it sees a lot of highway or many miles a year, need to do it. My thought would be if you are rebuilding the engine, it'd be cheap insurance to just do it (that way you don't have to worry about how much you use it), but if that is the only reason you are going to open up your engine, not worth it. My $.02

 

Both of my machinists have only seen Chevy's sink the seats on unleaded fuel

 

My '72 was the only car i owned from 1993-2001 and put about an additional 120,000 miles on it during that period. Engine was pulled in 2005 and rebuilt. Valve seat recession = NONE.

 

72 350s w 7a heads had induction hardened valve seats from the factory FYI

i would assume the 455 (dont know the head G or Ga maybe) had the same thing

 

Well aware of that. Induction hardness supposedly only goes approximately .030 deep, so i'm not sure how effective it still is after the two valve jobs these 269,000 mile heads have had.

 

LOL Ok after a single VJ I would assume its gone

 

I recall reading an article somewhere that said the government did a study of valve seat wear when lead was being phase out of gas. I guess they were concerned about all the government engines needing valve work quickly. If I recall it was decided that unless the engine was used at high rpm and under a heavy load that valve seat wear wasn't a problem. I don't remember where I read that, or if it was a magazine or Internet talk. Lead has been gone from gas for about 30 years now, I haven't heard of too many valve seat issues from untouched heads. However, I have personally seen valve seat fall out of heads that have been "upgraded". I'm sure the skill and quality of the machinist and materials needs to be considered. I'm sure there are many machinist and shops that have the skill to install hardened seat correctly. Obviously the people who did these heads didn't.

 

i just had my motor done by a very reputable machinist in Houston, recogmended to me by another member here.
He said it was a waste of money unless i plan to drive the car everyday/put alot of miles on it/ or race it. My old seats (67 400/442) were in good shape and took a valve job very nice. The odometer only shows 52,000 mi. and after opening up the motor and disassembling the car more and more, i believe the milage is true. It still had the nylon cam gear in it.