Are hardened valve seats really needed?

The need for installing hardened valve seats when rebuilding 59 Pontiac heads has been the subject of debate for some time.   While it certainly is not a bad idea there are a number of people who insist that if it is not done you can expect to have problems with burnt valves due to lack of lead and other additives in modern fuels.  

It is my understanding based on what I have read in the Smoke Signals and talking to many other classic car owners that hardened valve seats are NOT required unless you plan to drive your engine HARD.   Examples of hard driving would include such activities as regular use at the drag strip and hauling a trailer.    However for the vast majority of us who only drive our classic cars to the occasional weekend car show or to Grandma's house on Sunday, the extra cost of installing hardened valves seats is a waste of our limited money that could be much better spent elsewhere.

In addition, I had the engine and heads rebuilt on my 59 Bonneville several years ago.   The gentleman who rebuilt the engine for me (who is a professional mechanic and owns a number of high performance Pontiacs) told me not to waste my money on hardened valve seats.  I took his advise and now after several thousand miles my engine runs fine with no valve problems.

To answer this question once and for all I recently contacted Rick Gonzer who is the POCI tech advisor for 1959 Pontiacs.  I asked him if I needed to install hardened valve seats in my 59 Pontiac engine given that the car is used only for pleasure driving with no racing or trailer hauling.   This is Ricks reply:

"THAT'S PRETTY MUCH TRUE.  I NEVER ADD HARDENED SEATS TO MY EARLY HEADS,
BECAUSE IT'S NOT REALLY REQUIRED, REGARDLESS OF TODAY'S SHIT-CAN GAS..."

"THE ONLY TIME I WOULD EVER CONSIDER IT WOULD BE FOR A PAIR OF
LARGE-VALVE, LOW PRODUCTION HEADS (1967-UP), SUCH AS -13 OR -12 RA IIIs..."

So again the overwhelming evidence accumulated after many years of unleaded gas usage clearly shows that while hardened valve are important for performance race engines, or for heavy hauling duty where the engine is under a constant load, they are NOT needed for the vast majority of classic cars that see only occasional pleasure driving.  Spend your money on re-chroming or paint instead.

Don, we're just going to have to agree to disagree. My past experience working in a professional speed shop where we tore down engines and did all the machine work in-house is contrary to what you're being told.

I agree with your statement "they are NOT needed for the vast majority of classic cars that see only occasional pleasure driving" where occasionally means less than 3000 miles a year.

I also agree that they are a must if you intend to do any regular towing or are building a high performance engine.

Where we disagree is when the car is used on a regular basis. In this case you really should install hardened valve seats for the exhaust valves at least. I'll explain why.

In the mid 70's they started making heads using induction hardening so these heads had hardened valve seats straight from the manufacturer and the lack of leaded fuel wasn't an issue for these heads.

The old cast heads, like those used in our 59's, were soft compared to late model heads. Lead acts like a cushion which helped to significantly reduce the wear on the soft valve seats. Remove the lead and your seats will wear much quicker than normal. Most experts say you'll start to see the effects in about 20,000 to 30,000 miles. One of the first signs is a loss in vacuum, rough idle, or uneven vacuum readings.

Lead also helped prevent buildup on the valve seats and the valve head. A lot of the wear and tear is due to material sticking to the stock valves causing an uneven surface on the valve head which in turn causes the seats to wear faster.

Valves rotate ever so slightly as the engine runs. If material sticks to the valve head, as the valve turns it will eventually leave a very small open gap when the valve closes. This gap is what causes the seat to become pitted. Each time the engine fires while that small gap is open, you do additional damage to the valve seats.

If you rebuild your heads and use new valves you may see the effects sooner. I say may because there are 2 factors at play here. Newer valves are harder that the stock valves in our cars. Since the valve seats are soft and you've removed the cushion that lead provides, the seats can wear faster. However, since the new valves are harder it is more difficult for material to stick to the valve head which is what causes pitting in the valve seats. So when running unleaded fuel in our cars, newer valves will wear the valve seats faster but you are less likely to have pitting occur with newer valves.

I'm a firm beleiver that "if you got it, flaunt it". I think these beauties should be out on the street showin' their stuff. Personally, before I fell on hard times, my '59 was my primary driver in the summer months. I put well over 10,000 miles per year on her 3 years in a row including a few cross country trips. I have close to 45,000 on the car since I rebuilt the heads, and I still have the same vacuum readings I had the day after the overhaul. When I rebuilt my heads I put hardened seats in for both intake and exhaust valves and I have no regrets. It was well worth the extra cost.

I like your comment to agree we disagree and just leave it at that.   Thanks for sharing your opinion.  We all are in this together and love classic cars (especially 59 Pontiacs) which is what is important.  On another subject I purchased a Magic Cruise last month online that was complete except for missing the control knob.   It turns out the knob is unique as the design looks just like all the other knobs on the 59 dash except for having an arrow to indicate ON or OFF.   This month I found the correct knob for sale online and just purchased it!   What are the odds of that happening before the internet!    The modern computer and internet age has certainly been a boom for the classic car hobby.  This website is another example of where we can share our ideas and communicate in a way not possible just 15 years ago!

I also built engines and I agree with Michayos.
Even if I drove a lot with a 55 Belair original without problem.

Whaou Don !!! It is you who this famous button magi-cruise ... it happened under my nose!
The world is really small on Ebay !!!

Don…..good find on the Magi-Cruise. I purchased a complete accessory kit a couple years ago. It had a plain knob that matched the rest of our dash controls. I also have seen two variations of it. One was an arrow with a head and shaft, and the other was a triangle that covered most of the knob face, with one of the points to indicate off and on. Pontiac marketed the Magi-Cruise from 1959 to about 1963 or 1964, and never changed the shape of the knob to match the different shapes in later years. There were subtle differences in the upper edges of the chrome housing to accommodate the later dash shapes, but not the knob.

I've installed mine, but haven't connected it mechanically. One of my many projects for next winter is to transform it from a throttle hold to an actual stealth cruise control.

Just to weigh in on the valve seat question, I had mine done because it was only an additional $120 during a needed complete engine overhaul. I probably would not have had it done otherwise. I agree that the limited use our cars see (I'm lucky to put 500-600 miles a year on it,) would take a long time to develop valve recession in the heads. Hard use however, such as normal daily driving or serious power increases will accelerate the process. Finally, I consider myself just the caretaker of this car. It's comforting to know that it has been rebuilt to last, and I shouldn't have to do it over for that……John

Thanks for the info on the Magic Cruise knob John.    I didn't know there were so many variations on the knob design!   I attended a BOP show here in the LA area last weekend and spoke with Dan Santoro who has a magic cruise on his 59 Bonneville.  His knob has the black arrow on it the same as the one I bought.   I would post a picture if I knew how to do it.