The engine shop guy in one of Mike Bender's videos said hardened valve seats are necessary with the modern fuels. Is that correct? I thought the ethanol mixtures burn at a lower temperature.
I was under the impression that it is the lack of lead in the gas that causes the need for hardened seats. Lead is like a cushion in there.
It's my understanding that Lonnie is correct. However, it must be remembered that our T's were made before lead was added to gasoline, therefore hardened valve seats are unnecessary. They were originally designed to run on "unleaded" gas.
At least that's what I've read.
One of my favorite ridiculous ads of recent years was for a Model T "remachined to run on unleaded fuel". Tetraehtyl lead was just being introduced as the last Model T's were being made. It's very simple. The Model T was designed to run on unleaded gas because that's all there was. Rebuilding a T engine may include new valve seats, but it's because the old ones are too far gone, not because of the fuel.
If you are rebuilding your engine then hardened valve seats and modern valves such as Chevrolet 350 valves are a good idea. If you have the engine in the car, then recutting the seats and replacing the valves with the stainless steel Model T valves would be about as good as you can do and will work just fine. Royce Peterson is an advocate of using Fordson tractor valves which are a touch larger with larger stem diameter. The larger head size allows you to recut the seats in the block at a larger diameter and keeps them from being cut so deeply in the block.
I'm always a little concerned about seat inserts. Being of a different material to the block they will expand (and contract) at different rates as the engine heats and cools. This will set up stress patterns in the block but how much of a problem this really is I'm not sure. I tend to replace the seats if they need replacing but don't routinely replace them when I do the engine. So far seems to work out ok for me -Karl
The problem would be soft valve seats with a high compression engine which runs much hotter than the Model T. The leaded gas was necessary to raise the octaine to prevent pre-ignition and burning of the valves. With a low compression engine such as a standard Model T engine, you do not need to worry. However the harder seats and new harder valves will last a lot longer without doing a valve job.
One advantage of having hardened valve seats installed is the new valves will set high in the compression chamber. This allows the valves to breath better and provided a little more compression compared to sunken valves. Using hardened valve seats with 350 Chevrolet exhaust valves = No more burned valves.
Spray some WD40 around the top of each valve while pushing it closed and blowing compressed air in each intake/exhaust port will tell you if the valve is properly seated. If you see air bubbles in the oil around the valve seat....time to lap the valve in.
There is one risk in fitting valve seats, seat to large or bore to big or both, giving a thinner line of block between seat and piston. end result is the risk of a hot spot, warping the block. This block is now egg shaped around the valve seat on the piston side, can fit a several thou feeler gauge down the side.
I said it before to use a shop vac on the ports and
light oil around the valve and watch for leaks.
Next no lead / lead is a myth. Think of whats
worse a flathead Briggs lawnmower maxed out all
day ? Counter bore the block; seats in the freezer
warm the block and bang them in. Then we true the
seats with a seat grinder (just nip em) next some
bluing on the seats and check valve. Then almost
impossible to lap stainless valves that venders
sell now but will lap the seats. And then way back
believe it or not we used common cast iron pipe
and machined valve seats. That was before we had
all these venders now a days. Easy part is the
set up on a mill is pretty easy with inline 4&6's
compaired to a V block.
The the major advantages of hardened valve seats being installed in a rebuild, is that they restore the valves closer to spec. after years of use and the seats getting recessed. They definitely hold up better in the long run than seats cut in the block. It is definitely a job for a machinist though. So, if you're sending in your block for a complete rebuild, it sort of makes sense to spend a little extra and invest in hardened seats and maybe valve guides or oversized stems.
This has been kicked around for years. If you drive your T as much as you drive your modern car that may be a reason to have hardened valve seats.
And that's with putting a lot of miles on the engine.
The average T doesn't come anywhere near that.
When I fix engines and am having any engine work done in a machine shop, I always go for hardend seats. It really is quite inexpensive and at the mileage done in most Ts, will last forever... Generally the existing seats have sunk in. Bruce use to lay a valve on the block with the head In the valve hole. If the stem touched the block near the valve head, then the block needed new seats. These day I just have hardend seats installed.
Given the strength of Model T valve springs, I wouldn't bother, unless the seat was beat out so bad it needed replacing anyway. I certainly wouldn't do it out of fear of unleaded gas.
We always install new seats on the engine rebuilds as most all of the engines we see original valve seat is just a memory after 100 years.
It not for the unleaded fuel it's the fact that the block seats are no longer serviceable.
machined clear through to china.
Langs have an over size modern valve with a head diameter of 1.543" I haven't tried them yet but have put some in stock, for those seats only half way to China.
When inserting a valve seat into the block (or a head) it creates a mechanical interface (not molecular) between to metal surfaces. this is an impediment to heat transfer. The rule of thumb is that about 80% of the heat that goes into the exhaust valve from the hot gases, is transferred out of the valve through the valve seat and eventually into water. The impeded heat flow causes the valve to run about 100 degrees hotter, again a rule of thumb, and probably varies a lot from engine to engine. This causes more heat to run down the stem to be dissipated through the valve guide, and it it can cause faster guide wear.
I wonder how many decades damage like that would become noticeable to where there should be a repair made.
We have been using hard seats in all blocks, and heads long before unleaded gas.
Never had to do any valve and seat repairs on any rebuild in 48 years.
On a Model T the first thing that happens is the cheap valve will start burning, that is what takes a cast iron valve seat.
With hard seats, if a cheap valve burns, the seat is most time saved, with little, or no touch up.