The Stovebolt Site Forums The Shop Area Engine Shop to lead or not to lead - that is the question

Hi All
I have recently acquired a 1955 C3100, 235 inline 6, first series that the owner I bought from said the engine was recently rebuilt by the previous owner.

I examined the engine and it is clean, has no leaks and starts right up and idles well, has no indication of blue smoke, etc. I have no indication it has not been rebuilt, although my spring tests will now also include compression tests and vacuum tests (Just got a compression gauge, dwell meter, etc. to work on her after getting rid of those tools years ago)

The owner I bought it from was able to answer all of my questions on the engine but one, and that was regarding if the 235 was rebuilt with hardened valve seats for unleaded gas. The person I bought it from did not know, but was otherwise quite knowledgeable on the engine, which was a bit surprising to me.

So, as it sits in my garage waiting for spring, I am wondering if I should take up adding lead substitute I see available in the auto stores to each tank of gas. If I assume the head was also rebuilt with the block, and both were done within the last 5 years or so (Owner I bought it from only had it 2 years), then I would guess the shop would add hardened seats as a matter of standard practice.

I cannot think of any way to tell if this is the case, so I am leaning towards adding lead substitute to each tank of gas as a precaution. I should add I will only be driving the truck a few thousand miles a year for enjoyment, not work or daily driver

I would appreciate opinions or advice here - any other way to check for hardened valve seats? — The previous owner, who did not put a significant amount of mileage on the rebuilt motor, said he ran without additive. I am concerned I will hammer the valve train if no lead is in the gas and no remedial action was taken on the original head and valve seats

thanks to all who respond

Joe

The prevailing opinion is that hardened seats are not needed for normal running/driving of the 216/235/261 engines.

The valve spring seating pressure on a stovebolt engine is so low, along with the moderate cruise RPM and type of use most of these old rigs get, that hard seats are not really necessary. Now, if you intend to run full throttle for miles at a time with max gross weight, that's a different matter. If you want to add a bit of lubricant to the valve guides, run a 5% mixture of Diesel fuel at every fill up- - - -1 gallon of Diesel to 19 gallons of gas.
Jerry

Hi HotRod andTClederman

Thanks for the info - the idea that hardened seats are not necessary did not occur to me

Not to highjack....but what opinion would y'all have on a 68 I-250? No idea on seats, but looks rebuilt. At least with a spray can. LOL

Larry W.

I've rebuilt several 230's and 250's with no problems, and no special attention was given to the valve seats. The hard seats and/or stainless exhaust valves are mostly needed for high performance or heavy duty applications. A good 3-angle valve job with the proper seat width will do more to assure a long-lasting cylinder head job than doing a lot of exotic machining. A good rule of thumb for exhaust valve seat width is .090", or 3/32" if you're using fractional measurements.
Jerry

The scare was that the valves would wear themselves into the head. I think it was Hotrod that did an article on hardened seats years and years ago, their conclusion as Jerry said, unless you are running at high RPM all day long (like going down the freeway across the country and/or pulling a good load) it will take years to sink the valves into the head, and even then, it was a heck of a lot of years, and they were talking about a V8 with a bigger cam and heavier springs than most of the stovebolts are running. I would not worry about it unless you are driving cross-country or putting 20-30K miles a year on it.

Never taken heads off to specifically install hardened seats. If I've taken the heads off for other reasons, such as valve/seal replacement, rebuild the engine, I've had hardened seats installed as well. Probably wasn't necessary. I've also heard that hardened seats can cause problems, have never experienced it.

Rick

Problems:
1. not enough press fit - the first time the motor gets really hot the seat drops out, valve comes adrift, hits piston, game over
2. too much press fit - head casting cracks
3. empty wallet

I agree, to many things can go wrong compared to what might happen. If this was a dump truck, then yes on hard seats. I don't like the idea of them getting loose, it may never happen, but if it does! It's a risk not worth taking unless it's a really rare head.

When I was drag racing, I ran the same heads for 14 years, 12.5-1 compression on Methanol, average 250 passes a year or more. The valves seats only needed cleaned up a couple of times in all that abuse, methanol is a very dry fuel with zero lead.

Joe