***valves, heads, exhaust seats,...***

So I noticed that some other people were advised to change out his exhaust seats and valves to cope with unleaded gas. I'm pretty sure that I want to do the same for my 255 merc motor, but I'm wondering if at that point, should I just have the motor rebuilt??? Is it possible and/or even worth it to swap the valves and exhaust seats out without rebuilduing the motor??? I've never replaced either of those parts so I don't know how to do it or how difficult it is. Also, I was eventually planning on upgrading my intake manifold and heads. I wanted to slap on a set offenhauser heads, but I'm not sure if they will work if I'm running a stock bore and stroke. I know that edelbrock makes heads that will work with a stock set up, but I'm not sure if I want to go that route. As far as the intake manifold, I want to go with a Baron racing PM-7 Thikstun dual intake manifold with two stomberg 97s(http://www.baronracingequipment.com/...lManifold.htm). Does anyone know if that combination of the baron intake maifold and offy heads will work well with a stock long block? I guess that my goal for right now is just to pep up the asthetics in the motor compartment and I'm not building a race motor wich is why I'm slightly reluctant to start throwing together parts that I'm not sure will work well together. Any advice would be appreciated. Thanks!

i'll get the valve seats question for you... its a questionable thing i've ran soft seats and never had any problems, the lead was used as somewhat of a cushion for the valve seat to keep it from being damaged, it also kept the octane higher to reduce pinging... thats why a lot of the high performance setups in the 60s run like crap on todays gas, the lowest octane then is higher than our highest octane now. if you were to do a full rebuild i'd say go for it.... if you were going to have head work done, i'd say go for it..... but for the time being until you are going to be doing something anyways leave it..... just make sure to run the higher octane fuels and if you can find it, run lead additive every few tanks....... having hardened seats done is generally expensive, most shops will charge you around $400 to change your seats.... and the labor is whats expensive the seats them selves run under $2 a piece... i dont know about your heads to intake question though, i'd check what port volume is on the intake runners on the heads and the intake, if they're close then they can be compatable......

I just called today about having the seats done on a 6cyl. $15 per valve and then it was like 5 per seat, and there were a couple other costs, and the final bill would be $325

It's a little different with a flathead, the valves are in the block. So, is you were to do hard seats, you'd probably want to go ahead and do the bottom end as well. I mean, the motor's out of the car, so why not. I also have run soft seats on unleaded and you can get away with it for a while. In the end though, the valves will recede into the block and you're done.

I never fully understood how the valve recession thing worked until I read the explanation by Mr. Bob Parmenter. As I recall it, it is as follows:

When welding, you must have both surfaces to be joined together completely clean and free of foreign materials so that you get a good joint. If the joint is dirty, you can't weld it very well. That is what tetraethyl lead did for the motor. I dirtied up the joint between the valve and seat so that no welding could take place, because that is exactly what is happening in a motor running on unleaded. There is no foreign material in the fuel like there was in the earlier fuels using lead, so every time the valve seats itself, a little spot of weld takes place. Then, when the valve opens, that small piece of weld is torn from the valve seat and recession of the seat begins.

The other thing tetraethyl lead did was to place foreign material into the fuel/air mixture. This foreign material resisted burning and so slowed down the "explosion" initiated by the spark plug. With a slower "booooooooooom" instead of a "BOOM", the fuel was more detonation resistant. The speed of the burn can be likened to a football team. If the ball runner (the initial flame kernel) can travel down the field without encountering members of the opposing team, he can reach the other end of the field in short order. But, if there are foreign materials in the fuel/air mix (people trying to tackle him), he must bob and weave and that slows him down in getting to the goal. This explanation is perhaps too elementary, but it should give you an idea of what is going on inside the motor with unleaded versus leaded fuels.

yup.... the lead additive would be the cheapest way to run for a while, problem is its getting harder and harder to find lead additives, i dont know about other states but in california its nearly impossible because of the EPA

Thanks for the info everyone! Is there anywhere online that I can find the lead additive??? What company makes it???

i'm not even sure who makes the additives anymore.... i haven't seen it on the shelf here for at least 5 years but as i said california is much stricter on everything..... i think berrymans was selling it last time i checked.... you might also want to see if lucas makes one.... some of them are not actual lead additive but just something to substitute the lead

I think the main company that makes it is Stewart Warner ( yes the gauge company ), they sell it under diffrent brands. I have a bottle that came in my '51 Chevy. can't remember what brand it is, but it has the SW logo on the back and says produced by Stewart Warner.