Lead Fuel

[JHolslin]

I am dealing with a new project. 73 400 magnum.
will I need to run a Lead supplement or is this motor good to go??

[b5blue]

It "should" have 343 heads, they have the exhaust valve seats induction hardened. If they have not been cut quite a bit they could still be good to go. I ran a set of 343's for several years with no problems. (Check the casting # under the valve covers.)

[Kern Dog]

I'm pretty sure that the casting number is # 346.

[John_Kunkel]

The 346 heads have induction-hardened exhaust seats.

[myk]

I thought lead additives didn't work anyway?

[Kern Dog]

by 1972, the automakers were already expecting the lead in gasoline to be phased out. Compression ratios had dropped by 2 points in the 440!

[crj1968]

In my 30+ years of driving  I've never experienced any valve issues with unleaded gas in older engines.   

[ws23rt]

In my 30+ years of driving  I've never experienced any valve issues with unleaded gas in older engines.   

I also have experienced no valve issues with my old cars running on unleaded gas.

Maybe problems will only show up with extreme driving conditions?

[crj1968]

In my 30+ years of driving  I've never experienced any valve issues with unleaded gas in older engines.   

I also have experienced no valve issues with my old cars running on unleaded gas.

Maybe problems will only show up with extreme driving conditions?

Interesting perspective on the subject...

https://www.bellperformance.com/blog/bid/127758/Unleaded-gasoline-and-classic-cars-A-mechanic-s-viewpoint

[myk]

Well if that article is correct then the edict of having to change valve seats for unleaded fuel in older cars is now one of the biggest wive's tales that I've ever heard of...

[Pete in NH]

I've owned my 71 since it was new. In the mid 70's as the lead went away the 383 developed three burned exhaust valves. I was living in New Jersey at the time and making frequent trips to New Hampshire. The Charger had done that trip for many years without any problems but, when the lead went away those six hour highway trips were too much for the valves. when I pulled the heads the valves were clearly burnt and there were signs of seat regression. Fortunately, Chrysler had later heads for big block engines with hard seats and I built up a set of heads from those newer castings. These are still on the car today with no issues.

From my experience induction hardened  seats needed the lead for lubrication and cooling.

[John_Kunkel]

Maybe problems will only show up with extreme driving conditions?

Even the factory acknowledged no problems except in performance applications.

[b5blue]

yea 346, 343 a typo on my part. 

[JHolslin]

Im a new Mopar guy, so I should be able to see that Number casted in the head?

[Just 6T9 CHGR]

Im a new Mopar guy, so I should be able to see that Number casted in the head?

Yes...under valve cover...last 3 digits of part number

[JHolslin]

Awesome!! Thanks everybody!