E-body engine questions...

[eventhorizon]

Hi, I'm new here and have a couple questions.  When was the last year for the 340 and when did Mopar change to unleaded gas for it's engines?

[AprilsPink72Cuda]

Welcome to the forum.  I just wanted to let you know that I am moving your post to our engine section.  I hope you enjoy the site, and please introduce yourself in the Newbie's section!  By the way, do you have a Mopar?

[Pistol Gripper]

The last year for the 340 was 1973.  As for unleaded, I'm not sure about Chrysler specifically, but in 1973 they started reducing the amount of lead in gasoline and in 1975, when catalytic converters were used, unleaded was mandatory.

P.G.

[MEK-Dangerfield]

As I recall, there was low-lead, then no-lead gas. I think the no lead was probably manditory by 1975. 

  Mike

[kudakidd]

Some engines were prepped to run unleaded in 1971, the rest soon followed. 1973 was the last yr for 340's

[Street_Challenged73]

I'd have to agree with Kudakidd's response.  From my knowledge, I believe the 340's from '72 onward had hardened exhaust valve seats to accept unleaded fuel, as they knew the conversion to unleaded fuel was soon to follow in the next couple years.  They used the same heads as the 360's that were used throughout the '70s, so I'm pretty solid with my somewhat educated answer.

[Chryco Psycho]

on the big blocks the only heads with hardened seats are the 452 casting which was first used in 75