318 head on a 340

[moparmadman440]

Hey guys,

I have a quick question. I just picked up a set of 318 head(81 year casting) for a decent price. I want some J heads for my 340 but I am having a hard time finding some. Can some one tell me the pros and cons of putting these 318 heads on my 340. I was going to have them worked over and put some bigger valves in them. Thanks for any help!!

[rumblefish360]

This topic has come up before. Basicly, the ports are small. This will restrict the hi flow 340's like. If it's a stock app. no problem. Since your warming it up with bigger valves, flow will improve, but not like a 360 head would. (Apple to apple)
You also have to watch the cc's of the chamber. Some 340's had positive piston deck heights. The closed chambered 318 heads will hit the pistons.
Pick up a set of "J" heads from Aerohead. www.aeroheadracing.com $500 assembled, add $100 for "J" heads. They also offer head porting.

[moparmadman440]

thanks a bunch rumblefish, I knew I could count on some other dedicated mopar man to help me out. I thought that these heads would reduce the airflow but wasn't sure if it was just the valve size but also if it was the port size too. Thanks a bunch for the info.

[rumblefish360]

No problem dude.
The heads will reduce airflow. But, if it's just to get going or for a around town car, it'll do OK. The smaller ports will give up sooner than the bigger ports. This is easy to see. So, performance will suffer. That's why I gave the areohead url. Decent deal at a decent price.

[moparmadman440]

Hey rumblefish,

I tried that URL and it said "Coming Soon." I don't know if they just haven't finished the site or what. I may try and call them though. How much are "J" heads through them......... fully assembled.