340 Heads Flow Rate

[70 Challenger Lover]

Where are you guys finding the 308 heads? For years they have been recommended and for years I have been looking but I've never found any. I don't have the patience anymore for scouring junk yards. I check the spring and fall flings all the time as well but nothing.

What's the complete casting number?

[kawahonda]

I'll have mid 90s 5.9 heads for sale soon w/ ~100,000 miles on them.

[70 Challenger Lover]

If they have the 308 casting number, let's talk when you're ready to part with them. I have a 340 in waiting.

[Chryco Psycho]

I cannot remmeber the whole casting # but it was 5554308 or close to that

[erik70rt]

Sorry for the typo/confusion.   They end in 587

[Bullitt-]

Has anyone tried ordering re-manufactured 308 heads?

I looked up a few sources, Autozone lists & give re-manufacturer as Surefire at 1-800-790-9094 
Looked on Rockauto & price is significantly lower, $257.79ea including core & shows the same picture BUT shows "out of stock" so can't order online
https://www.rockauto.com/en/moreinfo.php?pk=3754311&cc=1086094&jsn=591
Summitt shows them under a different brand but uses the same part # 2D44 $432ea including core
https://www.summitracing.com/parts/vre-2d44/overview/make/dodge

[erik70rt]

I see the summit heads are the 308 heads and at a good price.  I assume they come with 1.88 intake valves standard.   Will they flow well with the 1.88 or should they be reworked for the 2.02?

[70 Challenger Lover]

I book marked them. Thanks for finding them. Had no idea Summit would carry them. So digging through my stuff, I came across another set of clean bare J heads. Has anyone been able to test these 308 heads against stock J heads to verify there really is a performance difference?

[bennydodge]

I'd be curious to know as well. I think the exhaust side is much better than the J head, although I've never seen a direct comparison. Maybe someone will chime in.

[bennydodge]

http://www.users.interport.net/s/r/srweiss/tablehdc.htm#Chrysler

Lots of Chrysler cylinder head info here.

[gzig5]

Not a huge difference in flow rates but the 308 head has a smaller closed combustion chamber than the 915 J head that I think will boost compression and get a better burn = more power, all else being equal.  If you are paying 600-1000 dollars to have a set of iron 308s ported, I think you'd be silly not to put a 2.02 intake valve in.  They are still way behind the potential of an Edelbrock/SpeedMaster/ProMaxx/TrickFlow aluminum head though.

[70 Challenger Lover]

If this is in fact the 308 head and it looks like it is, that appears to be open chambers rather than closed. The overall CC could be less though which would offer an in crease in compression ratio. Anyone have specifics of ccs of the 308 chambers compared to the older J heads? Or some sort of Dyno figures between the two?

[1 Wild R/T]

This is a 302 head, baby brother to the 308... They share the same combustion chamber...

[erik70rt]

http://www.users.interport.net/s/r/srweiss/tablehdc.htm#Chrysler

Lots of Chrysler cylinder head info here.

That chart is great!  But I didn't see a ported 308 with 2.02 intake valves.  Any idea on the flow of that setup?