CUDACOX
Well-Known Member
O.K. I know it most likely has been asked 1000 times,but here goes 1001! What years are the good 318 heads to use for a nice small block build? I have been told to use the 308's instead of my J's. Thanks in advance:salute:
308/318 Heads
- Thread starter CUDACOX
- Start date
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308's were made from '89-91, but they came on 360's not 318's.
But here's the thing, if you're building a 318 they may not be what you're looking for. 308's are open chamber heads (just like the J's), usually with a chamber of 65-72 cc's. They do flow better on the exhaust side than the J's or X's, but not enough really to warrant changing over from a set of J's if you already have them. Better to spend the money having a little clean up work done on the ports of the J's rather than starting over.
302's were made from '85-89. They came on 318's, and a are a closed chamber head (usually around 62cc's). They have the redesigned exhaust port, but they also have the smaller 318 ports. Better quench, but if you're building a high powered 318 the ports will be on the small side. Depends on your build, if you're only looking for 1hp per cube or so they'll work fine with larger valves and keep your port velocities up.
Magnum heads are the best of both worlds, they have a closed chamber design with the larger 360 ports, and flow well for an OE head. Not the best for port work, but if your intent is to make <400 hp they work good in stock form and come with 1.92/1.62 valves, so they can save you some money there over having a set of 308's or 302's opened up. Of course, they do require you to run a magnum intake, rocker set up, and oil through lifters and pushrods on an LA engine.
Next step would be the Indy/RHS X heads. For the price they're awesome, cheaper than doing a Stage 2 or 3 port on a set of J's or 308's, and pretty close to as much flow straight out of the box. But probably not necessary unless you're looking for around 400hp or more, and if you're building a 318 that would be a pretty hot build.
But here's the thing, if you're building a 318 they may not be what you're looking for. 308's are open chamber heads (just like the J's), usually with a chamber of 65-72 cc's. They do flow better on the exhaust side than the J's or X's, but not enough really to warrant changing over from a set of J's if you already have them. Better to spend the money having a little clean up work done on the ports of the J's rather than starting over.
302's were made from '85-89. They came on 318's, and a are a closed chamber head (usually around 62cc's). They have the redesigned exhaust port, but they also have the smaller 318 ports. Better quench, but if you're building a high powered 318 the ports will be on the small side. Depends on your build, if you're only looking for 1hp per cube or so they'll work fine with larger valves and keep your port velocities up.
Magnum heads are the best of both worlds, they have a closed chamber design with the larger 360 ports, and flow well for an OE head. Not the best for port work, but if your intent is to make <400 hp they work good in stock form and come with 1.92/1.62 valves, so they can save you some money there over having a set of 308's or 302's opened up. Of course, they do require you to run a magnum intake, rocker set up, and oil through lifters and pushrods on an LA engine.
Next step would be the Indy/RHS X heads. For the price they're awesome, cheaper than doing a Stage 2 or 3 port on a set of J's or 308's, and pretty close to as much flow straight out of the box. But probably not necessary unless you're looking for around 400hp or more, and if you're building a 318 that would be a pretty hot build.
theres a guy that has athread on 308 s here http://www.forabodiesonly.com/mopar/showthread.php?t=221217 the flow #s are darn near as good as my cnc ported eddys
CUDACOX
Well-Known Member
** I'm building a 318/390 stroker.
Title of tread say 308/318 heads....one would assume that you were building a 318....
and if you are building a 390....a 318 head is not a good choice at all..your J heads would be better then any 318 head
might want to update title
and if you are building a 390....a 318 head is not a good choice at all..your J heads would be better then any 318 head
might want to update title
So rule out the 302's. Even the stock J's or 308's are going to be your limiting factor for making power on a 390, you're going to have a hard time getting over 400 hp with any stock head even with the big valves.
I've got a set of ported 308's that flowed 264cfm @ .500", so you can get great flow out of them, but after porting, opening up the valves, milling etc the cost was pretty much the same as buying a brand new set of Indy/RHS X-heads with all the goodies, and those will flow just as much, if not a bit more, than my ported heads straight out of the box, AND get you a closed chamber head AND still have more room for porting.
I think that for any of the stroker engines now, even a 390, your best bet is a set of aftermarket heads. The cost has come down to the point that by the time you've fully rebuilt, ported, and bought all the necessary goodies for a OE head you could have bought an aftermarket head with all the goodies already on it that will match or outflow the ported OE head.
CUDACOX
Well-Known Member
Thanks.
MOPAROFFICIAL
Oogliboogli
Actually 302 heads were cast first in 1984 , came on roller blocks also first cast in 1984.
308 cast first in 1988 for roller 360 block first cast also in 1984.
The 302 head is 64cc Stock
The 308 is 72 cc Stock.
The 302 head is the worst flowing head of all 318 heads as cast. It also has the smallest intake port @119cc
The 308 intake port is the same as a J intake port and has improved exh ports.
I’m not gonna argue model year stuff, obviously stuff gets cast well before it hits the line and the next model year cars are built for like 5 months in the prior calendar year and those years I listed are just general model year ranges from the internet anyway.
Factory head CC’s vary quite a bit with all that stuff, my 308’s were uncut and ~65cc’s as cast, but most are probably closer to 72cc.
With all the aftermarket heads available now and the price of then I don’t think I’d even bother rebuilding a set of used factory heads anyway. After I had the 308’s checked for cracks, larger valves installed, ported and cleaned up I had as much or more money into them than what it would cost to buy an aftermarket set of heads and have them checked. Only way factory heads are worth it is if they’re required for your class or if you’re doing all the work yourself. Beyond that your money ahead with aftermarket heads and saving weight too. That was true 10 years ago when this thread was originally posted, and if anything it’s more true now with all the new cylinder head offerings that have happened since then.
MOPAROFFICIAL
Oogliboogli
There isn't a production 308 head that ever came 65cc on any engine, in any car , truck or van.
Happy Anniversary! 
Your faith in Ma Mopar’s production tolerances are completely unfounded. There’s a reason why pretty much all of the information out there says they were 65-72cc’s and mostly on the larger end of that range.
And I didn’t say they were supposed to be 65cc’s. I said the ones I have were in fact CC’d at ~65cc’s pretty much across the board for the pair and I’m fairly certain they were uncut when I got them. After some light bowl work was done after they were opened up to 2.02/1.60” valves they were closer to 66-67cc’s, which I personally verified, before having them surfaced back to 65cc’s to true them up a bit, which I also verified.
But hey, maybe I got the only pair of 308’s that were ever 65cc’s. Believe what you want, I honestly don’t give a crap. Saying every 308 head that was ever manufactured was exactly 72cc’s is just silly given the production tolerances on those heads. Certainly they weren’t all 65cc’s either, but there was definitely a fairly generous range.
CUDACOX
Well-Known Member
Wow! I forgot about this post! totally went aluminum heads,,,,, etc,, etc.. very happy with my little 318/390.
Nice! Yeah I dunno why it came back. I can say if I was gonna do it again I’d go aluminum heads and not look back!
Nice thread dig up. 10 YO thread! Whoa! LOL!
Good added information for sure. Good to re read this stuff.
Good added information for sure. Good to re read this stuff.
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