Can you put 340 heads on a 318? Any ideas about this?
340 heads are from a 68, 318 is a 74.

If the compression is stock the J-heads will kill the engine of low end performance unless you up the compression substantially.

if they are 340 J heads they are not from 68, late 70 & 71 used a J head w/ 2.02 intake valves later 340 used a J head w/1.88 intake valves as well as 360 engines which work very well on a 318

what's the difference in the CC's and the valve sizes between the 2

for LA's, stock 318's, save the 4bbl motors used 1.78/1.5" valves.

CC's ran from ~60-62 (early '920 castings, and 302 castings) to 66-68 (open chambered castings)

4bbl motors used 1.88/1.6 valve 360 heads, which ran ~ 72cc
"J" heads are essentially the same as the 360 heads on the 4bbl motors.

if the engine uses stock pistons, compression will be in the high 7's, low 8's. use KB167's, and your compression will be high 8's to ~9:1. if you use stock pistons, look for a short duration, high lift cam (lunati voodoo 40600 or 60401 would be my choice) and maybe install it an additional 2-4degrees advanced

yes you can... that's the fact, and don't need anything else to make them work. 4 bbls intake will be an extra "free" and easy bolt on point.

then if you want more, is the time to consider the rest of stuff around ( pistons, cam ), but strictly to the heads, is posible and definitelly a winning point

A 1968 340 head should be the "X" head with the 2.02" intake valves. They seem to have changed to the "O" head in 1970, but still had the 2.02" intake. Some "J" heads had the 2.02" intake, but most have the 1.88" intake. I used a set of 1.88" "J" heads on a 318 I put in my Dart about 25 years ago with the 340 cam. Ran pretty good. I ended up putting a 340 in it later, but used the same heads.

I did this to a '73 318:

Rebuilt junkyard 360 heads with the intake seat cut to 2.02".
Heads shaved .060" for compression.
'68 340 intake
TINY hydraulic cam- the smallest one PAW sold at the time.
Headers and a Holley 650.

REALLY woke that little 318 up!

Looking to do something nearly identical to what you did to your 318 ramrod. Did you do the work on the heads yourself? And did you do any port or finish work on the manifold?

my stock 88 360 headed 318 cop engine thats never been a part with about 190,000 miles sure woke up with the voodoo roller cam in my 85 truck

Ma Mopar did 360 heads for yrs on the 4-v 318s

600 cfm
LD4B
60710 lunati roller cam
258/264
207/213
.485/.485
comp 901-16 springs
all stock roller gear down to the 1.88/1.60 vales
headers/2.5 duals
904 high stall lock up TC
8 3/4-3.23 sg
29x15x15 M/Ts

gets 18 mpgs,merges with attude,runs triple didgets on the interstate and is a blast to drive now

not a lumpy racer but its sure better than any stock 318 anyday

I would run the 1.88 over 2/02 myself

unless your gonna rev the snot out of it

The heads were worked by a reputable shop about 25 years ago. I've used them on several engines and they STILL perform fine. Nothing special about them... No porting or even port matching. 360 smog heads from a junkyard. They had the cast bosses for air injection, but they werent drilled. There is a big bump in the exhaust port on these smog heads, you might could grind those out for increased flow on the exhaust side but I would ask one of the sharp cylinder head guys on the board first. The manifold is just a stock cast-iron 340 square bore piece, although I've read that those are very good manifolds.

Like scratchn said, the 1.88" might be better on the street. I frequently revved that little motor to 6500 RPM without a problem.

These days I would do a Magnum head.

you can remove the bump in the floor of the exhast port but its not needed

the floor is kinda a dead spot on flow,the roof and sides are whats worked,IIRC

I had a set of 587 heads with the bumps cast in but not machined for air injection, and they flowed better from about .400" and up than my 915 castings. These were used heads and no fresh valve jobs. About 10 cfm better at higher lifts. I seem to remember an article 30 years ago about a 360 SS Duster (Comstock?) running the 587 heads with the bump in the floor for better flow. I've heard the bump can be shaped for better flow. You'd have to get RyanJ or Brian (OU812) or somebody like that for details. I'm not a head porter. I pay those guys to do that stuff.

Some machinists do not like doing 915 castings as well as the later castings. They say that they cannot do as much with them as there is not enough meat to work with.

I would not do "just a head swap" just doing a head swap will hurt performance. Just look at the stock 4bbl motors they only made like 15 more HP AND they had a 800 cfm 4bbl instead of a 200 cfm 2bbl. The reason mopar did it was to keep NOX emmisions down and for no other reason.

On the other hand if you do something to dramatically get compression up a lot (like 3 points)then you can make more HP with the 360 head. Also putting larger valves PROPERLY will make more HP and will not hurt low RPM TQ. The only part of the port that has a significantly lower velovity with bigger valves is between the valve and valve seat, the rest of the port will see increased velocity because flow will be up INCLUDING low lift flow, low lift flow increases because for example at .2 lift and a 1.88 valve you have 1.18064 sq inches of opening around the valve but with a 2.02 valve you will have 1.26856 sq inches of area for air to flow through. The problem most people have when they increase valve size is they do not unshroud the valve in the chamber to match, just takes a few seconds with a grinder, another mistake is not opening up the bowl to match the increased seat size, any decent VJ will include this cut at no extra charge but it is suprising to me how many machinists do not do that cut.

Kool something i see that i have have the same year heads on the same block 318. I have 68 x heads on a 74 318 block. Im running in to some problems with my mopar. My are virgin heads someone told me just to sell them bec i would get a ton money and jsut put on 360 heads. But i should shave them down to 60 thousands? Mine sits in my drive in a 66 charger and it saids 125 or 120 per a clyiner is that normal? I should get higher if I shave them right and will help back flow? please help i goten far my project