ryan1964
Well-Known Member
Ok so I'm build a 318 stock bore flat top pistons new bottom end either a 454 lift cam or a 480 lift summit grind 4 speed is putting 360 J heads on it going to help it or hurt it
318 build
- Thread starter ryan1964
- Start date
-
Flat top as in stock or (near) zero deck aftermarket ? Hopefully the second one.
What rear gears ?
Got links to the cams or just copy paste their specs here.
Mopar44134
Well-Known Member
Switching to 360 typically drops compression a point or more. Older 318s were higher in compression. Cleaning up the ports on the 318 would be ideal rather than giving up compression.
You can mill the 360 heads by like .030-.040" I forget exactly and keep at least stock cr.
It’s not that simple. What you have to do is cc the combustion chamber of the head your using and cc the bore with the pistons your going to use at top dead center and figure your compression ratio that is your static compression ratio. Then with that AND your cam specs go to wallace racing calculators and figure out your dynamic compression ratio.
7:1=super doggy
8:1=still doggy
9:1=you will end up wanting more
10:1=now your getting somewhere
11:1=you better have an awesome engine
Builder and a spot on tune cause
Your coming into detonation
territory with pump gas.
Now to answer your question what year 318 and what heads does it have now?
7:1=super doggy
8:1=still doggy
9:1=you will end up wanting more
10:1=now your getting somewhere
11:1=you better have an awesome engine
Builder and a spot on tune cause
Your coming into detonation
territory with pump gas.
Now to answer your question what year 318 and what heads does it have now?
ryan1964
Well-Known Member
1970 and pretty close to zero deck
junkyardhero
Well-Known Member
junkyardhero
Well-Known Member
post up some cam #'s and let's see what's what.
with a 318 i'd err toward the smaller cam, especially if you don't have the compression, gears or stall to back it up.
shorter duration and tighter LSA with an early IVC will keep what little dynamic compression you have.
i see 480 lift which makes me think you're looking at a popular 480/280 cam, which is really what you don't want for a 318 unless you're pressing at a true 10:1 and backing it with a 4spd or a decent amount of stall.
with a 318 i'd err toward the smaller cam, especially if you don't have the compression, gears or stall to back it up.
shorter duration and tighter LSA with an early IVC will keep what little dynamic compression you have.
i see 480 lift which makes me think you're looking at a popular 480/280 cam, which is really what you don't want for a 318 unless you're pressing at a true 10:1 and backing it with a 4spd or a decent amount of stall.
I sure someone could come up with one since it’s almost a certainty that someone is gonna say go with a 360don't you have a formula for that?
junkyardhero
Well-Known Member
first person to mention going with a 360 gets pistol whipped.
*taps ear piece*
oh. uh huh. okay, well looks like we have a winner.
*taps ear piece*
oh. uh huh. okay, well looks like we have a winner.
PRH
Well-Known Member
I’d have to hear a realistic assessment of what the finished result is hoped to be before recommending 318 or 360 heads.
The milder the combo, the more I’d lean towards staying with the 318 heads.
I know of a few 318’s where 360 heads got swapped onto them, without the details being sorted out, that ended up pretty doggy.
The milder the combo, the more I’d lean towards staying with the 318 heads.
I know of a few 318’s where 360 heads got swapped onto them, without the details being sorted out, that ended up pretty doggy.
And the heads are? 675?
remytherat
Well-Known Member
Did it myself bigger cam then that 2.02 j heads stock stall 3.23s torker door stop tuned 650 dp the flow out weighed the comp loss
Later added spray won more money then the car and all the parts cost
That said the smaller cam will be better
ryan1964
Well-Known Member
Professor Fate
Push the button, Max...
OP, until you tell us what you want to end up with and then can give us a decent measurement of how far in the hole your pistons are (so we know what we're dealing with), all you're going to get is a bunch of people shooting blanks in the dark with no target to aim at. Just meaningless answers.
"Pretty close to zero deck" is so subjective, it could mean a quarter inch in the hole. What exactly do you want out of the motor when you're done?
"Pretty close to zero deck" is so subjective, it could mean a quarter inch in the hole. What exactly do you want out of the motor when you're done?
If it's apart can always take some off the deck also.
Dan the man
Well-Known Member
This most likely will stir up a hornet's nest. I wouldn't put 360 heads on a mild 318 build. In order for the 318 to fully benefit from the larger ports and valves of the 360 heads the 318 needs to spin 6,000 plus rpm's. The cam that the op listed most likely doesn't have this rpm capability and he didn't mention which intake manifold that he's using. If he's going for street performance I think that he would be better off with the cylinder heads he has now and clean up the bowl area, good competition valve job. Guys say that the heads can be milled 0.040" to help with the compression loss,and some have suggested to run aftermarket pistons at zero deck height, this could require a cut of 0.012". All of the 318's that I've dealt with had blind cylinder head bolt holes, so with a total of 0.052" being removed wouldn't this cause the cylinder head bolts to be " to short"? I've known guys personally that have ran 360 heads on their 318's only to hurt performance. And don't forget that the intake side of the heads have to be machined as well in order to maintain proper port alignment. Attention to every aspect of the build has to be taken into consideration.
Dan the man
Well-Known Member
For the cylinder head bolts I meant to long.
-
