Budget cylinder heads for a 318
Not saying port volume velocity etc.. ain't important. But most are not gonna port and or go with the perfect port size flow etc.. for application especially for a smaller displacement. To me say were looking to get 350 hp out of stock 318 heads we'd be talking probably about at least 10:1 cr and 230 degree cam but with say speedmaster heads you would be able to do it with a lot less cam and cr and would be the more streetable package, to me that's why factory does it this way especially with modern engines like LS and hemi lots of cfm and small cams to make reasonable power, cause making power through head flow is more streetable than larger cams. To a 318 with speedmaster heads would be like starting with a 5.3l LS short block and why put money into 318 heads ?
Just pretend I'm drinking a beer and rambling off my thoughts on it...cause I am.:D
I see your point. LS have a better port, its tall n skinny and velocity is abundant flowing 300's cfm vs sheistmaster.
I threw bait out there for the age old debate if when everyone used to say NOT to use 360 heads. "Kills the bottom end"
"kills the cyl pressure"
And so
[email protected]@.300
Why am I picking .300 lift?
Because it's a real good indicator of how well the head will do on average and the valve spends a good amount of time there x2 compared to peak. Ok...
So...Now its let's put some sheistmaster 170's something cc ports on that do
[email protected] as well... see?
Now I went with 175 on the j head.1.88 though I've seen a few more on 2.02 version. You get a 65cc chamber, or 68cc after minor seat blending and a new valve job.. that's stock 675 318@68cc
..but back to the comparison..The sheistmasters need a valve job to flow any better till .475- .500 lift. Yes they do 240's ootb..but lag below that and run with a regular iron head that is less port/more velocity.
Yes you can use'em, have the valve job fixed. Would it show a difference in the low end and over all snap of the throttle and any rpm..I believe it would.
Its basic.
2 ports...
One 15cc bigger than the factory designed port.
If both flow near the same, which makes more power?
Which would put you back in your seat more?
It's not always the cheaper route and not always the way to go..
But imo it's the truth. 160cc is already a jump from 125cc and I have ported a lot of 318 heads to 360 flow numbers and ridden in the cars that have'em. They amazingly pull hard @132-134cc port
[email protected] [email protected] [email protected].
There is a close relation to rpm/cid with port volume when it comes to efficiency and torque.
