x heads ona 318

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plumcrazy704406

plumcrazy704406

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Found a set of x heads, priced right, that I thought I would grab. Is there any advantage to putting these on a 318? heads are 69, block is 68.
 
yes....you will be able to run on the cheapest gas available cause your compression will be down around 7 to 1......

X..J heads on 318 will need to be milled a good deal to get the compression up if you have stock pistons in your 318...
 
AAActually, when you get to CC'ing, the X heads aren't much bigger than the newer 318 heads..........

I had an roller X head 318, with 9.5-1, 600 lift, it would build power past the limiter, set at 7500.....
Most say nahhh, I say, get em, build a 318 for RPM, and twist er up!
 
dodgetkboy78 said:
AAActually, when you get to CC'ing, the X heads aren't much bigger than the newer 318 heads..........

I had an roller X head 318, with 9.5-1, 600 lift, it would build power past the limiter, set at 7500.....
Most say nahhh, I say, get em, build a 318 for RPM, and twist er up!
Click to expand...


Yep, just have the heads milled .030
 
Actually you can cc several sets of sb heads and come up with different numbers each time. Varying quite a bit. My X heads when stock were 72 cc's. That was with no milling and stock valves.

How many cc's do the "newer" 318 heads generally run Bobby?
 
Most between the later 973 heads, and the 302 heads, run around 70cc..... My 302 heads on my truck were 61-66cc from chamber to chamber....

Been a long time, but I think I remember my 894 heads being around 68-71.

Of course, when building something for power, all my chambers end up being the same size as the largest chamber in all 8.... Just logic, right?

So, really, IMO, your not losing much compression going from a mid 70's 318, to a 894 head, because the later 318's were made to have lower comression, and the 894 head was made for a high compression engine.

eh??

Only drawback for the big port heads, is the loss of torque, and it's pretty noticeable when running in a heavier car, or low stall tc/high gear ratio type deal.

I still say run it!!!!!
 
I should add, with a smallish cam, the loss of torque isn't as noticiable as it would be with a larger cam, compared to say, the longer stroke 360. And, because the heads breath better, and the valves are bigger, even with a smallish cam, the power band will be higher on a 318 than a 360 with the same same, or a 318 with small port heads.

So really, in the end, as a whole, with a mildish street 318, you get too keep kinda the same power down low, and add, sayyyyyy, 1500rpm to the top end.

Really not a bad deal, if you know how to tune for big port heads.
 
dodgetkboy78 said:
Most between the later 973 heads, and the 302 heads, run around 70cc..... My 302 heads on my truck were 61-66cc from chamber to chamber....

Been a long time, but I think I remember my 894 heads being around 68-71.

Of course, when building something for power, all my chambers end up being the same size as the largest chamber in all 8.... Just logic, right?

So, really, IMO, your not losing much compression going from a mid 70's 318, to a 894 head, because the later 318's were made to have lower comression, and the 894 head was made for a high compression engine.

eh??

Only drawback for the big port heads, is the loss of torque, and it's pretty noticeable when running in a heavier car, or low stall tc/high gear ratio type deal.

I still say run it!!!!!
Click to expand...

Not positive but I think the 894's stopped in 70 then it was on to the 915's. Seems the information is sketchy at best. No biggie though as they are nearly identical heads anyway (valve size considered).

I have never cc'd any 318 heads. Just always took everybodies word that the chambers are smaller so you loose compression going to 360 heads. You shed new light on the subject with your findings. Back in my early days of wrenching I knew nothing about different chamber sizes and replaced the heads on a buddies 78 318 with some heads (587's I think) off my old 360 and it ran much better. Take off was about the same but top end was a ton better. This was in a short bed pickup so it wasn't super heavy.
 
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