360 heads to 318 block

[68Roadrunner]

Hi all, doing some upgrades to my 318 motor. Have a pair of 360 heads with standard rocker gear, edelbrock performer hydraulic cam and lifters, and edelbrock performer inlet manifold,and timing chain, all taken from a running 360 motor. I can't think of any reason why it won't all just bolt on to the 318 with no issues, but thought I would ask the question as I seem to recall hearing about having to skim the heads 60 thou, ( possible port match the inlet) and the need for adjustable rocker gear. Greatful for your relplies. Richard.

[DaveBishop]

yep you have to skim 60 thou and the inlet face as well but I cant remember how much. done this 40 years ago so my memory play tricks with me. I had a racer brown cam set that came with adjustable push rods. I remember buying them all from Garry's Shack in Battersea

[MilesnMiles]

Dave's right on the heads, but there more to consider. If you've already bought the cam and inlet my points won't help much,but..
The Performer inlet has the smaller 318 ports which from memory are much smaller than the 360 ports so somewhat wasting the new heads.
The other point is that there are much better cams like the Comp XE 262 or 268 grinds. I've used both on 318/360 motors and they work with stock converter but will make more power than the Performer cam.
At the risk of spending all your money, a higher comp set of pistons would really work well with those heads. 318 are low comp motors and those heads will have combustion chambers measuring 68-72cc which will impact on the compression.

Ps. Just re read your post. Not using the whole 360 motor instead?

[Blue]

Yep 60 thou. off the face and the corresponding amount off the intake face. dunno what machining prices are like in your neck of the woods but round here you'd be looking at several hundred pounds to get that done. You'll need adjustable rocker gear and pushrods as well. As Miles says check the manifold port size, not all are 340/360 sized.

[68Roadrunner]

well I have checked the inlet port size on the heads and the inlet manifold and they are both exactly the same 55mm x 25mm. the manifold is an edelbrock performer rpm, dual plane part no EDL-7176. edelbrock website recommends camshaft part no 7177 (PERFORMER RPM), which I have and matching timing gear (performer link true roller set 7803 (also have) and the valve springs (edelbrock 5777) are matched for the cam...

so are we saying that if you bolted some stock 360 heads to this inlet and then tried to fit it to the 318 block , the head bolts wont line up, thus needing to remove 60thou? also still don't understand why my set up would need mechanical rocker gear, when all this worked ok on the 360 motor. For all I know the heads may of already been skimmed and matched to the inlet?
miles I was planning on using the 360 block I have but its cracked, hence me wanting to try and utilise all the other bits it came with. blue cylinder head resurfacing up here is £25
waiting to be educated fellas, cheers Richard.

[DaveBishop]

you need to remove 60 thou because the heads are open chamber and the compression will be to low if you don't ( Unless they are swirl port) if you take 60 thou of the face then you have to have the inlet side milled so that you can fit the manifold bolts as they wont line up (done it found out the hard way) You have to either have adjustable rockers or push rods because after you mill the heads the original push rods are to long. Hope this helps

[MilesnMiles]

Ok , you have the Performer rpm which as you note does fit the 340/360'ports which helps.
Hi comp pistons and no need to skim anything. Might actually be cheaper to do Hi comp pistons and really gain some power.

[DaveBishop]

As Miles said

[68Roadrunner]

Right we're getting somewhere now.
1 so the heads will bolt on, but doing the machining work is really to increase the CR.
What make , and part no piston would you sujjest , and what compression ratio would It give.
What do we think of the spec of the cam I have ,or would it be better to replace .
Lastly (no machining work and new high comp pistons) could I keep the standard rocker gear.
Thanks for the info guys, better to have a plan now. Richard.ðŸ‘￾😀

[DaveBishop]

Hi compression pistons and you don't have to change anything else (couldn't get hi compression pistons when I did mine in the 1970s unless you had lots of money)

[Blue]

I'd be aiming for around 10 to 10.5 compression. You'd need to find a 318 piston that would give you that with the larger cc of the 360 head if such a thing exsists.
Ideally you'd want a flat top piston at zero deck rather than something with a raised dome. 30 thou. Quench is optimum for detonation prevention which is why you want zero deck and a flat top is best for flame travel which is important when the plug is off to one side. often to achieve all this you need to mill the head to get the correct compression ratio.
The Hughes website lists a good selection of pistons with the specs which is handy for working things out.

You thought this was going to be easy didn't you.....

[MilesnMiles]

http://www.campbellenterprises.com/pist ... istons.php

All there. Stock pistons about half way down the page. Note the compression ratios relative to the combustion chamber. I'd cc the 360 heads as they really do range broadly. Don't be surprised if, without skimming they're at 70-72cc.

[68Roadrunner]

Thanks for all this info fellas, kb hyper pistons look promising, will measure the chambers miles. I knew it wouldn't be easy blue