302 v 587 heads on a 318 and porting question

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qwk dust

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I have posted a few posts about our plan to build an ~400 hp 318. KB167 pistons at .030, a fairly stout cam etc and then going with 3.91 gears linked to a 904 with an appropriate torque converter.

I lucked on a set of 302 casting heads for $100 that had already been refurbished and are in excellent shape but have stock 178/150 valves. I plan on having 1.88/1.60s installed and I want to do the gasket and intake ports myself along with some radius work. I have never ported before so I decided to get some other heads to practice on. I got a pair of 587 heads in good shape for $75. Of course they already have the valves I want. I bet it is cheaper to have the machine work on these done since I wouldn't be increasing the valve size but I think the 302s with the valve job and porting would be better hp and compression choice.

Before I start practicing on these 587s, Am I making the right decision? We want a 10 to 1 motor and with the KB167s I think it would be easier with the 302s and a lot less milling of the heads....Maybe the cost will even out..302's need new bigger valves and less milling....587s don't need as much valve work but more milling.... Help me make sure I am practicing on the right heads! thx
 
Hold on now. I'm not up on the combo of parts here. The 360 head could be used as is and do well over the time and effort of porting a 302 head out. The milling is alot easier to do/have done.

I'd just want to know what the cam size and intended purpose of the car/engine build is.

If I was hittin the cam kind of hard, the 360 heads may be a cheaper alternative and still a decent performer.
 
At 400 HP you need the bigger port of the 340/360 heads. The small ports are great for throttle response and low end torque on the street, but will only flow enough to support 300-325 HP. Besides low end torque really won't apply to a 400 HP 318 anyhow.
 
C130 Chief said:
At 400 HP you need the bigger port of the 340/360 heads. / Besides low end torque really won't apply to a 400 HP 318 anyhow.
Click to expand...

LOL, I'm with that. Even more so when you have a high stall conveter and decent gears to get going.
 
What we are looking at is very similar to this build..
http://www.hotrod.com/howto/113_0304_318_small_block_build/index.html
They seemed to get the 302s to flow really well with that combo but we are also going to use the KB167 pistons so that extent of milling the heads to get the compression ratio we want would not be necessary.

The other option is outlined here but it sure looks like a ton of work to those heads in order to get the compression up and to get the intake to fit properly. There is also a question of valve train geometry with that much milling isn't there??
http://www.popularhotrodding.com/enginemasters/articles/mopar/0667em_mopar_318_engine/index.html
 
I'm with the guys that the 587's will flow more than the 302's in stock form. But (and this is just my opinion) to get to 400 hp on a 318 you'll still need to work on the 587's to get them to flow more. I'm not positive on the chamber size of a 302 but I think it's a few cc's smaller than the 587's so like you guessed you'll need to mill them to get the comp up. How much I'm not sure. I do know that if you replace the valves in the 587's with some good performance stainless valves that will also raise the compression because the head of the performance valve is pretty much flat and takes up some cc's. I found that out on my heads. Swapping the valves dropped the chamber size by 4 cc's. An advantage of the 302 heads are the closed chambers. They will allow more compression without detonation and don't need a ton of milling to get the compression up. But as far as milling the heads affecting the valve train geometry the only mod needed would be shorter pushrods. To sum it up each head has it's good points and bad points. You just have to weigh them and decide.

BTW: Here's a good thread by BJR that gives allot of good info on heads.

http://www.forabodiesonly.com/mopar/showthread.php?t=7733
 
One of the main advantages of oversized valves is that bieng larger in diameter, you can set them up higher in their seats. This will help with a head where the original seats have been resurfaced a couple times and the valves sit a little low. This will help low lift flow a lot making the "effective duration" of your cam longer. You'll get more out of a milder cam this way. Setting the valves higher on their seats reduces chamber size slightly, and nailhead type valves help that even more (as well as low lift flow). As for a 1.88 vs a 2.02, in a 318 you'll probably never notice a big difference as the small bore creates a shrouding issue which wipes out any advantage the larger valve might have provided. Personally, I'd run 360 style heads with 1.88/1.60's; backcut on the valve and a basic bowl clean-up. Mill to raise compression or consider a SMALL dome piston.
 
qd,
Had a nice chat with you this evening and hope that it helps you and your nephew out. Call anytime you need as I'm always here for helping folks out that need clairity in there builds, and the best part is it's FREE. Now how can anyone beat that.
 

Bobby, Thanks for the time! I enjoyed learning some more about head and motor building theory. My nephew gets back from his spring break vacation this week end and we are going to sit down and try to make some more decisions. Thanks again. Skip
 
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