Question-'318' Heads, Cam & Intake

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J

Jim Wyatt

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Have stock 70, 318, auto w/air. Was planning on replacing cam & lifters w/comp XE256H (256/268)(@50-212/218)lobe separation 110.0. Also, replace heads w/87-91(302 casting no.), and intake w/RPM air Gap or dual-plane performer?(have both). Will continue using Carter AFB Competition series (650 I think), and dual exhaust w/headers. Is this a waste of time? Will the heart shaped heads cause detonation problems on pump gas? Which intake will work best?

Thanks,
Jim Wyatt
 
The heads will help stop the detonation problems, and as long as it is going to be a street runner the mismatch on the heads and intake won't matter much. But I would use the performer instead of the air-gap. Just make sure that you use the 360 intake gaskets or you'll have a vacuum leak at the heads and intake manifold.
 
I agree on the Performer. The smaller runners will keep the velocity up and the throttle response crisp. The cam is a small one. You could step up if you wanted to. That one will perform well. The dual exhaust is an excellent idea with or without headers. The headers at this point will add some power.

The Comp series AFB is a 600 cfm carb and plenty for the task at hand.
 
Weiand makes a great Action Series manifold similar to the performer with the 318 size ports. Your combo sounds sound. Far better to have too little cam than too much on a 318... then there are 1.6 rockers.... :cheers:
 
BRG Racing:
I'm curious, why the 360 intake gasket on the 318 heads. Are the Edelbrock intakes designed for the 360. Yet, they work on a 318? Also, I assumed that the increase in compression, when using the newer heart shaped 302 heads... on a '70' 318 w/9.0 compression... would make detonation more likely. However, provided I understood correctly... You believe detonation would be less likely with 302 heads.

Thanks,
Jim Wyatt
 
Jim,
Because the ports in the intake manifold are the 340/360 size and would have a vacuum leak if the smaller 318 gaskets were used.
As for the chambers they are all about 60/62 cc's weather it would be the earlier or later heads. The chambers are more efficient than the older heads and are quenched where as the early versions aren't. With the heads being quenched this helps to stop detonation. The 302 heads won't like more than 30* total timing on the street with full exh. system.
 
BJR Racing:

Jack

Thanks for your time and information, As well as, to the others who also shared information with me.

I have replaced the heads and cam on this 318 before. I used a set of reconditioned X heads and went with a Mopar 340 cam. Most would probably know that isen't the best combination. At the time, I thought it was a good idea. As you can see, I decided to ask before I leap this time around.

Jim Wyatt
 
http://www.popularhotrodding.com/enginemasters/articles/mopar/0667em_mopar_318_engine/index.html
http://www.moparmusclemagazine.com/techarticles/mopp_0409_318_engine_build/index.html
http://www.moparmusclemagazine.com/techarticles/155_0312_318_long_block_bolt_ons/index.html
A few good articles to help you.
Late 70-80's 318 4V police engines used the 360 manifold, and sometimes the 360 heads with the 360 gaskets stock. The mismatch doesn't seem to hurt mild motors any, and sure does wake them up!

If you have to use a iron TQ manifold, the 71 model with the last three casting number digits 100 was the highest flowing stock version. Stock class racers used to pay extra for these. No EGR ports in the floor to disrupt flow. If I used a newer version, I'd find some way to remove the wierd thing that sticks 1.5 inches up from the floor, and plug/smooth the holes.
The Performer is a good choice, and also happens to be the only manifold I know of with the offset water neck, helpful if you want to use the late air conditioning compressor or are putting a motor into a late model car of truck. FYI.
Good luck, let us know how it comes out!
alan627b

alan627b
 
alan627b:

Thanks for the various reference articles. They point out several interesting options. Looks like I could be a little small on the cam. As was stated in reply #4... 1.6 rockers are available... should I decide I want more lift. At this point my car is more 'Show than Go', and I enjoy reliability with a modest MPG. After reading the articles, a few upgrades, or a 400HP '318', may very well be in my future.

Thanks again,
Jim Wyatt
 

I agree with the cam being to small. Go with a Xe262 or 268 from comp. Or get yourself a Voodoo. Can remember the number right now.
 
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