318 Buildup

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cosworth

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I have the original 318 from my 74 duster that had been partially freshened up when I purchased the car. Ive looked at doing a hemi swap and finally decided to mod the 318 and run with it.

Im going to use flat-top pistons and zerodeck the block, will most likely just upsize the valves in the head I have.

Problem is looking through mail order books such as summit/jegs I cannot for sure determine what aftermarket intakes will fit a 318 still using 318 heads. My stock manifold is a 2 barrel.

Any ideas?
 
Best thing to do would be to open the intake ports up to the 340/360 size. That way, you can run pretty much any intake manifold out there.
 
StrokerScamp said:
Best thing to do would be to open the intake ports up to the 340/360 size. That way, you can run pretty much any intake manifold out there.
Click to expand...

I think that would be mandatory to take advantage of the larger proposed valves.
 
Being new to these mopar engines i guess thats really what my question was. If there is a difference in intakes other than runner openings.
 
No difference, 318 and 340/360 are the same engines dimensions wise. Just the 340/360 has the larger ports and bigger bore. A 340/360 intake will bolt right to a 318 just the 318 intake ports are smaller but they can be opened up.

It might be cheaper just to get some 360 heads and put them on there instead of modifying the stock 318 heads. The 360 or 340 heads will bolt right on. They already have the larger ports and bigger valves so if you can find some just have them freshened. Since you are going to change pistons and have block zero decked you will still have good compression even with the larger chamber 360 head. The 302 head is also a good choice and can be picked up cheap.

Once a 318 has the better pistons, zero deck block, and 360 heads bolted on its basically a 340 with slightly smaller bore.
 
A regular Edelbrock Performer has 318 sized ports. As did the Edelbrock LD4B, and Holley Street Dominator (single plane). Any of these can be found used on the internet in the usual places.

A couple other questions about your build. Which flat top pistons? The KB167 has a taller compression height than other 318 replacement pistons. Zero decking with a regular 318 flat top would require a pretty healthy cut on the block. That will be expensive, and cause headaches with manifolds, pushrods, bolt length, etc... Upsize the valves? To what size? 1.88/1.60 is the size typical of 360 heads, and can be easily retrofitted. They will improve performance only IF the bowl area under the valve is opened up. If this is not done, little if any gain.

What about the rest of the car? Camshaft? To a certain extent, the heads should reflect the rest of the build and support future upgrades. 318 heads work really good on mild 318's, but if my goal was a 12 second street machine, I would skip them (and the rest of the 318).

Have you considered Magnum heads? There are some nice iron Magnum style replacement heads, which aren't too expensive compared to completely rebuilding and porting a set of 318 heads. Even junkyard Magnum heads are far better than all but the most radically ported 318 head. Plus a smaller more efficient chamber. You have to buy an intake anyhow...

Does the car run now? If so, consider building another engine while you continue to drive the car. This way you still have use of the car, can make other upgrades such as exhaust, rear end, transmission, suspension/brakes, etc... A junkyard builder isn't super expensive in the great scheme of things.
 
The cars not running right now its torn down. I have a 8.75 489 casting rear diff with suregrip and a 331 gear. Trans is a built 4 speed. Tubular front uppers with front and rear sway bars. Probably wont go all the way to 0 deck but plan on milling it to raise compression slightly. Looking at Voodoo cams right now but havent decided just yet.
 
If you get the right pistons you should only have to mill a little off the block to zero deck them. Look at compression height specs.
 
What about the 8007 Weiand Intake? I know some people like/them hate them. The one on a wornout 68 318 worked well with a 1406 Edelbrock.
 
That is an excellent intake for high performance 318. Use it. No worries.
 
I'd look into some Engine Quest Heads first. Stock heads for the 74' 318 aren't exactly "great". Using a 360/5.9L magnum with those heads, and you can be making 400hp+ for pretty cheap.
 
X2 with the KB167 pistons. I used them on my 318 with the 302 heads. I did not need to mill the deck at all and ended with a 9.5 compression. I am also using the Edlebrock RPM airgap intake.
 
Found a set of rebuilt 302 casting heads that came with the car. unfortunately looking closer my trans is a 3 speed.... so im in the market for a 4 speed......
 
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