318 Build Combo Critique

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JGC403

JGC403

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I picked up a 318 block last weekend that I want to build for the Duster. I wanted to build a hot little 318. Duster is a 4 speed manual car, manual brakes, manual steering, rear end is a 3.23 right now would like to put something like a 3.73 in it.

Block is a mid to late 70s block.
Block bored 0.020" over as long as the bores will clean up
Pistons; KB-167-020 (compression height 1.810"; +5cc piston head volume)
Head gasket: C5633-030 (4.040" bore, 0.030" compressed thickness)
Deck the block to a true 9.60" height
Stock Magnum cylinder heads (60cc chamber), mild port work, stock size valves
should have a quench height of 0.042"
compression ratio of 9.9:1
Stock magnum rods lightened
Stock 318 cast crank
Edelbrock Performer RPM Air-Gap
aluminum roller tipped rocker arms 1.6 ratio
1 & 5/8" long tube header summit brand
Comp cams XE (20-223-3) 268/280 adv; 224/230@0.050"; 110 LSA; 0.509"I/0.512"E Lift with 1.6 rockers
Stock Mopar windage tray
Holley 670cfm carb

I think it will be a mean little 318
 
Sounds like you put some thought into it; good luck and have fun.
 
You got it covered, ...Ignore ,the critical..that's a home run combination.....
 
Only thing I might change is to use a head gasket that matches the bore size, not 4.040.....combo looks good
 
Some notes:
- With your parts, an LA block, and a 60 cc chamber volume, I am getting the same 9.9 SCR. DCR will be near 8.15.
- I get a piston top that is .011 below deck with the stock LA deck height of 9.599. So we get the same quench gap will of around .041"-.042".
- The significantly lighter pistons and pins will absolutely require a crank rebalance.
- Do you have the AMC lifters and hollow pushrods picked out for the Magnum rocker oiling?

What is the planned use for this engine? Street? Pure drag race?
 
Interesting.... there is not much combustion mixture in there... Does it do something to slow, or mess up the combustion process? Or tend to detontate and thus you have to limit timing? Or what??

And would you really need to take care about this on, say, a 400 HP SBM street engine, that saw little or no strip time?

(Sorry OP, but this off-tangent question is SOP for FABO LOL)
 
nm9stheham said:
Interesting.... there is not much combustion mixture in there... Does it do something to slow, or mess up the combustion process? Or tend to detontate and thus you have to limit timing? Or what??

And would you really need to take care about this on, say, a 400 HP SBM street engine, that saw little or no strip time?

(Sorry OP, but this off-tangent question is SOP for FABO LOL)
Click to expand...


Crevice volume lends itself to detonation.................
 
nm9stheham said:
Some notes:
- With your parts, an LA block, and a 60 cc chamber volume, I am getting the same 9.9 SCR. DCR will be near 8.15.
- I get a piston top that is .011 below deck with the stock LA deck height of 9.599. So we get the same quench gap will of around .041"-.042".
- The significantly lighter pistons and pins will absolutely require a crank rebalance.
- Do you have the AMC lifters and hollow pushrods picked out for the Magnum rocker oiling?

What is the planned use for this engine? Street? Pure drag race?
Click to expand...

Have to find AMC lifter and new pushrods. I'll mockup the valvetrain and check pushrod length before I order them. I plan on getting it re-balanced, trying to get the rotating assembly as light as possible.

Mostly street use, some 1/4 mile track use and would like to get into some local AutoX events.

I wanted to go to a 1/16" top and second ring but to do that with a 318 using off the shelf pistons, I would have to go to forged pistons. So I'm stuck with the 5/64" top and second rings.

Could get custom made head gaskets, but they probably aren't cheap. Trying to keep the cost down as much as possible and only spending money where I have to.

Anyone know how much a forged 273 crank weights and how much a cast 318 crank weights?
 
With the gasket bore being a lot larger than the bore of the engine, the air and fuel that is forced in there will not ignite its a deadzone. So it won't ignite and help push that piston down and will contribute to an increase in emissions. I'm not sure on increasing the chance of detonation.
 
Sounds good.

Just wondering though why you wouldn't do it to a larger cubic inch engine to begin with it you are going to all the trouble and expense anyway?
 
4mulas said:
Sounds good.

Just wondering though you would do it to a larger cubic inch engine to begin with it you are going to all the trouble and expense anyway?
Click to expand...

I just want to build a 318 to see what I can get out of it. Trying to keep cost down as much as possible, that's why I'm using a bunch of magnum stuff I have laying around. Plus the magnum rods are lighter than the LA ones and the magnum heads flow better than the LA heads that I have.
 
[QUOTE

Anyone know how much a forged 273 crank weights and how much a cast 318 crank weights?[/QUOTE]

Bob weight is what balances. (the weight of the pistons, rings, pins, retainers, rods,rod bolts, and bearings for one cylinder) That weight is totaled and added to the crank throws on the balancer. The machinist then knows how much weight to add or drill out of the crank counterweights.You mentioned running a 4 speed. Whichever crank you use it needs to be drilled for a pilot bushing.
 
JGC403 said:
I just want to build a 318 to see what I can get out of it. Trying to keep cost down as much as possible, that's why I'm using a bunch of magnum stuff I have laying around. Plus the magnum rods are lighter than the LA ones and the magnum heads flow better than the LA heads that I have.
Click to expand...
Sounds like a runner... :D
Just so you know, there never is a end of the "seeing what you can get out of it". 318's are no different than any other engine, improvements never end.
how long till it runs??
 
toolmanmike said:
[QUOTE

Anyone know how much a forged 273 crank weights and how much a cast 318 crank weights?
Click to expand...

Bob weight is what balances. (the weight of the pistons, rings, pins, retainers, rods,rod bolts, and bearings.) That weight is totaled and added to the crank throws on the balancer. The machinist then knows how much weight to add or drill out of the crank counterweights.You mentioned running a 4 speed. Whichever crank you use it needs to be drilled for a pilot bushing.[/QUOTE]

Yes you are correct. I am trying to get the lightest rotating assembly using factory pieces. If the forged 273 crank is a little lighter than the 318 cast crank. So with the lighter rods I'm using the machinest might not have to add any weight with the forged 273 crank. Does that make sense? And it will be a lighter overall package.
 
318willrun said:
Sounds like a runner... :D
Just so you know, there never is a end of the "seeing what you can get out of it". 318's are no different than any other engine, improvements never end.
how long till it runs??
Click to expand...

If I could get 2 horsepower per cubic inch then I would done. Lol.
I'm not sure just got the block last week got to tear it down still. I'm new to the area and need to find a machine shop also. I'm just trying to work out a plan right now.
 
[/QUOTE]
Yes you are correct. I am trying to get the lightest rotating assembly using factory pieces. If the forged 273 crank is a little lighter than the 318 cast crank. So with the lighter rods I'm using the machinest might not have to add any weight with the forged 273 crank. Does that make sense? And it will be a lighter overall package.[/QUOTE]

I'm not 100% sure, but I'm reasonably certain that a cast 318 crank is lighter than a forged 273 due to the fact that the metal is denser. The reasons why cast 340, 360, and cast 440 cranks are externally balanced, they just don't carry the weight.
 
JGC403 said:
If I could get 2 horsepower per cubic inch then I would done. Lol.
I'm not sure just got the block last week got to tear it down still. I'm new to the area and need to find a machine shop also. I'm just trying to work out a plan right now.
Click to expand...
yeah, 2 hp per cube, 636 hp no power adders, street form? that's turning some wrenches :D
 
JGC403 said:
I just want to build a 318 to see what I can get out of it. Trying to keep cost down as much as possible, that's why I'm using a bunch of magnum stuff I have laying around. Plus the magnum rods are lighter than the LA ones and the magnum heads flow better than the LA heads that I have.
Click to expand...

Gotcha! Good luck, hope you get the results you are looking for.
 
I have a very similar engine in 360 form. Same cam duration/lift, mag heads, .040 quench, similar compression, headers, exhaust. Runs very strong...even in a truck with bigger tires and high gears. I live at altitude and I bet I lose 50-60 hp from that alone. So I can imagine what your 318 is going to act like. You'll enjoy it.
 
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