318 with a 4.00 stroke crank

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highwaystar

highwaystar

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I have heard of a few members building this motor. I was thinking last night, What the bob weight would be on this combo. It has to be light, lighter than the 340 and 360's right? If you are using good quality lightened Pistons and Rods. These things should fly... I would love to hear what some combos are that have been built and H.P. and Torque #'s if anyone has run one on a Dyno. I have the perfect 318 shortblock for a build like this. Also what are the cubic inches you are getting, Is it 392? And what are the current piston bores availible?

Thanks Alot Guys.
T.J.
 
Kieth Black, or icon as they are now called, has pistons for the 4" stroke 318. Eagle will tell you what bob weight they recommend if you ask thier tech people. I believe it comes out to be 390 cubes, and it should up the torque output quite a bit. I would use 360 heads as the 318 ports might be a little small for those cubes. 400 hp should be easy.
 
yes the bobweight would be pretty light especially if you something like a scat I beam rod that weight in at 595 grams ..the KB pistons are 437 grams. Plus those rods do not need any grinding to clear the bottom of the cylinder bores.

should not have to add any weight to a cast crank to balance it.
 
The problem that I see with this has nothing to do with bobweight and everything to do with flow. I think, should this really get looked at, that notching the bores and possibly offestting the heads to clear the valve shrouding issue should be done. a 3.94 bore putis the intake .045" closer to the wall and that is huge on a 2.02 or 2.05 valve.
 
Sounds like a perfect match to the O.O.T.B R.H.S heads that Brian and Indy have been working on with the 1.94 intake valve. what you think Moper, or is there still too much shrouding for those as well. I would love to here some Dyno results on the few cats that done these already.
 
I built one and Brian at IMM Engines offset bore the block to accept off the shelf Stroker pistons.
I used a 4.0" Scat Crank Cast, Eagle Rods and Icon Forged pistons. Came in at 402 cubes.
I am also running Brians RHS Heads exactly how he sells them. I believe the Bob weight came in right at 1700 grams or so. I need to look at the balance card.

Here is a picture of the motor....... It should make at least 480hp/500+tq I hope!

IMG_0959.jpg

IMG_0959.jpg
 
LOL

Moper...

I have a set of them too with the breathers.
The breathers are really nice heavy pieces too. Comes with PCV installed in one, and the other unscrews for cleaning.

Get both on ebay. around 130 bucks for breathers and the covers shipped if memory serves correct. Well worth the money.

These are especially nice due to the way the allen bolts are recessed into the cover, and that they are on the top so they are easy to remove.
 
moper said:
Mad, where'd you get tthe valve covers? They look cool.
Click to expand...

POSDAKOTA hooked me up with the link on ebay.............I think we paid $78.00 for them and another $40.00 for the breathers plus shipping. I tried to find the link for you but the cheapest ones now are $149.00
 
My buddy has the 4" crank in a 318, with out of the box Eddy's. Its in a 1968 Barracuda that his wife races. This is a street car with a tire swap, it has a full exhaust system on it & full interior.
It has ran a best of 10.99 @ 121 MPH. He does run alkhol in it.
This thing is a strong runner.
 
Hi Mike,
Do you know if he had any clearance problems with the valves or rods? That is impressive power for an old 318 block. I wonder how many racers sent them to the boneyard thinking they would never be any kind of performance engine. I would love to see a Magazine do a build-up on a 318 with nothing more than a 4" stroke crank, Scat rods, good pistons and a small hydraulic roller, and see what kind of power they could get.
 
moper said:
The problem that I see with this has nothing to do with bobweight and everything to do with flow. I think, should this really get looked at, that notching the bores and possibly offestting the heads to clear the valve shrouding issue should be done. a 3.94 bore putis the intake .045" closer to the wall and that is huge on a 2.02 or 2.05 valve.
Click to expand...

How much do you think there is to be gained by notching the bore?
I told a local friend this was something he should have looked into but he didnt listen to me. motor makes only maybe 430hp...I think it should have made at least 450, but I have been wrong before..
 
Mad Dart said:
POSDAKOTA hooked me up with the link on ebay.............I think we paid $78.00 for them and another $40.00 for the breathers plus shipping. I tried to find the link for you but the cheapest ones now are $149.00
Click to expand...

I found him a set for the same low price as ours.
Even for 149 bucks though, these valve covers are well worth it!!!
Plenty of room to clear any valvetrain setup, easy to remove in a cramped compartment, and a nice big fat flat sealing surface.

These things will never leak with any gasket.
 
POS Dakota said:
How much do you think there is to be gained by notching the bore?
I told a local friend this was something he should have looked into but he didnt listen to me. motor makes only maybe 430hp...I think it should have made at least 450, but I have been wrong before..
Click to expand...


Well the old hot rod mags used to all say to do it with a normal stock stroke for the 2.02 intakes. They used to say you need at least 15 hp more in increase to do any good. So it must have been worth 15hp or more. With the stroker crank likely a few hp more.

Hard to say how much but he lost some hp without one.
 
Any comments/concerns on how this motor would do under boost? I understand head choice would be key!
 
I'm planning to build a 390 also but a budget build, I know your better off with a 360, and I was planning on a 408 but once I added it all up,it would be along time till I could afford it.So I just bought a used low mileage set of Diamond forged 390 pistons on Eagle SIR rods in great shape from a member on this site for $450(should be 10.5 compression). So I'm thinking about an Eagle or Scat cast 4" crank for $300, then all it would cost is the ballancing, machine work for the block, and some rings and bearings, although the rings look useable. My 72 Duster already has a good 318 with Edelbroke intake, headers, and a 650 Holley so I have that covered and I already have a Comp XE274 cam that I can use. I also have a set of "302" heads with 1.92 1.60 valves installed, so I plan on porting them and opening the port openings to 360 size for an Edelbroke RPM Air Gap intake, then down the road get a set of the RHS LAX heads.

I put all this in the comp cams dyno program and got 414HP and 458TQ, with better flowing heads 425hp/461TQ and with a good roller cam 457HP/467TQ . Any way you look at it, even in mild form it should be a nice little motor in my 72 Duster with a 4 speed and 3:91s!!!!

Butch
 
392Mopar said:
I'm planning to build a 390 also but a budget build, I know your better off with a 360, and I was planning on a 408 but once I added it all up,it would be along time till I could afford it.So I just bought a used low mileage set of Diamond forged 390 pistons on Eagle SIR rods in great shape from a member on this site for $450(should be 10.5 compression). So I'm thinking about an Eagle or Scat cast 4" crank for $300, then all it would cost is the ballancing, machine work for the block, and some rings and bearings, although the rings look useable. My 72 Duster already has a good 318 with Edelbroke intake, headers, and a 650 Holley so I have that covered and I already have a Comp XE274 cam that I can use. I also have a set of "302" heads with 1.92 1.60 valves installed, so I plan on porting them and opening the port openings to 360 size for an Edelbroke RPM Air Gap intake, then down the road get a set of the RHS LAX heads.

I put all this in the comp cams dyno program and got 414HP and 458TQ, with better flowing heads 425hp/461TQ and with a good roller cam 457HP/467TQ . Any way you look at it, even in mild form it should be a nice little motor in my 72 Duster with a 4 speed and 3:91s!!!!

Butch
Click to expand...

The guy with the blue dakota on moparts?
If so those looked good to me. I was eyeballing them myself for something else.

If you used the RHS heads as sold by IMM and got a good roller cam...(there's a kickass solid roller on moparts right now that is perfect for you for 200 bucks brand new!) You would break the 500hp mark. That I am pretty sure of.

And you can do that with a scat cast crank...nothing exotic.
 
Yeah those are the pistons and rods, I've been looking at them since he posted them and going back and forth with emails and finally bit the bullet and bought them. I thought it was a good deal seeing as those pistons are $630 new!!!

Really, you think I could break 500HP with the right setup, wow. I'd be happy with 400-450 and a boat load of torque. Right now I have a late 70's 318 so in order to do a roller I'd have to use retro lifters which are big $. I'm thinking of looking for a cheap rebuildable 318 magnum and just build using that, for one I can build it while still driving the Duster and have the option of a roller cam.

Think its worth the $ to find a newer magnum motor to start with. figue I could probably make it up by selling my complete 318 after its build. I dont think 318 magnum cores go for too much.

Butch
 
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