318 with a new 4” crankshaft.

-
hwy2

hwy2

Well-Known Member
Joined
Mar 15, 2024
Messages
127
Reaction score
44
Location
texas
After previous posts here I am going to get a new 4” stroke eagle crankshaft new pistons and rods to match. What else should I look out for. Will the new crankshaft require balancing. Im going with the .040 over pistons to get 11:1 compression to make it a 392. Any advice will be appreciated.
KB hyper pistons
Speedmaster heads
Hyd Roller Thumper camshaft .514 int
Air gap dual plane manifold
Pertronixs 3 ignition and distributor
Holly 750 single pump
These are parts going back on
Stock rockers
 
Buy your crankshaft from Ohio crankshafts. The eagle crank is a piece of ****. Run more camshaft, like .575 lift, 290 duration 108 lsa. Have a valve job done on the seed blaster heads too. Stock rockers are a bad idea unless you mean mechanical style.
 
Last edited:
hwy2 said:
After previous posts here I am going to get a new 4” stroke eagle crankshaft new pistons and rods to match. What else should I look out for. Will the new crankshaft require balancing. Im going with the .040 over pistons to get 11:1 compression to make it a 392. Any advice will be appreciated.
KB hyper pistons
Speedmaster heads
Hyd Roller Thumper camshaft .514 int
Air gap dual plane manifold
Pertronixs 3 ignition and distributor
Holly 750 single pump
These are parts going back on
Stock rockers
Click to expand...
Absolutely, the rotating assembly needs to balanced, with the balancer, which you should get new. Take the flex plate (also new), rod bearings, wrist pins, locks and rings for the balancer too.

I’d recommend a new set of rockers (PRW work I think?), and you may have to get a correction kit from B3 for good geometry…check first of course.

Get the heads checked…probably need a valve job and have the guides honed proper. May need the heads surfaced.

Read the ring gap instructions for the hyper pistons, they like the top ring to have some decent gap.

That cam will want some converter. As such, might as well go single plane unless you already have the dual plane.
 
MOPAROFFICIAL said:
Buy your crankshaft from Ohio crankshafts. The eagle crank is a piece of ****. Run more camshaft, like .575 lift, 290 duration 108 lsa. Have a valve job done on the seed blaster heads too. Stick rockers are a bad idea unless you mean mechanical style.
Click to expand...
I was going to use same stamped rockers that it came with.
 
hwy2 said:
I was going to use same stamped rockers that it came with.
Click to expand...
They’re likely to flex with the added spring load and acceleration from the roller. Also, the ratios won’t get the listed lift figures from the cam. You’ll have to measure for push rods once together. And, you’re really going to want adjustable to get the preload right.

Not trying to discourage, just want you to get as much out of it so you’re not too disappointed with your build. Three people in a row are recommending against the stock rockers…
 
Does KB still make hypereutectic pistons for that combo? I think if they still do they would use the less desirable thicker 5/64th size rings
Having done a stoker build on a 340, I would buy the kit instead of piecemeal like I did. Maybe check out protocol tom in the classifieds.
Get the forged crank. You will have to pay for balancing anyways, but you won't have to pay for heavy metal. I paid $350 for balancing, and $380 for heavy metal. I also used hypereutectic only because I thought they were light enough to not need metal added, but was wrong.
 
dusterbing the peace said:
They’re likely to flex with the added spring load and acceleration from the roller. Also, the ratios won’t get the listed lift figures from the cam. You’ll have to measure for push rods once together. And, you’re really going to want adjustable to get the preload right.

Not trying to discourage, just want you to get as much out of it so you’re not too disappointed with your build. Three people in a row are recommending against the stock rockers…
Click to expand...
I have been through pushrod measuring process and preload I did get it right. If I get the 1.5 ratio will I need new push-rods.
 
dusterbing the peace said:
Absolutely, the rotating assembly needs to balanced, with the balancer, which you should get new. Take the flex plate (also new), rod bearings, wrist pins, locks and rings for the balancer too.

I’d recommend a new set of rockers (PRW work I think?), and you may have to get a correction kit from B3 for good geometry…check first of course.

Get the heads checked…probably need a valve job and have the guides honed proper. May need the heads surfaced.

Read the ring gap instructions for the hyper pistons, they like the top ring to have some decent gap.

That cam will want some converter. As such, might as well go single plane unless you already have the dual plane.
Click to expand...
Its a eagle forged 2 piece crankshaft, New rods and pistons. I already have dual plane. The motor was running but had a crack in water passage to the head bolt. Previous owner sealed it up with silicone and very loose torque. I scrapped it and got a new block. I went .040 over and have to get new pistons anyway. For the extra 1500 ill put in a crank and turn into a 392 i want to do it right. Is the flew plate important. I have considered b&m i have a b&m 2500-2800 converter now.
 
Your going through all of this and going to use the stock stamped rockers?








At least look at the comp magnum adjustable rockers for LA heads.
 
I’d stay away from the eagle crankshaft. Get a hold of prostock tom on this site. He sells molnar assemblies, way better quality components than eagle.

Stamped steel stock rockers are not going to hold up to that high a lift of cam.
 
hwy2 said:
Its a eagle forged 2 piece crankshaft, New rods and pistons. I already have dual plane. The motor was running but had a crack in water passage to the head bolt. Previous owner sealed it up with silicone and very loose torque. I scrapped it and got a new block. I went .040 over and have to get new pistons anyway. For the extra 1500 ill put in a crank and turn into a 392 i want to do it right. Is the flew plate important. I have considered b&m i have a b&m 2500-2800 converter now.
Click to expand...
Well if you use an eagle crankshaft it would be a one piece crankshaft but it will surely end up a two piece crankshaft! Just ask me how I know!
 
I've beat on an eagle forged crank in my 340 for 12 years. I've seen people break cast cranks.
 
Since you're planning on changing out every component on the 318 you might as well change the block to a 340 or 360 block so you can buy some quality off the shelf pistons.

Using KB hyper pistons at 11 to 1, if they even make one for a 318 bore with a 4" stroke crank is just asking for trouble in my opinion.

Also are you wanting to make power or just sound like you have power? Using a Thumper camshaft is a very poor idea if you want real power production.

Tom
 
Scody21 said:
Your going through all of this and going to use the stock stamped rockers?








At least look at the comp magnum adjustable rockers for LA heads my
Click to expand...

PROSTOCKTOM said:
Since you're planning on changing out every component on the 318 you might as well change the block to a 340 or 360 block so you can buy some quality off the shelf pistons.

Using KB hyper pistons at 11 to 1, if they even make one for a 318 bore with a 4" stroke crank is just asking for trouble in my opinion.

Also are you wanting to make power or just sound like you have power? Using a Thumper camshaft is a very poor idea if you want real power production.

Tom
Click to expand...
This project went sideways on me. I had just planned to put heads, intake manifold and a cam and found out. I had a hairline crack in block after all my pieces were together engine ran. and this was on a 318. I ended up having to take a block I bought for $100 to the Machine Shop and have it board over since I did all that I am considering just putting in a new crankshaft pistons and rods and turning it into a 392 and that’s what I want a 392. I know I can go over with the 360 and get to 418 but I want to 392 if I go this route. If not, I have a good crankshaft good rods, new bearings and I’m just gonna buy a set of pistons but for 1500 I can get a new crankshaft and rotating assembly to turn it into a 392 the more I’m finding out about this the more I just may leave it as a 318 40 over. If I have to get the crankshaft balanced and all set up, I do not have a good Machine Shop for that. I can’t even find somebody around where I live to recommend a Machine Shop only one that has been recommended is two hours away. First was sound now if I go this way I am gonna get a different cam. Possibly the lunati voodoo grind
 
If you have a 392, then i would say follow your passion. Do the people selling the stroker kit for $1500 also sell a balanced version of that kit? It would probably cost a bit more, but it would eliminate the need for a machine shop.
Although it seems like all you need to get the 318 going now is a set of .040 pistons. That might be the quickest and cheapest way. Throw some kb167's in there, which I believe are in the mid $400's, and that will give you time to save up to do your dream build right and time to research and find competent machine shops in your area
 
PROSTOCKTOM said:
Since you're planning on changing out every component on the 318 you might as well change the block to a 340 or 360 block so you can buy some quality off the shelf pistons.

Using KB hyper pistons at 11 to 1, if they even make one for a 318 bore with a 4" stroke crank is just asking for trouble in my opinion.

Also are you wanting to make power or just sound like you have power? Using a Thumper camshaft is a very poor idea if you want real power production.

Tom
Click to expand...
I've never seen any KB hyper pistons for a 318 bore/4" stroke. if you get an '85-up 318 or 318 magnum block you can run stock roller lifters on a hydraulic roller cam.....doing a 4" stroker, other than the "number" (392), there's no advantage to doing that over starting with an '89-up 360 or 360 magnum block for the stock roller cam....the 4" (nominal) bore rotating assembly options are less expensive than the 3.91" (nominal) bore options to offset the cost difference in the block if there is any.
 
Last edited:
There’s the old adage, cheep is expensive and expensive is cheep. Or buy once cry once. Meaning do you but buy the best you can afford and will stand up to the abuse of the power level your building to. Just look at how many motors Cletus has trashed the last few years cus they are on the ragged edge of power for the parts
 
hwy2 said:
Is the flew plate important. I have considered b&m i have a b&m 2500-2800 converter now.
Click to expand...
Flex plate is important, yes. It transfers the energy from the crankshaft to the torque converter. It sounds like you’re looking to be at least double the original power level, which would justify the move to a SFI flex plate, even if you don’t need it to pass a track inspection. It’s pretty cheap insurance.

That converter will at least allow for the choppy idle of the thumpr cam.
 
dusterbing the peace said:
They’re likely to flex with the added spring load and acceleration from the roller. Also, the ratios won’t get the listed lift figures from the cam. You’ll have to measure for push rods once together. And, you’re really going to want adjustable to get the preload right.

Not trying to discourage, just want you to get as much out of it so you’re not too disappointed with your build. Three people in a row are recommending against the stock rockers…
Click to expand...
That’s a right on for updated rockers. My daughter in law put a pushrod through one of hers. I put heavy duty rockers from Mancini on her stock la engine in her tow truck but you’re camming yours up.
 
You must log in or register to reply here.
-

Back
Top