Oh dear God! 318 stroker

-
Since we're all on the topic here, I hear that there have been some failures with the Eagle cast internal balance 4 inch crank. Does anyone know if these cast eagle 3.58 inch cranks have similar problems?
Eagle Specialty Products 103603580 Eagle Cast Steel Crankshafts | Summit Racing
I'd be running a set of 273/318 stock alloy full float rods and the .060 over Zollner pistons (355 CID) I had referrenced earlier with the skirts trimmed for crank clearance and a pair of valve reliefs cut. Re-worked 974 heads with 2.02 1.60, 4 angle and bowl cleanup and gasket matched to 1243 Felpro intake gaskets and port matched Weiand 7545 Xcellerator. Cam will be a factory hydraulic roller cam reground by oregon to grind 2067.
239/251 288/304 106 LSA 105/107 icl/exl and .335/.335 lobe lift, RPM limit of 6500.
 
Garrett Ellison said:
Since we're all on the topic here, I hear that there have been some failures with the Eagle cast internal balance 4 inch crank. Does anyone know if these cast eagle 3.58 inch cranks have similar problems?
Eagle Specialty Products 103603580 Eagle Cast Steel Crankshafts | Summit Racing
I'd be running a set of 273/318 stock alloy full float rods and the .060 over Zollner pistons (355 CID) I had referrenced earlier with the skirts trimmed for crank clearance and a pair of valve reliefs cut. Re-worked 974 heads with 2.02 1.60, 4 angle and bowl cleanup and gasket matched to 1243 Felpro intake gaskets and port matched Weiand 7545 Xcellerator. Cam will be a factory hydraulic roller cam reground by oregon to grind 2067.
239/251 288/304 106 LSA 105/107 icl/exl and .335/.335 lobe lift, RPM limit of 6500.
Click to expand...

I'm thinking the pin overlap might be adding to the Eagle crank failures. A good many of the failures are from people with engines far beyond any cast crank usage, like really high RPM or boosted applications (nitrous/etc.). Your lightweight skinny rods will help and the low RPM ceiling.

When they let go, it ain't pretty! That one lasted a good while under extreme use, but I bet Gary would have eventually broken a SCAT cast steel unit. I bet you'll be OK with the shorter 3.58" stroke, I hope so anyway. I just bought a crank like that from Eagle's Ebay store, a blem unit. LOL
 
Thanks Rodney! So far the deck height of the ‘85 hydraulic roller block I’m looking at for this one averages 9.67 with the present rotating assembly, but I’ve got plenty of piston crown if I need to mill them. I doubt I will with the generous .090 plus deep 967 chambers.
 
Bighead440 said:
I'm thinking the pin overlap might be adding to the Eagle crank failures. A good many of the failures are from people with engines far beyond any cast crank usage, like really high RPM or boosted applications (nitrous/etc.). Your lightweight skinny rods will help and the low RPM ceiling.

When they let go, it ain't pretty! That one lasted a good while under extreme use, but I bet Gary would have eventually broken a SCAT cast steel unit. I bet you'll be OK with the shorter 3.58" stroke, I hope so anyway. I just bought a crank like that from Eagle's Ebay store, a blem unit. LOL
Click to expand...

It's crazy you had to prove it's a 318 like it's impossible to make power with anything less than 340/360 guess that's the line where physics stops working. Sucks she let go on you, doing another 318 or moving on to something else?
 
Well, availability is the primary concern on crankshafts. Partly, the Eagle is just me “being cheap”, too, but I know even less about the Summit forged crankshaft that is presently available. Summit stipulates that weight addiction is often necessary, even though it’s over 15 pounds heavier than the the cast crank. So with that expenditure in mind, and bearing in mind that stiffer and precision machined cranks stress a block less, I checked with PROSTOCKTOM about a Molnar crank. I’m really thinking some beefier caps and a girdle on the late model block wouldn’t hurt anything, either! Well, maybe the budget, but… I wouldn’t say what happened to Gary was budget friendly either!
 
Bighead440 said:


These guys^ did exactly what you are describing, and 20+yrs ago, "Speed-O-Motive" offered a kit to make a "350" MoPar 318. The guys in the video had to relieve the bottom of the pistons near the pin bosses to clear the counterweights, but they used replacement pistons for a super-low compression 318 truck application. You could use a stock 360 crank and have the mains turned down, and the counterweights cut in a lathe to clear, or relieve the pin bosses like they did. The trick way to go would be get a Eagle or other aftermarket crank with 318 mains already and the 360 stroke (3.58"), and use SCAT I-beam rods and a piston by AutoTec or another custom piston, with your desired 318 bore based on a 360 compression height. AutoTec/RaceTec will let you change the bore on a shelf piston for little or no extra cost. Someone earlier posted a 4" shelf piston (SRP?) for that stroke, if your bores will allow. I like these unicorn builds, that's what makes this hobby fun, being creative and unique!!
Click to expand...

I didn't have that issue. I used Silvolite Pistons and paid attention to wrist pin height
 
273 said:
It's crazy you had to prove it's a 318 like it's impossible to make power with anything less than 340/360 guess that's the line where physics stops working. Sucks she let go on you, doing another 318 or moving on to something else?
Click to expand...

I don't own the Barracuda, it's "Gary's Garage" on YouTube. I am, however, building a 318 Magnum based 390 (dished pistons, RHS heads) for my '99 Dakota R/T ext.cab. It's a heavy truck and I want more bottom end but really don't need a 408, so I used an old 5.2 block from a '92 D-150 shorty that I upgraded to a 5.9 Magnum. I want to keep the original PCM, and I'm hoping 30" of displacement via stroke will work by just upsizing the injectors. I did that on my D-150 5.2->5.9 swap and it worked perfectly.

I have also done the 328" 318 trick, and I call it my "baby 340" LOL. It runs really well, with #302 heads, a 270s cam with 273 valve gear, a Street Dominator intake and a 625 Street Demon with headers. I want to do a flat-top 392" 318 with aluminum MP Magnum heads soon, I think they are the greatest thing for the street (4" crank motors)!!!
 
Garrett Ellison said:
Well, availability is the primary concern on crankshafts. Partly, the Eagle is just me “being cheap”, too, but I know even less about the Summit forged crankshaft that is presently available. Summit stipulates that weight addiction is often necessary, even though it’s over 15 pounds heavier than the the cast crank. So with that expenditure in mind, and bearing in mind that stiffer and precision machined cranks stress a block less, I checked with PROSTOCKTOM about a Molnar crank. I’m really thinking some beefier caps and a girdle on the late model block wouldn’t hurt anything, either! Well, maybe the budget, but… I wouldn’t say what happened to Gary was budget friendly either!
Click to expand...

My first 4" stroker was a SCAT cast unit (stronger than Eagle, but this was in '99 so nobody really knew then) I got from MoPar Perf. It had to have Mallory metal with lightweight SIR Eagle rods and Diamond dished pistons, which I thought was odd. The last one I did, I used Magnum 5.9L external balance and it worked fine. The steel cranks balance out fine, but costly and overkill for most realistic street applications. My last professional machinist used to circle track race some serious 360s and he refused to put Milodon caps on a 340 for me, he said a stock block will live better with OEM caps and not adding the outer cap bolts on the center mains. He said they used to add 340 stock caps to 318s and put the MP 340/360 ductile caps on stock blocks, after cutting off the outer bolt holes. I do have the Milodon caps on a 340/416, so we will see.
 
Thank You for the information on the caps! I can concur that the 4 inch crank engines are incredible for a street engine. So much so that the LA Mopar is my first consideration for A, B, C, or even most truck use.
 
273 said:
It's crazy you had to prove it's a 318 like it's impossible to make power with anything less than 340/360 guess that's the line where physics stops working. Sucks she let go on you, doing another 318 or moving on to something else?
Click to expand...
As has been pointed out numerous times, buy different members, that wasnt a "318" it was a 318 block bored to paper thin walls, with a 4" stroke crank. Ran good till it split a cylinder wall open and hydraulic broke in spectacular fashion.
 
Bighead440 said:


These guys^ did exactly what you are describing, and 20+yrs ago, "Speed-O-Motive" offered a kit to make a "350" MoPar 318. The guys in the video had to relieve the bottom of the pistons near the pin bosses to clear the counterweights, but they used replacement pistons for a super-low compression 318 truck application. You could use a stock 360 crank and have the mains turned down, and the counterweights cut in a lathe to clear, or relieve the pin bosses like they did. The trick way to go would be get a Eagle or other aftermarket crank with 318 mains already and the 360 stroke (3.58"), and use SCAT I-beam rods and a piston by AutoTec or another custom piston, with your desired 318 bore based on a 360 compression height. AutoTec/RaceTec will let you change the bore on a shelf piston for little or no extra cost. Someone earlier posted a 4" shelf piston (SRP?) for that stroke, if your bores will allow. I like these unicorn builds, that's what makes this hobby fun, being creative and unique!!
Click to expand...

I did the same thing , but I had options on pistons. S I went with Silvolites. Btw. My CI was 350.96.
 
Nothing wrong with the 318 other than the slightly smaller bore limits valve size before shrouding. A 3.5" to 4" stroke would aid torque, which for most street driven applications is what you want. With the huge number of core blocks available helps affordability. If you have a 340 or 360, fair enough, but nothing wrong with the 318.
 
I used to enjoy my 318 it was a 68 model.. I had it in a 72 demon with a 4-speed and 391 gears it had a set of X heads it was bored 30 over and had a 484 284 purple shaft...it would out run a 5.0 mustang with 3.73 gears....Tuff lil engine...MSD and blackjack 1.75 headers
 
Shorty Thompson said:
No replacement for displacement
Click to expand...
Yes and No, Displacement of fuel and air over time (cfm) with a somewhat narrow band of efficiency, are fundamental to power, to create X amount of power, it takes a Y amount of fuel and air (cfm) with some combo of cid x rpm x NA/Boost psi x efficiency.

So yes Cid is an important component but not the only one.
 
Last edited:
for a primarily street car it'll be easier to reach the needed power goals with a stroker. plus it'll be at a more friendly rpm with usually better manners than a smaller motor at the same hp. generally a bigger spread of torque, again street friendly. that's all. :thumbsup:
neil.
 
Good to see a fellow Kentish man on this thread!

Find the right 318 block and bore it to 4.040 and put all the nice 340 parts in!
Plus you can use the 340/360 heads with the bigger bore...:thumbsup:

I did a a plus 110 overbore 318, with turned down 340 pistons that I did myself.
Think its 336 cubes but its 'just a poorman's 340' lol.

Poly John from Kent UK
 
polyjohn said:
Good to see a fellow Kentish man on this thread!

Find the right 318 block and bore it to 4.040 and put all the nice 340 parts in!
Plus you can use the 340/360 heads with the bigger bore...:thumbsup:

I did a a plus 110 overbore 318, with turned down 340 pistons myself.
Think its 333 cubes but 'just a poorman's 340' lol.

Poly John from Kent UK
Click to expand...
be fine with a 4" stroker crank in it :lol:
 
polyjohn said:
Good to see a fellow Kentish man on this thread!

Find the right 318 block and bore it to 4.040 and put all the nice 340 parts in!
Plus you can use the 340/360 heads with the bigger bore...:thumbsup:

I did a a plus 110 overbore 318, with turned down 340 pistons that I did myself.
Think its 336 cubes but its 'just a poorman's 340' lol.

Poly John from Kent UK
Click to expand...
I would think the bore walls would be awefully thin.
 
A 318 bore is big enough for what most will build only the 273 bore size is questionable choice but it's even capable to do 400 hp without much effort. No reason for crazy overbore.
 
Change the subject mildly if you'll allow. Guy was wanting to buy the diffy I have for my Valiant. Says he's got a rebuilt 273 that he's wanting to sell. What's it acutally worth? It runs & drives now. curious.
 
If you read the famous 'Hinkles 426ci Poly build' they have sonic tested several 318LA blocks and...

They have the same liner wall thickness as a 340 block...:lol::thumbsup::drama:
 
You must log in or register to reply here.
-

Back
Top