Can someone explain stroker kits

[Princess Valiant]

So I am looking to rebuild my 360. It's a stock late 74 build for a 75 vehicle which makes sense since I took it out of a 75 RV.

As I am looking around at engine kits, I notice a rotating assembly kit to Make a 408 stroker run about a grand to 1500. Not bad considering people rave on about stroker motors.

I know there are still the heads and other stuff but what I really want to know:

What is a stroker ? Do you increase the bore or just the stroke?

How did stroker motors come about.....why didn't the factory stroke engines in the first place?

Can a stroker run on the street?? Any other general info?? Is 408 the only size for a 360 and are there any disadvantages??

 

[Johnny Mac]

A stroker by definition just has an increased stroke vs a stock engine. Bore size doesn't necessarily have to be increased, however most of the time its a byproduct of a rebuild.

As far as "why didnt the factory do this" in many cases they did. Most "engine family's" are just different bore and stroke versions of each other. In gm land this how you get everything from a gm 302, to a sb 400 from the factory using essentially the same block with just varying bore and stroke. In sb mopar comparison, not a huge difference in a 318 and a 360 other than bore size. You can "stroke" a 318 to a 390, just like you stroke a 360 to a 408. Bore size being the difference. Both with a 4 inch stroke.
The late model hemi's are pretty much the same example. The 6.1 and 6.4 are essentially bigger bore and stroke 5.7's.

When building from scratch, your thoughts are correct, there is little reason not to go with a stroker assembly. Cost is usually negligible when your purchase includes a new crank.

To get a stroker, the crankshaft is designed with more stroke, and the pistons are designed to have a different pin location, so they stay in the block when at Tdc.

408 is the common mopar sb stroker, and they are every bit as reliable as any other rebuild. The crank is just a 4 inch stroke. The only disadvantage I can really stretch to list is that pistons moving further in the bore have higher stress. Due to moving for a longer duration of time in the bore, before changing direction ( inertia ). This is why some big rpm engines are actually "de-stroked" ex. The hellcat is a 6.2 opposed to a 6.4, or a chevy 302 engine vs a 327
Thats my quick and dirty explanation

 

[Abodybomber]

Rani,that 4" arm is a wonderful thing,in stock muscle car type builds,like yours.Built a 408 myself,from scratch. I recommend : Scat rods,(better clearances,on bottom of bores on rod bolts,Scat crank ,over Eagles ...,& what piston \cylinder head combo,you choose?...Head flow,: at least a pocket ported factory heads,230-240 c.f.m...really helps everywhere power wise...I have no problems,with Keith Black hyper pistons on quality,KB 356 pistons cost extra,to mill the "to cut" domes down,& narrow the small con rod ends,to match Magnum 5.9 specs.(on stock la rods..).. No matter what kit you buy,have the damn thing at least checked for balance,bet it needs to be balanced. As for oil pumps,stock non high volume,with a stock pan,absolutely order Mopar part number P3690715,the hardened intermediate shaft.Cam choice,would depend on head air flow,rear gearing,& converters..

 

[Abodybomber]

If you decide to m?ake that "408" decision: That "low buck " 408 build ,will cost you 5-.…8,000 dollars...

 

[famous bob]

If you decide to m?ake that "408" decision: That "low buck " 408 build ,will cost you 5-.…8,000 dollars...

Rani, your turning in to a hotrodder, better be careful !! it`s a bug that will bite and last forever .

 

[Princess Valiant]

If you decide to m?ake that "408" decision: That "low buck " 408 build ,will cost you 5-.…8,000 dollars...

not that I don't believe you but care to share where that kind of money goes?? even with aluminum heads, I am not sure where the thousands and thousands go???

 

[RedFish]

Most folks don't know the Dodge Brothers supplied engines to Henry Ford for the first automobiles. The bros were building, testing, refining, fossil fueled engines for all sorts of machinery long before the automobile applications. Those engines were designed to run, either idle or under load at a predetermined rpm, forever and ever amen. One of the terms used was "square engine" meaning equal bore and stroke. The farther you move away from those principles in design the shorter the engines lifespan.
Since automobiles with constantly changing rpm and workload is so different from those industrial applications, and since the lifespan of the automobile itself was lessening with every year model,,, much of the engine engineering was tossed out the window. Pandering to the market wants was and still is auto mfgrs path to profit/success.

 

[Bad Sport]

not that I don't believe you but care to share where that kind of money goes?? even with aluminum heads, I am not sure where the thousands and thousands go???

Block work 1500 ?? Can vary
Stroker kit 2000-2200
Aluminum heads 1500-1800 (then potentially more work) $$$$$
Misc. = Valve train, cam and lifters, bearings, timing set, oiling, cooling, fuel supply ????

It adds up quickly.

 

[RustyRatRod]

not that I don't believe you but care to share where that kind of money goes?? even with aluminum heads, I am not sure where the thousands and thousands go???

It goes to stupid overpriced engine builders.

As to your question of why the factory didn't do it.......as already stated , they did. A 318 is a stroked 273. A 340 is a stroked 318 with a bigger bore. A 440 is a stroked 383 with a bigger bore. I know. The "correctors" are fixin to jump on. But I ain't talkin about the B 383. There was a seldom talked RB 383. You can pretty much divide Chrysler engines up by stroke if you look at it. All the other manufacturers did similar things. Chevy started with the 265 small block that eventually evolved into the 3.75 stroke 400. They went all the way with that one. I wish Mopar had.

 

[Abodybomber]

Custom machined work,custom matched clearance work,( clearing) crank throws,rod/ block clearances happen quickly,@ 60-100 bucks an hour.. Same for proper valve train setup s.... Only if you do the same a few times,you can pass your knowledge into saving money via less labor time to cost savings for customers...

 

[RustyRatRod]

That's why I try my damndest to preach to learn to do ALL you can yourself and SAVE some money. You can almost cut the price of a big name stroker build in HALF doing a lot of things including assembly yourself. Being broke all the time, I never understood why people would rather put a dent in their bank account than do it themselves. Plus, that gets them even MORE into the hobby. Those that pay for everything seem more like posers to me.

 

[Abodybomber]

That's why I try my damndest to preach to learn to do ALL you can yourself and SAVE some money. You can almost cut the price of a big name stroker build in HALF doing a lot of things including assembly yourself. Being broke all the time, I never understood why people would rather put a dent in their bank account than do it themselves. Plus, that gets them even MORE into the hobby. Those that pay for everything seem more like posers to me.

Rob,did all my own work,(clearances to .060" on rotator\ block clearances, side grinding shot peening stock rods..That was '06-07 prices,with roughly 7000-7500.. Flat tappet hyd cam,home ported Eddy heads....) You find a 408 short block,maybe 3.5-4 k,I wouldn't trust a crate block...

 

[hemichuck]

Ive built several strokers and I never had $5000 let alone $8000 in a motor. If your not going crazy and shop around you can get a kit and have it balanced and build the short block for under $2000. You dont have to buy heads or cam or anything else to make them work. I think when I had the 408 Magnum in my Dakota I had $3500 in the entire engine(and I thought that was expensive) Shop around.

 

[diymirage]

Can a stroker run on the street?? Any other general info?? Is 408 the only size for a 360 and are there any disadvantages??

yes ma'am

I run one in my 71 duster and she is a torque little thing
even with 3.23 gears the only problem I have getting off the line is keeping the N50s from spinning

partly due to the nature of strokers, but also partly due to the cam I run in there, there is a ton of torque available almost instantly (hence my avatar message, more torque at idle then a Honda has at redline)

if build to the same standard as you would build a 318, a 340 or a 360, then a 408 will be just as reliable

 

[318willrun]

It goes to stupid overpriced engine builders.

As to your question of why the factory didn't do it.......as already stated , they did. A 318 is a stroked 273. A 340 is a stroked 318 with a bigger bore. A 440 is a stroked 383 with a bigger bore. I know. The "correctors" are fixin to jump on. But I ain't talkin about the B 383. There was a seldom talked RB 383. You can pretty much divide Chrysler engines up by stroke if you look at it. All the other manufacturers did similar things. Chevy started with the 265 small block that eventually evolved into the 3.75 stroke 400. They went all the way with that one. I wish Mopar had.

Rob, just making sure Rani doesn't get confused. A 318 is not a stroked 273, or a 340 a stroked 318. They changed the bore to get the extra cubes, not the stroke. Cranks are the same. The 360 would be an example of a stroked 318, with a bigger bore also...

 

[RustyRatRod]

Rob, just making sure Rani doesn't get confused. A 318 is not a stroked 273, or a 340 a stroked 318. They changed the bore to get the extra cubes, not the stroke. Cranks are the same. The 360 would be an example of a stroked 318, with a bigger bore also...

You're 100% correct. Sorry. I didn't get much sleep last night, plus I am worried about Kitty. She insisted on going to work this morning.

 

[318willrun]

You're 100% correct. Sorry. I didn't get much sleep last night, plus I am worried about Kitty. She insisted on going to work this morning.

Very glad Kitty feels good enough to "insist", and has the energy to go to work. For certain I knew you just mistyped.

 

[needsaresto]

Back in the day,before there were stroker kits,hot rodders did it themselves. Swapping a forged 440 rb crank into a B block was a common way to go,and still is.

 

[RAMM]

It goes to stupid overpriced engine builders.

Damn triple R, that smarts!

I'm $90/hr and I FREQUENTLY cannot charge for the full amount of hours I have in a stroker project. I'm not slow and have modern equipment. There is no such thing as a 5 minute job. J.Rob

 

[RAMM]

Being broke all the time, I never understood why people would rather put a dent in their bank account than do it themselves.

Lots and lots of my customers would rather have me take on the liability if ANYTHING goes wrong. I'm not talking about wealthy people either. J.Rob

 

[RAMM]

So I am looking to rebuild my 360. It's a stock late 74 build for a 75 vehicle which makes sense since I took it out of a 75 RV.

As I am looking around at engine kits, I notice a rotating assembly kit to Make a 408 stroker run about a grand to 1500. Not bad considering people rave on about stroker motors.

I know there are still the heads and other stuff but what I really want to know:

What is a stroker ? Do you increase the bore or just the stroke?

How did stroker motors come about.....why didn't the factory stroke engines in the first place?

Can a stroker run on the street?? Any other general info?? Is 408 the only size for a 360 and are there any disadvantages??

You never stated you intended purpose for this build. Perhaps a stroker is not necessary. Strokers add a minimum of $1500-$2000 in parts and can "snowball" the machine work and other peripherals. J.Rob

 

[spl440]

Rani, your 360 is basically a factory stroker 340, so you have a stroker to begin with. typically the 360 got a bad rep because it came out in the emissions era and they dropped the compression quite a bit. How do you think a 340 would perform with 7.5 to 1 comp? You 360 with the basic upgrade and some compression would put a smile on your face and leave some dough in your wallet. even a warmed up 360 will over power a 255/60/15 tire.

 

[fratzog lover]

The other overlooked option is a 3.79 crank. Around 390 cubes from a 360 is nice. The price is the problem as K1 and Molnar are among the few to offer it. There are tons of 4 inch options. I will build one of these before I die.

Molnar Technologies

 

[Infecteddog]

A stroker simply has a larger stroke than stock, for class competition they destroking is also done. The bore needn't change at all to stroke a motor and may not on a 318 build but likely will with a 340 or 360 block since better cores are worth more. The longer stroke typically pushes the operating range down everything else the same.

273, 318, 340, and 360s all have very similar blocks. 273, 318, and 340 all have the same stroke size but difference bore sizes. 3.91 for 318s, 4.04 for 340s, 4.0 for 360s, something around 3.65" for 273s. The A engines predating them were fairly related and there were factory strokers in that line. The 360s weren't loved partly since they started as a truck motor and went in at a time when steep gears were becoming increasingly less common. Wearing all the 340 parts like they did several years in the A bodies, they typically lacked the 3.55 and 3.91 gears that weren't so rare half a decade before.

408 is a .030 over 360 with 4" stroke. 410 is .040 over, same as a cherry bore 340 with 4".

You never stated you intended purpose for this build. Perhaps a stroker is not necessary. Strokers add a minimum of $1500-$2000 in parts and can "snowball" the machine work and other peripherals. J.Rob

A person needn't be wealthy to value their time. Example I always find interesting is "cheap projects" that none of their owners can invest the time to fix until finally they're parted.

 

[67Dart273]

The best examples that I know of re: "factory" strokers are Chevy.

You start out with (I know, 265) but let's say 283

265, 283, 302 (we used to call 'em 301) are all same stroke.

I believe 307 were 327 stroke cranks in a 283 bore block

327 was a 4" bore block stroked, and 350 was stroked again.

So 302, 327, and 350 all used same 4" bore, just different stroke cranks

On later 350s of course the main bearings were larger. I don't remember all that anymore, I think some of the 327s were larger main sizes, too

267 and 305 was 350 stroke, smaller bore

400 was a siamesed block, just like the Chrysler 400 and was both bored and stroked over a 350

Now, this does not mean you can easily convert. There were changes over the years, in main bearing sizes, etc