Why didn't the factory use "stroker" specs ?

[Racer57]

Never really thought about it before. But if strokers are so great, why didn't the various factories do it ? Less durability ? If that's the case, then why do it ? I do not mean to come across like an azzhat, I'm just curious because I've never heard anyone say anything about it.

 

[Chryco Psycho]

Essentially Ford & GM did , if you look at the engine block diamentions the others used very short & light blocks .
For example a small block Chev can use a 6" aftermarket "long" connecting rod while the LA Mopar uses a 6.125 Con rod standard .
The Mopar blocks are far taller , also Longer rods also slow the piston at TDC & BDC this allows more time for complete combustion , this equals better fuel efficiency .
By using a shorter piston & retaining the longer rods you can easily increase the stroke while maintaining better rod ratio over the other brands & reduce rotating mass . Longer rod ratios also lower the side loading of the piston at high rod angles reducing wear .
So basically the engineering is better in the Mopars & even stroked reasonable they have better results from other brands .

 

[Mr Cuda]

Strokers. Personally, I am not a fan. The factories made 3, the ford 400, which is a horrible engine and the chev 400 had 4"x4" bore and stroke.
They came out as a crutch to make torque and move weight in the low compression era.
The most famous stroker is the 225 slant six. Its also the most oversquare at 3 1/8 bore and 4 1/8 crank.
The slant is the best stroker because the factory gave it enough block height to get a proper piston skirt, rod length to go with the stroke.
There is a tradeoff, (negative) to put more crank in a block with making the piston skirt shorter.
But hey, strokers are a cheap way to put more cubes under the hood. More torque moves weight.

 

[TIMINATOR]

Ford 400 is poop because of the head design, limited years of sale and with big crank journals theres more rotating weight too.
A 400 chebbie has a 4.125" bore and a 3.75" stroke. It also has a short 5.565" rod that is even shorter than the pathetic standard 5.7" regular chebbie unit. The aftermarket makes 5.850" and 6" rods for them, but those are still shorter than the Mopar rods. SBMopar has another advantage over the SBC, as the valves cross the deck on the centerline, not behind it so larger valves can be used on our Mopars too.
Back in the days before cheap stroker cranks came out, I used 6" sbc small journal (2" diameter) rods with .060 under sbc rod bearings on offset ground 360 cranks for a few extra cubic inches.
The 400 chebbies 4.125 bore allows the heads to be unshrouded more out to the larger gasket size too. I have done lots of 440" on 400 blocks at .060 over! A plus for the bow tie guys.... But, to get any real sized cams in SBCS requires a small base circle cam to clear the big ends of the rods too.
And just to show how the engineers screwed the pooch on the new LS motors:
you have to pull the heads to remove the lifters!
The lower rocker cover flange is so close to the springs that u can't cut the seats for larger diameter springs! Tool steel springs and titanium retainers, big bucks!
They could have made the block 3/8" longer so a bigger bore was possible too.
The oil pump is crank mounted so the required 15" long pickup tube mounted to the caps empties of oil when not running, so it fills the bearings and lifters with air on startup until the system primes! AND, the pickup tube is sealed at the top with a 15 CENT O ring that shrinks and splits after 4 or 5 years causing an air leak there even further slowing down the pumps priming. Those are the reasons that LS motors kill lifters at around 100,000 miles, and ya gotta pull the heads to change them. Oh yeah, to replace that O ring requires pulling the pan and removing all of the front accessories! On a AWD or 4 WD that requires pulling the engine too!
RB and small blocks have that nice tall deck height too, contributing to making more power.
Mopars use a higher nickle content in the blocka and heads to make them stronger and less corrosion prone too.
AREN'T YOU GLAD U RUN MOPARS!!!!
They are my favorite! That's why I'm currently doing a half inch, 7.100 rod 512 for my 72 Challenger...
TIMINATOR

 

[Xcudame]

After grinding crankshafts for years, I realized most Chrysler crankshafts were forged until the 318 LA came out and the the 360. But at least with the 360, Chrysler had enough sense to increase the main bearing size allowing more main/rod journal overlap. That's also way the RB crankshafts have a bigger main size than the B block - more overlap. Much better metallurgy now gives more strength so the main/rod overlap isn't as big of an issue as it was in the 60's. Looking at the dimensions of big block Mopars, I always thought the 383/400 should have been 426/444 and the RB engines should have had a 4.15 or 4.25 stroke. But keep in mind, metallurgy wasn't great and Mopar engineers wanted to build tough engines! I think that's why they used the dimensions that did.
As a parting shot, I also realized that if you only rebuilt Mopar engines, you'd better be a specialty high dollar shop (race motors), or you'll starve! More money to be made with Ford and GM engines as they seemed to wear out quicker!

 

[TIMINATOR]

They do and that's because the others are more cast grey iron (softer) and the mopars have more Nickel for strength and some tin to keep the iron more malleable and crack resistant.
You can port 2 sets of sbford heads in the same time it takes to do one set of mopar heads!
P.S. the last offset stroker 360 I did with chebbie rods ran 11.60s at 117 on street tires thru the muffs, 4.10s, 3000 stall in 1998. Comp solid street roller, 750 dp, torker II intake in a customers 72 Çhallenger.
I bought it last year.
TIMINATOR

 

[Xcudame]

My understanding from machinists that repair engine blocks, Mopar blocks can be pre-heated with a acetylene torch and stick welded with a high nickel rod very easily. GM and Ford blocks not so much!

 

[TIMINATOR]

Actually they can be welded with a 200 amp D.C. WIRE WELDER! Heat a decently large area to just below a dull red, make a short pass less than an inch and a quarter and reheat the area around the weld, not the weld itself until its all that same color. Then weld some more and reheat. Repeat until finished and slowly over 15 minutes bring down the temp of the block, head, intake or exhaust manifold. I just did an intake and exhaust manifold that were both missing the corner bosses last week. I've done lots of blocks too.
The aftermarket blocks can all be done this way too because of the better grade iron. Stock big block chebbies too.
TIMINATOR

 

[TIMINATOR]

Back to why didn't yhe factory use "stroker specs".
They built a block, figured out the largest cubic inches possible, then dropped the initial size down by 30 or 40% so they could make it bigger every few years as a sales gimmick!
TIMINATOR

 

[540HemiCuda]

Let's remember, the vast majority of engines went into grocery getters, not hot rods. So when you get to designing and testing dedicated high performance engines, you have to think price as in the Hemi. It literally cost a third of the price of the car to option. You would also need more head development. The 440 already used the same head as the 383 so it was maxed out. And then there's the fact that we didn't have tires that would hold what they were already building at the time. Even wider wheels and tires were no match for a stock 440 on the street. In fact, traction and the driver's ability (or inability) to launch when street racing was often the deciding factor. Not horsepower. More torque via a stroker would have been even more of a handicap to many drivers when they cannot hook it up.

And then there is the issue of insurance. Insurance rates and restrictions on what was already available was one of the death knells of the muscle car era. Along with emission regulations coming on line, gas prices going up, etc...............

 

[NxCoupe]

Having lived in the 70s, what's been left out of this discussion is one of the key factors why cubic inches were restricted 440 to 460 in these cars and that was insurance. The bigger the engine size, the larger the insurance premium. It got to where a 21 year old guy with a 440 RT was paying more for insurance than the car payment. That happened around 1970 or so. Then the oil 'embargo' happened and everyone was screaming our engines were too big and got poor fuel economy. The insurance companies are also why all the big 3 put engine size designations in the VIN so people couldn't lie about the engine size in their car to get cheaper insurance.

 

[Challenger RTA]

can be welded with a 200 amp D.C. WIRE WELDER!

A friend of mine I know is a good welder. He fixed some cast for me and I was just amazed How good he really is. It never broke again. All he did for a few days was weld on railroad trucks all day long.

I have a question about just cast cracks. Is it a good thing to drill the ends of the cracks on cast? Or it doesn't matter?

 

[TIMINATOR]

Depends on what and where. Irontite tapered and threaded inserts are better. Start about 1/4" past the crack, drill, taper ream, tap, red loctite, and tighten until the tapered insert breaks off just above the surface. Then drill, tap, etc the next hole with about a third diameter overlap. Repeat until about 1/4" past the end of the crack, then grind flat and you are good to go. Diesel guys will do a 3"+ crack and it will last forever.
Google the technique.
TIMINATOR