3.79 Stroke CRanks

[mullinax95]

345man, in case you got lost in all this, so far we have speedomotive.com, 4secondsflat.com, and Callies as sources for this crank. Wasn't that the whole point of the thread, or did I miss something?

Also he asked what was everyones input about one crank making more power than the other. That's why there is a debate going not just the source of where to buy the crank.

 

[340srule]

LOL, You have a good combo against the comp. But, I think we'll just disagree on this. I'll say you have street parts to the day I die.
Cast cranks are not race cranks. I wouldn't want to run around or race 700 HP on a cast crank. You go on ahead and do so. Not me.

Your preety happy that you have 520 HP. And thats good. I'll be straight up honest and say I'd be happy as well. But thats not what I'd call a motor for racing. It's low powered with a cast crank.
In a race arena, it is asking for trouble IMO. And 11's is not fast. If it is for you, then thats great and I take nothing away from that or you.

DO NOT be insulted or come back screaming at me, I'm just trying to put into focus a race car. Not something I'd call a street strip car that I would drive everyday to and from work and anywhere else.

For me, that is what you drive. It is simply a case of different strokes for different folks.

I'm sure your engine builder is capable. Why you bring him up is beyond me. But ask him, would he himeslf build a 700 HP engine to go racing with your parts or would he step up to the plate with better parts?

11's ain;t fast.. i'll bet none of your cars listed will ever see it...by the way,as far as "cheap street parts", my pistons probably cost more then any of your cars..

 

[ramcharger]

I'm real curious as to how a 3.79 stroke 4.030 bore engine will make more hp then a 4.00 x 4.030 assuming that good flowing heads (300 cfm+) are used on both (Indy, W-2, W-9, Brodix, etc.), and the cam is set up for the hp peak to come on at the same rpm and reciprocating weight was kept the same. Someone please enlighten me what the theory is behind this. I'm ready to learn something new today!

I know someone here on this forum that broke their cast crank running 540-550 hp. He did a LOT of racing though. I'm not saying that a cast crank won't handle 550 hp, I'm just saying that I don't know for how long. Put a 150-200 shot on top of that and you got a grenade. Neither the block nor a cast crank can handle that kind of abuse, not to mention the SIR rods. it's all about fatigue resistance. Think of a paper clip. You can bend it so many times until it breaks. I beam Rods under this kind of hp bend minutely and eventually, they just can't take it any more. That's why H-beams are designed the way they are, with two flat planes perpendicular to the crank to resist any bending under higher hp loads in an attempt to mitigate fatigue failure.

Jim Szilagyi (the engineer for Mopar Performance) says that the upper limit for a stock block (assuming it sonic checks out) is 500 hp. I think that with proper set up and machining that limit can be pushed up to 550, maybe a bit more with aluminum rods, internal balancing, superlight pistons etc. With nitrous on top of all that, I would definitely use a MP racing block.

Mr Szilagyi also says that cast cranks are good to 500 hp and no more than 6,000 rpm in a stroker application. Can that number be exceeded? Yes, but for how long? Cast cranks reach their limit and start to crack, those minute cracks propagate over time then the crank snaps, forged cranks reach their limit then start to bend which resists cracking.

The big question is, a motor dropping a bottom end is not a pretty sight. Not only is it expensive, but what about the guy in the other lane when the bottom end lets loose at 125+ mph and oils the tires? What about the spectators? I know I don't want to explain to his wife and kids that I killed their husband and daddy just to prove a point and be cheap (assuming I'm still alive).

I personally, (and this is of course, my opinion, and we all know about opinions! lol!) will pay the money for a forged crank and racing block if I'm exceeding 500 - 550 hp for my, the other competitor and the spectators safety.

I hope I'm not stepping on anyone's toes here, and I don't want to sound like I'm preaching, but I've seen the ambulance out on the track more than once and it's not good for anyone involved.

 

[haplo555]

well of course a forged crank is better, but i run a cast crank in a light altered, that run 8.20 shift at 6200 , the motor is a 417 ,w5 heads alcohol injected making 700 at flywheel, altered weights 1950, been runing motor for 6 years no problems yet????????? Rpm is what kills a cast crank.

 

[ramcharger]

well of course a forged crank is better, but i run a cast crank in a light altered, that run 8.20 shift at 6200 , the motor is a 417 ,w5 heads alcohol injected making 700 at flywheel, altered weights 1950, been runing motor for 6 years no problems yet????????? Rpm is what kills a cast crank.

There are always exceptions to the rule.You're running alcohol in a very light altered. We both know alcohol is way easier on parts in comparison to a gas motor on a 200 shot in 3000 lb car. I'm guessing that you're not running SIR rods and have done quite a bit to reduce reciprocating weight. Plus, not many people know how to make 700 hp @ 6000-6200 rpm without N20. Also, is that a 30-35 year old factory crank? I'm guessing not. I'd still tear it down once a year and have it magnafluxed if I was sitting behind it.

BTW: That sounds like a bitchin' build you got there. Care to share?

 

[rumblefish360]

You make a good point Ramcharger. Haplo's car is light and can take more stress this way. I was going to do the same about a co-worker. He runs a rail with a S/B 355 chevy engine. He also runs the 8.90 index I think it was. He told me the best thing about this was he didn't need to make a ton of power or turn crazy RPM's to achieve this goal. I loved the storys and his take on his end on things.

Haplo, I'm not trying to diminish your car/engine/achevements/yourself in anyway. Hoping not to step on your toes about this, but if the same engine is in a 3400 lbs. car, do you think it would last for 6 years?

BTW: That sounds like a bitchin' build you got there. Care to share?

Yea, no doubt. Inquiring minds wanna know.
Also, can I ask for a picture of the altered? Sounds like a way cool ride.

 

[rumblefish360]

11's ain;t fast.. i'll bet none of your cars listed will ever see it...by the way,as far as "cheap street parts", my pistons probably cost more then any of your cars..

WOW! You really seem to be taking my posts as an insulting one. And your post(s) seem to be leaning toward insulting me. Why is that. Act like an adult and not a child for cryin out loud. Your making yourself look poor. Seriously.
(Whcich I find really odd. Like way odd.)

Let me point something out.

11's aint fast...

Like I mentioned in the previous post, for a race car...no, for a street strip car...yes. If it's fast for you, then great. Really. I think it's great your doing 11's. I think 520 HP is great. I just don't think it's fast for a race car.

i'll bet none of your cars listed will ever see it..

This is like a child daring someone. Cooooooooome on man! About running 11's, what if I haven't...so what. How do you know what I have run? Your sentence is like you have to prove it or shut up. DO I really need to prove myself to a childish poster? Acting like a 11 year old. Stop itttt.
(Your latest round of reaplies are like your supppper pissed off. At what?!?!?)

by the way,as far as "cheap street parts", my pistons probably cost more then any of your cars..

I do not remember calling your parts "Cheap" but they are "Cheaper" than full on race parts. If you find this insulting, or if I did dead out call your parts cheap, I'm very sorry. But a cast crank is cheaper than a fordged carnk. Thats the bottom line. It's cheaper.

I do remember saying somewhere that you should not use cheaper parts for a superior build. If you think cast cranks are OK for 700+ HP builds in a heavy car, then OK. Say it. I'll just say different. Then it ends. If you want to carry on that venue, prove it different. I'm open to learning.

And your pistons. What ever they are...if they cost more than my car or cars, thats really nice. Who cares? What is the point of pointing out that your pistons are more expensive than my car costs?
A poor boast. (And baby like, which is a strange way of you handleing things from what I remember. I allmost feel like your throwing yourself on the floor in a fit.)


Now you atempt to badger and demean myself just because you spent more money on something than you think I spent on my cars. So what if you did. I guess spending big money on parts gives you the OK & green light to go and insult someone and there opinions.

Sounds like a rich little spoiled brats game. To that end, I can only think of 1 thing to say, "Get a life!" I told you straight up before, don't be insulted and come back screaming. But you seem to do so anyway.

By what you have posted here today, you not only insult me, (Actually, only tried and failed) but anyone trying to do things on the cheap. Well, guess what, theres alot of us trying to do things on the cheap here.

Alot of people do not want to spend a ton of money to go fast and are try to max. out there parts or just a simple cruiseing machine on the cheap. Whats wrong with that? Oh wait, they didn't spend big money on pistons? So silly of me to forget.
Then they didn't make big power like you so the insult is theres as well. They didn't travel into the 11's so there slow **** and cheap bastards right?

LOL, You really are showing yourself as 1 sad person.
(Which, again, I find reallly surprising and really freaking odd!!!)
I'd like to carry on with this, but I do not want to muddy up the thread. Someone hear is asking for help. Insulting is not helping, boasting on what you have as a weapon against me doesn't help.

What helps is your exp. on what you have done, facts about what you have used and IF you know someone that has done it for fact with something, then I would say that is an acceptable thing to mention.

An example would be the "349 on the cheap" Thread that BJR posted. I would have never thought about doing that myself, but he posted the numbers, facts and how to's about it. Now I can make a mention to someone about it. I didn't do it, but I know this guy that has a cool trick you might want to look into, you can find it here, and provide a link or say where to find it.

Tell me, how does your last couple of posts help?
How does your (attemped) insults help?
Is this really you or is this some drugggged up idiot posting on your behalf? Because I can not think of a post before this one where you go off like this. I guess I better start to search the forums.

I'm speechless from here. Past dealing with you have allways been pleasent until my opinion is different than yours. I really do not get this.

 

[BJR Racing]

Ramcharger,
The way that I see the 3.79 stroke engine being better is the fact that the bore to stroke ratio and the rod to stroke ratio's are keys to making power not just CI's. And as Mrmopartech has stated and you well know that CI's alone dont make a car run faster, and more CI's dont necessarily mean more power, but they do make more Tq. to a point and at what rpm that they make the Tq. and that these are the benifits of a larger stroke and mainly for the street IMO.


Now to say that a car that runs 11's is fast, sure it is and at what weight is it? But now to say that 550 HP needs part A,B, and C to do it well this is a matter of personal opinion and choice. As it can be done a number of different ways and this is up to the person thats doing it. Just as the 322 CI engine that we just ran thats running mid 7's in the 1/8 and we just started, so far we ran 7.53 @ 96 mph. This 1/8 mi. time would be mid 11's and it's not a 408 or a 394 CI engine. But the geometry of the engine is working at it's peak or close to it's peak potential, and yes it's a cast crank with KB pistons. Will it last who knows and for how long is anyones guess, but a well thought out engine will make more power and last longer than the average engine or average stroker, as all things will be working together all the time and at all rpm ranges within reason. This 322 CI engine has a 6500 rpm limit and should last at this for years, but then again they are just parts and anything man made is destin to fail reguardless who builds it or where it came from.

As Mrmopartech has stated some of my engines may be the exception but they are very well thought out and planned, carefully machined and carefully assembled so anything is achieveable but at what cost. And this is to the end users satisfaction, which is different than everone elses ideas. Get 10 racers together and you'll get 10 different answers, this is the nice thing about discussions, you'll get all kinds of ideas and thoughts, some for and some against this is just the way of the world guys. So dont get upset, but take it for what it's worth and go on. This is JMO.

 

[345man]

how do the ratios and geomtry come out with the 3.58 stroke cranks in a 340? and can they make alot of power?

 

[BJR Racing]

The B-S ratio is 1.137 and the R-S ratio is 1.710, the B-S ratio is fine but the R-S ratio is off a bit and needs a longer rod. But basically the 349 on the cheap engine with a larger bore.

 

[BJR Racing]

I would say power in the 500-550 range and Tq in the 500-520 range Hp at 5500 and Tq at 4500 very good street stump puller.

 

[haplo555]

will have to find picture and post, and ram charger your right, 71 360block bored 100 over with 1/2 fill hard block ,eagle 4.00 crank. Lunati Bulit pro mod rods with small chey big end 6.300 rod but very light also crank has been lighten with cpr pistons and chey pin i think bob weight was 1920 . also w5 have been ported to max, and of course a roller cam. and alcohol injected. The Key is light weight part and low rps And rumble fish no tow hurt, like i said 8.20 and not turning over 6500. If you want to go faster better have a forged crank.

 

[BJR Racing]

Yep light weight in the engine and the car are the keys to keeping a cast crank living, less load/stress. Alcohol is a big help also as it stops detination with high compression. And is easier on the engine than race gas.

 

[rumblefish360]

haplo, that sounds like one interesting build and a good use of parts.
A 100 over 360 ! Yikes! Thats opening it up. Whats the price tag on those rods?

 

[jjr426]

haplo, that sounds like one interesting build and a good use of parts.
A 100 over 360 ! Yikes! Thats opening it up. Whats the price tag on those rods?

Why you cant afford them. LOL Sorry rumblefish i couldnt resist i just finished reading the whole thread and it seems you upset someone oh well your entitled to your opinion too just move on i say. Justin

 

[rumblefish360]

LOL @ jjr. Ya made my eyes pop big on the first sentence.
Not really upset, I think he is when I called his race car slow. It is and it isn't slow. It's all realitive. I'm happy as a pig in slop with my 400 C.I. Magnum. Fast it is not! Maybe low 14's on a good day. But to someone somewhere, it's fast. Perhaps that 21 year old ricer I left behind this afternoon.

I'd also be upset if my "Race car" went that fast after I pumped in parts, time and money into it. Also, at the same time, if my next track car goes and turns a 13, thats OK too. LOL. It all depends on many factors and where your OK with what you have vs. what you spent vs. how well it performs.

I am confused by his replies, but, it is what it is.
Whaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaat-ever.:evil3:=;

 

[340srule]

LOL @ jjr. Ya made my eyes pop big on the first sentence.
Not really upset, I think he is when I called his race car slow. It is and it isn't slow. It's all realitive. I'm happy as a pig in slop with my 400 C.I. Magnum. Fast it is not! Maybe low 14's on a good day. But to someone somewhere, it's fast. Perhaps that 21 year old ricer I left behind this afternoon.

I'd also be upset if my "Race car" went that fast after I pumped in parts, time and money into it. Also, at the same time, if my next track car goes and turns a 13, thats OK too. LOL. It all depends on many factors and where your OK with what you have vs. what you spent vs. how well it performs.

I am confused by his replies, but, it is what it is.
Whaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaat-ever.:evil3:=;

Race car? not here..street car with full interior running 11.0's through full exhaust,that beats up up on race cars yes!!!..14's my tow vehicle runs that..lol..

 

[rumblefish360]

Sorry there bro. But this is what leed me to believe your car is race more than street;

"street parts"...no!! i don't think so,

Along with another thread I read where you say your car see mostly track and limited street. Something about low miles on the street but most miles @ a 1/4 at a time.

Sounds like race car to me. But if you wanna say everyday car, thats fine by me.

Whaaaaaaaaat-ever

 

[BJR Racing]

Aren't we geeting off track here guys? I thought this was about 3.79 stroke cranks? And where to get them? Not who has the fastest stroker engine. Or what car it's in.

As for the 3.79 stroke crank I would love to have a nice forged one but right now I have too many irons in the fire, and I would prefer one over the 4.00 counterparts. Anytime you add more stroke the associated parts have to go with it, meaning better rods, pistons, so is it really feasiable to build a stroker for the cost or is it just a want to thing? To me if I wanted a 400 + CI engine I would have started with a big block and just used the 3.75 stroke crank, now you can get what ever rod lenght and piston combo you want. I guess it's more about availability for me than just doing it in a small block frame. But once again this is JMO.

 

[ramcharger]

Ramcharger,
The way that I see the 3.79 stroke engine being better is the fact that the bore to stroke ratio and the rod to stroke ratio's are keys to making power not just CI's. And as Mrmopartech has stated and you well know that CI's alone dont make a car run faster, and more CI's dont necessarily mean more power, but they do make more Tq. to a point and at what rpm that they make the Tq. and that these are the benifits of a larger stroke and mainly for the street IMO.


Now to say that a car that runs 11's is fast, sure it is and at what weight is it? But now to say that 550 HP needs part A,B, and C to do it well this is a matter of personal opinion and choice. As it can be done a number of different ways and this is up to the person thats doing it. Just as the 322 CI engine that we just ran thats running mid 7's in the 1/8 and we just started, so far we ran 7.53 @ 96 mph. This 1/8 mi. time would be mid 11's and it's not a 408 or a 394 CI engine. But the geometry of the engine is working at it's peak or close to it's peak potential, and yes it's a cast crank with KB pistons. Will it last who knows and for how long is anyones guess, but a well thought out engine will make more power and last longer than the average engine or average stroker, as all things will be working together all the time and at all rpm ranges within reason. This 322 CI engine has a 6500 rpm limit and should last at this for years, but then again they are just parts and anything man made is destin to fail reguardless who builds it or where it came from.

As Mrmopartech has stated some of my engines may be the exception but they are very well thought out and planned, carefully machined and carefully assembled so anything is achieveable but at what cost. And this is to the end users satisfaction, which is different than everone elses ideas. Get 10 racers together and you'll get 10 different answers, this is the nice thing about discussions, you'll get all kinds of ideas and thoughts, some for and some against this is just the way of the world guys. So dont get upset, but take it for what it's worth and go on. This is JMO.

Excellent information BJR!

will have to find picture and post, and ram charger your right, 71 360block bored 100 over with 1/2 fill hard block ,eagle 4.00 crank. Lunati Bulit pro mod rods with small chey big end 6.300 rod but very light also crank has been lighten with cpr pistons and chey pin i think bob weight was 1920 . also w5 have been ported to max, and of course a roller cam. and alcohol injected. The Key is light weight part and low rps And rumble fish no tow hurt, like i said 8.20 and not turning over 6500. If you want to go faster better have a forged crank.

Thanks haplo! That sounds like a killer build and I'm looking forward to pics and a movie if you got one. I'd like to hear it run too.

 

[hemichuck]

I was just cleaning out my shop and found a MP 3.79 crank under the bench. I thought about using it in my 340 Swinger but it seems like overkill for my combo.Who still makes a piston to use with these cranks? I might be better off just selling it.

 

[MiradaMegaCab]

K1 has 3.79 cranks for 340 and 360 mains.

I used the K1 3.79 crank, K1 6.125 chevy style rods, this let me use an off the shelf Diamond forged piston. Diamond only charged 32 bucks extra for relocation the valve notches.

Flatlander racing has the K1 cranks for 689.