Stroke a 383 Mgnum or 400 engine?

[Challenger_7]

Hi again good friends.
You remember I was asking about which 440source kit to use for the 400 block I have in my 71 Chally convertible, and after some debate, and based on my use of the car (street plus power), it was agreed best to use the 400 >> 451.

But now, after searching for the past year, I believe I have a lead where to get the 383 Magnum engine that used to sit in the car, or maybe just a 383 Magnum, but not necessarily the matching no one.
At this point I am very much tempted to go for stroking the 383 Magnum. Please help me out, and here are the two issues.
1. 383 Magnum or 400
2. If 383 to be used, 440source offer 2 types
   A. 383>>496 (4.250" stroke/6.535" rod)  Approximate Bobweight: 2150) or,
   B. 383>>438. (3.75" stroke/6.760" rod)  Approximate Bobweight: 2100) ??
WHilst the above means little to me, but I suppose option B means smaller travel, higher RPM and therefore better throttle response?
Whatever...please advise.

Thanks again, Farouk

[Runner]

id go with the 400 block,  they look the same as a 383 and have more cubes. id opt to do a 470 though (dont know if 440source offers a kit for that or not,  but im sure muscle motors does.


  a 438 must be a .060 over 383 block?  i think diamond sells a shelfed .030 over stroker piston for the 383 to make it a 431.  i believe the next motor i biuld will be a 431 simply because i have 2 nice .030 over 383s sitting here ( one is the numbers matching block for my roadrunner and most likly wont see an engine bay for a very long time.... if ever again.)

[firefighter3931]

Farouk, if you go with a 470-496 combo.....you will need a set of aftermarket heads to get the most out of it. 

The 3.75 stroke 451 (400 block) or 431 (383 block) makes a very nice street combo and you can get by with a stock head. The bigger displacement will cost more due to the supporting components required to make it perform up to expectations. On lowdeck engines my preference is for a 3.75 stroke build to keep the engine happy ( better rod ratio & less side loading of the cylinder walls) and durable. 



Ron

[RD]

have a friend who has a 11 to 1, 451ci stroker that makes 634hp at the flywheel and 612lbs tq. 

[firefighter3931]

have a friend who has a 11 to 1, 451ci stroker that makes 634hp at the flywheel and 612lbs tq. 

Yep, that'll work ! 

What's the combo Jamey ? Roller cam and some very nice heads for sure ! Probably a tunnel ram or a Dominator on a single plane....



Ron

[RD]

have a friend who has a 11 to 1, 451ci stroker that makes 634hp at the flywheel and 612lbs tq. 

Yep, that'll work ! 

What's the combo Jamey ? Roller cam and some very nice heads for sure ! Probably a tunnel ram or a Dominator on a single plane....



Ron

you nailed it ron..  mopar stage VI's with a victor intake a 1050 dom, and a roller cam.   its in a 72 challenger that absolutely screams (6 speed richmond).  it is really fun to get plastered back in the seat in!  did I mention he has the nitrous hooked up for shitz and gigglez  he is nutz, i know.

[firefighter3931]

That sounds like a KILLER combo Jamey !  Any plans to get it out to the track ? If ya get a chance....post a pic or two !   



Ron

[Challenger_7]

Thank you buddies for the input, and sorry for coming back so late. I have been busy with the other engine which dveloped an oil leak at the end of the crank shaft and had to be removed again. Hopefully it is ok now.

Ron, I do agree with you on the the smaller stroker of the 383 for the same reasons we agreed on the 400>>451. If I get the 383 at a reasonable price, I will go for it otherwise will stick to the 400.

However, if I do go the 383 way, and get the 438 kit, any idea what is the max HP I can get out of the standard heads, i.e. without much add ons?
Secondly, if I do add on whatever needed stuff, what is the max HP I can get (without N2O) and still have a smooth running engine for daily cruise?

Runner 440source have a kit for 438, and for the 400 block they have kits of 451, 470, 500 and 512. Check them out.

Regards, FArouk

[is_it_EVER_done?]

Challenger_7: The 400 block is so much stronger than the 383 block that using a 383 is a waste of time, performance and money, especially if you plan on BUYING a 383 instead of using the 400 you have. Since the blocks look identical, what could you possibly gain?

Also, going with a 451 instead of a 470 will decrease longevity/durability due to the short piston that a 451 uses. If you really want the 451, the 512 is a better choice as they use the same piston. So why would you give up 60+ cubic inches, and a bunch of torque?

Though I addressed this point in one of your other posts, you are not going to have access to torque plates for the boring/honing of your block (correct me if I'm wrong on this), so having a stable piston (longer) is going to be a big factor for longevity/durability and power.

Believe me that I my suggestions are taking into consideration your geographical location, cost of importing parts, your intended use of your car, available machining technologies, and your subsequent need for low maintenance, power and longevity.

Do what you want, but I assure you you will be more than happy with a 400 based 470! There is no point in buying a 383 block just to achieve decreased displacement and a weaker unit, nor is there any benefit in doing a similar build in your 400.

[firefighter3931]

Farouk, if you have a 400 block available....i would use it. You can order up a complete 451 kit from Brandon and he now has a balancing option available which is well worth it. 

The cylinder heads are where the power is made....the better the flow the stronger it will be. With a set of stock heads that have the usual 3 angle valvejob and cleanup you can make 450hp or there abouts with the right supporting components....headers, cam, intake manifold carb etc....


Ron

[Ghoste]

What is it that makes the 383 blocks weaker than the 400 ones?

[firefighter3931]

What is it that makes the 383 blocks weaker than the 400 ones?

The 400 engines have a much beefier main saddle which helps with high HP applications. Nuthing wrong with a 383 for a nice stout strret build, inmo. 



Ron

[Challenger_7]

Hi again. Looks like my head is bouncing like a ball again trying to decide, but this time much less

Ok, first decision now taken, will stay with the 400 block and forget the 383. I will only buy it if it is the orig engine that was on my car, and will store it in a safe place.

Now on the issue of 451 as oppsed to 470, and I do not mean to start a fresh debate.
I went back to my original thread converting 400 to 512which is_it_EVER_done? pointed out and read it carefully, as well as the post made by Challenger 340 Dyno'ing the EDDY 451 on the engine he built, which produced in excess of 560 HP on the 451 kit, which is more than what I am looking for in terms of HP, whilst still maintaining a smooth week end driver.

My only question here, is it true that the 470 kit offers more durability to the engine than the 451? I was under the impression that it was to the contrary, but reading the two threads mentioned above, the main emphasis and comparison was between the 512 and 451, and based on my intended use, the 451 won.
So which is it, is the 451 better or the 470

Thanks again.

[is_it_EVER_done?]

Challenger_7:  The 451 kit uses a piston with a CH (compression height) of 1.320 inches. The 470 kit uses a piston that has a CH of 1.480".

A longer piston is more stable (less rock), so a longer piston will keep the rings more "square" to the bore which helps the rings seal and reduces blow-by, oil contamination, oil consumption, and ring wear. A longer piston will also decrease wear on the cylinder bore and the piston itself.

Not only is there a difference in the CH of the two pistons, but the actual length of them is much more than the CH differences would indicate since the 1.320 (400-451) piston is also used in the 400-512 cubic inch kit, and also the 440-543 cubic inch kit. This requires the 1.320 CH piston to have a shorter than average skirt so that it will clear all the different strokes.

The 1.480 CH (400-470) piston is not only longer than the 1.320 piston due to its longer CH, but it has a longer skirt, so it's overall length is much greater than the 1.320 piston. --- The 1.480 is also used in the 440-512 kit, but the piston is designed for the 400-470, so the skirt is not shortened to fit multiple applications.

Since you have never said if you have access to torque plates, I am certain you don't. If you don't know what torque plates are, they are thick steel plates that bolt on to the block to mimic/approximate the forces that the heads cause when the heads are installed/torqued. They are used primarily in the final honing operation on the cylinder bores so that the cylinders are round when the engine is assembled as it has been found that the cylinders will distort slightly when the heads are installed.

Don't worry about this as ALL the factory engines were machined without torque plates, and Millions of performance engines were also built without them, but since the 1970's, most all performance builds are done with torque plates. BUT, a short piston (more rock) in a non-torque plate machined cylinder (not perfectly round), will obviously increase the undesirable factors that I stated in paragraph 2 above.

I could go on, but just these fundamentals should show you that a 470 is going to be a much more durable engine choice for your situation. Plus the added torque of the longer stroke is substantial, and is about as much fun as you can have with your clothes on! But the fun factor is just a side benefit, as the durability and ease of maintenance is the main factor.

[Runner]

thats a good read  is it ever done.   the 451 biuld is assuming your using a long rod and not the shorter 6.358 rod.   the ch of a 6.358 rod 451 is 1.722 .     i diidnt realize that a 512 and 451 used the same piston but with a shorter rod-longer stock combo.      a 470 sure looks like the right way to go with what youve outlined.

[firefighter3931]

Well, i'm still not convinced the 470 is the "right" displacement for this build for several reasons :

(1) Farouk is planning on using a set of stock heads....the 470 really needs a good flowing head to get the most out of it. A 470ci engine will be all done at 4500 rpm with an unported oem head.

(2) Rod ratio will be inferior with the short rod 470 engine. Couple that with a head that is really to small for the application and that spells out a poor performing combo. Longer rods work very well with smallish cylinder heads.

(3) the 451 will maintain a 440 type 1.80 rod ratio with a much lighter bobweight meaning it will rev fast and be less stressful on the bottom end....a win win situation.

(4) 451 cubes will be better suited to a smaller flowing head. There are many 451's that have logged mucho street miles w/o any durability issues....it is a proven combination. The short rod 470 will sideload the cylinder more than the 451 will. A 1.32 CH piston is no big deal....especially with the reduced sideloading of a 1.80 rod ratio.


Those are my thoughts on the build....and that's how i would do it given the parameters outlined in the original post. 




Ron

[Challenger340]

Just my opinion, no flamer intended.

I prefer Rod ratio (451), over Piston Skirt length (470), especially with stock Iron heads. I'm with Ron, Firefighter3931 on this one. Everyone is a product of their experiences.

Also, in my experience, I've found the 451's to be extremely durable engines. Many we built, were still going strong 10 plus years later, a few are still running today !
Poorly, yes, but still goin !
They weren't grannied !
We built lots of them in the 80's with stock LY Rods and ARIAS # 7751 Pistons.
Never had Skirt issues.

Just for trivia, I invite anyone to check, ARIAS was the FIRST manufacturer to stock/build an "off the shelf" Piston for that application with the 1.094" Mopar Pin, back in "those days".

As for Torque Plates, we use them for the final .005" of honing, and, we remove & retorque, no less than 3 times per side during stone changes/cooling, and to check repeatibility on the cylinder.
But no matter, as was stated, lots of engines run fine that weren't Torque-Plated.

Just my 2 cents, no offense to anybody.

Bob out.

[Challenger_7]

My oh my

Ok lets add some more input here, and forgive sometimes for misleading you. True Ron (firefighter3931), I did mention stock heads as a possibility, but did not want to limit myself to that, especially after seeing what figures were presented by Challenger340 in his 451 combo. So for me, I would replicate all what Challenger340 did on his engine, with his permission This will certainly give me lots of power, more than I had hoped for.
I only paused here in view of the CH comparisons introduced by is_it_EVER_done? and wondered if I should be concerned with this. I also wanted to make sure that the size comparison I am now considering is properly noted, i.e. 400>>451 or 400>>470 as opposed to 400>>512 previously discussed.

So gentlemen, considering that I will go all the way, heads, headers and whatever is needed short of Nitros (at least for now), are you still voting for the 451 aginst the 470, in spite of the longer CH?

is_it_EVER_done? you also refer to honing with torque plates, true we do not have this here. They hone, but no torque plates. One thing though, I have concerns going as far as 470 and dread to think with all the add-ons, will I be able to use the power generated, taking into consideration I do not wish to change the stock look of the car, i.e. no massive wheels.

Cheers, Farouk

[Challenger340]

I'll try and get off my ass this week, and scan some "actual" dyno sheets on the 451 Farouk.  It may help in your decision.
It wasn't my engine, just one I did for a Customer.

Apologies, but it's "that" time of year again. Just sooo busy !   

Nothing wrong with the 470 deal either, just needs more head flow as Ron says.
and,
from the 451 sheets, as you'll see, the 451 is pretty much "all done" at mid 5,000 rpm's even with "cost effectively" worked EDDY heads, and nice "driveable" camshaft. 580's & 570's.
Very "useable" power curve for the street, in my opinion.

The 470 would peak earlier still, or require more $ for headwork. You can spend money until the cows come home, your choice. I'm not trying to discourage you, if you wanna go "all the way", but all means "go for it".
We could start a new thread to compare a 470 to a 499, then a 499 to a 528, then a 528 to a 540, 540 to a 572, etc., etc.

It all boils down to "what" will put a smile on your face ? and, for "how much" ?

Bob out.

[is_it_EVER_done?]

Firefighter and 340: I'm somewhat shocked that you guys still believe in the long rod myth, as virtually all the supposed benefits or disadvantages of different rod ratios have been proven to be non-existent. This has been known fact for many years now, and frankly, with your levels of experience and expertise, you should be well aware of this.

Before it was disproved, I too used to be a believer, as this was one of those "absolute facts". All the logical concepts (and supporting math), of cylinder sidewall loading, piston dwell and speed having an effect on head flow, torque curve tailoring, and all the other "wonderful" changes that could be effected by rod ratios were very seductive. BUT the best and brightest engine builders/developers, and every auto manufacturer has proven the long rod approach to be (at best) worthless, and if a "too short" piston is selected just for rod length, it becomes a detriment to durability and power. This has been proven beyond any shadow of doubt.

The whole rod ratio theory has been proven to be nothing more than a reincarnation of Zeno's dichotomy paradox. In other words, even though the logic and math of the benefits and disadvantages of differing rod ratios are totally provable, the "real world", and empirical/scientific data proves them false (which is the definition of a paradox).

All the theory, conclusions, and mathematical proof that continues to get thrown around comes from the 20's and 30's studies for military aircraft engines (which operate a full throttle, high altitude, thin air, and around 2,200 RPM). If any of the conclusions had any merit originally, it was in the aircraft usage arena.

As these theories became "fact", factory engine development followed what was (at that time) absolute. -- Fast forward 30 year to the 60's. Smokey Yunik (who was always looking for an edge or cheat) decided to arrive at the "perfect" rod ratio for his NASCAR engines. He had even written a book on "speed secrets" that included the long rod theory.

He tried dozens of rod ratios with dyno and track tests. After a year plus, his statement was  "the rod connects the piston to the crank, nothing more, nothing less". ALL the pluses and minuses that were "known and accepted" for differing rod ratios proved to be non-existent. This in itself should have proven the whole rod ratio theory and related math as a paradox, but people are extremely reluctant to "let go" of their beliefs, so others continued testing, and continued, and continued.... Not one person could ever show any benefit whatsoever to a long rod!

Fast forward to today. None less than Reher-Morrison decided to put the rod ratio theory to the test a few years ago. Keep in mind that they have a multi-million dollar engine development budget, and are amongst the best engine builders/ automotive engineers to ever grace the earth. They built a big block Chevy engine about a dozen times, as identical as humanly possible, except for differing rod ratios and related pistons to maintain identical compression ratios.

The largest difference that they recorded was single digit horsepower, and torque differentials. The difference was not even outside the statistical norm for even the same engine on different dyno pulls. NO improvement or shift in torque or horsepower curves, NO improvement or decrease in head flow, combustion, cylinder wear, or ANY other element! This was the same result that they had found with 30 years of engine builds, but now it was scientifically proven.

To read what David Reher thinks about rod ratios, click the following link. It is 3 (short) pages long, and the "next page" button is at the bottom of each page. His thoughts on rod ratios start at the bottom of the second page. == http://www.rehermorrison.com/techTalk/10.htm


If David Reher's scholastic textbook isn't quite enough evidence, how about Jon Kaase? Another of the elite top, smart, and best engine builders of our time, he has also won two Engemasters competitions, and is so sought after that even at $90,000.00+ per engine, he has a waiting list measured in years. His testing resulted in his championing the short rods with a longer piston combination. His pro stock engines run rod ratios in the 1.3's and his "durability" engines run ratios in the low 1.4's. Some builders are at 1.29

Here is Iskandarians comments. == http://www.iskycams.com/techtips.php#2005

Do a Goggle or other search (rod ratio myth, or other keyword combinations) if you need more proof. 

The Mopar engines we are addressing on this site were designed in the late 50's. That makes the design about 50 years old! While other manufacturers were designing engines with more modern technology in the 70's and later, Chrysler stayed with our ancient iron. Fortunately it was damn good to start with, but as GM and Ford and all the imports built newer, more modern designed engines as technology advanced, the Mopar community was left behind, partially because there was no parts made for our engines, but even when parts became available, the Mopar community tended to cling to the 50's and older technology and beliefs instead of learning and applying the tech advancements to our engines. 

I can hear the outcry already --- "Those are race engine developers/builders, what possible correlation does a 800 inch pro stock or pro comp engine, at a rod ratio of 1.29, and operating at 9,500 RPM have to do with a street performance engine"?

Lets step out of the stone age for a minute an take a look at what has transpired in the automotive world as far as rod ratios go. Keep in mind that these are all street engines built for durability. GM has produced 10's of millions of engines that range from 1.4's to the 1.6's, Fords range from 1.4's to 1.7, Even the Viper was 1.69, and the new 392 Hemi that may be offered in the new Challenger is1.61.

Not enough proof? How about 100 Million imports such as Honda at 1.48 to 1.62, Toyota at 1.54 to 1.69, Nissan at 1.58 to 1.71, Mazda at 1.56 to 1.58, VW at 1.55, BMW at 1.60, Porsche at 1.66, etc., etc.

While we weren't looking, the whole world changed to short rod ratios, and dramatically improved engine durability. 250,000+ miles out of a car is quite normal now.

Designers found that a shorter deck height with a shorter rod will exert less cylinder sidewall loading than a longer rod/shorter piston, due to the fact that a longer piston has more sidewall/skirt area to disperse such loading over a larger area, and since a longer piston is inherently more stable than a shorter piston, resulting in less rock, and more stable ring sealing, ring thicknesses could be reduced, which reduced friction. So the short rod/longer piston improves durability and performance while also decreasing wear.

Since the rod ratio differential "facts" have been disproven, all the opinions on how stock heads would make a 470 (somehow) perform at a lower level than a 451, also become baseless. Keep in mind we are only talking about a 19 cubic inch difference between the two engines.

I'm sorry this is harsh, and I certainly don't intend it as a "flame", but there are too many myths that permeate the Mopar web boards, and continue to get passed along as "fact". Some (like this rod ratio theory) have been scientifically and irrefutably proven to be false. It's an obligation to those that are learning, and relying on the information they gather from these sites, that these myths get busted so that they don't get incorporated into their projects, and worse yet, get passed along as fact!

I will re-state for Challenger_7, I believe that I have proven that a 470 based 400 is the best choice for your situation. A set of Eddy heads will only make it that much better, (stock heads will work, though not the best choice for either build). A 451 will work just fine if that's what you want, but with its shorter piston, coupled with no access to torque plates, It's not your best choice, but build what you want, as I'm sure you will be happy either way.

As far as cost differential, there is none. Nor do you have to modify your car (though I would suggest a pair of sub frame connectors even with a stock engine). The extra power of either engine will provide plenty of torque for improved drivability, and will actually decrease the need to spend money on things like lower gears, valve train components designed for high RPM, and other "racy" type parts. However with the large increase in torque with either engine, you should invest in a good clutch.

[firefighter3931]

That's a very well written response. I don't think we're disputing the fact that a short rod combo can't build power. It's just not the best choice with a port limited engine....which a BB mopar is, especially with a factory sized head. We could get into the whole CSA arguement and how it affects velocity and stalls big engines at lower speeds....but that's another subject. 

Compare a BB chevy with a BB mopar and you will see two different ways of making power. The BB chevy has short rods and the heads have big ports. perfect for high rpm operation but not so good for low end power. Contrast that with an RB mopar which has a tall deck, longer rods, better rod ratio but a small cylinder head. Now you've got a torque monster compared to a peaky high rpm engine....and we all know that torque rules on the street. That's why the mopars would allways kick chevy tail on the street. 

Of course this discussion is about basicly stock engine configurations....prostock 90k builds notwithstanding. With a small head like Farouk is planning to use....the better rod ratio build will carry the torque peak longer and make more power. Jumping up to a bigger head like an Indy or Edelbrock changes the parameters of the build somewhat...and with increased port volume rod ratio becomes less critical....but the engine's behavior will change. Big ports and short strokes make for peaky power curves. It might ultimately make more power but will that power be functional to the end user.

Bob has some dyno data that supports the long rod BB Chrysler build. What works good in a honda or toyota or ford or chevy....doesn't necessarily work in a chrysler..


Isiteverdone....i can appreciate you opinion on this subject and am quite familiar with the prostock theories and such with regards to rod ratio etc...I'm just not convinced that it's really applicable to old technology....which is what we're dealing with here. 


Ron

[is_it_EVER_done?]

Firefighter: did you even READ my post? I spent a couple of days digging up the data that disproves rod ratio theory, and you then respond with rod ratio theory!

You then continue as if I didn't even address your other points! Then come back with the same (scientifically disproven) arguments that were contained in the posts I addressed!

I am at a loss from this point on. What can I say or show? I am totally dismayed?

Be aware that this isn't a contest to sway others (at least it SHOULDN'T be), but is instead a venue to offer real data and advice to those that are asking. Simply restating your beliefs as a way to invalidate presented data, is not a reasonable, or valid response! Nor is referring to Chrysler engines as though they exist in some alternative dimension, with a set of realities that are opposite of the ones that exist in our physical world.

The fact remains that the theory has been disproven via scientific, analytical testing. Not on pro stock engines, but big and small block engines just like the ones that grace many millions of cars. If you choose not to believe it and ignore it fine, but at least the information is now available to others, so I've done what I can. 

[Challenger_7]

is_it_EVER_done? I wish to thank you for the extent of research that you have gone through and the time taken to elaborate on your point. This is exactly what this great group is all about, sharing and providing information. Some theoretical and some earned through practice.
I am also very grateful to Ron and Challenger340 for their valued input in the area of their experience too.
With what you have said, I must respect the references you have made, and seeing Ron with his experience accepting that with bigger heads the "myth" becomes irrelevant any way, and seeing that I did say I will be prepared to go all the way, then I see myself swaying more in the direction of the 470.
I had no idea about what was being discussed but am able to follow it all. Seeing the "Myth" is broken, or in my case not relevant, then common engineering sense does vote for the longer piston and shorter stroke (rod).
But just to know what my new considerations are, pls help me here.
If I do indeed go for this combo, am I expecting a high revving engine or still the same?
I will go for heads, headers, inlet, carb and whatever is needed, and would certainly appreciate specific recommendations from you all.
Am I expected to use a special camshaft too? If I do, do I use the stock lifters or improved ones?
I am intending to use one of those "crossed" exhaust systems, as reading about them convinced me that they are good. Is it so?
You mention improved clutch and I have always wondered about this. Any recommendations?
Finally, the magic question, without going madd about add ons and stick to the items mentioned above, what sort of HP do I expect?
Once again, I thank you all for your very valued input and time given to this issue.

Regards, Farouk

[firefighter3931]

Firefighter: did you even READ my post? I spent a couple of days digging up the data that disproves rod ratio theory, and you then respond with rod ratio theory!

Yep, i read your post....but it's obvious you didn't read mine that well. 

I think you're missing the point in an attempt to disprove what you consider to be theory which is in reality fact. Long rod combinations will make better power with a small cylinder head....that is fact.

Take a 190cc intake port with 215cfm max flow and drop it on a short rod 454 chevy and see what happens. Wanna guess ? 

Like i stated previously, rod ratio becomes less relevant as cylinder head flow increases. To say that short rods work with any combination is simply erroneous. You're welcome to prove me wrong....just build it and show me the numbers. 



Ron

[firefighter3931]

I see myself swaying more in the direction of the 470.

Farouk, there's nothing wrong with a 470...it will make excellent power. You will definately want to use an aftermarket head and select the other components based on the car's intended usage. In this instance a shorter rod will keep the piston height more reasonable allthough side loading will be increased. It will still last for many miles of street use and be durable. 


Ron