360 or 383 build up

[rallye72]

What would be the benefit of building a 383 over a 360? Would the 23 extra cubes out weigh the 150 or so extra pounds?

[fastmopars .inc]

well if its an a-body build a small block and if its a b-body build a big block.

you can make a small block perform kind of like a big block for lots of money, or you can fit a big block into a small car for lots of money.
it all comes down to what approach you want to take and what your idea of the ultimate street car is.

[madmax4073]

Yeah but a big block is just plain cool. The ladies love those big inches.

[fastmopars .inc]

yes but when those big inches are turning the back tires and the car isn't going anywhere, you aren't going to win races unless your racing an import.
basically if your gonna build a big block your gonna need to spend the extra money everywhere else, either beefing it up so it doesn't break or putting money into traction devices to prevent the tires from spinning.

[madmax4073]

Spinning tires = fun

[rallye72]

You guys are like the little angle and little devil on my shoulders
I have a dart I will drop a V-8 in at a later time. Once I grenade the slant 6 (yea, I know good luck) But I just gathering the parts as they come. I can pick up a 360 and a 383 for pretty cheap. Don't need both.

[rumblefish360]

You can lighten the big block preety well with alum. water pump and housing, heads , intake and headers right down to a small blocks stock weight.
The 383 will like to rev. Like a small block, it has a short stroke.

The 360 is a small block that thinks like a big block, larger stroke than it's brothers. It will make peak torque and HP sooner than it's sb brothers.

The only extra expense in the big block is a few dollors more in heads and maybe pistons. Barley worth the mention considering the power it will make over the small block.

Bang for the buck? Who cares. They both rock. It is a close call ethier way. Both guaranted (sp?) to be fun when your done.

[72Challenger]

Well, to answer you original question, it's not really the extra 23 inches that gives the 383 it's edge. There are really 2 advantages:

1) The larger bore allows for larger valve sizes, which means greater air flow potential. Ultimately, power production is all about airflow.

2) The shorter stroke allows a higher RPM at the same average piston speed. Assuming that piston speed is the ultimate limit on RPM range (a big assumption, there are a lot of other factors, but that's a major one), the higher RPM means even more airflow. At an arbitrary limit of 4000 ft/min piston speed, a 360 will spin 6700 RPM and move 698 CFM, a 383 will spin 7100 RPM and move 787 CFM. This assumes 100% volumetric efficiency for both engines.

Combining both these factors, it is easier to achieve high volumetric efficiencies with the larger valves, allowing you to make use of the higher rev limit.

[hedgehog]

Ingoring all other factors such as conversion costs(if applicable) and other things, i would build a 383 over a 360, no hesitation.

[fastmopars .inc]

okay well if he could ignore all conversion costs why would you go with an overweight 383?
i would pick up a complete 495 lbs aluminum indy block that makes over 1000 hp and drop it straight in and burn rubber all the way to the border and back, with 5 ladies in the car because since i can ignore the cost i am gonna make my dart a removable hard top, and stretch it a few feet, add that third bench you know?

okay the 340 is the same as a 383 just about 40 cubes smaller and willing to make the same horsepower, a little higher in the rpm range, while cutting a little bit down on low end torque. yes we all know torque gets the car moving but a dart is light, a small block dart is about as light as they come and when you have a car thats around 3000 lbs race weight it doesn't matter what kind of tire you put under the back, if it makes more than 400 hp your gonna have fun putting the power to the ground, especially on the street. yes a big block weighs about 150 lbs more than a small block but that's up front, over the front tires, that's a really bad place to put extra weight. have you ever worked on a big block dart? tried to change spark plugs? not the easiest job to do.
basically if you want to go 9 seconds and keep it streetable yes a ladder bar rear with a 451 in the front is the hot ticket, if you want to go 11's and keep it nice and streetable a tight small block will do it just fine, and it will still handle and brake just fine. if you have the money to make it a successful big block car than go ahead and do it, but if big block darts are that great, why aren't they everywhere?

[Slingshot383]

And a 383 will live a long time spinning and shifting at 7100 rpm with stock crank and stock rods. OK, stock rods that have been shot peened and with good bolts installed. Cam and intake selection will make a difference on performance.

[madmax4073]

Magority rules. You have to go with the big block

[ohioDemon]

i think it would depend on what kind of parts you have now. i went smallblock because i had block,crank, and other components. if i would have had to buy bigblock parts, i would bypass the 383 and go straight to 440.

[toad490]

there's no replacement for displacement. End of story.

[MOPARMANJAMES]

In considering the choice between the two engines you need to ask yourself what you want to do. If it is roadracing, you might opt for the lighter weight 360 to save wear and tear on the brakes and tires.
If it is drag racing you choose the 383 since it is one of the most overlooked hands down great wedge designs that was ever made.
If I were making the choice just based on a street strip car, the 383 would be a clear winner even if it weighed 100 pounds more than it already does if my only choice were these two engines.
Look at the advantages, rod to stroke ratio of 1.87!!! over the 360's of 1.63, this is a tremendous mechanical advantage.
Bigger bore, bigger valves, more airflow with less shrouding already mentioned.
What hasn't been mentioned is most came with a steel crank,
the lifter bores are at a much better angle than with a small block,
the block is much stiffer than the 360's, you can use cheap 440 rods and custom pistons for an incredible 1.99 rod to stroke ratio
if you choose to.
You can use more cam without having piston to valve clearance problems you do with a smallblock.
The oil pump is and filter are much better located on the big block(all you small block guys remembering your headaches yet?)
How about all those silly oil galley plugs that are forgotten during small block assembly?
Iv'e built both and run both, the 360 is a nice little engine, actually as Smokey Yunick said "It was the best smallblock that Chevie never built", with it's tall deck and long rods.
But the 383 is a class apart, to me it's that much better.

[shelby340]

There are a couple variables you have to decide on before you make your choice.

How much power do you want to make? If around 1hp per cubic inch - it would be hard to justify the 383. If you want to go up around 500hp well then it gets hard to justify the 360 because of the second question.

How much streetability to you care about? If your making 500hp with a 360 your going to have a motor much more nasty than a 383 making 500hp.

What about doing maintenance on the motor after it is in the car?
Changing plugs or the starter or whatever is going to be a PITA if you have a 383 as opposed to the 360.

Really, you are the only person who can answer the question. How much does each of these factors mean to you and weigh the pros against the cons. Remember though to do whatever is going to be exciting for you and save practicallity for minivans.

[rallye72]

Originally posted by shelby340
[B]There are a couple variables you have to decide on before you make your choice.

How much power do you want to make? If around 1hp per cubic inch - it would be hard to justify the 383. If you want to go up around 500hp well then it gets hard to justify the 360 because of the second question.

How much streetability to you care about? If your making 500hp with a 360 your going to have a motor much more nasty than a 383 making 500hp.

What about doing maintenance on the motor after it is in the car?
Changing plugs or the starter or whatever is going to be a PITA if you have a 383 as opposed to the 360.

]

I want the most power, With this engine streetability is no issue. I would like about 450 without spray. By the way, what is PITA? I'm not good at computer lingo. I finally learned LOL.

[shelby340]

You want the most HP, no concern for streetability. Go with the 383. You don't have to spend a ton either if your creative.

PITA is an old one: Pain In The A**

[George G. Leverette]

I havbe a 74 Duster with 360 as daily driver it is equipped with some goodies, Mopar short block (mistake) eddy RPM heads and intake with Holley 750 CFM carb, .092 bars, frame connectors PROTRANS 727, 8 3\4 rear 215x60x15s up front 235x60x15 out back.
The 68 barracuda is getting a 383 from a 68 RR installed with original BB manifolds and basically the same suspension as the Duster. The BB install is a PITA even with the Schumacher motor mounts. Some questions are what exhaust system will be used, under hood clearance is critical, closeness to the master cyclinder is close and the right side exhaust system clearance is very close.
Promised myself that I would never put another big block in an A-body after the 440 in a 73 Duster. The performance difference between these two engines will be minimal in street form, and the big block will not have AC or power steering where the 360 has factory air and a firm feel box.
Unless you have a lot of patience, money and experience get the 360 drive it for a while and when an overhaul is due stroke the sucker and have over 400 cubic inches.
But ther is nothing like a big block in an A-body.
Check www.bigblockdart.com

[Eats4dz64]

Im running a 383 with the .484 purple shaft cam and edelbrock heads, and making about 430hp. I also have a friend that is running a 360 with mass port work and the same cam making 380hp. My 383 is in a 64 a-body and the only PITA is having to remove the passenger side header. Plug changes, starter changes and oil changes are all a piece of cake. And the distributor is where it belongs "IN FRONT!".

I was going to build a 451 out of a 400 block I aquired, but since I found out that K.B. is making some half desent piston for the 383 I think Im going to stay with it. Feels good when people ask what motor you got after making a quick pass and them expecting you to say 440 or stroker, then they get that Holy Crap look when you tell them its a 9.5-1, 484 cammed 383.

Heres a good page to read, maybe this will help you decide. http://victorylibrary.com/mopar/rod-tech-c.htm

[MOPARMANJAMES]

Originally posted by Eats4dz64

Heres a good page to read, maybe this will help you decide. http://victorylibrary.com/mopar/rod-tech-c.htm

That article was one of the most contradictory pieces that I have ever read. I have done a lot of reading and it's true that most manufacterers prefer a rod to stroke ratio of 1.75:1, but these are family car engineers.
The article states that longer rods are better for higher revving engines with smaller ports and carbs, What a load of crap.

It also says long rods make less low end torque due to low vacuum caused by the piston moving away from TDC slower at lower engine speeds, yet does acknowlegs that the piston dwells around TDC longer, making higher cylinder pressures and more power! a direct contradiction since power is derived from torque!

Smokey Yunick was a respected engine builder, He said "use the longest damn rod you can fit in the engine!"

[hedgehog]

The longer the rod, the slower the piston speed is at any given rpm compared to a shorter rod. The slower the piston speed, the less pull it has on the port(if you will). The longer rod will make more power at a higher rpm(not necessarily high rpm) than the shorter rod because it takes more rpm to drain the port than the shorter rod. Changes in piston speed be it stroke or rod length will affect power output at given rpm points or ranges.

[MOPARMANJAMES]

You have two engines, a short rod engine and a long rod engine,
same displacement, same heads, etc.
They are spinning at the same RPM, so it takes both pistons the same amount of time to complete a revolution.
The long rod piston however, spends more time at TDC, then, I'm guessing accellerates away from TDC at a quicker rate than the short rod piston.
The long rod piston then spends more time at BDC than the short rod piston, so, I can see no advantage in cylinder filling to the short rod engine since the intake is still open at BDC so if anything, the advantage would go to the long rod engine.
I think in terms of the time it takes to fill a cylinder vs the time it takes for the combustion to build pressure, the long rod design far overcomes any small disadvantage in fill time if any.
That's why I thought the tech paper was contradictory, I thought the max piston speed was higher on a long rod engine due to higher dwell times at TDC and BDC.

[MoparMarcIdaho]

I have had some good running small blocks.BUT I have had some great running big blocks too.As far as in stock trim,the B and RB motors win hands down.Whats a hundred pounds extra weight compared to the fact that the bigger motor does better by accident than the small one does on purpose?next.

[Eats4dz64]

I didnt find anything wrong with this explanation of ratios. In some of the examples they use way wrong applications in parts but there are only making references to how different the parts would be, not telling you to use those parts on those motors. In one area he says a 600carb on a 440. Well duh we all know you wouldnt do this but the only point was with a very high ratio you would see a large motor with a carb that may seem a bit small.

I 100% agree with the web page.

[MOPARMANJAMES]

Originally posted by Eats4dz64
I 100% agree with the web page.

I don't, can you explain why you agree? I need some type of logical explanation as to why things work the way they do, I slow like that!

Furthermore, I can't remember which magazine it was, but I know it was a Chevy engine, and they built 2 engines with the same bore, same stroke, just different rods and pistons and the longer rod engine made more horsepower and torque throughout the
ENTIRE RPM RANGE. They tried to match the total weight of the rod/piston assy on both engines and both had the same compression ratio.

That pretty much wraps it up for me. Less stress and loading, more power, better reliability.

[Eats4dz64]

Both engines at the same rpm the short rod is traveling faster. I think you took the dwell time too far. Its not that the piston just sits right at TDC for a long time, its that for the first 3rd of the down stroke is at a slow piston speed. The shorter rod is quicker to respond to small changes in the stroke wich causes the higher speeds when the longer rod is less affected by these changes.

[hedgehog]

Two engines, same displacement, same bore/stroke but different rod lengths. Yes at 5000 rpm they are both turning 5000rpm. Average piston speeds are identical. However, rod length is not used to calculate average piston speed. It is used, however, to calculate instantaneous piston speed. Which we figure at every degree.

The Chevy engine in the magazine was one example, one only.

Smokey Yunick was primarily a small block chevy engine builder. Back in his day they didn't have the heads that are available today. If they wanted to make more power at 8000 or whatever rpm they had to use as long as rod as possible.

Lets look at two factory engine designs: A 440 Mopar- look at how small the intake ports are compared to some of the other bb heads such as rectangle ports. The rod ratio is 1.8. If it had a shorter rod say like a bb chev at 6.135", that would give a 1.636 rod ratio. That faster piston speed would drain that intake port in no time. The peak power rpm would drop drastically. It would probably work good for a tow vehicle however. Now the 427 chev rectangle port. Look how big those ports are. Now the rod ratio is 1.63. The designers of these two engines knew what they were doing. That huge port on that small of an engine needs a shorter rod to have any kind of low speed power on the street. If it had a 440 rod, it wouldn't fall out of a tree.

[rumblefish360]

Not for nothin, but at the power level needed for a street car to perform well, lets just say between 400 and 450 HP, the rod ratios and other little things like this will not matter as much as would a well balanced combo and a good selection of parts to use on an engine, never mind changing it.
Strokers can be a bit more custom. But they can be done on the cheap (So to speak) as well without getting nuts on rod ratio and everything else.
A stock 360 or 383 with a solid bottom end with stock parts will perform great with a balanced combo.
If it stood next to an engine totally trick out with these tricks, you would never know the difference if you drove them both.
Didn't Smokey Yunick once say something like the "360 is the best small block engine Chevy never built."

[MOPARMANJAMES]

First and foremost Hedgehog, you are absolutely killing me with your 427 chevy example, your telling me if you put the 440 rods in it it's going to fall flat on it's face due to the big ports???
Okay, you mean just like the longer rods and big ports that are in a 426 HEMI?!?!
We better recall those slugs and get them fitted with Chebbie rods!!!
What you guys seem to be saying is for the first portion of the stroke the long rod piston moves slower than the short rod piston. This in turn has an adverse affect on the vacuum signal to the carburetor, which causes erratic fuel mixing at low rpms.

I say that yes, this is sometimes the case if you use too large a carburetor/intake/head/cam for your application, you will have this drop in vacuum and the engine will hesitate, as it would with any engine, and I concede that the characteristics of a long rod engine may accentuate these symptoms.

However, in my experience, most Mopar intake runner sizes, including max wedge, have been relatively fine for producing both low, mid and high end torque in a 383.
Heck, I knew one person who ran an 11:1 383 with tunnel ram and two 650 double pumpers with progressive linkage and a Mopar .620 purpleshaft and it responded like it had injection. It was in a 3000# car with 4.56 gears and ran 10.9's at sea level, when torn down, we noticed that the vaves had been hitting the pistons ever soo gingerly!
I should metion that I once put too large a carb on a 383, an 850 with a single plane and it did bog until I increased squirter sizes and accelerator pump cam.

Anyway, it's been a hell of a topic and I'll still choose longer rods when I have the choice. I'm out.