are there any disadvantages to a 383? being a 350 block installation should not be an issue i'm assuming? pros are they have more torque then a 350 of the same make up?

 

A 383 has 33 more cubic inches than a 350, that's the advantage.

 

interesting, everyone always makes a 383 seem to be such a superior motor compared to a 350. thanks for the straight answer!

 

It's superior because it has more cubic inches. More cubic inches means more air on each stroke. More air means you can burn more gas. More gas means you can make more torque.

 

with a 400 crank doens't it have a bit longer stroke as well?

 

Yes, that's why it's a 383 instead of a 350. The longer stroke is irrelevant otherwise.

 

so which route would you go if you had the choice of a 3838 and 350 running roughly the same HP. am I splitting hairs at this point? thanks for all your imput-

 

If you built them equally, the 383 would make more power than the 350.

If you've got a working 350 core with a good rotating assembly, you can save money and rebuild it as a 350. As soon as you need to replace rotating assembly parts, it quickly makes more sense to build it as a 383.

 

If they were built for the same power, the 383 would operate at lower RPMs, would have more torque at any RPM.

 

With the longer stroke I wonder if you are trading something for that extra torque. Me thinks that the engine will not rev as easily (due to stroke) and may be slightly less fun to drive. But I have not compared them in a test drive. 383's are popular for pickup trucks so...

 

The "reving easier" thing is way down there in the effects category.

It does raise the piston speed, which could be argued to increase wear.

But, again if peak HP was the same between the two engines, the 383 is going to be a lot easier to drive - it'll be a much better butt-dyno combo.

 

Building an identical 383 and 350 with all the same parts except for more displacement, they will make the same amount of HP because the bore size is the same although it could be at a slightly different rpm but the 383 will make more torque.

Torque is what you feel driving stoplight to stoplight.

 

so just for clairification, 383 has a bit longer stroke, which increase cubes, and makes is a 383 vs. 350. It's NOT bored bigger? I've heard, (maybe from uninformeed) that a 383 has thinner cylinder walls due to boring and makes it more suspect to cracking the block? if it's just a longer stroke this theory would be a myth, correct?

 

A small block 350 has a 4.000" bore x 3.480" stroke...a 383 is typically bored and stroked, 4.030" x 3.750". Boring .030 is unlikely to impact cylinder wall strength, nor are you going to hit the water jacket. 350's are commonly rebuilt and bored .030 to make a 355.

 

A "383" is typically built from a used 350 block. The "original" ones used 400 SBC cranks with the main journals turned down from the 400 size to 350 size. Since the typical used 350 block needs the cylinders bored to clean them up, the typical stroker 350 is .030" over.

Do the math: 4.030" squared, divided by 4, times pi (3.14159) gives you the area of the base of the cylinder. The 400 crank stroke is 3.75", so multiply the area by that, you get the volume of one cylinder. Multiply by 8 for the number of cylinders, you get 383 cubic inches (rounded).

Do the same thing with a stock bore 350 with a 4.000" bore, you get 377 cubic inches (rounded).

Does a "383" have "thinner" cylinder walls than a stock 350? Yes, but so does a 0.030"-over rebuilt 350 (355 cubic inches).

As to the comparison as originally stated, the OP said "same power". That's not the same thing as "same parts". Put the same heads & cam in/on a 350 and 383, and the 383 will have more power because it has more displacement, more stroke "lever arm", and will therefore produce more torque. Horsepower = torque times RPMs divided by 5252, so the higher the torque at any given RPM, the higher the HP. To make a 383 with the same power as a 350, you would use a cam with lower duration, which increases low RPM torque.

It all fits when you understand what goes into all this.

Just to muddy the waters a little, the factory makes a "383" crate engine that has a 4.000" bore and 3.80" stroke.

 

so in a nut shell, a 383 assumes the same risk of of block fracture as a remaned 350 ie 355. I was just told that 383's are prone to block fracture? maybe in racing with 600+hp, I don't know, I was just asking the informed (you guys) as if this has any truth to it or not? thanks dan

 

The OP also asked about disadvantages of a 383. I am in the process of getting parts together for one, and it's taken a lot of research to match up parts successfully. Here's a short list of 383-specific parts:

- pistons (different skirt length?)
- crank (obviously a longer stroke)
- small base circle cam (so your rods don't hit the camshaft)
- factory clearanced connecting rods (have been ground in a few spots)
- block has to be ground near the bottom of the cylinder wall for connecting rod clearance
- aftermarket oil pan clearanced for extra swing of the crank
- once the rods are on the crank, the rod bolts may have to be ground as well

Nothing here some smart shopping and a die grinder can't fix, but more difficult than your average engine rebuild. If I had it to do over again, I probably would have went with a 350 for simplicity. Sure, it won't get you into the 11's without a serious race setup, but a 350 would still be fast enough to get me into trouble.

 

i'm buying this motor from a builder near me. there were 2 options a 383 or a 350, making the same power, but the 383 having more torque. I guess those are my fears, a 350 seems more simple than the 383, but for not much more $$ I can get the extra torque. I'm opting for the 383, just hope I don't have any problmes. that's why i'm leaving it up to someone who know's what they are doing.

 

you dont need a small base circle cam if you use a modern stroker rod setup like eagles H beam stroker rods

My cam just happens to be small circle cam but thats only because it has .600+ lift. A standard circle will work in some setups


there is no big difference in a 383 vs 350 other than a slightly longer stroke/rod setup with smaller piston compression height. It has no ill effects basically.

I'd use a modern day stroker kit and not use a 400 crank based setup. Get a kit thats been designed for 350 mains/journals/etc and has stroker clearanced rods for the cam

 

Well that's a horse of a different color. If someone else is putting it together, then there is no replacement for displacement. Go for the 383.

The only thing I can think of, is that a 383 is externally balanced if they used a cast crank. That is, the harmonic damper, flexplate, and rotating assembly are all balanced together. That makes replacing a flexplate or damper down the road more difficult, if they happened to have used a cast 383 crank.

 

Different pin height.
Obviously.
True.
Maybe, maybe not.


It would be nice to see the specs, including cam, for each engine.

Both external and internally balanced 3.75" cranks are available. External balance isn't that big of a deal, it's a standard flexplate or damper regardless - commonly available in either configuration.

 

Now that I think about it, you're right. I remember seeing the externally balanced flexplates in the Summit catalog.

I'm not speaking from personal experience, but I always thought the small base circle camshaft was to give a bit more clearance between the cam and the rods, much more than just taking a little bit off the rod near the big end and making sure the engine turns over smoothly.

 

Stock rods with the big ol' rod bolt head sticking up can have problems with hitting the cam, and small base circle can help that. H-beam rods with cap bolts pretty much eliminate the problem.

Buying a stroker kit, which has the crank, rods, & pistons included, can save a lot of hassles and surprises.

 

My old 383 had none of those. 350 block bored .030". 400 crank with the mains turned down to fit into the 350 block. Stock 400 rods and rod bolts. Stock cast 350 pistons. Camshaft had .550 lift but I don't remember the duration. It was enough to push my car into the 11 second range before the engine finally blew up after 2 years of racing following many years of street use in different vehicles.

 

True. Stock 400 rods preclude a lot of issues (but you still had to clearance the oil pan rails, right?).

 

SBC 400 stock connecting rod length = 5.45"
SBC 350 stock connecting rod length = 5.70"

That shorter rod length has to help out some with interference issues.

 

Not really. The rod bolts on stock 400 rods have their shoulders knocked off for cam clearance, which still often isn't enough for aftermarket cams. The overall length makes almost no difference to clearance, though.

 

It would make sense to me that the shorter 400 rod would have less chance of hitting the bottom of the cylinder bore or interfering with the cam.

I am no engine machinist though

 

Changing the length of the rod changes how far the small end of the rod sticks up into the cylinder towards the piston. Clearance isn't a problem in that direction. Clearance problems are when the big end of the rod hits the bottom of the bores or the cam lobes.

Changing the length very slightly changes the rod angle by a few degrees, which can have a tiny effect on clearance around the big end, but not much.

 

Since we are on the discussion of 383 strokers, I have a question. What are the pros and cons of using 6.00" rods versus 5.7" rods in a 383 build? I recently bought a Eagle rotating assy. from Summit http://store.summitracing.com/partde...0&autoview=sku and it was suggested to me to go with the 6.00" rods for better performance. I await the gurus advice and opinions. Thanks P.S. What size harmonic balancer is reccommened for a 383? I see they range from 6.610 to 6.250 to 6.375 and some are fluid damped and some have a elastomer core. Any ideas which is better?

 

another question how high of a C/R is too high for a 2 bolt or are 4 bolts recomended for all 383s and how much do you think it would cost to get splayed caps thanks
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hey BADMAN how much power do you plan on making those H beams are a bit over kill arent they i cant wait to see your motor built if you put those to use

 

I'm looking at about 475-500 HP. On any performance build I would go with a 4-bolt main block,it's simply stronger. I'm looking for durability considering I'm going with AFR195 heads,TPIS Mini-Ram, and a high lift Comp cam. Also trying to get the most bang for my buck using the best components I can afford. Hopefully I will be installing this winter, work lately has been a 7-day a week job. Will post pics once I get build started.

 

do you think 195s will be enough hell with that lightweight set up id run some 210cc and rev the hell out of that thing IMHO

 

A 6" rod gives you slightly more dwell at the top of the stroke, at the price of a higher wrist pin which leads to poorer ring support and more piston rock. For street use, you'd never notice a difference, and the 5.7" combination is usually cheaper.
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2 bolt and 4 bolt blocks are virtually the same strength. Either one is more than strong enough for anything you could keep on the street. If you were building a real performance engine out of a stock block, you'd want the 2 bolt block, because you could have it machined for splayed 4 bolt caps.