me and a buddy were talking about these two engines and he was saying the 383 had a ton of torque and the 400 was junk.

my understanding is the 383 is a 350 block with a 400 crank.

the 400 is basicaly identical to the 350 except for the bore of the cylinders and of course the larger stroke of the crank.

so why is it that the 383 can put out more torque than the 400 when they have the same stroke and the 400 has a larger bore.

it would just seem easier to run the 400 unless i'm mising some critical information

any thoughts or ideas would be welcome.

i think it has to do with the 350's 5.7 inch rods versus the 400's 6 inch rods.

i may be wrong,wouldn't be the first time!!

the length from the top of the piston to the bottom of the rod is the same though, so I don't see how rod length would matter. in fact they make kits so a 5.7" or a 6" rod would work.

the 400 small block usually gets a bad rap for overheating. I realy liked my old 77 chevy heavy half that had a 400sb but in the summer it would almost over heat going threw a drive thru.

I've ran mine for a year now and it usualy sees around 220 to 230 is that too hot:evil:

no, no, no... First of all your buddy would be one of these guys who thinks he knows it all. Only the narrow minded still believe 400's are junk and overheat all the time, blah, blah, blah. Certin delemias do come up with higher compressions, but that is beyond a streetable motor. Basically the 383 was designed/is so big because it gets more cubes and the same stroke of the 400 for more torque then a 350. This all comes without the need for steam holes to be done to your heads and in many areas around the country 400 blocks are becoming very hard to find and increasingly expensive.

A 383 will make no more torque then a 400 if the same parts are used. The 383 also will not out do a 350 by too much hp wise. The 383 is a torque motor, just like a 377 is a high end HP motor. A 400 is superior in hp numbers by far if you use the right cam and cylinder heads.

Overall it is really a stupid debate. I personally think the power and torque come a bit easier with a 400. Also you generally see a bit more hp on a 400 then a 383 with the same torque numbers, but it really depends how you build them.

In terms of the 3.75 to 4.00... I think you are thinking rod length... and actually both is the same, however many people are building long rod motors to cut down on quench and deck height and 4.00 rods are very popular to impore the rod angles of the 400.

Thanx Cap'n, I had a feeling that was the answer but I needed a little reinforcment.:D

383 is actually a 350 block punched out .030 over, utilizing a modified 400 crank, balancer and flexplate/flywheel. Street racers run them for low end torque.
400 small blocks are decent motors,but because of the steam holes and thin area between cylinders they are highly prone to cracking, this is a motor that you don't want to overheat!
For the cost, its easier just to pump up a 350, monies well spent!:skull:

With the same parts on both of them the 400 will make more torque and HP than the 383. The stock rod for a 400 is 5.56" long and often used in 383's. I think it is too short but that is a whole nother topic. You can get pistons to use 5.7" rods (stock 350) in either a 383 or a 400. With a 6" rod either the top ring is really close to the top of the piston or the oil ring runs into the wrist pin hole requiring supports. Both of which I don't like. You also run into problems with having to use a small base circle cam when you go 6" rod and clearance the block a lot.

If you can find a good deal on a 400 block run it! If not build your 350 into a 383.

The 400 overheating/siamese bore issue does get be a concern when you are running 12 to 1 compression ratios, and then o-ring them and are usually good to go. I have yet to see a real overheating problem in any I have built or been a witnees to building. If you have steam holes in the head and a good cooling system you don't have a problem. Most of the problem comes with people trying to drill their own steam holes and screwing up, trying to run stock cooling ststem stuff or 350 radiators with a pumped up 400, or detination (Even if you don't hear pinging!!!)

Either way both are great motors! I like my 383.

Originally posted by jeenjer
Thanx Cap'n, I had a feeling that was the answer but I needed a little reinforcment.:D

Right on Cap't. 400's are kick ass motors, with a 4 core radiator and maintenance they do NOT have cooling issues. Have had mine for over 6 years, NEVER once had a problem..............and the torque is amazing..........especially with TPI.

I'd take a 400 over a 350 each and every day.

Originally posted by CaptCrunch
no, no, no... First of all your buddy would be one of these guys who thinks he knows it all. Only the narrow minded still believe 400's are junk and overheat all the time, blah, blah, blah. Certin delemias do come up with higher compressions, but that is beyond a streetable motor. Basically the 383 was designed/is so big because it gets more cubes and the same stroke of the 400 for more torque then a 350. This all comes without the need for steam holes to be done to your heads and in many areas around the country 400 blocks are becoming very hard to find and increasingly expensive.

A 383 will make no more torque then a 400 if the same parts are used. The 383 also will not out do a 350 by too much hp wise. The 383 is a torque motor, just like a 377 is a high end HP motor. A 400 is superior in hp numbers by far if you use the right cam and cylinder heads.

Overall it is really a stupid debate. I personally think the power and torque come a bit easier with a 400. Also you generally see a bit more hp on a 400 then a 383 with the same torque numbers, but it really depends how you build them.

In terms of the 3.75 to 4.00... I think you are thinking rod length... and actually both is the same, however many people are building long rod motors to cut down on quench and deck height and 4.00 rods are very popular to impore the rod angles of the 400.

Now before I read the rest of this thread, I just wanna say, I NEVER said the 400 was junk. I just said a 383 would make more torque. Ok I'll finish reading now.

OK, OK, I have to admit after reading this thread I'd say that 383's and 400's sound like they put out about the same numbers. So do whatever you want Jeremy.

That is the best thing about these posts... lots of info and opinions that hold merit. I always re-evaluate stuff and listen to what people had to say.

Heck... I used to love strokers for my drag cars, but now I'm all about destroker motors. You can always change your mind and their are always new ideas and products to help you along too.

Some of your notes on the 400's are notable, but I think alot of these are just over played because too many people tried to make them too cheaply. I've seen way top many wheel stands on the lights to down talk a 406 these days!

Originally posted by CaptCrunch
The 383 is a torque motor, just like a 377 is a high end HP motor.

I was under the impression that a 383 was a .030 over 377.

The 377, 383 & 400 all have that 3.75 stroke.

The main advantage of the 400 is it's extra cubes, which on a hot street motor would amount to about 17-23hp, all things being legal.

The main advantage of the 377/383 is it's more efficient cooling due to not having siamesed bores. This allows higher compression ratios and more cylinder pressure without running into detonation.

If I was choosing between two motors...

for a truck I would go for a mild cam, low compression 400 with a nice big radiator.

for a car i would go 383 with high compression and a big cam. Also a big radiator though. Cool water is nice.

Originally posted by nakona

#chmod a+x /bin/laden



:D Now THAT's some funny shit... :D

there is no replacment for more displacment. its that simple, its all about inches. i now the 406 in my jeep will run on a 383. anybody?

Originally posted by nakona


I was under the impression that a 383 was a .030 over 377.

The 377, 383 & 400 all have that 3.75 stroke.
.
.
.
The main advantage of the 377/383 is it's more efficient cooling due to not having siamesed bores....


Nope.

377 = 4.155" x 3.48" (5.7" or 6.00" rod); a 400 block and a 350 crank with "spacer" main bearings.

It's a "destroked" 400. Since it uses a 400 block, still has the siamesed bores. Better for sustained high rpm applications, like circle track.

my understanding from what i've read in my small block chevy books is a 383 is accomplished by combining a 400 crank and a 350 block. then a 377 is the opposite with the 350 crank and the 400 block. 383 is built for torque, but i say just use a 400. 377 is for Horse power, and it is sopposed to wrap up faster due to the shorter strock.

Originally posted by Lloyd


Nope.

377 = 4.155" x 3.48" (5.7" or 6.00" rod); a 400 block and a 350 crank with "spacer" main bearings.

It's a "destroked" 400. Since it uses a 400 block, still has the siamesed bores. Better for sustained high rpm applications, like circle track.

Nope?

I'm not going to say that you can't de-stroke a 400. I simply don't know because it would never occur to me to use the inferior 400 block to get the same 377/383 inches.

But I'm going to tell you that MY statements can be verified by looking in the PAW parts catalogue.
So please... don't tell me "nope".

Yes, you CAN get 377 CID by a factory-bore 350 block with a 400 crank. There's a semi-infinte number of ways to get a 377 displacement. In practice, you seldom open up a 350 to find a serviceable on-size bore - especially with a surface condition suitable for seating a new set of rings. It is ASSUMED when one is discussing stroker buildups that a 0.030 over bore is used. This allows a used block (instead of a new one) to be used, permits proper honing with a torque plate, etc. I've never heard of anyone building a SBC stroker on a new block; although I'm sure it's been done, it's not the norm. Nor is it normal to sink one to many kilobucks into a stroker build on a used block without having it bored and honed. How many 377-inch stroker 350's have you seen come out of a reputable shop? Normally a 350 with 400 crank is a 383. Normally a 377 is a destroked 400. You can make a 383 by going 0.060 over on a 400 block and using a 350 crank - do the math. But, most 400 blocks have cylinder walls too thin to support a 0.060 overbore, so if someone came on here making a blanket statement that a SBC 383 was made that way I'd be happy to tell them "nope" also. I stand by my comment as a matter of the way it works in the real world, not the PAW catalog.

Hold on....

I need to do a reality check...

I'm saying that when you talk about a 377/383 that you're talking about a 350 block and a 400 crank.

The other way around would be the oddball combination.

Now, are you agreeing, or disagreeing?

P.S: The PAW catalogue IS the real world.
People can holler at each other all day long about what's what, but when you go to the parts book you find out what reality actually is.

Reality check, register 9! :D

I agree that a 383 is a 350 block and a 400 crank, although you can (in theory) make one the other way. I disagree that this combination is commonly referred to as a 377 (although you can make one that way). When you say 377 to someone who's been in this game for a while, they think 400 block / 350 crank. Just because it would never occur to you to do that doesn't mean that everyone else suffers from that same mental block.

Yes, by all means check the parts book. I think the fact that those spacer bearings for the 350 crank / 400 block combination are readily available and commonly used should indicate that the 377 (the one I'm referring to) isn't such an "oddball" and it's been done routinely. It's a very good engine and it definitely has it's place and purpose. Tell ya what, get out your local yellow pages, look up a local auto machine / speed shop, tell'em you want to build a "377 Small-Block Chevy" and get a price and part number on the crank bearings. Then ask them what combination they are for.

Similarly, the 400 block with the 3.25 stroke crank from the 327 makes something in the 350 range (depending on bore). This combination is the street origin for the NASCAR engine. And if the 400 block is so "inferior" why is it used THERE, where really big money is at stake? GM seized this concept and now markets a new block specifically for this purpose: https://www.spoperformanceparts.com/ part # 12480045 or 12480046. The fact that destrokers aren't as trendy doesn't make them a less valid combination. From a financial perspective they're much more firmly rooted in reality than stroker engines.

Obviously at least one knowledgeable person agrees with me (CaptCrunch) because it was his comment on the 377 that started this whole thing.

Also see here: http://www.speedomotive.com/Stroker%20Kits.htm

Been outta town, but think I'll chime in here... Lloyd is on point. So no real need to repeat what he has said.

In terms of the PAW catalog... I have to laugh a bit at that. Just cause PAW doesn't sell it doesn't mean you can't do it. PAW has a lot of stuff but come on... there are literally trillions of parts out there. Heck I plan on a 502 block bored over .030 and destroked :cool: , who do you think sells that stuff over the counter as a kit... nobody! Gotta love custom combos and parts.

In all reality... if you wanna know what is feasable and what isn't... talk to some of the real player engine builders like Ling., Musi, Jorgenson, etc. These guys can make dang near anything you want.

And the last thing... the 400 block has some flaws, but they are over played by people who don't know what they are doing... don't have a bigger radiator... don't have the heads modified for steam holes, guys who try to make a bammer motor with mountians of cash and no brains. No stock sbc is gonna stay together much past 600 ponies. This is why guys block fill, sleeve, buy aftermarket blocks that cost thousands of dollars, and when compression gets nasty and the rpm's are killer they run titanium rods that cost a ton and o-ring. Obviously this is probably past what anyone is trying to put in their 4x4, but it gives you and idea. Overall I have seen way too many 406 cars doing while stands on small slicks and running in the single digits at the strip, then drive 3 hours home for a wash and then out for a cruise/show night.

ahh... we must of posted at about the same time...:rasta:

the most common 377 motor is a 350 crank, spacer bearings or I believe there are a few crank versions out now for this combo. I know a couple guys that run this combo with good results. One even happens to be in a lifted 79 3/4 ton mud truck. That motor is a happy camper screaming through mud pits.

I think a lot of the reason strokers are more popular is the torque they make, which is ideally what you want on a street car. The destrokers are great for long durations at high speed and rpm's (but you also have to have the lower end to survive as well), but besides that.... they are also great for drag race classes that require you to run a radial or a small cheater slick. It really aids in traction off the line. I built a 377 about a year and a half ago with an old buddy of mine and he put it in a 2wd S10 truck. That sucker just plain ripped! Can't remeber his launch rpm, but he was launching at crazy rpm's and sticking like crazy glue. And he would dang near be on the bottle the rest of the way! He ran tens which ain't bad for a pretty stock suspension, but enough babbling on my end.

There is a lot of ways to crack an egg. Not pointing fingers or meaning anything bad towards anyone, but... Overall I think the more people need to learn basic combustion engine theory... not just a memorized list of parts for a combo from a magizine or catalog. Learn about stroke and bore... learn about how valve timing affects power, learn about air velocity and fuel on a motor, learn about port sizes. This is all key in knowing how to build a motor well.

OK, we don't actually disagree enough to have an argument, so... that's a wrap.

I'll let you know how my 400 acts as soon as I put the 426 'Stroker" kit in it. Gonna be MEAN......:D :p :beer:

That shiat is gonna kick some ass:usa: how much hp and torque is that gonna make:question:

Originally posted by jeenjer
That shiat is gonna kick some ass:usa: how much hp and torque is that gonna make:question:

About 450Hp and 500 Ft. Lbs. of Torque ..... before the Nitrous gets hit....:eek: :eek:

This is some great info for someone like myself thats thinking about doing the stroker conversion to my tired 350 thats in my fj40. Ive got a few questions and i'm kinda new at the the motor rebuilding so bare with me.

1. The storker web site that Lloyd posted uses the 5.565 long rods from a 400 in one of their kits. Tiaged says these are to short, why? Whats the pros and cons of using this rod verse the 5.7" rods?

2. I have a '72 4bolt main block and plan on using a cast crank from Summit. Do I need to have the block clearenced to fit the crank? If so, what part of the crank makes contact with the block?

3. What is a small base circle cam and will I need one? Are these cams any more expensive or harder to find?

Thanks

Triaged believes the long rod myth.
I would build it with the 5.56 rods so I could use off the shelf 350 pistons.
but if you are using aftermarket crank it may be set up for longer rods
there is no power in rods so run what you have or is cheapest in the long run

Originally posted by mj
Triaged believes the long rod myth.
I would build it with the 5.56 rods so I could use off the shelf 350 pistons.
but if you are using aftermarket crank it may be set up for longer rods
there is no power in rods so run what you have or is cheapest in the long run

I have to disagree with this. Longer rods give a longer dwell time at TDC (and BDC). Most of the performance machine shops I know won't even touch a stock 400 rod, they go with the 5.7's

Just my .02

If longer dwell time is better, wouldnt the 6.0 rods be best?

Does anyone know what a small base circle cam is?

Yes, 6" (or longer) rods dominate high performance, high-$ buildups. Particularly in pro racing. Chrysler used 6.123" rods stock in LA engines and these are a popular swap especially when a custom-ground crank is indicated by some other factor. By increasing dwell time combustion pressures and temperatures stay higher for longer and allow you to extract more energy from the same fuel-air charge - by burning more of the fuel near TDC. Most standard flat-tappet cams are of a small base circle design. My last 383 used an Isky 201292.

So small base circle cams are NOT roller cams but hydraulic?

What about block clearancing for the stroker crank. Does every 350 block need it?

Thanks for the reply guys. I was begining to think that everyone quit reading the post.

Small base-circle cams may be flat-tappet OR roller; it depends on what you get. (Rollers may be hydraulic also). Small base-circle is the standard configuration; the large base circle permits steeper ramps and more agressive profiles for a given lifter type (particularly flat-tappet). You generally run into a large base circle on an agressive solid-lifter application where the grinder is trying to get maximum surface area under the curve; with the advent of rollers and roller-retrofit kits, these are progeressively less common.

It's a safe bet that the block will need some clearancing. Perhaps some won't, but I've never seen one.

Combustion efficiency isn't the total of the effect. The other end of the stroke (BDC) with a longer rod and greater dwell time permits a long-duration cam to fill the cylinder more efficiently due to the momentum of the column in the intake runner. Similarly, the extra dwell time at TDC allows a longer cam with more overlap to scavenge better; both due to the momentum of the exhaust column AND the intake, since both valves are open for a while here.

Triaged believes the long rod myth.

I know all about the fact that a shorter rod makes more torque (just a bit). If that is the myth that you are refering to...I don't care! I would still use a 5.7 rod because: It is easier to find good rods in 5.7" (does anybody even make a 5.56" aftermarket rod?), there is less side load on the piston/cylinder wall, and in the higher rpm's there is just a bit less max piston acceleration.

I have to admit that as much as I like to do things right I am also cheep! So in that case I would prob. use 5.7 rods to build a 383 and 5.56 rods to build a 400 (but only because I am cheep!)

Thats what I needed to know. Thanks:)

Thought y'all might be curious to know that there's one more way to arrive at 383". GM is selling a 383" crate engine on a stock 350 bore. They used a 3.8" stroke instead of the normal 3.75" so they'd arrive at 383".

Oh, and there's no such thing as a '72 4-bolt 400 block. If you're talking 350 block, sorry for jumping in on that.

TEX