the shorter stroke of the 350 allows the engine to rev faster as there is less rotational inertia. It also is easier on rods and pistons as velocity is decreased at equal RPMs and also has less side load on the cylinder walls.
Tq is decreased as there are less overall cubes and less mechanical advantage/leverage on the crank centerline..

 

not a whole lot of advantage to that motor on the street. a similarly built 400 will make more torque, more HP at virtually every RPM and blow the doors off the 377 car.

K

 

Killer, I agree and disagree. While if both cars were set up the same (to take advantage of torque) the 400+ engine would win. If everything were eaual you are right the 400 "should" make more power and torque.

Now if both cars were built to make the most out of the engine installed the difference would be MUCH less than you think.

A 377 is an RPM engine, they love to spin. Like most large bore short stroke engines.

I agree with Killer that for a street car they are not the best choice. There is a place for them and I know some people love them. I would take a 383 or 400 over them for a street car.

Royce

 

I think one often overlooked aspect of less cubes turning faster then bigger cu in is the VE go up with rpm on a given motor. In other words, a 500 cu in pro-stocker turning 10,000 rpm will actually ingest more then 500 cu in of air and fuel merely due to the increased velocity in the intake and heads making a ram effect into the cylinder.

So if you took a 377 turning fast enough to get 110% ve, and compare it with a slower turning 400 at 100% ve, the 377 will actually be a bigger motor in terms of flow due to the extra 10% of ve. 377 x 10 % 37.7 or 38 cu in. 377 + 38 = 415 cu in.

Anybody follow that theory of mine? I was following that 427 vs 454 thread and was waiting for someone to point that out but it never was considered in the thread.

 

I think one often overlooked aspect of less cubes turning faster then bigger cu in is the VE go up with rpm on a given motor. In other words, a 500 cu in pro-stocker turning 10,000 rpm will actually ingest more then 500 cu in of air and fuel merely due to the increased velocity in the intake and heads making a ram effect into the cylinder.

So if you took a 377 turning fast enough to get 110% ve, and compare it with a slower turning 400 at 100% ve, the 377 will actually be a bigger motor in terms of flow due to the extra 10% of ve. 377 x 10 % 37.7 or 38 cu in. 377 + 38 = 415 cu in.

Anybody follow that theory of mine? I was following that 427 vs 454 thread and was waiting for someone to point that out but it never was considered in the thread.

I can understand your point, but we're taking these non-scientific terms like "RPM engine" and "loves to spin" and trying to tack on a quantitative attribute to them. The problem with both motors is that unless you spend the money on internals, you're not going to run more than 5500RPM. A 350 CID chevy motor with stock internals is about a 5500 RPM redline motor. Why then, would a 377 with the same stroke be able to rev any better? A 377 with some high buck internals will probably be nicely efficient at a higher RPM, because of the large over-square. The issue is that stock rods are going to stretch above 5500 or 6000 on a regular basis, not to mention the fact that those big 400 CID slugs on the end of them weigh more than a normal 350 slug does. So now you're talking high dollar rods, a big cam and some upper-end heads to make your 110% VE at 6700RPM. Furthermore, to do that you've lost a bunch of power between 0 and 3000 RPM and your motor is basically a race-only setup.

So I guess what I'm getting at is not only is a 400 a better overall choice, but dollar for dollar if you want to start spending money on internals and give the 400 a bullet-proof bottom end like the 377 will need, you'll see the difference even more.

K

 

Killer i see your point but, I think you are assuming a few things and missing the point. 56Maynard put it VERY well. I agree 100%

I don't think you would go through the hassle of building a 377 if you weren't going to spin it. If not why even build it. Stock rods will take MUCH more punishment than people give them credit for. A cast crank and stock rods will spin 6500 and live. By making the stroke shorter that even gives them more RPM potential. You would not build a 377 with the same parts used in a low RPM 400. That doesn't mean either is better, that just means they are different. As I have always said (along with others) it ALL depends on the combination and the intended use.

If what you say was cut and dry, no small block would ever be able to beat a big block, PERIOD. I have put a lot of big blocks on the trailer with my small block (even before it was blown). There is more to making a car go fast than cubic inches. The more cubic inches you have, the more POTENTIAL you have to go fast or make power. It doesn't mean the bigger engine always DOES make more power or go faster.

Now if you want to start putting limitations on it, like below X RPM then things change. He didn't say which engine would be better under 5500, by nature the 377 is not going to compare to a 400 in that situation (if built the same).

I also agreed that the 377 is not the best street engine in most cases. Though if you put it in a nice stick car with a 6speed and steep gears and you would have a blast driving it. This is where the whole combination things comes up. Put that low RPM 400 in that same car and I'd take the 377 over it anyday. The 400 would be like driving a tractor. (get my point?).

Finally he was not asking if a 377 was "better" than a 400 he was just trying to get info on a 377.

Royce

 

My theory shoulda been qualified with a great big "In general" but yeah internals will definately make differences in reliability/safety in the upper rpm ranges. I just kinda tossed it out there for discussion.

Personally, I've spun the same cast crank to 7300 rpm reliably for 3 seasons straight but definately dont/wont recommend the use of em up there for obvious reasons. The availabilty of all the cheap aftermarket cranks nowdays dont justify the danger messing with stuff like that.

Please dont anyone attempt this 7300 stuff based on what I got away with years ago. It just too damned easy to drive in your own oil and hurt yourself or the other guy in the other lane.

 

i ran a build on my desktop dyno and was very surprised at the results.i ran a 406 block with 327 crank with original 327/365 ,302/290 cam as they are the same,with most of the build i have on a 406 that i have, making about 450/460 with iron heads and 11-1when i was using it.the result was 511/6500 rpm and 443 torque at 5000 rpm.it still had 280 h.p. at 9500 rpm.it was best mid-upper range.thats a motor.

 

i was talking to a friend and he brought up the 377, i was Curious about it, thanks guys i learned something from everyone. and will prob build 350 not a 377. but thanks 4 everyones input


GoneNova/406,
would you run my 350 build on your desktop dyno ? what all do you need to figure out my HP & Torq ?


Mustangsaly

 

Killer i see your point but, I think you are assuming a few things and missing the point. 56Maynard put it VERY well. I agree 100%

I don't think you would go through the hassle of building a 377 if you weren't going to spin it. If not why even build it. Stock rods will take MUCH more punishment than people give them credit for. A cast crank and stock rods will spin 6500 and live. By making the stroke shorter that even gives them more RPM potential. You would not build a 377 with the same parts used in a low RPM 400. That doesn't mean either is better, that just means they are different. As I have always said (along with others) it ALL depends on the combination and the intended use.

If what you say was cut and dry, no small block would ever be able to beat a big block, PERIOD. I have put a lot of big blocks on the trailer with my small block (even before it was blown). There is more to making a car go fast than cubic inches. The more cubic inches you have, the more POTENTIAL you have to go fast or make power. It doesn't mean the bigger engine always DOES make more power or go faster.

Now if you want to start putting limitations on it, like below X RPM then things change. He didn't say which engine would be better under 5500, by nature the 377 is not going to compare to a 400 in that situation (if built the same).

I also agreed that the 377 is not the best street engine in most cases. Though if you put it in a nice stick car with a 6speed and steep gears and you would have a blast driving it. This is where the whole combination things comes up. Put that low RPM 400 in that same car and I'd take the 377 over it anyday. The 400 would be like driving a tractor. (get my point?).

Finally he was not asking if a 377 was "better" than a 400 he was just trying to get info on a 377.

Royce

Well I guess we can just agree to disagree. I'm sure in some circles in which CID is a limiting factor you would be better off with a 377, but dollar for dollar you'll always have a better chance with more cubes. I"m sure you've put some big blocks on the trailer with your smallblock, but that's really an exception to the rule. The whole reason people build bigblock motors is that they need the cubes, and its the oldest trick in the book, because it always works! :thumbup: Dollar for dollar, you'll nearly always be ahead with a 400.

Furthermore, I did get the impression that he sort-of asked which was "better" than the other, because he asked of the "advantages" of building a 377. Given that you can spend extra money making it into a 377 or just build a 400, the advantages in nearly any situation are voided. That's my point.
K

 

The advantages that most are missing is the longevity at RPM and the Tq multiplication one can ultilize by having lower gears with the higher RPM engine.

 

Killer,
You are still missing the point. Not a big deal. Just don't want you to think I am blowing smoke. There are a LOT of slow big blocks out there and plenty of slow small blocks as well. If both engine are built to the hilt and are making maximum HP then you are right the larger engine has the advantage. The truth of the matter is, most of the cars on the street are not "maxed" out. Most of the cars at the track fit that description too (on average Joe night). This is the difference. You are asuming an optimized 400 against an average 377 in that case you are right. You said yourself max rpm or 5500, I'll give you your 400 with 5500RPM max and take a 327 that has no rpm "limit" attached and blow the doors off the 400. I used that as an example to make my point. Once again it's all about combination, it's that simple. If you build the car to make the most of the 400 and it's torque it will be a heck of a car, the same can be said for a 377 with it's rpm and HP. With the few details that were provided there is just no way you can say which engine is best for his situation. There are very few substitutes to cubic inches but there are a few.

By saying the 400 is only good to 5500rpm you are saying, it is a very mild build (far from maxed out). With that said a slightly more "maxed" out smaller engine will be just as good if not better.

Once again I am not pushing the 377 and I personally see few applications that I would build one for (one being a stick car with steep gears, pro touring type car).

If you have the choice between a 350 and a 377 build the 377, it will make more power and RPM better than the 350, it's a win win situation. I would take a 383 or 400 over a 350 any day of the week, for all different applications.

Royce

 

yep, I understand your point very well. The issue that you have is that you're saying maximum possible intake flow is not dictated only by CID (lets leave ports, valves and cam etc out of this and assume they're all optimized for the application) but also RPM. That I agree with. If you have a 500 CID motor that can only turn 3500 RPM and a 350 that can turn 7500, you'll have your day with the 350, assuming, again, that other variables don't hinder you (traction etc etc).

I definitely don't think you're blowing smoke, I just think perhaps I never communicated my opinion/point as well as I wanted to! I respect your opinion, Royce.

I also have an issue with the term "maxed out." Holding CID constant (say 377 and 400) you would have to arbitrarily dictate an RPM point at which you would say that each motor, as defined probably by aftermarket availability, is "maxed out." I personally know a guy who has a 434 stroker smallblock who's setup is built to 7400 RPM with a stock block (see 1BAD80). 400's can spin if you spend the money on them.

So what this whole issue comes down to is this: does the shorter stroke and over-square characteristic of the 377 reduce the stress on the internals (piston acceleration/velocity) to a degree that in any situation it is more practical to build than a 400 in terms of the maximum airflow each motor can produce at its maximum "safe" RPM as defined by a parts setup that costs the same for each motor? My point is that I don't think so, and I also don't think that a stock 350 chevy will spin 6500 RPM. Not for long anyway. Furthermore, as I mentioned earlier, the slugs on the end of those rods are heavier than the original 350 slugs, because they're bigger. Lastly, even if you do think you can make a few passes at 6500, is it really practial to stretch those stock parts right to their limit, hoping that you never ever miss a shift and stick it to 6800 one time? I just think its a lot to bank on...

ANyway, fun discussion. Good points-

K

 

I'd like to add to the discussion.

1. If a guy had a 400 block and a 350 crank laying around it would make perfect sense to put the two of them together. If he needed something to occupy his time.

2. When the machine shops in your area lack the capacity to provide proper machine work it makes sense to use a crankshaft that will require no special work to be done on the rods for them to clear the oil pan, block and camshaft. That is if you have hefty rods with large bolts.

3. In spite of the fact that I own two 400s, and love the torque, I really like to hear short stroke engines scream in a 4-speed car.

Larry

 

Killer, I guess we are just looking at this from two totally different perspectives. You keep saying "stock" where in his post did he say he had a stock 350 cast crank that he planned to use. This is why I say there are not enough details to give good advice. Maybe he has a forged 350 crank and a set of H-beam rods, along with light weight pistons, this would change the whole discussion. To me it seems he is gathering info to make a decision. I just want all the info to be out there for him to make a choice. I am not trying to steer him either way.

I personally spun my old 385 short rod (stock 400 rods 5.565") nodular cast crank to 6500 regularly. That very engine is still together in my friends Nova. He has a bad habit of over rev'ing it (not used to an engine with that much power and that revs so fast). Despite that it is still healthy. If the parts are matched and balanced well. A little stress relieving, beam polishing, shot peening, goes a long way. Too many people think you just buy stock parts and throw them together. That's not the best way to get the most out of the parts. A bone stock 350 will not want to spin to 6500, I agree. This is a HOT ROD site so I assume when building these higher HP engines most of us know to use the proper parts or to modify the stock parts to live.

Now you said you have a friend with a 434 built out of a stock block, that in itself goes against the things you are saying. Most people (that know) will tell you using a stock 400 block to build that engine is not "recommended". I know people do it and that's proof just how strong some stock parts are.

When I say maxed out, I was saying if you got everything possible out of the engine with no limitations and both wee built equally. I don't want to get into awhat if this and what if that, situation. I was speaking in general and not listing specific parts or combinations. I was only trying to prove a point that you can't flat out say one engine is better than another without knowing more details and what the engine/car will be used for. There is more to it than cubic inches.

Royce

 

A cast crank and stock rods will spin 6500 and live.

A bone stock 350 will not want to spin to 6500, I agree.

This is part of where my confusion lies. I guess what you were saying was if you modify those stock parts appropriately, you can make due with them?

Now you said you have a friend with a 434 built out of a stock block, that in itself goes against the things you are saying. Most people (that know) will tell you using a stock 400 block to build that engine is not "recommended". I know people do it and that's proof just how strong some stock parts are.

Well you could look at that either way. We're talking about a guy who's spent 30+ years working on GM motors and tunes drag cars regularly. He knows exactly what to look for in a block and happened to find a good one, which he also had to use a short fill on. This is definitely not an endeavor for the faint of heart, and I really don't think it speaks to the strength of stock parts that much. This is kind of like the example of the engine masters making a 12.5:1 motor run great on pump gas. Doesn't mean street motors should be run 12:1, it means there's a guy out there who really knows is dog doo and can make it happen. Again, you and I have different perspectives, lol.

I personally spun my old 385 short rod (stock 400 rods 5.565") nodular cast crank to 6500 regularly. That very engine is still together in my friends Nova. He has a bad habit of over rev'ing it (not used to an engine with that much power and that revs so fast). Despite that it is still healthy.

See, to me this sort-of contradicts the point of the 377. Here you're telling me a 3.75 stroke motor is living with stock components all the way to 6500 and beyond. So if a 377 and a 400 with reworked stock components can run to 6500 reliably, we've lost another reason to entertain the idea of building the 377.

When I say maxed out, I was saying if you got everything possible out of the engine with no limitations and both wee built equally.

Yep, that's one of the things that perplexed me. We have to arbitrarily dictate in a rather a priori fashion that a 377 normally will live with its (again, for the sake of argument) reworked stock components X number of RPMs further than a 400 and thus prove its efficacy to build. My problem with that is that very few people have run a 377, fewer still have a similar 400 for purposes of comparison and that leaves us saying "a 377 spins better." Which is a statement rather void of meaningful data. I guess that's also what you meant when you said "not enough data to make a decision per application etc" so perhaps we agree on this point.

K

 

Ah what the heck...

I just plain prefer a short stroked engine to begin with... Simply take a light weight 3.50 stroke crank which can be had for a fairly moderate price... Add a set of light weight rods (Howards makes some great sportsman light weight pieces) and some very light weight pistons (prefer J & E`s) add a set of Dart Pro 1`s (230`s...?) a huge solid roller cam and

"a 377 spins better."

:thumbup:


Everybody runs a 400 but the 377 concept was born because a few years ago alot of the great componets we have for 400`s did not exsist... But someone had a brain storm and decided to try a 350 crank in the 400 block (of course made special bearing spacers) and found the damn thing even with a cast crank would turn mega RPM and hey that allowed for more gear which in turn also allows for more flexability in the setup...

Put it in a light setup and it will fly... Also in a street machine this has the same impact as the 427/454 debate did (TORQUE)


Also one last thing put a set of 180 degree headers on it and it would sound like a whole swarm of hornets... Make all the ricers heads spin a 360 :thumbup:


dat .02 thang...

 

LOL, this is almost funny now.

You can have two engines that both will spin lets say 7000rpm. That doesn't mean they both have the same powerband, so just because my 385 would go to 6500 doesn't mean it would be making as much power from lets say 5500-7200 as a 377. Once again it comes back to the whole basis of building a performance engine COMBINATION period. That is really all there is to it. If you "need" more cubic inches to make your goal or your combo work then by all means you should build the larger engine. I'm just saying many time less cubes will get the job done if the rest of the combo is there. Way too many variables to even argue the point. I will just leave it at this, you cannot say a 400 is "better" than a 377 in every way. It just isn't that simple. Bigger "can" be better but, smaller can beat bigger and does more than you know. If that is the way you want to look at it, that's fine (no harm).

If the way you thought was "reality" then all big blocks would be in the 8's or better and no small blocks would be able to break into the 10's. The fact of the matter is there are some outrageously fast small blocks out there. I am not knocking a larger engine, I am just saying make the combination right either way.

Royce

 

bigger should be better, but my old 327 has smoked a many big block cars of all makes. then turn right around and have some young phucker with a 5.0 mustang smoke me. it's all in the COMBINATION! i've took my same 327 & out run a few 406's & 383"s. they would get me out of the hole, but i would come on strong on the upper end. & yes stock cast 3.25 (307) crank with "b" rods & arp bolts & i spun it 6,800 rpm for four years. the last day it was running i had dosed a gt mustang out in front of where i worked at (5 cars), & on the way home at around 2,500 rpm it let go.

 

If the way you thought was "reality" then all big blocks would be in the 8's or better and no small blocks would be able to break into the 10's. The fact of the matter is there are some outrageously fast small blocks out there. I am not knocking a larger engine, I am just saying make the combination right either way.

whoa buddy, that was never my message. My simple message is the same one that's been understood throughout the ages, cubic inches = potential for power. This is fact. I never said a smallblock can't be fast, or that a motor with fewer cubes than another can't beat a larger motor. In fact I've said the opposite of that at least once in this thread.

Reality is this: if you want to get into the 8's and you have a 400 block, put a 400 crank in it, not a 350 one, and you'll be glad you did! :thumbup:

K

 

I've got a 377 stroker in my drag car.Works great in light car 2800 lbs. revs fast some times to fast making it hard to keep up with shift points. Turns between 7600 and 8000 with trw forged pistons.Motor has about 600 runs on it with nothing but new bearings and rings every couple years.Stock Chevy rods with polished beams,shot peened, and arp rod bolts, stock Chevy steel crank.

 

I've got a 377 ...Turns between 7600 and 8000 with trw forged pistons....Stock Chevy rods with polished beams,shot peened, and arp rod bolts, stock Chevy steel crank.

I believe you. Try that with a 400 crank. a couple of twenty passes at 6500 and you'll be looking for your balancer or changing main bearings.

And contemplate this:

6500 rpm 110mph 26" tire
4.56 gear

7500 rpm 110mph 26" tire
5.30 gear

That's a lot of extra grunt you can pick up....more than 23ci will make for you.

 

LOL, this is almost funny now.

You can have two engines that both will spin lets say 7000rpm. That doesn't mean they both have the same powerband, so just because my 385 would go to 6500 doesn't mean it would be making as much power from lets say 5500-7200 as a 377. Once again it comes back to the whole basis of building a performance engine COMBINATION period. That is really all there is to it. If you "need" more cubic inches to make your goal or your combo work then by all means you should build the larger engine. I'm just saying many time less cubes will get the job done if the rest of the combo is there. Way too many variables to even argue the point. I will just leave it at this, you cannot say a 400 is "better" than a 377 in every way. It just isn't that simple. Bigger "can" be better but, smaller can beat bigger and does more than you know. If that is the way you want to look at it, that's fine (no harm).

Royce

I have built a few of the destroked engines for both drag and circle track. If a customer runs alot of gear and likes hi RPM, I build the short stroke engine. If they run less gear or if a customer has a big budget, then the long stroke engine is in order. If you really want a nice little RPM loving package try a 4.125 bore with a 3.25 stroke. It yields 348 cu. in. and revs like you wouldn't believe. I built one for a customers drag car in a cu.in. / lb class and he was more than pleased. It's all about the COMBINATION.

 

swvalcon,
Exactly my point. Sounds like you have it dialed in.

topfuel,
I have a friend that ran a engine combo like you listed, it was a VERY fast rev'ing engine. I can see where it would be a LOT of fun in the right car.

You just can't say COMBINATION enough. That is the whole key to a well performing car (no matter what size the engine is).

I am not sure where people get the RPM limits of "stock" parts. I have a buddy with a drag 66 Nova. He built a budget engine 383 (not one I would recommend) it had the same type of nodular cast crank I mentioned earlier, with stock GM rods (not bushed but, machined for full floating pistons/pins), huge roller cam, tunnel ram, etc... he shifted the thing at 8000RPM the crank is fine to this day.

If things are set up right, balanced, the stock stuff will take some insane abuse. I don't like to push the limits like that but, I have no issue with spinning a well built small block (even with stockish parts) to and above 6500.

Royce

 

Glad I found this thread, I'm currently wrestling with which to build, 380 (4.165 bore x 3.480 stroke) or 415 (4.165 bore x 3.800 stroke). After pricing them both out the 380 is quite a bit more simply because of the quality of parts needed to turn those rpms reliably. To turn 8k with consistancy you'll need a solid roller package, rev kit, shaft rockers, splayed block, great bearings, good rods, and good rings, and that's just to be able to rev that high relaibly. The 415 doesn't quite require that quality of parts, but it'll make slightly less power but more TQ. The 380 long block, built the way I want it, will cost about $2600 more than the 415. Here are the exact parts I'd have in the 380 short block;

J&E 10.4:1 CR forged pistons
Crower Maxi-Lite 93 Stage-4 6.0" billet I-Beam rods
4340 forged crank
Oliver splayed caps
file-fit plasma moly rings
ARP main studs and rod bolts
SFI damper and flexplate
internal balance

And this is NOT for a regular street/strip motor. I'm looking at a serious bracket competitor. It'll be going in a 3000# car with tall gears so I think it'll be able to take advantage of the quick rev of the short stroke. Any advice?