KyleF

Do you car about handling at all? In this case, I believe forced induction would be the route to go to minimize nose weight.

pologreen1

Depends on purpose. hp/weight with BBC is silly. 150lbs more is nothing in the scope of things for a street car.

Mine is built to make 1200 on nos. A 632 will make 1200n/a.

MatthewMiller

KyleF and I agree that the difference in longevity between a 377 and 400 is probably meaningless. I would actually argue, again, that for a given power level, the 400 will be more reliable because it can achieve that goal at a lower rpm.

This gets back an argument in a different thread. First, torque at the crankshaft isn't what determines the rate of acceleration of a car. Force at the contact patch is what determines that, and that force is determined solely by the power the engine is putting out at any given road speed. So we would never build an engine to achieve a peak torque goal. That would be idiotic. Second, the torque of an engine at any rpm and throttle opening is created by the the stroke multiplied by the cylinder pressure. The cylinder pressure is greater with a bigger bore. So a bigger bore creates just as much extra torque as a longer stroke. A longer stroke does not necessarily make a "torquey" motor.

The reason any race engine wants the biggest bore is that it allows for bigger valves and less shrouding. That's always a plus for power production. Guess what? Race engine builders also want the most stroke - that is, they want the most cubes they can use, because displacement always makes more power. Most series, though, are limited to a certain displacement. So in those situations, builders will typically choose the biggest bore they can make work, and then spec the stroke to meet the rules. But the OP doesn't have such a limitation, so it would be dumb to spend time and money to destroke a 400.
^^^Exactly.

Also, an engine with large bore and small stroke tends to not be as efficient, because it's hard to get an efficient combustion chamber shape with it: it becomes too flat and has too much surface area and cools the mixture down too much. So in series where fuel efficiency matters, we don't tend to see oversquare engines. When F1 went from no fuel limits to nothing but fuel limits, suddenly the highly oversquare screamers disappeared and we started seeing less radical bore:stroke ratios and much lower rpm.

Have you ever actually ridden in or driven one? They sucked giant donkey *****. They had very little power, and were good for only 15.1@94mph in a 3200lb car. Godawful. Chevy knew this, of course - they didn't build it because it was a smart way to make a strong street engine. They built it because the the Trans Am series it was made for had a 302cid limit, and the cars had to have a certain number of production versions built to get homologated. But anyone with any sense would rather have had a 350 (I don't think the 400 block was available back then) for a street or no-rules race car.

PS - Forced induction adds weight too. The best way to go depends on the purpose of the car. But for light weight, the best route is a max-cube SBC with natural aspiration, really good heads and cam, etc. Or better yet, buy a 468 LS: you can shave another 100lb of the nose compared to the SBC, and you can make 600hp or more with total ease. Literally your only barrier to power with that engine in a C4 is getting an intake that will breathe well enough and still fit under the hood: you'll need to be doing surgery on the hood.

bud40oz

the 400 block with a 350 crank for one does not require the extensive machining to make it work where as with a 350 block you have to cut the block to allow for the bigger crank, a 350 crank in a 400 block just needs the proper bearings to go from the standard 350 crank main journals of 2.450 to the standard 400 main journals of 2.650 which boils down to a guy can technically do that build with no machine shop involved unless you plan on boring and line honing and all the other good stuff involved. also a de-stroked 400 will take a lot more abuse with the smaller stroke, the 400 cranks tend to beat themselves up a bit and are externally balanced with the use of counter weights on flywheels and harmonic balancer. the 350 crank is a time proven winner and was in production for how long? 40-45 years or so. they quit building 400 withing 10 years or so because they didn't hold up well. so in my personal opinion if i have the choice and what i plan on doing with the old 1970 air boat small block 400 engine i have had sitting in the garage corner for 15 years is de-stroking that sucker and mashing the gas pedal to the floor i like the high rpms.

also the main reason most p[eople use a 350 block with aftermarket 400 cranks is probably because a real 400 small block in good condition with no cracks is actually getting hard to find now days. i am one of the guys who saw this day coming and every time was asked, hey you wanna sell that??.... Noopppppeeeee...
and the 377 383 385 thats just a difference of boring 350 crank in a 400/ 400 crank in a 350 is the same cid's just different bores change the numbers

drcook

I am going to throw out another little wrinkle into this discussion because of what I am thinking and because I am slowly reaching the end of my budget.

My engine is pretty low mileage, so I am thinking of going the stroker crank route, but not the .030 overbore. So instead of ending up at 383 ci (.030 over) it ends up at 377. I can afford a series 9000 crank, the rods and reuse the pistons (I believe) and rering and bearing and keep within my budget (because I also have to do the transmission).

Have any of you experienced a 377 built this way ? Keeping in mind I am building a spirited cruiser that will never see a track. Just nice rides through the country, hills and mountains that are to the south and east of us.

Part of the problem is that there is only one good shop left in the area that does engine related machine work and they know it. Their prices have inflated accordingly.

KyleF

It's not just the added weight, but where it is located. It doesn't make that much difference in a straight line and a properly set up chassis can use the weight transfer for added traction. The first 60' being very important to ET.

Why don't you see autocross and road race cars with big blocks? Why do BBC cars from the factory and aftermarket parts have different spring rates?

Anyway this thread is about 377s, different ways to achieve that displacement, and which way is optimal. Not if you should go BBC.

bud40oz

drcook, no matter which way you go with it a 377 or 383 or 385. will be a huge improvement over the stock engine.i am 100% sure of that. and as far as machine shops go, it's the same around here. Back 30 years ago i think we had 4 of them in town, now were down to 1 guy who is so backed up you have to plan 6 months ahead of time. last time i was in his shop he just gave me tools and said here. do it .. he had about 50 engines sitting on the floor in there. i think for the most part the younger generation is happy to have a big chrome tip and booming speakers instead of a hot rod.
but look into it, i have seen dyno tests with 383 engines with stock tuned port with in my opinion very poor output as far as numbers. if you are running stock intake system. i would spend the money on throwing that whole set up in the garbage can and get something that breaths much better. keep in mind flow equals power like 383vette said. intake, heads and cam are a good place to look for more power before you spend thousands at a machine shop for building a stroker motor. i don't know what you have going on now. but i personally would spend money on say a set of gm performance fast burn heads. a good cam, intake and a set of tuned headers to match the power band youre shooting for, it sounds like you want in the range of idle to 5000 or so for cruising around and romping it down when you wanna go. just keep in mind again. an engine is an air pump, the more air it pumps.... the more power it has

kirby-57

I think everybody is forgetting one thing here. tune port the intake will only let you turn so much. got to have air and fuel to make power.

bud40oz

yeah, i am not tuned port i am old school carb i love the sound of a good old 4 barrel hitting hard... i forget that most people here are totally against taking the tuned port computer stuff and slamming it as hard as you can in the driveway.
i am not bashing technology and i will totally agree that the new ls based engines are awesome with all the tech n stuff but its simply not in my budget. and as far as the computer system in my 91 vette goes, its not even obd 2 its obd 1 that's like an apple computer from 1983 man, its junk. but that's just how i feel about it... sure an apple computer was top notch fancy stuff in 1983 but that doesn't mean i keep one around in my den today

and fyi anyone who says well the tuned port was a torque monster , yes it was/ is decent for stock, but you should go read the article super chevy did on the testing of stock l98 before and after when they took tuned port off and put a performer rpm air gap with a barry grant carb... same engine put out 363 hp. that's well over 100 hp increase over the stock set up

pologreen1

Several here have serious big blocks in their autox road race c4's.

I already said they weigh about 150 more and even at 200, it does not matter with 1000 na in a street car.

Benny42

A Mini-Ram fixes that right quick, its a bolt on deal.

bud40oz

tom, i think you are getting mixed up here. a 400 engines crank has a stroke of 3.75 while a 350 engine crank has a stroke of 3.48.. so no both versions of a 388.. 377 whatever you want to call it, do not have the same stroke if you put a 400 crank in a 350 block, it has a stroke of 3.75 with cylinder bore of 4.00 if you put a 350 crank in the 400 block it has a stroke of 3.48 with a cylinder bore of 4.125 350 block has small piston big crank. 400 has big piston small crank both are the same cubic inch in the end though the 400 block and 350 crank set up is cheaper to build imho since it does not require extensive machining from a shop. both a bad *** engines non the less and like others have said sure why bother de-stroking a 400 and that's all fine too.. cubes do equal power also i guess the bottom line here is there is a lot of ways to go about it and this stoke vrs destroke thing has and will continue to be talked about for a long time to come.. i think the article 383 vette quoted , or wrote is actually very informative and the guy clearly knows what he is talking about on the subject. i felt like i shouldn't of even commented after reading all that. but thats why you posted the question, you wanted people thoughts and opinions right? bottom line either one of those engine builds would be pretty sweet to have in a c4. i think we can all agree on that lol

as far as the 350 crank in a 400 goes.. look at it as a 350 engine bored 125 thousanths over size. compared to the usual .030 bore thats huge.

MatthewMiller

On a build for performance it honestly didn't occur to me that anyone would reuse a stock crank from either engine. Aftermarket forged crankshafts are pretty common and not necessarily all that expensive these days, that it wouldn't make sense to use a stock cast crank for anything but the mildest of builds. The 3.875" crank in my 396 was able to completely balance internally, for example - no counterweight needed on the flywheel. And it's good for way more rpm than I'm using. So to me, the longevity of either stock cast crank is just not relevant. As to the scarcity of good 400 blocks, I would defer to other people's knowledge. That could certainly make it less attractive an option.

Cjunkie

bud40oz

mathew maybe you could buy a crank from say jeg's and have it shipped to home.. my point is you do not need expensive extensive machining for the 350 crank to go in a 400. and i am also not going to get into the age old stroke destroke argument with anyone here. so i am done with this thread and if i made anyone angry i appologize

449er

This statement was always true UNTILL the LS based small blocks came to be!

MatthewMiller

Agreed. But my point there would be that you also don't need expensive machining to put a 400 crank in a 400. So there's just no advantage to intentionally reducing the displacement of a 400 block.

There is a flip side to this point when discussing LT engines, though: in order to use LT heads on a gen-1 SBC, you need to some work like plugging steam holes on the heads. So for someone starting with an LT1 or LT4 C4, sticking with the 350 block and machining for the 400 (or larger) crank may not be any more expensive.

You didn't make anyone angry at all. We're just having a discussion and sharing knowledge. This entire thread boils down to a discussion of increasing stroke vs decreasing stroke.

drcook

I was reading Lingenfelter's book this morning and in the chapter about displacements, he speaks about the 400 block. He says that other than blocks that had core shift, a lot of the so-called issues with overheating came from people putting other heads on the 400 block and not drilling the required steam holes into said heads. This is on page 13 of his book "On modifying small-block chevy engines".

The book really doesn't cover LT1/4 engines, is really geared to the Gen1 SBC but is a really good read and does a lot of discussing what you all are talking about. If you do some careful shopping, you will be able to find a decent copy for not much. I found my copy online at a small used bookstore on the east coast for $9.00. I see them on the web for prices ranging from $15.00 to $66.00.

Of course a lot of the principals he talks about are upward applicable to the Gen2 SBC's

MatthewMiller

Good reference. I have no doubt that's true. As I understand it, to adapt LT heads would require steam holes to be drilled plus the welding/plugging of a couple water passages. I guess on the block, I don't know what would be required to use the LT's geared water pump and optispark. The latter is required to use the PCM. So there might be a fair amount of work involved in converting over to a Gen 1 block like a 400. OTOH, it sure would be fun to gain 25 extra cubes!

Tom400CFI

Wow this post is chock full of cow dung.

Your going to have to cite the source for your claim that; "they quit building 400 withing 10 years or so because they didn't hold up well". I'd like to know what reputable, reliable source claims that, please. Now, I'm not a reputable source....but I'd BET, that they discontinued the 400 for emissions and CAFE reasons. In 1980, when they cut off the 400, GM was all about the small bore 305 for emissions and fuel economy....not because of any problems with other SBC's of the time.

All 350 cranks are "externally balanced" in the rear after '86, so...

400 cranks are "proven" too....just as much as stock, cast, 350 cranks are.

You can clearance a 350 block for a 3.75" crank with a die grinder....don't need a machine shop for that, but...who builds an engine w/o going to the machine shop, anyway??


Finally, "350 crank in a 400/ 400 crank in a 350 is the same cid's" -is not the same. A stock bore 350 block with a 3.75" crank is a 377 (376.99). A 400 with a 3.48" crank is a 372.05


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