RickyBerg

I had a Mercruiser Racing 377 Scorpion in a boat once, it was a nice biuld with a beautiful steel crank and rods, a Mercruiser tunnelram with a nice plenum on the top and fuel injection, heads where just as nice with stainless valves and so on.
A real nice smallblock.

But..

Despite all the nice parts its still a smallblock..

To get to the goal (thats what we all aming at?) a well put to gether and mildly mofified 454 would do a much better job then that fancy 377 smallblock..

I know you smallblock guys will hate me now..

//Ricky.

Les

No hate here, Ricky. I have a smallblock and a bigblock, both old school and built to be angry- not crazy like some folks, but still angry. They both thrill me in different ways. For pure, straight line performance cubes are king. But, there's still something special about wringing out a 7000+ RPM smallblock.

gkull

Yes, but at the end of mile did they go the same distance?

I deleted something wrong in my previous post.

I thought about it some more. lets agree on a couple of things. We have two motors each of 377 ci. One is 4.155 bore and 3.48 stroke and the other 4.00 and 3.750 stroke.

lets agree that the cylinders are like 46 cubic inches each.

Lets also agree that it takes a little less that the full 180 degrees of rotation for the pistons to go from top dead center to bottom dead center.

lets also agree that we have each motor spinning the same rpm


Now you need to agree to logic. Did both 46 ci get filled in the same amount of 180 degrees or time?

The only thing i can think of is you are getting confused with something you might have heard about rod length. Longer rods actually have higher piston speed moving to and from TDC and BDC than their short rod counter parts

68post

I've always heard that the shorter stroke engine of the same CI will make more topend power, and that the longer stroke engine of the same CI will have more torque "off-idle".

As a general rule.

What about the thought that you should always build the largest CI engine that's within your budget, because it will be easier to reach your HP and TQ goals ?

vette427-sbc

I think its as simple as cost...
You are rebuilding your engine and want to add some cubes. Do you buy a stroker kit and get 383 ci?
Or buy an aftermarket block with new pistons to get 37x ci?
I would think most people on here stroke their motors because its cheaper and easier.
And if you already happen to have a 400 block, why would you de-stroke it?

Shark Racer

I'm planning on building a 377 one of these days... 4.000 bore and 3.75 stroke.

Oh, you meant a 4.155 bore and 3.48 stroke...

Manuel Azevedo

Everyone is going to dream up a reason why one combo is better than another. But when it comes to a street engine as most are doing on this forum cubic inch's is the king hands down! All these creative combos are ok but they only exist because of rules for some classes of real race cars which almost non are ever really driven on the street. People want to talk about oh my ---what ever turns 7000rpm so it must be the best is a lousy way to judge a combo, 7000rpm means nothing and is nothing for a true race engine. Build what you all want it is your money but cubic inch's rule in gross power bar none! The only time a smaller engine car runs faster is that the smaller engine can and does make more power per cubic inch, and in a lot of race classes cars run pounds per cubic inch so the smaller engine is king a lot of the time there. If one want to compared street engines in talk without real track time of different combos, you can talk such as a Ford 289 to a Chevy 283. Similar cubic inchs achieved with bore on the Ford and stroke on the Chevy, which do you think runs harder?

68post

The one with the better cylinder heads, of course.

RickyBerg

I can agree on that.

But..
The starter of this thread did mention "street friendly" and i would say that if the street was my goal i would rather go for a longlasting grunty bigblock intead of the smaller high rpm choise.

However, im not really shure what "cfm friendly" means..?

63mako

Those with a 400 block build 406. Those with a 350 block build a 355 or a 383. If you have a 400 it has 400 mains. Why buy a 3.48 stroke crank with 400 mains or jump though the hoops it takes to build 377 when you can use the existing crank or buy a 3.75 crank for the same or less money. Most don't spin their street engine up past 7000 RPM and if you are a forged 3.75 stroke will take it as well as a 3.48. Got guys on here that are running 4" stroke SBC to 7500 RPM.

PaPaPork

can someone educate me in plain "non engine builder" style on whats the point in de-stroking? I don't get it... the engine will run higher RPM's due to shorter stoke? but since we change the crank and associated peripherals to build the destroked motor why not change the same parts to stock stroke and have higher torque trough the RPM band even if it will be a bit shorter(will end sooner but since torque is higher from idle up this would compensate the shorter red line) . Going that route why not stroke it and have a higher torque than stock and destroked motor...


I appologize if I don't make sense, just trying to understand why would I want to turn a bigger engine into a smaller one (for street/ recreational use)

bluedawg

I went with the 400 because i wanted torque lower down. Ive been lead to beleave that you can rev the *** out of a 377 due to piston speed, but if you cam a 383 or a 400 to the same rpm range wont the 383 build more torque and or power? If you wanted the same magic number on top end power, could you use smaller parts ie cam, intake runner and lower rise on the manifold and reach the same numbers related to hp at a higher rpm with the 377? When i planned on my engine using the shp block the cost was identical for the short block between the 377, 383 and 400. Ive also been lead to beleave that with increased stroke you can run a larger camshaft and have the same caracteristics as a smaller engine with a smaller camshaft. I guess that the same would hold true with more bore and less stroke with the ability to build power at higher rpms on the same camshaft right? With a good balance job can't you also rev the *** out of a 383 or 400? Wouldn't more cubes dictate more power?

Crepitus

I read a dyno test a few years ago with a 383 compared to a 377. I hoped to find it but could not. iirc the 2 were very close, closer than I expected, with in 10 hp/tk every where with the 383 ahead below about 4000 and the 377 above.

Belgian1979vette

Just as I expected.

68post

Torque @ lower rpm is directly related to the higher piston speed of the longer stroke, and the better high rpm power of the shorter stroke is directly related to lower frictional losses and better breathing of the larger bore.

When you are restricted to run a certain CID as a maximum - it is usually beneficial to do it with a larger bore version. Think 302 Z/28 vs. 305 .

Cstraub69

Rod length has nothing to do with piston speed. What ever length the rod is all it does is connect the piston to the crank and travel the distance that the stroke is.

Ok the engines are equal in CID but the bores and the stroke are the same. Bore is fixed, it doesn't move. Stroke, well it moves and the larger stroke moves more distance to make the CID. Hence the engines are both the same CID and go to the same rpm, BUT the longer stroke engine travels more distance than the shorter stroke engine.

Cstraub69

Less stroke does not put as much demand on intake track. You guys are limited by hood clearance in your hotrods. Piston speed puts demands on intake tracks. More stroke, more piston speed more demand on plenum volume.

Cstraub69

OEM 400 blocks are rare these days, but the SHP block is not and it has a 2.450" main so there are no hoops to jump through. On OEM 400 blocks King makes a main bearing that drops right in.

CID is still CID and most street cars are going to 6500 rpm max.

Cstraub69

Piston speed still plays a major factor in induction and cam selection.

Let me ask the board this, a small block build that is 427 CID, what head would be better 227, 235cc, or 250, or 300cc?

Little Mouse

Cstraub69

His original first couple of posts mentioned street friendly and a little over 370 cu. by using a 3.48 or 3.50 stroke crank with a big bore to get there not the usual smaller bore longer stroke. So i don't know why everyone starts bringing up bigger engines of both bore and stroke.

I still say for what most everyone on this forum " only lower rpms wanted " the longer stroke with its greater leverage is better.

Of course anyone buying an aftermarket block with its high costs would not waste any money on buying a 4.00 bore block or not take advantage of longer strokes.

Piston speeds don't get that high with the longer stroke when the vast majority of owners on this forum only want to turn 5500/ 6000 rpm tops and wanting to cruise around at much lower revs in there street cars the vast majority of time.

old-mobiles used to run around with 4.250 stroke engines they were kept at these lower rpms so it worked.

Yes i would want the big bore short stroke if i could only build to no more then 377. But i think of 7200 rpm as wasting the SBCs only real best attribute.