[Durango_Boy]

Okay, lets look at small blocks VS big blocks, but using similar displacements.

Say, the 'W' block 348, vs the SBC 350.

Power to weight ratio goes in favor of the small block, but does the big block make more lower end torque because of the differences in bore and stroke?

Still on to another 'W' big block, the 409, compared to a bored SBC 400.

The 400 is known for it's low end grunt...and how does that compare to the option the 409 gives you...excluding the huge handicap or cost to build.

Feel free to discuss other similar displacement between the BBC and SBC divisions.

[Vettezuki]

Originally Posted by Durango_Boy

Okay, lets look at small blocks VS big blocks, but using similar displacements.

Say, the 'W' block 348, vs the SBC 350.

Power to weight ratio goes in favor of the small block, but does the big block make more lower end torque because of the differences in bore and stroke?

Still on to another 'W' big block, the 409, compared to a bored SBC 400.

The 400 is known for it's low end grunt...and how does that compare to the option the 409 gives you...excluding the huge handicap or cost to build.

Feel free to discuss other similar displacement between the BBC and SBC divisions.

Mmm, fascinating question I don't know the answer to. At first I thought it'd be almost completely a function of bore/stroke, but then I thought, hey, the heads and intake you can put on a BBC are quite different aren't they? I'm really guessing, but maybe back in the Paleozoic era before they had trick computer models for optimizing head flow, the larger heads and intake (w/ typically longer runners?) on a BBC would inherently tend towards better breathing and torque on otherwise similar displacements. This is pure speculation on my part, but I'm sure BRUTAL64 might have some input on this subject.

[Durango_Boy]

Originally Posted by Vettezuki

Mmm, fascinating question I don't know the answer to. At first I thought it'd be almost completely a function of bore/stroke, but then I thought, hey, the heads and intake you can put on a BBC are quite different aren't they? I'm really guessing, but maybe back in the Paleozoic era before they had trick computer models for optimizing head flow, the larger heads and longer runners (typically ?) on a BBC would tend towards better torque on otherwise similar displacements. This is pure speculation on my part, but I'm sure BRUTAL64 might have some input on this subject.

You have some good insight, but another factor to consider is compression. Big blocks tend to have much higher compression and much larger cams. That plays a lot into it, combined with a bore and stroke, might make it a winner over a small block of similar displacement.

[Vettezuki]

Originally Posted by Durango_Boy

You have some good insight, but another factor to consider is compression. Big blocks tend to have much higher compression and much larger cams. That plays a lot into it, combined with a bore and stroke, might make it a winner over a small block of similar displacement.

What was the largest Gen I SBC from the factory?

[Durango_Boy]

Originally Posted by Vettezuki

What was the largest Gen I SBC from the factory?

The 400 was the biggest to my knowledge. It can be stroked out to close to 450 I THINK...I don't remember.

My 400 block is bored +.020 and will use stock crank and rods for a final of a 6.6L 405.

[Vettezuki]

Originally Posted by Durango_Boy

The 400 was the biggest to my knowledge. It can be stroked out to close to 450 I THINK...I don't remember.

My 400 block is bored +.020 and will use stock crank and rods for a final of a 6.6L 405.

I know BRUTAL64 has a 400 in his Vette, and it's a SBC. As I recall he chose that displacement primarily because of the exhaust valve size he could use . . . . Imma gonna PM him to get in this thread.

[Durango_Boy]

Yeah I chose my SBC 400 because I like displacement and I like torque.

I did a roller retrofit so it's a roller engine and I had even more cam choices.

I chose some -12.5cc dish pistons to go with the 64cc heads to give me a final static CR of 10.15:1. The heads are aluminum Vortec heads with 200cc intake runners and larger valves.

I'm putting on an Air Gap Vortec manifold with a 750 cfm carb, and sticking the whole thing in front of a TH2004R for a nice low RPM while cruising.

I'm hoping for about 450 HP at the wheels.

[enkeivette]

If the BB had a larger bore and a shorter stroke wouldn't it be a better platform for higher rpms?

The difference would be marginal. Probably just a matter of where which engine saw peak torque. HotRod did an article on this a while ago, two similar displacements, different bores and strokes. The power was similar but one developed the power sooner. Thought it was actually the engine with the 0longer stroke surprisingly, but I don't remember so I'll keep my mouth shut.

I'm with VZ on this one. If you were able to get similar heads/ comp/ intake flow then the difference would only be a matter of where the engines developed max power. But seeing as how BB heads typically flow much more air and the cam profiles are consequently bigger. If you have the money, and are willing to live with the weight penalty, my money would be on the big block.

[enkeivette]

And sorry DB, but if I were you I'd expect to see 450 at the engine, if that. Engines always make less power than expected, especially after they put that power through a C3 IRS.

Let me find the quote:
"Dynos are typically heartbreakers for those owners whose motors were never before tuned on a dyno... A good deal of the testing was done with large volume long tube type headers with open exhaust. Fantastic numbers are seen under these condtions but how close to real world power was an engine dyno under these conditions?" -Richard (Magnaflow Rep)

[BRUTAL64]

Interesting thread.

First you can NOT compare a "W" engine to a SB or BBC. Why you ask. That is simple there is NO combustion camber in the head.
The deck is cut at an angle and the pistons are wedge shaped in the crown. So why does it not compare to other chevy engines????
GM used the 348 TRUCK engine because at the time that was the ONLY BIG BLOCK it had. So it was a stop gap measure. Early in it's Hipo development GM discovered -because of it strange chamber combo- that cam timing/specs were unique to this type engine. So the "W" was not easy to build for horsepower. Yes the the 409 was fast but limited to what could be done horsepower wise. That why the Mark IV was built.

400 ci is the biggest production SBC. First GEN !
The reason I used it was because of it's 4 1/8 inch bore. Easy to make horsepower.

BB vs SB -- that is not so easy. BBC has bigger bore spacing thus more cubic inches and larger ports. Also rod ratio is a little better-- but that is not a big point in a street engine.

SBC is lighter and with all the after market stuff -- can be made to make as much horse power as you want.

Which one is better--- do you like your women with BIG BOOBS or smaller compact boobs.