Hey gang,

I seem to hear regularily here that all a 496 offers is an increased and flatter torque curve?
Based on what?
A simple CID change with all of the rest of the parts remaining the same?

If...the heads and cam and intake/carburetion can support the sxtra CID, then it makes sense to me that a 496 will make more HP based on the HP/CID result. My previous 468 made 1.2 HP/CID.

So in my case.......am switching to a MUCH better head (AFR CNC 305's), more cam, more compression. Along with a lighter set of pistons and lower drag rings.

Personally, I don't think all I'm going to get is a torque increase.

Now, if all you change is the stroke, and the heads, cam and intake are only adequate for the 468....then I agree that all a 496 will do is increase torque. But just don't see it if the supporting components can handle the extra CID.

Comments....no flame throwers please.....to hot here to put on the flame prrof suit!

Ron

John L., may he rest in peace, said that a good set of reworked -781's or -049's could support up to a 540" motor so I do figure that the heads on a 468 if worked over some will do a 496 easy!!

In fact, I bought a new pair of Merlin ovals for my 496 b/c of him... That and I was afraid of getting hosed locally trying to get a shop to rebuild my good, -781's worth the money..

It is actually the cam timing events that govern where power is made..

And My old copy of Ed Staffel's book, "How to build Max Performance Chevy Rat Motors" on page 51 has a table of motors that held everything constant EXCEPT stroke. 478"=3.76"s, 509"=4.00"s, 525"= 4.125"s, 540=4.25"s, and 572=4.5"s..

Funny thing about the table is that both power and torque held at pretty much the same rpm levels to a point and that it was the cams and heads and stuff that set the rpm points and since they didn't change, they stayed pretty much constant..

Sure, bigger stuff raises the rpm power production limit as long as you have good enough CR. to take advantage of bigger is better..

pdq67

Ron, the logic of your comments is not debatable. Of COURSE , it will make MORE POWER! Again, its all in the 'system' balance. Tweak the system to optimize for the additional 30-40 cubes and it's going to out HP the smaller motor every single time.

Maybe this will help. graemlins/thumbsup.gif
link (http://www.rehermorrison.com/techTalk/20.htm)
Mitch.

Longer strokes always result in higher torques with everything else held constant because of the increased distance from the crank center to the rod center (lever arm). HP is the result of both torque and RPM, so increased power output is not guaranteed unless they both are capable of reaching about the same RPM. If the 468 out revs the 496 by a bunch due to shorter stroke then it may put out more peak HP:

HP = Tq * RPM/5252 (Tq in ft-lbs)

Anyway, to me the really important number is not peak HP but average torque over the expected RPM range.

I think that head flow is a common limiting factor. If you put the same head on both engines and they can rpm to use all the hp the head can give they should both have similiar hps. The 496 should make more torque and at a lower rpm. IMO the advantage of a 496 is that it makes its hp at a lower more street friendly rpm. If you say turn both to 6000rpm the 496 should be able to utilize a bigger/better flowing head and make more hp. In this case though you could turn the 468 to say 6500 rpm and make the same hp as the 496 at 6000.

Sounds right to me, but even though the peak HP may be the same with the 468 @ 6500 RPM the 496 would probably get you from A to B quicker because of the wider powerband.

Thanks for all the comments. In reality, I'm not comparing apples to apples because I'm changing a lot more than just the CID.
Ron

The next motor that I build will probably be a 496 (454+.030" now). I will be re-using my '049 oval ports maybe with a little more port work, same Isky roller cam, about .5 point higher SCR, same carb and intake (HP950 / AirGap).

I don't expect to make much additional peak HP, but quite a bit more torque in the mid-range. With this setup I should be able to take about 300-500 rpms out of the engine (6000-6200 instead of 6300-6500) and reduce the rear gear to a 3.90 or 4.10 and not lose any performance. This should make alot nicer street car.

You will make more power if your cylinder head flow and minimum cross sectional area will support the extra cubic inch.

Just stating the obvious. The AFR305 with CNC chamber will support 500ci under 7000 rpm.

IMO

MAT