468 vs 496 - Page 5 - Chevelle Tech
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post #61 of 97 (permalink) Old Nov 15th, 19, 7:59 PM
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Re: 468 vs 496

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Originally Posted by 68Chevele View Post
As I was told years ago was an engine with a larger bore short stroke will make more power by the heads being less shrouding around the valves + you are able to spin the engine higher for more power. Now the thing with that is you have to make everything else in the combo work for the big bore combo.
Bingo. The stroke doesn't have to be "short", though. The valves being unshrouded by the larger bore seems to be the key and when combined with as much stroke as is practical, or allowed by rules, nets more power and RPM potential. But you need the larger valve and the correct cam to optimize the advantage of the larger bore.

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69 Malibu Stock 307, Reverse Manual TH350, 4,500 Stall Edge Converter, 4.56 Spool 35 Spline 12 Bolt

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post #62 of 97 (permalink) Old Nov 15th, 19, 8:20 PM
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Re: 468 vs 496

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Originally Posted by Tommy the Cat View Post
Bingo. The stroke doesn't have to be "short", though. The valves being unshrouded by the larger bore seems to be the key and when combined with as much stroke as is practical, or allowed by rules, nets more power and RPM potential. But you need the larger valve and the correct cam to optimize the advantage of the larger bore.
A longer stroke, especially with no increase in rod length, does NOT allow more rpm potential. It's the opposite. Increasing stroke and increasing rpm do not go easily hand in hand.
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post #63 of 97 (permalink) Old Nov 15th, 19, 8:34 PM
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Re: 468 vs 496

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Originally Posted by Tommy the Cat View Post
If the two bore and stroke combinations you listed are built with the same heads, cam, intake and exhaust.. all things being equal apart from the bore/stroke resulting in the same displacement the dyno wouldn't show nearly identical power curves?

Scott, I know you have forgotten more than I will ever know about building engines and I believe that you are 100% correct that the shorter stroke will prevail if optimized but I'm talking about when all things being equal apart from bore/stroke in a street car.

For instance- if a guy already had off the shelf heads, cam, intake, carb, ignition, exhaust and needed a short block, should he buy a smaller bore, longer stroke 496 or a bigger bore, shorter stroke 496? It's been proven time and again that the two engines will make nearly identical power curves.
The longer stroke combination is going to have more demand on the induction and at a lower rpm. Piston speed and peak piston acceleration is what dictate demand. For the same displacement, the stroker engine is going to want a different designed induction to be optimized. If both engines are optimized, they will be very close on power but they will not be built near the same. Different configurations require different approaches. The two engines would, however, have very different power curves because they are two different engines. If a guy already had an induction package, he would have to look at the details of the induction to decide on which configuration to build. The stroker would want a little more valve and port area so if the heads were a little big for "496ci" then he would be better off with the stroker. If the heads were on the small side for "496ci" then he would be better off with the shorter stroke engine. I may be speaking in small differences here and picking pepper out of fly**** but I'm addressing the question as best I can. How MUCH different the two engines would be may be irrelevant to other things but none the less. Bottom line is, we're talking about two different engines, especially comparing e 468 to a 496. Your point of view is not "hilariously flawed".

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post #64 of 97 (permalink) Old Nov 15th, 19, 8:39 PM
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Re: 468 vs 496

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Originally Posted by steelcomp View Post
A longer stroke, especially with no increase in rod length, does NOT allow more rpm potential. It's the opposite. Increasing stroke and increasing rpm do not go easily hand in hand.
Perhaps I didn't phrase that correctly. The larger bore allowing a bigger valve increases the RPM potential. Combine that advantage with a longer stroke and you net more power.

Better?
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69 Malibu Stock 307, Reverse Manual TH350, 4,500 Stall Edge Converter, 4.56 Spool 35 Spline 12 Bolt

76 C20 VortecPro 496 628HP 655 lb/ft TH400 Edge Converter, 4.10 14 bolt
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post #65 of 97 (permalink) Old Nov 15th, 19, 8:54 PM
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Re: 468 vs 496

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Originally Posted by steelcomp View Post
The longer stroke combination is going to have more demand on the induction and at a lower rpm. Piston speed and peak piston acceleration is what dictate demand. For the same displacement, the stroker engine is going to want a different designed induction to be optimized. If both engines are optimized, they will be very close on power but they will not be built near the same. Different configurations require different approaches. The two engines would, however, have very different power curves because they are two different engines. If a guy already had an induction package, he would have to look at the details of the induction to decide on which configuration to build. The stroker would want a little more valve and port area so if the heads were a little big for "496ci" then he would be better off with the stroker. If the heads were on the small side for "496ci" then he would be better off with the shorter stroke engine. I may be speaking in small differences here and picking pepper out of fly**** but I'm addressing the question as best I can. How MUCH different the two engines would be may be irrelevant to other things but none the less. Bottom line is, we're talking about two different engines, especially comparing e 468 to a 496. Your point of view is not "hilariously flawed".

The main take-away I'm getting here is to let a pro handle it! Thank you for taking the time to help us understand. There's so much more to building a good combo than I care to learn.
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69 Malibu Stock 307, Reverse Manual TH350, 4,500 Stall Edge Converter, 4.56 Spool 35 Spline 12 Bolt

76 C20 VortecPro 496 628HP 655 lb/ft TH400 Edge Converter, 4.10 14 bolt
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post #66 of 97 (permalink) Old Nov 15th, 19, 8:55 PM
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Re: 468 vs 496

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Originally Posted by Tommy the Cat View Post
But as Scott said earlier, if the two combinations are optimized to exploit the unique advantages the bigger bore wins every time. Dave has proven that many times over. I'm sure Scott has too. But that wasn't the point that was being made; the point was the wive's tale about small bore/ long stroke= low RPM "truck engine" and big bore/ short stroke= high RPM and no torque is false. The longer stroke does not have a torque advantage in and of itself nor does the short stroke have an RPM advantage in and of itself.

The heads, cam, intake, exhaust, ignition, etc. determine the personality of the engine, not the bore/stroke relationship given a set C.I.D.
The bore and stroke are the foundation. They set the stage for everything else that's going to happen. A longer stroke engine will have a lower rpm torque advantage and can be exploited as such. It doesn't mean you can't turn high rpm with a longer stroke engine, it's just not going to give you the same returns. A shorter stroke engine will favor higher rpm hp and tq and can be exploited as such. NHRA Pro Stock is a perfect example. They can run any bore/stroke combination they want. More rpm means more power. To get more rpm you need more induction. To get more induction you need a big intake valve, and to get a big intake valve you need a big bore. For a given displacement, the bigger the bore, the shorter the stroke. Back to the two 496's...the 4" stroke 496 will out-rpm the 4-1/4 stroke 496 all day. Or lets call it an even 500ci. The current Pro Stock configuration is a ~4.7" bore and a ~3.5" stroke. There's a reason for that. Bore size=big valve=more rpm=shorter stroke=more rpm=less piston speed=more rpm=more power...it's about more rpm. Again, the 4" stroke 496 will run circles around the 4-1/4" stroke 496 all day because it has more rpm potential and can make more hp/ci by turning more rpm. It's just math and physics.
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post #67 of 97 (permalink) Old Nov 15th, 19, 9:02 PM
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Re: 468 vs 496

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Originally Posted by Tommy the Cat View Post
Perhaps I didn't phrase that correctly. The larger bore allowing a bigger valve increases the RPM potential. Combine that advantage with a longer stroke and you net more power.

Better?
In simple terms, yes but the longer stroke brings with it some drawbacks, mainly piston side loading and friction which increase with rpm. The gains are offset to a certain degree. It took the mountain motor guys a long time before they could safely get any decent rpm out of those huge stroke engines. Mainly, they had to keep increasing deck height and rod length with the added stroke but in the end, stroke is still piston speed and pistons will only start and stop so fast. Piston speed is a big issue with strokers, both for induction reasons because of increased demand, and for physical reasons simply because they want to come apart.

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post #68 of 97 (permalink) Old Nov 16th, 19, 11:58 AM
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Re: 468 vs 496

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He's got a 327 for sale right now.
Nobody liked my 327 didn't sell.......do I care, not a bit
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post #69 of 97 (permalink) Old Nov 16th, 19, 12:20 PM
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Re: 468 vs 496

I get what you're saying Tommy.

I read the Hot Rod test years ago where they compared two chevy engines with the same displacement but different strokes and found negligible difference.

The topic kind of strayed from 454 vs 496.

The 496 has longer rods to help neutralize the longer stroke and generally will benefit from the 42 extra cubes by 42+ hp throughout most of the operating range.

A bigger bore is even better as it will unshroud the valves and breathe better. But a 4.5" bore block and different pistons is $3000+ more.

Decisions, decisions
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post #70 of 97 (permalink) Old Nov 16th, 19, 3:37 PM
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Re: 468 vs 496

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Nobody liked my 327 didn't sell.......do I care, not a bit
Any specs on the 327?


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post #71 of 97 (permalink) Old Nov 16th, 19, 4:10 PM
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Re: 468 vs 496

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Nobody liked my 327 didn't sell.......do I care, not a bit
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Any specs on the 327?
https://denver.craigslist.org/pts/d/...998935832.html

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post #72 of 97 (permalink) Old Nov 16th, 19, 4:18 PM
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Re: 468 vs 496

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Are those heads the Trick Flow "double-humps" ?

Beautiful engine

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post #73 of 97 (permalink) Old Nov 16th, 19, 6:55 PM
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Re: 468 vs 496

I have talked to Mark about that engine but don't have a lot of info on it. I don't really have a use for it so I didn't ask too many questions. Hopefully he'll come back and fill us in. If I needed a small block I would already own it, though. He's including a lot of good stuff with it.

70 Camino...Roller

69 Malibu Stock 307, Reverse Manual TH350, 4,500 Stall Edge Converter, 4.56 Spool 35 Spline 12 Bolt

76 C20 VortecPro 496 628HP 655 lb/ft TH400 Edge Converter, 4.10 14 bolt
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post #74 of 97 (permalink) Old Nov 16th, 19, 9:15 PM
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Re: 468 vs 496

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Are those heads the Trick Flow "double-humps" ?

Beautiful engine
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post #75 of 97 (permalink) Old Nov 17th, 19, 6:38 PM
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Re: 468 vs 496

Cam spec's?

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