V8 Long Stroke for high Boost
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Teching In
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V8 Long Stroke for high Boost Hi all guys, I had this doubt that I would like to share with you to know your thoughts on it, and if possible, to know if anyone has had any experiences on it.
In the boost usually engines with a large thickness of the cylinder walls are preferred, I have seen on average, that around the boost, for example, many use the lsx 427 instead of the lsx 454, I guess it is for the smaller bore and therefore a greater thickness of the walls, and consequently a greater solidity of the block under high boost.
So by logic, building an engine for high boost, wouldn't it be convenient to just increase the stroke, using dedicated connecting rods and crankshaft, instead of increasing the bores? It would increase the displacement, and maintain a good block strength under high boost .............. why then around, the majority increase the bore?
In the boost usually engines with a large thickness of the cylinder walls are preferred, I have seen on average, that around the boost, for example, many use the lsx 427 instead of the lsx 454, I guess it is for the smaller bore and therefore a greater thickness of the walls, and consequently a greater solidity of the block under high boost.
So by logic, building an engine for high boost, wouldn't it be convenient to just increase the stroke, using dedicated connecting rods and crankshaft, instead of increasing the bores? It would increase the displacement, and maintain a good block strength under high boost .............. why then around, the majority increase the bore?
Big bore, short stroke is ideal.
Mike Moran built a 5" bore space big bore BBC with a short stroke for his TT combo, makes stupid power.
People don't usually boost the LS 454 because the gasket between the cylinder bores is really, really thin.
Boosted 440", 427" and 388" are way more common mostly because turbo engines like to rev, big stroke means big piston speed means big frictional losses and limited rpm.
Hell there are guys out there like Capizzi making 1,300-1,400hp on sbe 5.3's at 8,500+ rpm.
Mike Moran built a 5" bore space big bore BBC with a short stroke for his TT combo, makes stupid power.
People don't usually boost the LS 454 because the gasket between the cylinder bores is really, really thin.
Boosted 440", 427" and 388" are way more common mostly because turbo engines like to rev, big stroke means big piston speed means big frictional losses and limited rpm.
Hell there are guys out there like Capizzi making 1,300-1,400hp on sbe 5.3's at 8,500+ rpm.
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Longer stroke usually means more block side loading in combination with higher piston speeds and reduced piston material, putting more stress on everything.
With blocks that have big bore spacing and tall decks, it is less of an issue than with an LS.
Running less displacement and more boost is always an option. V8 guys are a decade behind import guys in that ideology.
With blocks that have big bore spacing and tall decks, it is less of an issue than with an LS.
Running less displacement and more boost is always an option. V8 guys are a decade behind import guys in that ideology.
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Teching In
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thanks everyone for the answers guys, they were very useful, do you think an engine with the same bore and stroke would be good for an american v8? It would combine the advantage of having a good thickness of the cylinder walls and a not too long stroke
- Over Square is when the cylinder bore is wider than the stroke. (High revving, lower torque production)
- Under Square is wen the cylinder bore is narrower than the stroke. (Low revving, higher torque production)
Great example is the 5.3 LS, bore is 3.780 inches and stroke is 3.622 inches so an over square design that incorporates a thick cylinder wall.
Now if we toss a stroker crank shaft in with a 4.00" stroke we get 363ci and an under square design which as we all know with strokers makes more torque but won't have the rpm of the original 5.3 crank.
Back in the day we ran a very short stroke BBC Olds heads 430 cI was a nitrous engine that eventually turned Procharged. Engine builder was out of Chicago his name escapes me now. High RPM, small cubes for weight break, big bore for heads. Insane little engine it was.
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Teching In
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The block is very relevant. Let us know what block you plan on using and a power goal/intended application/ET/Weight etc. (IE drag car, 1000hp, stock block, 3000lbs 8.50's) Then we could suggest a bore/stroke. If you are talking factory LS 4-bolt blocks, then you leave them alone. There already isn't enough meat between the cyls on the 6.0 blocks for big power and stroking them pulls the piston out of the bore and rocks them, additional sideloads, etc... If you are running a tall deck aftermarket block, then that's much different! They are designed to handle greater bores/strokes. All comes down to cubic dollars in the end. If you want a "big" motor you pay "big" $. Which may or may not be necessary depending on your power/ET goal.