What characteristics would an 83mm crank feel like?
11-07-2008, 01:39 AM
#1
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What characteristics would an 83mm crank feel like? ....in a 6.0L block? With a stock 101.60mm bore and 83mm crank from a 4.8L it would technically be a 329ci 5.38L. With a .030" over, it'd be a 333ci 5.46L. What do you suppose it would feel like compared to a normal 6.0L? Would it mimic the old school Chevy 327, and Ford 302 with high winding characteristics?
This isn't a cost:hp/benefit analysis. This isn't a "There's no replacement for displacement" thread... I just want to know what it would feel like to drive a lightweight vehicle with such a powerplant. What type of valvetrain would be needed to make such a short block create impressive power?
Anyone done it before?
This isn't a cost:hp/benefit analysis. This isn't a "There's no replacement for displacement" thread... I just want to know what it would feel like to drive a lightweight vehicle with such a powerplant. What type of valvetrain would be needed to make such a short block create impressive power?
Anyone done it before?
11-07-2008, 10:59 AM
#3
i guess u would need some basic engine math to begin with:
i have a similar thought about this type of engine, my example is
4.065 l92 bore aluminum block liteweight and large bore
(4.8) crank, needs to be balanced for heavier 4.065 bore piston
compression height is around the same for all oem ls pistons
4.8 stock conecting rods pressed with oem 4.065 l92/ls3 pistons
may not work entirely, since newer ls pistons use floating pistons
but u get the idea= 341ci
i would use along with a low duration aggressive lobe cam
oem 243 milled heads, to achieve a 10.75-11.0:1 scr
better than stock valvetrain, strong springs, better than stock clamp, i.e. studs or at least arp head bolts
ls6 intake, ported tb, lt's, free flowing exhaust, etc.
it may not be a power tq monster, but should make for a quick revving
fast recovering engine with a manual trans. perhaps would work well for street car. or road car if your into carving corners and such
i have a similar thought about this type of engine, my example is
4.065 l92 bore aluminum block liteweight and large bore
(4.8) crank, needs to be balanced for heavier 4.065 bore piston
compression height is around the same for all oem ls pistons
4.8 stock conecting rods pressed with oem 4.065 l92/ls3 pistons
may not work entirely, since newer ls pistons use floating pistons
but u get the idea= 341ci
i would use along with a low duration aggressive lobe cam
oem 243 milled heads, to achieve a 10.75-11.0:1 scr
better than stock valvetrain, strong springs, better than stock clamp, i.e. studs or at least arp head bolts
ls6 intake, ported tb, lt's, free flowing exhaust, etc.
it may not be a power tq monster, but should make for a quick revving
fast recovering engine with a manual trans. perhaps would work well for street car. or road car if your into carving corners and such
11-07-2008, 11:33 AM
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Say the engine in question would go into a lightweight 3000lb chassis, rwd, manual 6. 4.88's in a respectable rear end, 26" tires. Like you hinted at, NemeSS, LS6 heads untouched, shy of milling them down to reach an 11:1scr with 92 octane. Fast 90/90 and supporting intake/exhaust. With a bump stick such as the Comp 273 high lift on XER lobes (224/230, .581/.588, 114) and supporting valvetrain mods, what could one come to expect from a motor such as this? Where would the power start to come on and what would the curves look like?
11-07-2008, 12:27 PM
#5
TECH Fanatic
It would FEEL slower than a 6.0L. Not only that it would BE slower and more expensive to build, but you said cost wasn't a concern.
Just how far do you plan to rev your shorter stroke mill? 8500? Higher? What intake will support power well above 7500? FAST runners are too long. Untouched 243 heads aren't a real good idea for this build either. 7900 on a 6.0L stock bottom end is done regularly on a drag car I'm familiar with. It uses a single plane intake.
The upside is you could impress the "troops" with your innovative build, if not with the car's performance. Savvy engine guys would probably laugh when they saw the FAST on your 8500 rpm screamer.
You asked.
Just how far do you plan to rev your shorter stroke mill? 8500? Higher? What intake will support power well above 7500? FAST runners are too long. Untouched 243 heads aren't a real good idea for this build either. 7900 on a 6.0L stock bottom end is done regularly on a drag car I'm familiar with. It uses a single plane intake.
The upside is you could impress the "troops" with your innovative build, if not with the car's performance. Savvy engine guys would probably laugh when they saw the FAST on your 8500 rpm screamer.
You asked.
11-07-2008, 12:50 PM
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I'm not planning anything. I'm not buying parts, not considering this for a future build, not doing anything really other than brainstorming. I had no preset goal of a high red line, though I knew it would be up there. The idea just came into my head as a "what would this feel like if it was built"?
I asked, and I received. Thank you fellas.
I know full well the bigger CFM motor will rule the street. I know displacement makes this easier. I know in an oversimplified way, the heads determine the horsepower and the displacement under those heads determines rpm at which that horsepower is made, therefore the torque.
How would you build such a motor? Say if it were set up to run in a bracket racing class where sanctioning bodies limited the displacement to 5.4L? I don't know if there is such a class...again, just thinking out loud here.
I asked, and I received. Thank you fellas.
I know full well the bigger CFM motor will rule the street. I know displacement makes this easier. I know in an oversimplified way, the heads determine the horsepower and the displacement under those heads determines rpm at which that horsepower is made, therefore the torque.
How would you build such a motor? Say if it were set up to run in a bracket racing class where sanctioning bodies limited the displacement to 5.4L? I don't know if there is such a class...again, just thinking out loud here.
11-07-2008, 01:19 PM
#7
I've run 327s with big cams, been in cars with built 302 sbcs. Yeah they rev nice when you blip it in neutral, but really are sappy on low end torque, and don't pull as hard as a larger engine built to the same level. Back then trannys with OD were mia, so 4.56s/4.88s needed to crutch the smaller engines with a Muncie really sucked after a while.
Cam technology was stone age... "off road" Z/28 cam for the historians. So you would have the advantage of the roller with faster ramp action to help with a broader power band. So figure instead of pulling hard > 4,500, you start to "get on the cam" (another blast from the past) at a lower rpm. But the bigger engine with the same cam would pull much harder from the bottom to the top.
Moved on to bigger engines, haven't built a sbc smaller than a 400 in a long time. Bang for the buck just isn't there for short stroke engines, but the mystique about these engines still exists. Guys even now will go on boards and ask what they have to do to make their 350 sbc into a 302/327 cause they heard from their dad/uncle/fillintheblank how great the 302s/327s revved.
Cliffs: bigger engines "feel" better all the way up the rpm band. And as far as better revvability from short stroke engines... the bigger engine pulls the load better, so in reality, they actually rev quicker when it counts... accelerating a car.
Cam technology was stone age... "off road" Z/28 cam for the historians. So you would have the advantage of the roller with faster ramp action to help with a broader power band. So figure instead of pulling hard > 4,500, you start to "get on the cam" (another blast from the past) at a lower rpm. But the bigger engine with the same cam would pull much harder from the bottom to the top.
Moved on to bigger engines, haven't built a sbc smaller than a 400 in a long time. Bang for the buck just isn't there for short stroke engines, but the mystique about these engines still exists. Guys even now will go on boards and ask what they have to do to make their 350 sbc into a 302/327 cause they heard from their dad/uncle/fillintheblank how great the 302s/327s revved.
Cliffs: bigger engines "feel" better all the way up the rpm band. And as far as better revvability from short stroke engines... the bigger engine pulls the load better, so in reality, they actually rev quicker when it counts... accelerating a car.
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11-07-2008, 01:20 PM
#8
what old sstroker said is correct,
if u were regulated to use such an engine and in a class then i
would see the need and popularity of it.
but if doing for just experiment purposes, then i would not be against it.
i have thought of it myself, since the parts are easy to come by
4.03 bore pistons are readily available and can be pressed to stock 4.8 rods, the 4.8 crank can be balanced to the new weight of pistons, etc., a 6.0 lq4 block could be used.
nothing out of the ordinary is really needed. imo
if u were regulated to use such an engine and in a class then i
would see the need and popularity of it.
but if doing for just experiment purposes, then i would not be against it.
i have thought of it myself, since the parts are easy to come by
4.03 bore pistons are readily available and can be pressed to stock 4.8 rods, the 4.8 crank can be balanced to the new weight of pistons, etc., a 6.0 lq4 block could be used.
nothing out of the ordinary is really needed. imo
