big bore short stroke for FI application - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

racesloth · 11-17-2018, 11:26 AM

Has anyone done a 4.8 crank on a 4.125 bore in a boosted application? I was thinking about a combo like that in an LSX block or a sleeved TSX block with BR7 heads and an LS7 intake on 18-20lbs of boost for 1/2 mile outings. Seems like it would rev real nice.

AGP Turbo · 11-17-2018, 11:43 AM

That doesn't overcome the crap pushrod, heavy valvetrain problems that the LS motors have when trying to rev high. That's why LS motors work best limited to about 7000ish RPM. If you set that limitation in stone for reliability, suddenly a 427's make a lot of sense. And bigger engine lower boost= less heat anyway, smaller engine displacement never seems to be a better way to go.

stevieturbo · 11-20-2018, 06:00 PM

Do you have a gearing problem that you need to consider something that need to use very high rpm's ?

At the end of the day, a smaller motor will still have to work harder to make power so unless you need beyond say 8k....is there really much point in going downsize so much ?

racesloth · 11-21-2018, 05:19 AM

I noticed that oversquare set ups always won the enginemasters challenge before they messed up the competition. I would like to see what the piston speed of a 427 (4.125 x 4") at 7000 rpm is compared to the piston speed of 350 (4.125 x 3.267") at 8000 rpm.

Piston speed of 427 at 7000 = 4667 FPS while 350 is 4356 FPS

A 3" stroke at 8500 rpm's is only 4250 FPS

I see AGP's point that the valve train would be expensive and becomes the new stress point. High RPMs is where the DOHC engines shine. But an LS engine sounds so sweet at those rpms. I remember an N/A corvette at lights out back in 2011 that reved >8k and no car at the track sounded better...

Maybe for the 1/2 mile stuff (when I get back to the US) I will just use my turbo Mustang and keep the Camaro as a street car...

SSBUSDRVR · 11-23-2018, 08:25 AM

Was it this one Racesloth? Buddies Car. Current 1/2 WR LSx All Motor 199.73 mph. Have never heard a better sounding NA LS Car in person but not many Rev to 9200. One heck of a Car and one great humble guy. If anyone’s at PRI it will be at the ProEFI Booth.

racesloth · 11-24-2018, 12:27 PM

No it wasn't that one unless it was a different color back then. I think pro-line did the work on the car at lights out...

11-17-2018, 11:26 AM	#1
racesloth Dan Drives: 2010 Camaro 2SS IOM Join Date: Nov 2013 Location: Georgia, USA not the other one Posts: 1,041	big bore short stroke for FI application Has anyone done a 4.8 crank on a 4.125 bore in a boosted application? I was thinking about a combo like that in an LSX block or a sleeved TSX block with BR7 heads and an LS7 intake on 18-20lbs of boost for 1/2 mile outings. Seems like it would rev real nice. __________________ Dan 2010 IOM SS YSI-B, Pat G Cam, Ported CTS-V Heads, ARH LTs MBRP 3" exhaust http://www.camaro5.com/forums/showth...&highlight=ysi

11-21-2018, 05:19 AM	#4
racesloth Dan Drives: 2010 Camaro 2SS IOM Join Date: Nov 2013 Location: Georgia, USA not the other one Posts: 1,041	I noticed that oversquare set ups always won the enginemasters challenge before they messed up the competition. I would like to see what the piston speed of a 427 (4.125 x 4") at 7000 rpm is compared to the piston speed of 350 (4.125 x 3.267") at 8000 rpm. Piston speed of 427 at 7000 = 4667 FPS while 350 is 4356 FPS A 3" stroke at 8500 rpm's is only 4250 FPS I see AGP's point that the valve train would be expensive and becomes the new stress point. High RPMs is where the DOHC engines shine. But an LS engine sounds so sweet at those rpms. I remember an N/A corvette at lights out back in 2011 that reved >8k and no car at the track sounded better... Maybe for the 1/2 mile stuff (when I get back to the US) I will just use my turbo Mustang and keep the Camaro as a street car... __________________ Dan 2010 IOM SS YSI-B, Pat G Cam, Ported CTS-V Heads, ARH LTs MBRP 3" exhaust http://www.camaro5.com/forums/showth...&highlight=ysi

11-23-2018, 08:25 AM	#5
SSBUSDRVR Drives: '11 2SS/RS IBM/BLK M6 Join Date: Mar 2011 Location: Central FL Posts: 3,748 View My Garage	Was it this one Racesloth? Buddies Car. Current 1/2 WR LSx All Motor 199.73 mph. Have never heard a better sounding NA LS Car in person but not many Rev to 9200. One heck of a Car and one great humble guy. If anyone’s at PRI it will be at the ProEFI Booth. __________________ '11 IBM 2SS/RS Built and Tuned by Vengeance Racing Vengeance PCM Vengeance Racing Mast Black Label LS7 Headed 416 ProCharger Stage II D1X Race ,Monster Triple,Alky Control Meth Inj, Forgestar F14 Drag Version and a bunch of other blah blah blah.838/688 at 12lbs Street Friendly

11-24-2018, 12:27 PM	#6
racesloth Dan Drives: 2010 Camaro 2SS IOM Join Date: Nov 2013 Location: Georgia, USA not the other one Posts: 1,041	No it wasn't that one unless it was a different color back then. I think pro-line did the work on the car at lights out... __________________ Dan 2010 IOM SS YSI-B, Pat G Cam, Ported CTS-V Heads, ARH LTs MBRP 3" exhaust http://www.camaro5.com/forums/showth...&highlight=ysi

11-17-2018, 11:43 AM	#2
AGP Turbo Drives: All things Turbocharged Join Date: Dec 2010 Location: AZ Posts: 1,199	That doesn't overcome the crap pushrod, heavy valvetrain problems that the LS motors have when trying to rev high. That's why LS motors work best limited to about 7000ish RPM. If you set that limitation in stone for reliability, suddenly a 427's make a lot of sense. And bigger engine lower boost= less heat anyway, smaller engine displacement never seems to be a better way to go.

11-20-2018, 06:00 PM	#3
stevieturbo Drives: it changes Join Date: Nov 2010 Location: Norn Iron Posts: 1,126	Do you have a gearing problem that you need to consider something that need to use very high rpm's ? At the end of the day, a smaller motor will still have to work harder to make power so unless you need beyond say 8k....is there really much point in going downsize so much ?