rm builder ---- cam ?s
10-11-2005, 06:15 PM
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rm builder ---- cam ?s
i have 2000 hp500 efi long blocks with 420 mega blowers with nickerson - holley 750s v6 moduals im running 5 lbs boost and have almost 17 inches vacuum at idle. the motors run great but it just feels like theres more there , could the efi cam be holding me back ? im going to be pulling the motors so i can upgrade the transmissions this winter so the motors will be sitting in the garage anyway perfect time to swap out the cams. the boat is 88 fountain 12meter icbm trs drives. what would you think about the crane 741 for this application with stock comp, stock heads, and 5 lbs boost do you think that would wake it up a little ?
thanks kevin
if i wasnt pulling them anyway i wouldnt change them but since thell be out a cam change would be easy
we always want more dont we
thanks kevin
if i wasnt pulling them anyway i wouldnt change them but since thell be out a cam change would be easy
we always want more dont we
10-12-2005, 09:54 AM
#5
MarineKinetics
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Re: rm builder ---- cam ?s
Kevin,
The 500 EFI and the 741 are the same lobe family, however there are significant differences in the placing of the valve events. The 741 is 6*/ 8* longer in duration than the 500EFI with 2* less LSA. Due to the placement of the centerlines on the 741 the majority of the increased duration is not evenly distributed. On the intake side, 5* of the 6* increase is placed on the IVO (Intake valve open) side and, 6* of the 8* increase on the exhaust is on the EVC (Exhaust valve close). The 741 also has (67* vs 78*) 11* more overlap than the 500 EFI. These are not typically the directions you go in with forced engines running under 6000 RPM. The next step is to address your current components, performance goals, and budget for upgrades. All your major manfacturers offer grinds that are blower specific for these applications. Hope this has helped with your question
Bob
The 500 EFI and the 741 are the same lobe family, however there are significant differences in the placing of the valve events. The 741 is 6*/ 8* longer in duration than the 500EFI with 2* less LSA. Due to the placement of the centerlines on the 741 the majority of the increased duration is not evenly distributed. On the intake side, 5* of the 6* increase is placed on the IVO (Intake valve open) side and, 6* of the 8* increase on the exhaust is on the EVC (Exhaust valve close). The 741 also has (67* vs 78*) 11* more overlap than the 500 EFI. These are not typically the directions you go in with forced engines running under 6000 RPM. The next step is to address your current components, performance goals, and budget for upgrades. All your major manfacturers offer grinds that are blower specific for these applications. Hope this has helped with your question
Bob
Last edited by rmbuilder; 10-12-2005 at 10:06 AM.
10-12-2005, 02:25 PM
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Re: rm builder ---- cam ?s
thanks bob, best speed i saw was 76 mph but that was before i fixed head gaskets on port motor now both motors run great but trans is starting to slip so i cant finish prop testing till spring i have two hubers 1200 s coming for the boat i would like to see mid 80s but its a tank.
long range plan is to tear down motors in 2 years drop compresion, new heads, cyclone headers ect. just thought if a quick cam change would make a differance it would be easy to do since they will be out of the boat til spring
thanks kevin
long range plan is to tear down motors in 2 years drop compresion, new heads, cyclone headers ect. just thought if a quick cam change would make a differance it would be easy to do since they will be out of the boat til spring
thanks kevin
