Why does my engine top out at about 5100rpms? - Page 2 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

gabet40 · 09-17-2002, 04:42 PM

ok so its not exactly a racing distributor, and i know i should upgrade to an MSD, but do you think this is whats limiting my RPMs?
i think i need to get into my ECU as well and make sure theres nothing in there thats limiting it

Stroker · 09-17-2002, 06:30 PM

gabet40, I would tend to agree with the others that have suggested valve springs. I don't think it's your HEI dizzy, I've used the same unit with no problems to 6,000. I have a budget built 350, 8.7:1, crappy 882 heads, Crane 266, 1 5/8 headers, GM aluminum duel plane intake, 600cfm carb. That engine in a heavy 3/4 ton has no problem reving to 5500 in first or second. It's also possible that the EFI ECU could be leaning you out at higher RPM, could it possibly have a built in rev limitter. Good luck let us know what you find....Stroker

gabet40 · 09-19-2002, 05:15 PM

well i finally hooked my computer up to my ECU and sure enough, the Base Map Cell Size was set at 500 RPM, meaning that my Base Fuel Map was only set up to calculate fuel ratios up to 5000 RPMs. well i went ahead and changed that figure to 650 and sure enough, i flew right up to 5700. i havent topped it out yet but obviously that was my problem.
however im still interested in the recommended springs for my cam. at $67 and some work, do you think itll be worth it?

09-17-2002, 04:42 PM	#26
gabet40 Registered User Join Date: Dec 1999 Location: Modesto, CA Posts: 565	ok so its not exactly a racing distributor, and i know i should upgrade to an MSD, but do you think this is whats limiting my RPMs? i think i need to get into my ECU as well and make sure theres nothing in there thats limiting it __________________ Current owner of 2016 2500 Silverado Midnight Edition. Former owner of: 69 1/2 ton, change from long/fleet to short/fleet, shaved door handles, shaved tailgate, 4/6 drop, power windows, 700r4 72 blazer, 350 with Holley Commander 950 DFI, crane energizer cam, 350 tranny, dual sanderson blockhuggers/magnaflow exhaust

09-17-2002, 06:30 PM	#27
Stroker Registered User Join Date: Mar 2001 Location: Moore, Ok Posts: 1,149	gabet40, I would tend to agree with the others that have suggested valve springs. I don't think it's your HEI dizzy, I've used the same unit with no problems to 6,000. I have a budget built 350, 8.7:1, crappy 882 heads, Crane 266, 1 5/8 headers, GM aluminum duel plane intake, 600cfm carb. That engine in a heavy 3/4 ton has no problem reving to 5500 in first or second. It's also possible that the EFI ECU could be leaning you out at higher RPM, could it possibly have a built in rev limitter. Good luck let us know what you find....Stroker __________________ 72 SWB parts and pieces Oklahoma

09-19-2002, 05:15 PM	#28
gabet40 Registered User Join Date: Dec 1999 Location: Modesto, CA Posts: 565	you guys are gonna kill me well i finally hooked my computer up to my ECU and sure enough, the Base Map Cell Size was set at 500 RPM, meaning that my Base Fuel Map was only set up to calculate fuel ratios up to 5000 RPMs. well i went ahead and changed that figure to 650 and sure enough, i flew right up to 5700. i havent topped it out yet but obviously that was my problem. however im still interested in the recommended springs for my cam. at $67 and some work, do you think itll be worth it? __________________ Current owner of 2016 2500 Silverado Midnight Edition. Former owner of: 69 1/2 ton, change from long/fleet to short/fleet, shaved door handles, shaved tailgate, 4/6 drop, power windows, 700r4 72 blazer, 350 with Holley Commander 950 DFI, crane energizer cam, 350 tranny, dual sanderson blockhuggers/magnaflow exhaust

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