Max RPMs for a 402 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

1-PU70 · 10-15-2016, 12:38 PM

What is max RPMs for a stock 402?

hugger6933 · 10-15-2016, 12:48 PM

In stock form I'd say you are running out of fire and fuel about 5000 or a little less. The ignition isn't gonna let you rev too high with points bounce and on top of that by those rpm's the fuel is gonna be running out.
On the other hand I had a modified 402 in and old Chevelle, and I kept a 7600 rpm chip in the rev limiter.

davepl · 10-15-2016, 01:47 PM

On the dyno my 402 nosed over around 5100 and was all done by 5500. That's with a =slightly= better than stock cam. So if you're stock, at 5250 I'd say shift it. Even 5000.

Alex V. · 10-15-2016, 03:17 PM

Valve float and pure air intake capability should limit it to not much over 5 grand, but I've heard tell of GM performance cam kits for 427's back in the day that advertised "Guaranteed satisfactory operation up to 9,200 RPM" - the rotating assembly of a big block Chevy is no weak piece.

Overdriven · 10-16-2016, 11:56 AM

Quote:

Originally Posted by Alex V.

Valve float and pure air intake capability should limit it to not much over 5 grand

My thoughts exactly. It's a truck motor and the valve springs are over 30 years old so I can't imagine it being any good over 5 grand. I'd limit it to 5,000 unless you upgrade the valve springs, cam and intake.

**schwoch1** · 10-16-2016, 10:35 PM

When the valves start to float, shift, than make a mental note to shift 100 RPM earlier the next go around

I am guessing that around 4500 the engine is done as far as power and torque are concerned!!!

Mike

Ken B · 10-17-2016, 06:45 AM

Quote:

Originally Posted by schwoch1

When the valves start to float, shift, than make a mental note to shift 100 RPM earlier the next go around

I am guessing that around 4500 the engine is done as far as power and torque are concerned!!!

Mike

Exactly my thoughts on that 402.. Every engine is different. Without running your engine myself and getting a "feel" for it there is no way to say for sure. With that said I totally agree with Mike. It is my opinion a bad idea to upgrade the top end of an engine for more RPM without upgrading the lower end. Bad things do happen...

davepl · 10-17-2016, 12:41 PM

Why speculate? Here's a picture. This is with the stock 396/325hp cam (instead of the 396/310hp stock cam).

10-15-2016, 12:38 PM	#1
1-PU70 Registered User Join Date: Apr 2000 Location: Bradenton, FL Posts: 1,036	Max RPMs for a 402 What is max RPMs for a stock 402? __________________ 1970 CST/10 402,700R4,3:73 posi,AC,PS,PB,TLT,PW,Buckets with heaters

10-15-2016, 12:48 PM	#2
hugger6933 Registered User Join Date: Oct 2008 Location: Marianna Arkansas Posts: 7,262	Re: Max RPMs for a 402 In stock form I'd say you are running out of fire and fuel about 5000 or a little less. The ignition isn't gonna let you rev too high with points bounce and on top of that by those rpm's the fuel is gonna be running out. On the other hand I had a modified 402 in and old Chevelle, and I kept a 7600 rpm chip in the rev limiter.

10-15-2016, 01:47 PM	#3
davepl Registered User Join Date: Aug 2006 Location: Redmond, WA Posts: 6,332	Re: Max RPMs for a 402 On the dyno my 402 nosed over around 5100 and was all done by 5500. That's with a =slightly= better than stock cam. So if you're stock, at 5250 I'd say shift it. Even 5000. __________________ 1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible

10-15-2016, 03:17 PM	#4
Alex V. Registered User Join Date: Mar 2013 Location: Campbellsville, KY Posts: 888	Re: Max RPMs for a 402 Valve float and pure air intake capability should limit it to not much over 5 grand, but I've heard tell of GM performance cam kits for 427's back in the day that advertised "Guaranteed satisfactory operation up to 9,200 RPM" - the rotating assembly of a big block Chevy is no weak piece. __________________ Alex V. ------ 1967 C10 Suburban, 350/NP435, Green/Green, PS, PB, HD cooling, charging, shocks, and springs. 1985 GMC C3500 SRW, Sierra Classic, 454/TH400, white/blue.

10-16-2016, 10:35 PM	#6
schwoch1 Local Detroit diesel nut! Join Date: Apr 2008 Location: Burlington, WI Posts: 175	Re: Max RPMs for a 402 When the valves start to float, shift, than make a mental note to shift 100 RPM earlier the next go around I am guessing that around 4500 the engine is done as far as power and torque are concerned!!! Mike __________________ Nothing cool anymore, I am old and boring....

10-17-2016, 12:41 PM	#8
davepl Registered User Join Date: Aug 2006 Location: Redmond, WA Posts: 6,332	Re: Max RPMs for a 402 Why speculate? Here's a picture. This is with the stock 396/325hp cam (instead of the 396/310hp stock cam). Attached Images __________________ 1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible



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