Damage running at high RPM's for extended periods? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

BIG CTY · 03-29-2007, 08:56 PM

I have a a 66 with 250 straight 6 and 3 speed manual. I run the absolute $hit out of that truck when I drive it. Seems like you cant break the 6! What I was wondering is this...what damage can I do running my truck at 75-80 mph for extended periods? According to my tach, my RPM's are over 3500? Thoughts?

BIG CTY · 03-30-2007, 10:20 AM

OK guys, maybe its a stupid question - but SURELY someone has an opinion!

Eliasj123 · 03-30-2007, 12:28 PM

There's no definite answer.

You're not going to break any particular thing, so to say. But you are putting a lot of stress and wear & tear on your engine and tranny.

You might blow a rod next time you drive it like that or you may never blow a rod.

Keep in mind that it's an old engine and tranny and it wasn't designed to be a race car. The easier you are with her, the longer she'll take you..

Just don't be surprised when something breaks..

Elias

Frizzle Fry · 03-30-2007, 12:55 PM

I wouldn't worry about 3500 RPM, but I'd try to stay south of 5000... Higher RPM=exponentially higher wear and tear.

Fred T · 03-31-2007, 02:04 AM

I agree with Mike. I had a 250 in a 74 that I bought new. Did a lot of highway driving at 90+. Sold it with about 140K on the engine, it still ran good and didn't use much oil. Engine was still tight.

When GM designed the new six, they used as much of the SBC design as they could. Just by nature of the design, the crank has more counterweight than the V8. But the bearing, rods and pistons are from the SBC.

It was the previous sixes that didn't like to spin fast. Crank weights were huge, bearing tolerances looser, and rods were prone to stretching. On a 235 or 261 I usually avoid running over 3.000 rpm for extended running, unless the engine has been built for it.

Also, a lot of damage is done to the long stroke engines by lugging hard at low speed. Once it starts knocking at low rpm, you need to back out and downshift to avoid broken pistons and rod damage.

combustion · 03-31-2007, 03:07 AM

Quote:

Originally Posted by BIG CTY

I have a a 66 with 250 straight 6 and 3 speed manual. I run the absolute $hit out of that truck when I drive it. Seems like you cant break the 6! What I was wondering is this...what damage can I do running my truck at 75-80 mph for extended periods? According to my tach, my RPM's are over 3500? Thoughts?

if you wanna rev high get a k24 n/a civic. i love k series motors

http://www.youtube.com/watch?v=Hn-F6H6RNEo

leftcoast66 · 04-02-2007, 01:39 AM

I wouldn't be worried about revs like that, but like frizzle said, 5 k often I'd b worried about.

btw, why would u wanna put the effort into a civic?...

hewlett2002000 · 04-02-2007, 01:58 AM

thats a high revin SOB in that video. but i read this on somebody's post the other day. beating a honda is like banging a fat chick, everybody can do it but who wants to brag about it?!!!!

BIG CTY · 04-02-2007, 10:57 PM

Thanks everyone, 'preciate the info!

Iron-Butt · 04-03-2007, 05:29 AM

I like 6 cyl. they run good and hard.

03-29-2007, 08:56 PM	#1
BIG CTY Between the earth and the sky Join Date: Oct 2006 Location: Chesapeake, VA Posts: 822	Damage running at high RPM's for extended periods? I have a a 66 with 250 straight 6 and 3 speed manual. I run the absolute $hit out of that truck when I drive it. Seems like you cant break the 6! What I was wondering is this...what damage can I do running my truck at 75-80 mph for extended periods? According to my tach, my RPM's are over 3500? Thoughts? __________________ Chris - 1966 C10 Shortbed Fleetside, 1991 GMC Sierra 1500 Extended Cab, 1993 Blazer Sport 4x4 My other rides: 1969 Chevrolet Impala SS427 Convertible 1976 Dodge Tradesman B200 2002 Nissan Maxima 6 speed 2004 Mercedes Benz CL500

03-30-2007, 10:20 AM	#2
BIG CTY Between the earth and the sky Join Date: Oct 2006 Location: Chesapeake, VA Posts: 822	Re: Damage running at high RPM's for extended periods? OK guys, maybe its a stupid question - but SURELY someone has an opinion! __________________ Chris - 1966 C10 Shortbed Fleetside, 1991 GMC Sierra 1500 Extended Cab, 1993 Blazer Sport 4x4 My other rides: 1969 Chevrolet Impala SS427 Convertible 1976 Dodge Tradesman B200 2002 Nissan Maxima 6 speed 2004 Mercedes Benz CL500

03-30-2007, 12:28 PM	#3
Eliasj123 Registered User Join Date: Oct 2006 Location: SoCal Posts: 108	Re: Damage running at high RPM's for extended periods? There's no definite answer. You're not going to break any particular thing, so to say. But you are putting a lot of stress and wear & tear on your engine and tranny. You might blow a rod next time you drive it like that or you may never blow a rod. Keep in mind that it's an old engine and tranny and it wasn't designed to be a race car. The easier you are with her, the longer she'll take you.. Just don't be surprised when something breaks.. Elias

03-30-2007, 12:55 PM	#4
Frizzle Fry Registered User Join Date: Aug 2005 Location: Hillsboro Oregon Posts: 6,449	Re: Damage running at high RPM's for extended periods? I wouldn't worry about 3500 RPM, but I'd try to stay south of 5000... Higher RPM=exponentially higher wear and tear.

03-31-2007, 02:04 AM	#5
Fred T Cantankerous Geezer Join Date: Aug 2002 Location: Bel Aire, KS Posts: 6,264	Re: Damage running at high RPM's for extended periods? I agree with Mike. I had a 250 in a 74 that I bought new. Did a lot of highway driving at 90+. Sold it with about 140K on the engine, it still ran good and didn't use much oil. Engine was still tight. When GM designed the new six, they used as much of the SBC design as they could. Just by nature of the design, the crank has more counterweight than the V8. But the bearing, rods and pistons are from the SBC. It was the previous sixes that didn't like to spin fast. Crank weights were huge, bearing tolerances looser, and rods were prone to stretching. On a 235 or 261 I usually avoid running over 3.000 rpm for extended running, unless the engine has been built for it. Also, a lot of damage is done to the long stroke engines by lugging hard at low speed. Once it starts knocking at low rpm, you need to back out and downshift to avoid broken pistons and rod damage. __________________ Fred There is no such thing as too much cam...just not enough engine.

04-02-2007, 01:39 AM	#7
leftcoast66 Registered User Join Date: Sep 2006 Location: Covington, WA Posts: 770	Re: Damage running at high RPM's for extended periods? I wouldn't be worried about revs like that, but like frizzle said, 5 k often I'd b worried about. btw, why would u wanna put the effort into a civic?...

04-02-2007, 01:58 AM	#8
hewlett2002000 Registered User Join Date: Dec 2006 Location: Cleveland, Tx Posts: 1,619	Re: Damage running at high RPM's for extended periods? thats a high revin SOB in that video. but i read this on somebody's post the other day. beating a honda is like banging a fat chick, everybody can do it but who wants to brag about it?!!!! __________________ Respect: 1. A feeling of appreciative, often deferential regard; esteem. 2. The state of being regarded with honor or esteem. 3. Willingness to show consideration or appreciation. When you fail to show consideration to others values you are showing disrespect.

04-02-2007, 10:57 PM	#9
BIG CTY Between the earth and the sky Join Date: Oct 2006 Location: Chesapeake, VA Posts: 822	Re: Damage running at high RPM's for extended periods? Thanks everyone, 'preciate the info! __________________ Chris - 1966 C10 Shortbed Fleetside, 1991 GMC Sierra 1500 Extended Cab, 1993 Blazer Sport 4x4 My other rides: 1969 Chevrolet Impala SS427 Convertible 1976 Dodge Tradesman B200 2002 Nissan Maxima 6 speed 2004 Mercedes Benz CL500

04-03-2007, 05:29 AM	#10
Iron-Butt 454 club Join Date: Oct 2002 Location: Oklahoma Posts: 1,348	Re: Damage running at high RPM's for extended periods? I like 6 cyl. they run good and hard. __________________ David 1965 Chevrolet c-10 454 automatic Custom bbw swb. 1965 Chevrolet C-10 swb (Sold) 1963 Chevrolet C-10 6 Cyl automatic with dual exhaust, pb, ps and 17's. R.I.P "I will miss you. 1967 Chevrolet C-10 6 Cyl Custom lwb 1939 Chevrolet Coupe, 350 v8 automatic. 1935 Chevrolet 2 Dr Standard in the works. 2015 Harley Davidson Street Glide. 2023 Chevrolet Stingray Z51 Convertible. I never want to grow up.



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