BB vs SB redline
Racer
Joined: Feb 2003
Posts: 330
Likes: 0
From: Enon OH
Re: BB vs SB redline (Grinchia)
Two possibilities:
A) GM was being conservative with the performance of the small block, possibly to encourage sales of the big block.
B) The small block is made of inferior components when compared to the big block.
A) GM was being conservative with the performance of the small block, possibly to encourage sales of the big block.
B) The small block is made of inferior components when compared to the big block.
Le Mans Master
Joined: May 2003
Posts: 5,642
Likes: 1
Re: BB vs SB redline (TerryMathews)
the government got bored after they finished installing the tracking devices they got from alien beings behind everyones ears and sabotaged gm's tachometers and manuals. :shocked:
Le Mans Master
Joined: Dec 2003
Posts: 5,727
Likes: 38
From: Fremont CA
Re: BB vs SB redline (munday)
My LT-1 has a 6500 redline. The only Big Blocks I know of that are this high are the LS6 and L88's. L82's had higher redlines than the LS5's in 73-4 also (6000 RPM.)
Drifting
Joined: May 2003
Posts: 1,634
Likes: 2
From: Melbourne, Victoria, Australia, the World
Re: BB vs SB redline (Solid LT1)
My 68 L89 (also L71's) has a 6500 redline as well.
Another thread (is it a legit 69 BB?) lists the redlines for all the optional motors in 69
5300 = 350/300
6000 = 350/350
5600 = 427/390/400
6500 = 427/430/435
:cheers:
Another thread (is it a legit 69 BB?) lists the redlines for all the optional motors in 69
5300 = 350/300
6000 = 350/350
5600 = 427/390/400
6500 = 427/430/435
:cheers:
Drifting
Joined: May 2003
Posts: 1,634
Likes: 2
From: Melbourne, Victoria, Australia, the World
Re: BB vs SB redline (Grinchia)
Can someone explain to me how a big block, with greater rotating mass and further piston travel, has a higher redline than a small block? It's counterintuitive!
-Roy
-Roy
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Re: BB vs SB redline (Grinchia)
GM redlines for my 454 LS6 is 7000 continuous and 7500 for short drag bursts.
Just because the motor can rev doesn't mean it is making horsepower. If the heads can not support the rpm you are just wasting your time.
With the proper heads and cam the motor even at redline is pulling like crazy and you hate to shift.
With undersize heads and cam you are just waiting for the revs to build so you CAN shift.
If you have time to sit and watch the tac climb you need more motor :lol: :lol:
Just because the motor can rev doesn't mean it is making horsepower. If the heads can not support the rpm you are just wasting your time.
With the proper heads and cam the motor even at redline is pulling like crazy and you hate to shift.
With undersize heads and cam you are just waiting for the revs to build so you CAN shift.
If you have time to sit and watch the tac climb you need more motor :lol: :lol:
Race Director
Joined: Mar 2001
Posts: 11,322
Likes: 1
From: Living in the Hartland
Re: BB vs SB redline (norvalwilhelm)
A well put together all forged bb will out rev a poorly put together all cast sb before coming apart, it really depends on the parts and how well they are put together, this is assuming both can build power to the same rpm level.
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Melting Slicks
Joined: Jun 2002
Posts: 2,844
Likes: 99
From: Orrtanna Pa.
Re: BB vs SB redline (norvalwilhelm)
I have to agree here with Norval.When I was recurving my HEI I was doing a lot of back road stomping,and and from a low speed roll punching the throttle,I couldn't keep my eye on the tach long enough to see what the red line was.Swung to at least 6500 and I'd grab the next gear.With the right heads and cam,I don't think there's such a thing as a redline on a street engine.
Thread Starter
Pro
Joined: Oct 2003
Posts: 641
Likes: 2
From: Storm lake Iowa
Re: BB vs SB redline (The Money Pit)
With the right heads and cam,I don't think there's such a thing as a redline on a street engine.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
Re: BB vs SB redline (Grinchia)
As the engine gets larger the max. redine is reduced. Look at the rpm of small gas engines used in model planes about 20,000, motorcycle 4 cyl. about 10,000, cars from about 4500-7000.
The difference in RPO engines has more to do w/ parts selection like cams solid or hyd.
The difference in RPO engines has more to do w/ parts selection like cams solid or hyd.
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Re: BB vs SB redline (Ganey)
Piston speed can not go beyond a certain limit without gauling??. A big bore short stroke engine outrev's a long stroke because of piston speed.
That said , forget about the motor comming apart and just think of seat of the pants feel. One more really pulls strong starting at 5000 and even at 7500 you hate to shift but common sense tells you , you better or it will come apart.
Another stock motor, no cam, no heads pulls all the way from idle but by 5000 you are just watching the tac and waiting to shift. This motor even if it didn't come apart would slow down if you tried to rev to 7500.
My big block will go from idle to rev limiter now set at 7000 faster then the tac can move, you will not see it , I set the shift light at 6200 and as fast as it blinks on you hear the rev limiter hitting.
Before the rev limiter I often saw the tac needle pointing straight down at 6 oclock and once saw it go to about 7 or starting up the other side.
With heads and cam rev limit is set by how good the internal parts are and piston wall speed.
That said , forget about the motor comming apart and just think of seat of the pants feel. One more really pulls strong starting at 5000 and even at 7500 you hate to shift but common sense tells you , you better or it will come apart.
Another stock motor, no cam, no heads pulls all the way from idle but by 5000 you are just watching the tac and waiting to shift. This motor even if it didn't come apart would slow down if you tried to rev to 7500.
My big block will go from idle to rev limiter now set at 7000 faster then the tac can move, you will not see it , I set the shift light at 6200 and as fast as it blinks on you hear the rev limiter hitting.
Before the rev limiter I often saw the tac needle pointing straight down at 6 oclock and once saw it go to about 7 or starting up the other side.
With heads and cam rev limit is set by how good the internal parts are and piston wall speed.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: BB vs SB redline (norvalwilhelm)
My buddies 555 ci KB blown alki AA nostalgia drag car does 9200 rpm on the computer readout after every run. I don't really understand how motors that large with stroke can even hold together. but the same is true for all the Pro Classes in NHRA
[Modified by gkull, 1:05 PM 4/21/2004]
[Modified by gkull, 1:05 PM 4/21/2004]
Safety Car
Joined: Jan 2000
Posts: 4,143
Likes: 0
Re: BB vs SB redline (norvalwilhelm)
Piston speed can not go beyond a certain limit without gauling??. A big bore short stroke engine outrev's a long stroke because of piston speed.
Two of the Hottest high-revving chevy motors from the factory were the 302's and the 409's.....
Now look at their proportions :
302 - 4" bore with a 3" stroke
409 - 4.312" bore with a 3.50" stroke
Wow - If you can keep the head gaskets from blowing.....no wonder their capable of 10-grand in just a few seconds ! :shocked:
Yeah, there's the cam, valve springs, heads, & mess load of other things to consider.........but :chevy made both High-Revving Small blocks & Big blocks ! :cheers:
Although I think BIG is badder. :lol: :cheers:
Safety Car
Joined: Jan 2000
Posts: 4,143
Likes: 0
Re: BB vs SB redline (Grinchia)
...It's counterintuitive! -Roy
Okay - to overcome the Mass of the engine and the physics of "not" wanting to rev up quickly........hot rodding techniques can compensate through Large valves, higher spring pressure, and radical cam grinds.
It's a 'force' and doesn't come as natural forcing a larger stroke engine to perform up to 7,000+ grand which is why they make 125# springs & 0.700 lift cams and 2.300 valves !!! <these are BBC specs> :D
Drifting
Joined: Feb 2002
Posts: 1,906
Likes: 0
From: Berlin
Re: BB vs SB redline (Grinchia)
All OEM engines (AFAIK) are limited by top end components. The valves will float, the ignition will stop working right, or the engine simply won't breathe enough to go faster. The internal components have a higher tolerance than stock redline. This is done to keep away from lot of expensive repairs when a part isn't manufactured quite right or somebody accidentally shifts incorrectly.
Le Mans Master
Joined: Oct 2002
Posts: 5,714
Likes: 6
From: Silver City NM
St. Jude Donor '05-'07
Re: BB vs SB redline (Grinchia)
Hmmmmm...this thread is puzzling the heck out of me. Are you guys ONLY talking about STOCK motors, or are you including the smallblocks that are taken to over 9000 RPM every Sunday at NASCAR and NHRA races???
The STOCK Z-28 302 was taken to 8000 (and above) with no problemo. Of course, it was loaded up with HD parts. If you are going by the redline on the tach or in the owner's manual, then factor in that GM didn't want to keep replacing motors when guys took them to stratospheric levels. The biggest advantage of the smallblock is the tremendous RPM it could produce. That is, until people "discovered" the boring/stroking idea and the "econo-big block". :lol: :lol:
Dep
[Modified by DJ Dep, 4:25 AM 4/22/2004]
The STOCK Z-28 302 was taken to 8000 (and above) with no problemo. Of course, it was loaded up with HD parts. If you are going by the redline on the tach or in the owner's manual, then factor in that GM didn't want to keep replacing motors when guys took them to stratospheric levels. The biggest advantage of the smallblock is the tremendous RPM it could produce. That is, until people "discovered" the boring/stroking idea and the "econo-big block". :lol: :lol:
Dep
[Modified by DJ Dep, 4:25 AM 4/22/2004]
