Hey Guys,

Me and my friend have been arguing for months about what point our cars should shift at. Mine specifically! I noticed another topic about a 502 posted and figured I should ask about my engine. Heres the deal
He has a 79 Malibu with a 350 -
Stock bottom end
High Performance Flat Topped Pistons
Mild Cam
750 CFM Holley Carb
Minimal Head work
Headers and all the rest of the fancy bolt ons

He Shifts at 6500-7500.... I think thats a pretty good range for a small block

He insists though that in a race he could shift upwards of 8500 RPM although he has yet to...!

Now,... If I'm racing, I have a 1968 396 SS motor
The bottom (crank,pistons,rods, bearings) are stock although the motor was completely rebuilt about 35-40,000 miles ago.
750 CFM Edelbrock Carb
Weiand Intake Manifold
Stock Heads
The only thing I have (which is wrong) is my tremendous - radical .650 lift cam

I shift my BBC at 5500 in a race and normally at 4000.
He says that I'am an idiot for shifting a Big Block that high and hes going to laught at me when I blow my motor,...

Is that too High of an RPM range for a BB 396???

I think you will be the one laughing, if he trys to spin that 350 to 8500 rpm.

I'm not completely sure, what the bottom end of my 396 consist of. (I didn't build it)

At the track I try to shift @ 6000 rpm.
On the street it rarely sees more than 5000-5500 rpm.

One of the biggest limiting factors on the rpms for a big block is the weight of the valve train.
The valves and valve stuff tend to be heavy, and is often the rpm is limited by that.

There are guys on this site who spin 427 big blocks to 7500 rpm regularly.

But remember 396 and 427 engines have a shorter stroke than the 454, so they can do that.

Originally posted by Thad:
I think you will be the one laughing, if he trys to spin that 350 to 8500 rpm.

At the track I try to shift @ 6000 rpm.
On the street it rarely sees more than 5000-5500 rpm.

These comments about my car are coming from someone who thinks his car is a rocket. Thats what I said,... although, he's convinced that his motor is "BUILT" and that 8500 is just perfect. I can't wait for the laugh,.. for once it will be on him!

I know are cars are pretty comperable. I'm running 3:73's on Mickey T 29X12.50X15 Sportsmans, but I think that my toque is just a little higher then his (wink wink) which is what is going to get him...... HE HAS YET TO RACE ME IN THE QUARTER MILE MIGHT I ADD! or at all for that matter

I told him put "Put your money where your mouth is" and he just grunts and walks away.
All talk,.... don't ya hate that!

There's no way a stock set of connecting rods are going to hang on to those pistons over 8500rpm, that's a lot of metal to be changing direction.

Secondly, even if he COULD rev to 8500 and keep his engine together, it would be making no power in that rpm range if he really has a "mild" cam. A cam that was making peak power at 8000-8500 rpm would barely run and he'd need something like a 5000 stall converter to even be worth while racing. So basically, the rpm that you can rev your engine to before it blows up, has nothing to do with how high you should rev it to get the best ET.

I run a 454, and with my cam and converter, I redline at 6500, usually shifting around 6200-6300. But that's with a forged crank, polished rods, and hypereutectic pistons. No way i would spin it that high stock. Once again though, my cam is designed to make peak hp around 6200-6300rpm, so going any higher than 6500rpm is a waste of time.

BTW 5500 should be no problem for a 396 due to the lighter pistons as far as BB's go, and the short throw of the crank.

A 396 2-bolt motor with stock rods and a cast "Nodular" crank can rev to 6200 - 6300 without worry. If you have a forged crank and a 4-bolt main and either the good rods or upgraded with ARP rod bolts as a minimum, 7000+ is easy as long as the valvetrain is up to the task.

I'm completely stock on the bottom end, but I am running a 4 bolt main.

What's begining to interest me most is misconceptions we both had in general.

Is this Forum headed for

BIG BLOCK V.S. SMALL BLOCKS

Please be advised, he's probably going to see this forum,... I can't help it but tell him "I TOLD YOU SO!"

Yeah, good luck with 8500.... I will state that I had a totally stock cast 350 lower end, (2-bolt) and it saw 7000 more than once, so they will hold togeter at least that high smile.gif I also had a big cam, but even then, that was too high an rpm to make any power. I figured out that my fastest times were shifting at 5500, even with the big cam....

If he needs to figure out what rpm to shift at, go to the track and try shifting at different rpms, and watch your timeslips. You'd be suprised at where it really wants to be. smile.gif

I think it's dumb when people are so hung up on how high their engine will rev. I'd be more concerned on what rpm made the most power and go from there.

My 454 is a two bolt main, but has all forged internals (Lunati crank, LS-7 rods and Wiseco pistons). I have spun it to 7,400 before on a chassis dyno, but don't turn it that high regularly because there is no point in doing so (small solid roller cam). A friend of mind that races Super Stock Modified Production has regularly spun his big block to 7,400-7,600 and it held together with basically stock forged parts. However, make no mistake this engine is meticulously assembled and balanced. For most of the engines people are running on this board I can't see a need to spin them past mid 6k.

One thing evryone is missing is that unless it is a solid roller you will float the valves BIG time long before you see that much rpm. Talk about scattering valve parts.....

Originally posted by 69bigblock:
One thing evryone is missing is that unless it is a solid roller you will float the valves BIG time long before you see that much rpm. Talk about scattering valve parts..... re-read my post. You don't necessarily have to have a roller cam. The problem is the difference in weight between a hydraulic lifter and a flat tappet lifter. Solid roller is just icing on the cake :D

There is no sense in twisting a motor much past its power peak, your just wasting time you could be accelerating in the next gear. Any radically cammed Big block will go to 7500+ RPM with a good solid flat tappet or solid roller. My 396 would go right to the end of the tach (8000 RPM) and never float a valve. It all depends on the cam profile and the valve springs. Roller cams have more radical ramps and much heavier valve train components - lifters, springs, etc. so more pressure is required. Hydraulic flat tappets and hydraulic rollers have even more valve train mass and are generally weight limited. It might surprise most of you to find out that most NHRA Super/Stock engines run cast iron cranks because they are about 4 pounds lighter and are routinely turned over 8000 RPM.

Passenger car 396s have rod problems (especially the bolts) if you try to spin them much over 6000RPM. Like has been said the valve train is heavy and must be upgraded. The rest of the motor is fine even a cast crank will take much more than you would think.

Danspeed, you are NOT an idiot and your self-imposed 5500 rpm redline is perfect IMHO for a stock 396, even mimicing the redlines on the factory tachs. You are anything but an idiot sir. But please be wary of advice given by them! ;)

Kenny and I must be idiots as we've taken our rats over 7. I used to do it regularly and just reinstalled a 7400 rev chip I got from Bill Burke. I shift at 6800 and the motor sees 7+ between shifts. I bounce off the 7K chip too often. :D

Really easy to do in a well-built, solid cammed short stroke 427. 5500-6000 is a perfectly adequate redline for a stock rat.

Originally posted by Mike Feudo:
Passenger car 396s have rod problems (especially the bolts) if you try to spin them much over 6000RPM. Like has been said the valve train is heavy and must be upgraded. The rest of the motor is fine even a cast crank will take much more than you would think. Why would anybody believe that!?
No offence but the rods 6.135" and stroke 3.76" are the same as a rev happy 427.
My car with it`s factory 425 HP 427 and a cam change regularly went 7500 +
Even popped near 9000 one time on a missed shift, no problems even after many years of hard running.

It's funny, the machinist ( old timer) that redid my 427 was saying how he actually preferred cast cranks. Forged are more prone to cracking. The next day he called me to tell me there were 5 cracks in my fancy #7118 L88 crank!

I didnt have the guts to ask him, so I'll ask here.....

Do you think stalling the engine on 5000 rpm clutch drops would crack the crank?? ( that was back when I had big gumbo DRs and ladder bars on the car.) It HOOKED. Too well, I suspect. It took me a few "stalls" at 4500 rpm to figure out the thing was dead hooking, so I tried one at 5000. Oh, it hooked, then I hear a thump! Either the wheels had come back to the ground or I simply hit the limit on the front suspension. Only did that once.

All that foolishness SOLD me on the Centerforce dual clutch though.

The hydraulic cammed factory engines have soft rods and are nothing like the 375-396 or the 425-427 motors. Treat them differently and no problems will arise. The ZZ 502 is more like the high performance 396 & 427 and will take most anything you care to throw at it with the proper valvetrain items.

Originally posted by 427L88:
Kenny and I must be idiots as we've taken our rats over 7. I used to do it regularly and just reinstalled a 7400 rev chip I got from Bill Burke. I shift at 6800 and the motor sees 7+ between shifts. I bounce off the 7K chip too often. :D
The 427 BBC has considerably less rotating mass than it's big brother, the 454 BBC. In addition to bob weight piston speed is the limiting factor for stock parts. The longer the stroke the faster the piston has to travel to cover the distance of its stroke during the engine's revolution. If piston speed is higher than the limits of the crank, rods and pistons, the strain will result in failure. For example, the apx. piston speed for a 427 at 7,000RPM is 4,375 feet per minute (fpm). The same RPM for a 454 is ~4,666 fpm, or ~7% more. 4,000 fpm seems to be the benchmark that engine builders concerned with endurance (i.e., off shore boat racing) tend to target on the high end for 454 engines.

The following maximum piston speeds are from the book, Performance Tuning in Theory and Practice, by A.G.Bell.

Stock Motor - 3,500 fpm (cast crank, stock rods and cast piston)

Heavy Duty Motor - 4,000 fpm (forged crank, peened rods w/ good bolts, forged piston)

Drag Racing Motor - 5,000 fpm (forged crank, alum rods, lighweight pistons, etc.)

Harold said it correctly. The pass car rods and Hi-Po rods are not the same not even close. Another thing to watch are the early 65-66 Hi-Po rods they are not up to much of anything and should be replaced with later stuff. If you took the 425 HP rods to 7500 rpm even with bolt replacment you are very lucky.

My friend has had his 375hp 396 since it was new in his 66 chevelle, and winds it out to 7600 on a regular basis. The engine is all stock. I don't know if I would do that with my engine, but he has gotten away with it for over 35 years so far. But I must add, he did carry extra rockers, pushrods and springs in the glove box and the tools needed to change them on the side of the road.

Originally posted by Mike Feudo:
Harold said it correctly. The pass car rods and Hi-Po rods are not the same not even close. Another thing to watch are the early 65-66 Hi-Po rods they are not up to much of anything and should be replaced with later stuff. If you took the 425 HP rods to 7500 rpm even with bolt replacment you are very lucky. Not being argumentive here, but can you tell me what the differance is between the pass/truck rods and the hi-perf rods? other than 3/8" vs 7/16??

Here's another question,...

It just so happens that at the beginning of this month my brother bought himself a classic 72 Nova. With his car came a big block 454. He was nice enough to just give me the engine. At this current time I am a automotive student. I am in need of a project for engines and transmissions. I asked the guidelines of the course and they told me I could build whatever I wanted as long as it ran. I decided as a special treat for my car I would save up and buy all the high performance parts to build a 454 for my Chevelle. I happen to really like my 396/375. The motor is just incredible and I have to say,... it doesn't compare to any of the cars I've driven. It just seems overly powerful for a 396. I like the motor but I am on the quest for even more horsepower,... just like many of you who surf the performance pages of Chevelle tech. The block has a 4 bolt main and I'm looking at a total rebuild. Whats beginning to confuse me is all this talk about 396/427. Is a 454 a better motor. And does it even matter what the cubes are if your rebuilding the motor ground up. All this talk about longer stroke is confusing me???
Please clear up this up for me,
Dan

BigRed-L72, The high performance forged rod has a raised bump on the side of the rod's beam that the standard rod lacks. Aftermarket rods, like the scat "H" beams are about 50 grams lighter however, are relatively inexpensive and have upgraded rod bolts although i have never seen the chevy bolts fail while i have seen aftermarket bolts break.... Danspeed1, The 454 has a 4" stroke while the 396s and 427s have a 3.76 stroke. All the late blocks are pretty much the same and i'm told that the low performance blocks are actually stronger in the main web area because they only have two bolt holes instead of four. Any big block can sustain huge amounts of power because the block is so strong if it's not overbored too far.

I would also like to know the structural difference(s) between the 3/8 and 7/16 rods, excluding the popular "truck" rods.

Ken, obviously I was being facetious, er sarcastic when I referred to us both as, well, whatever....

Dan,

In a very general sense, you can make an earlier torque peak with a longer stroke motor. While I can't compare my 427 with say, Ken's 454 ( his having greatly superior heads and a roller canshaft), but if we "held them equal", in order to match the output, in HP, of the 454, it would be likely that the 427 would have to have a slightly higher peak torque rpm, that is, you'd have to spin it a bit higher to make the same power. And, as Ken superbly points out, piston speed is a prime measurement of that rpm, and speeds in excess of 4K, as Ken reports, cause MUCH greater loads in things internally.I've always considered 7K to be where it got a bit hairy, but clearly, those pistons speeds would be much greater in a longer stroke motor, so the loads would be increasing dramatically at far lower rpms.

Simply put, you have to spin a smaller motor higher ( and, of course, gear your car accordingly) to equal the "power" of a larger displacement mill. That requires very good parts( BEST RODS YOU CAN GET OR GM 7/16" AT MIN) and engine assembly and still carries a risk that shifting/redlining at a much lower might not.

I LOVE the 427. But if I was a weekend bracket racer, I believe I would opt for more stroke and lower operating rpms for the pure parts longevity issue. Given that, it's easier to get a 480-510" car easily into the 11's than a 427-468 car. Again, if racing, I'd go to at least 4.25" stroke and spend my time getting the chassis to hold the torque.

For pure fun, spinnin' up a rat-on-a-stick is WHY I built my car in the first place. Not for show, not for ET, just for driving fun. For that purpose, a well built 427 ( or even 454) can't be beat.

Anyway, a long-winded opinion on a slow Friday pm.....

Originally posted by 427L88:
... and spend my time getting the chassis to hold the torque... As I have been, seems like every waking minute, lately... :rolleyes:
Building big motors is easy. Getting them to hook is the obvious challenge.

I routinely spin my 396 2 jet to 11,500 at the drags.....boy are you guys wimps!

The early rods have a notch missing on the bearing side - you can actually see the bolt with the cap bolted in place. Later passenger car rods are OK in a driver, but I wouldn't push them as far as the truck "thumb" rods. The webbing on the big end is round and your thumb will fit perfectly in it. They were made stronger to handle the heavy-a$$ 4-ring truck pistons. They'll handle quite a bit, particularly with aftermarket bolts. The late model 454 HO 7/16 bolt rods are supposedly stronger than anything other than the L-88, but I can't see it. The beam is noticeably thinner, but maybe they put the material in places where it matters more. HTH.

Hey Guys,

See,... Where my confusion comes into play is that I always thought that all big blocks were created equal; the only difference was in displacement. As far as my knowledge goes (limited), you can stroke a big block and change the rod length both longer and shorter in some cases. Although I never really was told what you gain each way. Let’s say I have an original 454 Block with a 4 bolt main. Is that block the same as a 427 block or a 396 block? I know the displacement is different but is the actual length of the cylinders different from block to block also,... or are 454’s just made up of different components, be it, a different crank and different rods. Is it even possible to put a 427 crank and rods in with 454 pistons. The idea that I'm getting is that all these motors/blocks are totally different and run totally different. It's just not making any sense to me because technically, in my mind at least,... I'm thinking you can bore a 427 out to a 454 so whats the difference?
Thanks for taking the time to impart all this vast knowledge and experience upon me. I'm really interested in learning about this so I can someday pass the information on.
Dan

Dan,

Some early 396's can be bored to .155" over and will take untouched a stock 454 rotating assembly..

Heck, my .060" overbore '75 P/U 454 block swallowed my 4.25" stroked crank untouched to make my 496..

AND I bet It would take a 4.375" crank fairly easily...

pdq67

PS., it is said that if you can't push an old-fashioned wooden pencil between the cylinders through a freeze-plug hole, it is probably good to bore that big.. BUT personally I would sonic check it before going that big..

The difference between a good 427 and a good 454 are very minimal at best. Its like the debate between a good 327 vs a good 350. Choose your challenge and enjoy it!If somebody tells me a 350 isnt as good as a 327 ,I'll build the 350 smile.gif

Dan, 427 and 454 bloacks are nearly identical except for sonme casting differences along the years. Both have 4.25" bores. THe difference is the crank stroke, 4 for a 454, 3.76 for a 427. 396 blocks generally have smaller bore and cannot be opned up to 4.25" bore.

Rods are the same, pistons are different to accomodate the differnce in crank stroke between the 454 and 427.

Hi Danspeed1, The 396, 427 and 454 blocks share external dimensions. They are exactly the same, however the 396 and 427 have the a 3.76" stroke while the 454 has a 4" one. The rod length is the same 6.136" in length with the pin being located about .120 higher in the 454 piston which makes for a slight weight reduction. The high performance rod has two different models, one has 3/8 rod bolts and weighes appx. 817 grams while the later model rod has 7/16 bolts and weighes about 870 grams which more than offsets the 454s lighter pistons. When geared properly the 454 seems to pull quite a bit harder, especially in high gear. I've heard from very knowledgeable people that the small rod bolt model is stronger because it has more material in the bolt area. My 454 would flatten out at 7200 RPM while the short stroke motors would go over 7700 RPM with power with the same ZL-1 cam. The 454 pulled a lot harder than my 396 with much less gear. While it true that most high performance 396s can be bored to 4.25" i don't recommend it as the 427 blocks can go still bigger and can still be bought pretty cheaply. Any great big bore can be had by buying an aftermarket block and bores of up to 4.625 can be used. The 427s and the 454s have the same 4.25 inch bore so swapping out the rotating assemblies will get either displacement. The 454s are externally ballanced and require a different harmonic ballancer and flywheel or a rebalancing of the assembly.

Originally posted by Harold Sutton:
They are exactly the same, however the 396 and 427 have the a 3.76" stroke while the 454 has a 4" one. The rod length is the same 6.136" in length

When geared properly the 454 seems to pull quite a bit harder, especially in high gear.

My 454 would flatten out at 7200 RPM while the short stroke motors would go over 7700 RPM with power with the same ZL-1 cam.

swapping out the rotating assemblies will get either displacement. So if what your saying is correct,... It would be possible for me to take the 454 Block and change the crank to 427 with a 3.76" stroke, and considering all the rest of the parts are the same, (rods) the engine would act like a 427 but have the displacement and power of a 454? Cool!

Dan

P.S. is there really an intense difference or would someone like myself not notice anything?

Danspeed 1...you would have a 427 nothing more, nothing less.

Bringing this back up...anyone come up with a scientific argument on why the dimple rods are stronger than passenger car rods? Dimensions or metallurgy? Seriously, I am just curious.

8500 rpm is posible to run on a small block

BUT ! Bring lot's of Cash to the table

a hi reving small block is like trowing money away you wont get there faster

it will be cheaper to build a strong BBC and at the end there is no subtitution for Cube..

Slightly off topic, but isn't this how the big block got its nickname (as the rat)? The way I heard it, if you over-revved the engine it would drop a valve and "rat" on you. A long time ago, in a galaxy far, far away, I knew a guy that could make it look like the problem was not from over-revving, that way the repairs (not the cost of the modification) were covered by the warranty.