xxwarrior36xx

I am going to buiold a 383 and am wondering wht you have in it and what your red lines are. I am hearing they don't rev, and was wondering some examples.
Thanks alot guys

FstBrd6point3

I was told mine would be somewhere just shy of the 7K range, but I dunno if I woudl ever take such an expensive motor that high lol. My brother's friend said hima nd his dad never even spun the race car past 6500 when they were still racing. I dunno man, I will find out for sure ina few days.

Changa2

The 'Rule-of-Thumb' is 4,000 ft/min'. So for a 3.750" stroke it comes out to 6,400 RPM.

I built an expensive 383 with Ductile Crank an Rods (4340) and forged Pistons. I have only a couple tho miles on it and I'm kind of chicken. Just ordered a 5,500 chip for it.

Your engine may well turn 7,000, but the bigger question is: 'Will it perform at that RPM'. I don't know your intended use but for a Streeter that sounds like a bit much for a 383.

There are a lot of factors to consider, as you probably know. Let's see what some of the more experienced guys have to say.

GreenProStreet

That is a brilliant rule! Never heard of it though. Thx!

Where do you want it to spin to and how high it can spin are two different entities in them selves. Planning out you motor, and picking a powerband will determine where you will make your torque or horse power. But for the street, and with a big stroker like a 383, you probably wont want to see the high side of 6500.

A motor can spin as high as it wants, but it is in the balancing (and blueprinting) will determine if it will blow up on you. Taking away metal, or adding malory will balance the throws of the crankshaft to the weight of the piston and rod.

The srewtiny of this process will determine your redline.

-

BTW- If you throw together pistons, rods and a crank together without balacing, you are throwing away about 3/4s to 7/8 of the life or your bearings and eventually your whole motor.

Patrick007

Wow.. according to that Rule of Thumb of 4000 ft/min... my Briggs go-kart engine should redline at riiight around 13,000 RPM. hehe. If only I had a titanium top/bottom end. Oh well

Patrick DeGrosse Jr.

FstBrd6point3

I prolly will never spin my motor past 6,000 RPMs, but I was told that it could see 7, the entire rotating assembly of my motor is balanced, which is good, but like you said, the power band of a 383 is not going to go to 7,000, either is the air flow capability of my TPI set-up. I think when I install all of the MSD ignition stuff in my car, I will probably set my spark cut to around 6200, I really see no need for spinning the motor faster than that, nor do I want to put it in any sort of compromising position.

AlkyIROC

Typical engines are usually in the 6300-6700 range. If you build an engine that makes power above that rpm then some lightweight internal parts are required. Lighter pistons and con rods are the number one parts that need to be light. A 30 pound piston produces more stresses than a 25 pound piston. The higher you rev the engine, the higher the stresses are put on those parts.

That's why good rod bolts are always needed. All that weight is moving up the cylinder then suddenly stops and is pulled back down. If a rod bolt breaks then the piston will try to go out the top of the engine. At 7000 rpm this will happen in a fraction of a second.

The "rule of thumb" is good but having lighter and stronger internal parts can help out a bad situation.

The briggs and Stratton engine "could" go that just just because of how light the piston and con rod is. Don't expect the stock parts to handle it though.

Anytime you use aftermarket parts such as crankshafts, con rods and pistons, the engine should be rebalanced anyway.

88irocz28

Talking about how many revs a motor could theoretically pull, I remember reading about a model airplane engine made by by *** that revs up to, believe it or not, 50,000 rpm . I don't know whether the engine is balanced or not but it is a single cylinder two-stroke design that displaces about 0.025 cubic inches. IIRC, it was made for a glider that climbs under it own power. Once the plane gets up high enough, the engine can be killed by remote from the ground, allowing the aircraft to ride the thermals. I guess *** wanted the engine to weigh virtually nothing and went the for the tiny, high revving design. Even the 0.060 engines I had on my control line planes revved like mad. too bad *** didn't give those engines a real throttle. the only way to control rpms was to rich or lean out the mixture. Their radio controlled aircraft had real throttles though. Far from being 383s but just a point I thought I'd contribute .

jcb999

of WWII. It reasoned that with at that time state of the art metalary, that was all a steel rod internal combustion engine could go and remain reliable.

I dont think its quite as valid at this time as it was in history. But, its still a good starting point..

For point of reference, a 3.3 inch (about winston cup stroke) stroke motor at 8000rpm is 4400fpm and they turn them closer to 9000 most the time.

The underlying issue is do you have the airflow to feed the motor at 6000+. Most times the answer is no.

With the long stroke, torque falls off very fast as rpm increase.

But, when you cut to the chase, you want to turn it only as fast as you need to so it will be at the rpm of peak torque in the next gear. That will be a different rpm for each shift. Get a rev limiter and set it 200 rpm higher than the max 1st rpm.

JAY87GTA

I thought the redline was determined by the valvetrain as much as by the bottom end. For example, you can run it to 7 grand, but if the valves start floating at 6500, what's the point? If you're still running the stock spider retainer for the lifters I wouldn't trust it over 6, I've heard bad stories about them bending and allowing the lifter to rotate, whiping out the cam and worse.

RB83L69

I've heard that rule of thumb too. It makes pretty good sense to me.

jcb, don't forget the WC guys only want to go 500 miles (or 500 laps), and they often build what those of us who build circle-track motors call "501 mile motors". Those guys figure out how many actual operations the engine goes through during a typical race, and build the motor to just barely hang together that long. I can recall a couple of races that were red-flagged and then finished the next day; that caused as many as 8 or 10 extra parade laps; and several engines expired during the last 5 laps.

In any case, I would not recommend a street engine build with any intent of runnign past 6500 RPM. Too many other things beside the engine itself can suffer greatly as a result of that abuse, including transmissions, human body parts, alternators, etc.

For a 383 with typical high-quality street parts (TRW type forged pistons, ARP hardware, etc.) 6500 is plenty. You'll tear up so much stuff at that RPM that you won't feel tempted to go farther.

I don't mess around any more with the smaller small blocks like a 383 if I want real performance, but I think my recommendation is still valid.

jcb999

to that level of continous stress. I bet 500miles on a WC smallblock is tougher than 50K miles behind us streetracers/parttime draggers.

xxwarrior36xx

Thanks alot guys! Alot of very helpful info. I guess whoever told me that was way off! "Light weight stuff" what is that? Like forged cranks and roller rockers or what?

Again thank you guys. I like the rule of thumb and will use it. Thank you.

JAY87GTA

When they refer to light stuff, they're generaly talking lighter rods/pistons, lightened crank, rockers with lighter tips, titanium valve spring keepers, stuff like that. It helps the durability of the bearings and stuff, plus helps the motor rev a little quicker, but generally costs more than can be justified on the average street motor.

Tom84L69

warrior, i think whoever told you that 383s don't like to rev was saying that in comparison to a 302 or 327 or even a 350. The longer the stroke, the less willing an engine is to rev, all parts being equal.

Lighter rods and and pistons definately help engines to rev safely, just get heads that will support the airflow.

I'd still like to beat your future 383 with my 305!!

xxwarrior36xx

Well tomL69 I'd like to see you try it. You can beat it now but you just wait..my day is coming, when I will win.
AJ
Oh yeah who's is faster now?...ohh yeah mine runs.
Again thank you guys for all your help! I greatly appreciate it.

383 Smoka

My engine produces power to about 6500 RPM...

Jeikbristar

Mine was originally built for my buddy's dad's dirt track car, the memory on the tach and his dad told me that it has seen 8000 rpm with no issues. Of course though the only original part of the motor is the block and it had work done to it, so really it just all depends on how it's built

AlkyIROC

Nothing like reviving a 21 year old thread.

I shift my current 588 BBC engine at 7400 and the playback tach shows that the rpms go to 7600 before making the shift. The camshaft and all the internal components can easily go to 8000 rpm but I don't push it.

skinny z

Old thread but still an interesting subject.
They'll rev as far as you can put money into them. You just have to get better parts and better machining practices the farther you want to go.
The question might better be asked, what does it take to go x RPM?

Alky, didn't you start with a 383 when there was a Race City?

Komet

So what does it take to spin 7k? Forged bottom end, solid roller cam, full roller lifters?

TTOP350

iTrader: (8)

Reliably im assuming, i did it with stock cast bottom end, better cam, and valvesprings. Doesn't mean it made much power up there but it was fun. It was also a play engine so it didn't really matter

skinny z

7k in what capacity? Drag racing, with it's limited time at peak RPM takes less to keep together than say an open road event engine that'll be at sustained WOT or nearly so for minutes at a time. Or a 7k circle track engine is another matter still.

The basic recipe for the bottom end would be a forged crank, rods and pistons but there are plenty who have the cast parts and drag race at that level. I was regularly shifting my 70's vintage (NOS 70's that is) cast rotating assembly to 6500 and it held together for a long time. Overheating on a holiday road trip is what killed it.
But that's a risk I would no longer be willing to take (and I'm not) so I expect my factory forged crank and aftermarket rods and pistons to be able to handle that. While others might, I don't think I'd road race cast parts. At least not for very long.

Stock block is perfectly fine. Get a good oil pump. Go for internally balanced and use a quality damper.

The valvetrain is where 7k needs attention. My stock Vortecs floated a few valves on a 6500+ missed shift. Probably saw 7000 there and that bent a couple of valves (exhaust IIRC). A guaranteed high revving package, within the constraints of the cam profile, would be the lightweight beehive or conical springs and the equally light retainers. Tool steel is my choice. I've been advised that a 3/8" pushrod would aid in stability however the 5/16ths have been working so far.
I'm going to say a full roller rockers too. Yes, there are stock racing classes than mandate the OEM stamping but unless I'm in that class, I'll step up. I also prefer steel.
With the above including the forged bottom end and detailed valvetrain, I'd be comfortable in any racing platform.

Cost? The shortblock fully machined with new parts should be less than $5000. Blue Print's 383 forged shortblock is $4900.

The heads, cam and lifters are about the same whatever the application. You can easily go 7000 with a flat tappet cam. Solids are better but a hydraulic would work. It's actually easier to rev a flat tappet as it's lighter than the roller versions. That said, rollers go to 7k everyday and it's done with the aforementioned springs and retainers. There are other springs that'll do the job but the beehives have more than shown their capability.
Seeing as the cam, lifters, springs and hardware are universal in any build, is that cost included to go 7k? FWIW, I just laid out $1500 USD for those parts (not including the retainers as I had them).
Rockers are $500+/-.

Add the heads, induction and ignition of your choice.

Say goodbye to $10,000 for a 7k ready turnkey engine. I didn't see a longblock offering from Blue Print that I'd be safe with sustained 7k.
YMMV.

Most definitely. I'd think the above assembly would be all that.
One tipping point is the crankshaft. Scat's cast steel crank is said to be plenty reliable and happy to 7000. I'd prefer a forged steel although the cost offset is 500 bucks. $300 vs about $800. (Scat for Scat).
RPM kills a valvetrain in a hurry so attention there, I think, is vital. Shaft rockers would be nice but maybe marginally overkill for 7k. 8000 for sure. But any Super Stocker may tell you otherwise.

Fast355

iTrader: (2)

I have buzzed mine ~6,500 rpm a few times, but it now has the fuel kill at 6,000 rpm and shifts are commanded at 5,500 1-2 and 5,750 on the 2-3 and spins to ~5,900 on the upshifts. With the 218/228 @ 0.050 cam in mine, power flattens out at ~5,500 rpm although the curve is very flat past 6,200. Just do not really gain much spinning it higher than 5,900 so I figure why stress it. I am over 90 mph by the time it makes the 2-3 shift anyway as it is at 5,900.

AlkyIROC

Yes I did. It was an old school 383 with stock 400 crank, stock rods and rod bolts, stock cast 350 pistons. It had a solid lift camshaft that was around 0.550 lift. I spun the engine to 7000 rpm and after 200 1/4 mile passes, the rod bolts finally let go and completely totaled the engine. Pulled the intake and the heads off and threw the rest into the scrap metal dumpster at work. The heads have 5 visibly bent valves.

QwkTrip

iTrader: (22)

Those rule of thumb for max piston speed is based on the old SBC engine of yesteryear. It's easy to buy better parts these days and spin it faster. But most people don't have the top end to make power at high rpm anyway so usually a moot point.

skinny z

I did similar but with 400 CID.
Never took it much past 6000 but on one occasion with a friend and on a long downhill, IIRC (it was 45 years ago) I think sustained RPMs were north of 6k for a minute or more. I never determined what caused the resulting misfire after that run but not long after it dropped a valve and that was that. I suspect I floated a valve at that RPM, bent it, and it eventually snapped. Total destruction.

skinny z

This is true. I'd go for top end forgings if I were to build this.
As for a top end, I was surprised to find my 255 port CFM heads would support 383 cubes up to nearly 7000. That's at 100% VE. I doubt though that I'd see that kind of CFM once the intake is in play.
I'd say it's a safe bet that something like AFR 195's would be up to the task.
This is simulation/calculator data but I think there are probably more than a few examples on the WWW.

dale383

Hey all I know it’s an old thread but I’m about to start my dale truck build. I’m gonna be doing a 383 I’ve found a cam to allow me to go above 7200 with the power band. I’ve got a built 383 lined up was going to throw a scat lightened crank and forged rods at it. Along with afr 195 heads, the question I have is what I take do I need to run and do yall have any specific cams that would allow me in that range. It’ll be paired up by a Muncie m21 trans. Any help is appreciated and yes ik it’s not logical but hey its gonna sound like a racecar

ShiftyCapone

iTrader: (7)

Depends on many factors but valvetrain stability is where you should focus on. Any of the cam makers can give you their opinion if you call them up.