WOT RPM, custom engines
 

A buddy and I always talk about rpm. I'd love to hear who turns what RPM at wot. Not talking factory mercruiser stuff, but custom built hyd roller cammed engines in pleasure boats. Engines like 540's, big roots blown stuff, whipple engines, etc.

He is skeptical about anything over about 5300RPM, for longevity and parts breakage. I assume with today's good hyd roller lifters, endurance springs, and overall good parts available, 6000 shouldnt be too crazy to turn. Granted the engine is cammed to run there with good results. I dont like the idea of loading down a big blown healthy cammed engine with a big prop so that its only turning say 5100 rpm at wot and max boost. Seems to me like a invitation for heat and detonation????

So, what do you turn yours too and what setup??????

My last engine I was spinning it to 6000 rpms. Never an issue!

5800-5900 no problems

5700

5600-5900rpm depending on outside temps
Custom 575sci's - chilled - hyd roller -ECM re-map

580 cu 4.0l whipple 5800-6000rpm 8lbs boost hydr lifters..pushing 23k lbs with arnesons

cool air 6-6100,heat of august 5800. Not realy custom,500efi with stock crank.


116octHustler dyno pull 911hp 11.5 lbs,Whipple
http://px5.sfstatic.com/thumbs/0000/20/57/70275.jpg



[YOUTUBE]http://www.youtube.com/watch?v=k5m4Cbnt5NQ&list=UU9NnkS05oUQI0qnjFD8nflg& index=5&feature=plcp[/YOUTUBE]


[youtube]http://www.youtube.com/watch?v=yYRR0tN5TxA&list=UU9NnkS05oUQI0qnjFD8nflg& index=34&feature=plcp[/youtube]



















.

It depends on the engine, parts and application but anywhere from 5400-6600 rpm. All hydraulic rollers.
Eddie

Eddie has one of the best answers here as the actual parts and engine build will determine whats a good safe rpm max for any given engine build. Things like valve and valvetrain weights, stability, lifter type, spring pressures, boost levels, etc. will determine in each actual final build state what is the best max long term rpm level. A general across the board rpm range for all engine types is a mistake and would leave some engines just fine and others in trouble! Almost no higher horsepower marine engine will last as long at 6500 rpms as it will at 5500rpms and the actual hours at these rpms will help determine real average engine life. Normally most well built normally aspirated marine engines at 5500-6000 rpm limits will outlive supercharged or turbocharged marine engines running at the same rpm limits, there is no changing that difference. Also remember that generally higher rpm performance engines cost more to build than medium rpm range marine performance engines A new twist to the old addage: "Extra RPM's cost money, How fast to you want to Spin it?!" If you're building a short blast race engine then you will approach rpm limits differently than you will if you are using a recreational endurance marine performance engine, THEY ARE NOT THE SAME PERIOD!
JMO

Best Regards,
Ray @ Raylar

I was generalizing a bit in my original post, assuming we are talking about custom engines running quality forged cranks, forged aftermarket rods, quality roller lifters and springs, performance cylinder heads, and camshafts that are within reason for a marine high performance build. Of course there would be no point in spinning a stock 330 to 6000 rpm unless breaking it was the goal.

My original concern, is lets say you build a custom blower engine, 4" stroke crank, and a cam/head package that makes peak hp at say 6000rpm with a blower. Then, you install that engine in the boat, and prop for 5000rpm, near where the engine is making peak torque.

Are you better off spinning the engine at its peak hp rpm or at its peak tq rpm for longevity?? And is it true that overpropping so that spinning it at peak tq is hard on the drives and transmissions?

I was always told overpropping would do more damage than good.

Very good thread , i'm learning every day hangin around here....:nicethread:....:readinghelp:

I spin my 598ci N/A with a hydraulic setup to 6000rpm all the time, and would have no issues with going to 6200rpm if it was still making power that high.

It probably wouldnt live long at all if I threw a 36" prop on it and lugged it down to 5000-5200rpm. The heat in the chambers would lead to detonation, eventually getting everything so hot that the end result would be preignition, and I would wind up with an expensive paperweight.

So help me out here......and this may be more prop question than engine. My current engine has rev limiter set @ 5600 rpms....was stil make power all the way up till then but torque started to drop at 5300ish. My current prop i can only spin to 4900.....maybe 5000 if its over trimmed. This prop is in stock form. It doesnt make sense to me to be able to drop prop pitch and still be faster with a lower pitch prop but at only 4900 i am leaving 80+ hp on the table. Would i benefit from dropping pitch and running higher rpm?

In my opinion, yes, I'd go down in pitch to get the wot rpm where the engine makes the extra 80hp. While you may not gain a bunch of speed, i would think your engine/drive would be happier.

Im guessing that if I posted this poll 15 years ago, we probably wouldnt see as many people turning 5600+rpm with pleasure boat engines. Seems that todays valvetrain technology opens things up a bit for us, campared to the old flat tappet hyd cams and light spring pressures.

i spin my 540,s in my cat to 6200 rpm,but normal crusing at 65 mph is around 3300 rpm,the nice thing is the way it accelerates from 60 mph on up,if i prop it to run 5200 rpm max,it is not getting to its max powerband and acceleration is poor at best,plus detonation risk increases from lugging .just my opinion,but it works for me!

So here is my dilema. Having engines built as we speak. Builder says ok to run at 5600 rpm and my mechaninc wants me at 5200 WOT. Guess i need to ask them more questions.

Give us some details on the builds pete. Many mechanics are just that, mechanics. I'd listen to the builder on what's best for the engines.

Wayne, you are leaving almost 90 hp on the table. Look at your dyno sheet. Prop down to get that power out.

what details are needed? heads, valves, lifters, pistons? Im unsure what you need to know

Dyno sheet, valve springs, cam specs, lifter style, cylinder head model, etc

Limiters have 6000 chips in them and I'm up on them alot spinning 36's. This year we'll be lowering the gears in the lowers to 1:36 instead if the 1:50 and reprop again! Still looking for more!

Me too..... Every time I go out at least once. :D Dart blocks, Callies cranks, Oliver rods, JE pistons with Isky ToolRoom springs, morel hyd roller lifters and AFR heads. Crane gold rockers and stud girdles on top.

95% of my time running is between 3500 to 4000RPMs.



5 seasons so far without having a valve cover off (knocking on my wooden desk as I type!!)
:D

on the dyno today. Not sure if he will give me cam specs since its custom.

if you paid for it, he should give you specs, maybe not every detail, but most!

I spin my blown efi 509 to 6000 regularly and for one particular poker run every year, I step down in prop for better acceleration as there is a very long, winding river on the run and spin it to 6200 to 6300 on the straights. Sure sounds nice up there.

The answer...it depends on the length of the stroke. The shorter the stroke, the more tolerant the BBC engine will be to increased RPM. Most of the Super Cat engines were 3.75 or 3.80 stroke and they raced at 7500 RPM...I think :drink:

and yet we spend all kinds of time and money for the other 5 %

fixx
 

i would look into labbing your prop,you will pick up rpm just from that,,i picked up 600 when i did mine years ago but thats on a volvo ultra prop..

600" N/A tunnel ram BBC - 6800 RPM

Solid roller!:party-smiley-004:

7,200 to 7,400.... 598s, 3.3 Whipples, Solid Roller! Had BPM 1.36 drives and 40 Pitch props. No more options at the time. Take out the chips and let her eat!!!:party-smiley-004:


http://www.youtube.com/watch?v=dZz74XZnFUA

Fack!

I don't have the Whipple but the 598 at 7500 does make some music.

Whos the 2012 High Rpm Master?:boat::hitit:
7500+? If so what you running Hull and Power?