max RPM on a engine
 

hi guy s im building a 496 with my old 454 and now the big question ! what is the max rpm I should put on my engine ! I have a merctran trany with a TRS outdrive and I don't want to destroy it ! lol im gonna have around 425 hp with 525 lbs of torque my screw is 14 inch by 23 of pitch ( 14 im not sure cause I have try to mesure it with my tape ;s) so if I want 5300 rpm WOT what rpm I should put with the engine free ? thank you guy and hope you are able to read that thread ! im speaking French so ... a little bit hard to explain my point clearly ! lo, have a nice day !

Ayuh,.... Yer doin' Ok with the french to english, except for this,..??

"so if I want 5300 rpm WOT what rpm I should put with the engine free ?'

What do ya mean, "put with the engine free ?"

I donno how tolerant the Trs' are to rpms,...

A factory balance motor, is cam'ed to 'bout 4800 rpms,...

If yer motor is gonna be a Machine Shop, fully balanced motor, 5300 rpms might be safe enough,...

Anyways,... the combination of the induction, cam, 'n exhaust have to be matched to each other,...
If ya want 5300 rpms to be yer sweet spot,...
Build the motor to do that,...

I spun my 600HP 454's to 6500RPM in front of my TRS. If your HP peak is @ 5300RPM I'd think 5500 rev limiter would be sufficient. If that's what you are asking?

but what kind of trany you have between ? cause if i could push my engine at 6500 rpm without breaking all in the back its sure i would !!!! lol

I think the added rpm helps the TRS live longer. Smaller pitch prop and keeping the engine from peak torque area takes the load off them. And the trannys will take more torque with RPM too.

here's a hint: it will ALL break at some point!

At 425Hp you will be out of your usable powerband @6500RPM. So there is no sense in spinning your engines to 6500RPM. My original engines started life a Merc 420's and I believe peak power was around 5200RPM. My 600HP 454's made peak power at 6500 and I propped accordingly. With my new cams they make less HP but, carry more torque. They now make peak power around 5800RPM so I have propped up to only pull 5800RPM. Funny thing is my boat still runs 79mph both setups, cruise is better now.

Which is a win!

Do you miss the music from 6500RPM though?

6500RPM in the race boat sounded great!
But, my first ever built BBC's @ 6500RPM that I assembled myself scare the s#it out of me... Yeah, they did sound awesome!

425hp, pour un 496, c vraiment pas beaucoup...

[ouais cest sur mais cest ma base je vais upgrader le set up dans une couple dannee mon probleme cest la transmission que tout le monde me dit que cest le point faible alors je vx pas me ramasser a booster un moteur en fou mais que mon pied ou ma transmission suive pas pis que je me ramasse pu de bateau ! lol le vrai probleme cest que des merctrans fais par borg Warner cest pas tres connu pis je suis pas capable davoir de spec precis a savoir ce quelle est capable de prendre ! idem pour le pied ! mais cool de savoir que je suis pas le seul a parler Français sur ce site ! lol

bienvenue,Core....suis pas un expert, mais si je peux t'aider...

so si tu sais ou aller chercher les spec pour ma transmission pis mon pied je vais le prendre volontiers ! lol sinon je vais pause des question la semaine prochaine ma etre au boat show de miami ;p lol

how does one say "wtf, over?" in French?

We'll now this is different! But cool none the less! I guess?? For what it's worth. I ran my 454 which was also built for high rpm and ran 70's @6500rpm. I'm now reconsidering changing a few things to give longer life to my setup. This was also a TRS that ran flawlessly.

thank guy for your help ! i think im gonna finaly play safe ! i will try to take a cam with peak hp at 5400 but with more torque so i m gonna play with the pitch of the prop so now i just have to find friend with prop to try ;p lol cause 500$ to try a prop its a little bit expensive lol but i think with a 27 i could have good result !! ( now i have 23 )