obs 7.3 rev limiter

97stoker350 · Jan 4, 2012

i was just wondering wat the max SAFE rpms are for the obs 7.3 or is the tach telling the truth to start getting out at ~3300?

morefuel · Jan 4, 2012

I read somewhere that it isn't recommended that you pull it over 3000 rpm for extended periods of time because it can pull the piston in half.

davey99ps · Jan 5, 2012

$hit, I'm in trouble then cuz mines been over that plenty of times

97stoker350 · Jan 5, 2012

so ~33, 3400 for a few seconds wouldnt hurt anything?

Hotrodtractor · Jan 5, 2012

morefuel said:
I read somewhere that it isn't recommended that you pull it over 3000 rpm for extended periods of time because it can pull the piston in half.

Who ever told you that line of crap didn't know what they were talking about.

That being said the two items that really cap the physical RPM capabilities in these motors is the lower end balancing (overbalanced from the factory) and the valve train. The valve springs, push rods, and rockers are really what hold it back. Take a look in the aftermarket spring thread in the 7.3 upgrade section going right now for a few more views on the subject.

97stoker350 · Jan 5, 2012

would i pick much up from puting 910 springs and chromoly rods in?

davey99ps · Jan 5, 2012

97stoker350 said:
would i pick much up from puting 910 springs and chromoly rods in?

No, they just help keep your motor together when you start making hp.

97stoker350 · Jan 5, 2012

well how much rpms will the motor hold by puting them in

Arisley · Jan 5, 2012

Well, I have a simple set of 910's in. I have stock pushrods. I am the school that says if something is going to break, make it the pushrods, they are cheap. I have seen 4300 a few times. Still holding together.

Sorry, you have to find the breaking point for your self. I don't know, and I will not go out and find out for you.

BTW, your results may vary from mine.

Powerstroke Cowboy · Jan 6, 2012

Arisley said:
Well, I have a simple set of 910's in. I have stock pushrods. I am the school that says if something is going to break, make it the pushrods, they are cheap. I have seen 4300 a few times. Still holding together.

Sorry, you have to find the breaking point for your self. I don't know, and I will not go out and find out for you.

BTW, your results may vary from mine.

Do you have a sound clip at 4300?????

Arisley · Jan 6, 2012

Nope, sorry.

Hotrodtractor · Jan 6, 2012

Powerstroke Cowboy said:
Do you have a sound clip at 4300?????

Left the line at about 4400 or so - probably was at 3800-3900 at the big end of the track.

YouTube Video

Powerstroke Cowboy · Jan 6, 2012

I think it sounds pretty good up there!!! Thanks...

samoht517 · Jan 6, 2012

That sounds awesome. Hows tunes are you running to get it spinning that fast

Hotrodtractor · Jan 6, 2012

samoht517 said:
That sounds awesome. Hows tunes are you running to get it spinning that fast

That is far more than tuning to do that..... but its Wildman programs on that run.

Magnum PD · Jan 6, 2012

How much does having a race balanced rotating assembly help?

Hotrodtractor · Jan 6, 2012

Magnum PD said:
How much does having a race balanced rotating assembly help?

That helps keep it alive, but does not really help spinning the RPMs - that is a combination of parts and tuning that was put together to work where it does in the RPM band. I've had that motor over 5600 on several occasions - but the limitations on fuel delivery kept me from running it there at the track.

Arisley · Jan 7, 2012

Yeah, mine qat 4300 was still pulling (hard), Tony's tunes also. Might be something in common there. But it was not pulling anywhere near what it was at 3600. I hate rev limiters though. Dammit, if I wanna throw my truck in low gear at 75MPH, I probably need it to be there. And even if it is it's last gasp at life, I want it to be trying it's heart out.

Basically, I want to make the decisions, not some stupid digital machine that has no awareness of what is really happening in my world at any given time.