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Max RPM

R

richie

Regular Contributor
8.1 MPI 385hp gas...

What i

8.1 MPI 385hp gas...

What is the max rpm I can safely run this engine in the slip with transmission in neutral.
 
"It's got a built in rev l

"It's got a built in rev limiter, so, that decision is already been made for you!
In any case, I'd say 5000 rpm."
 
"You can run it at WOT if you

"You can run it at WOT if you want to, but I don't know why you would. The rev limiter will limit your RPMs to 5150."
 
"Ayuh,...

Why on earth woul

"Ayuh,...

Why on earth would anyone Ever want to freewheel a motor above 1500rpms,..?? Anyway,..??..??"
 
"On diesels, it's a very c

"On diesels, it's a very common test to test the air intake limiter at WOT out of gear. Maybe the OP is a racer and wants to test the rpm limiter as well on this gasser?? Otherwise, ur correct, not much benefit on taking the engine much above the max ignition advance in neutral. 3000 rpm will do that. 5k might get the dock neighbors excited..."
 
"So, you lurk here as well, eh

"So, you lurk here as well, eh?

My buddy Dave W. loved to test the rev limiter of his rental cars by nailing it to the floor in neutral...and leaving it there! He then dropped it into gear, which was not what you would expect (and you wouldn't know this since none of you are nuts!) The ECU prevents the tranny from engaging until the rpms drop, so it simply stayed in neutral, popping away at 6 grand on the limiter.

Jeff

PS: The Myth Busters (love that show) tried dumping a car in reverse at 50 mph to slow it down. The result was--nothing. The programmers thought of that one too!"
 
I popped the tranny in reverse

I popped the tranny in reverse on a 56 Buick once. Never again. It really made a racket with the wheels trying to go backwards at 40 mph.
 
"I'll bet! The Myth Buste

"I'll bet! The Myth Busters should have used older cars, without the ECU/ tranny interface.

I'll bet they get lots of viewer mail and re-try that myth.

Jeff"
 
"I know what happens when you

"I know what happens when you try to impress your buddies by dropping a '74 LTD in gear at WOT. You try to find all the pieces of the driveshaft, then have those buddies help you push it home before your dad needs to go anywhere.

This never happened to me but I read about it on the internet. Yeah, that's it , I read about it on the internet."
 
"Great thread. I know that pre

"Great thread. I know that pre 94, the rental Caddy's had the rev limiter but it disengaged when you jammed it into gear while on the limiter in neutral. The valves float and then long smokey burnout. Just ask the two austin tx cops that were standing next to the car that just finished giving us directions to the strip bar. I was innocently riding and protesting... uh huh.

Oh... and I also know that when you put a brick on the gas in a 289 powered 69 ford waggon, it sits screaming, valves-a-float until it overheats and seizes... But then runs fine after cooling off.

And i can think of no reason to sing a big block boat engine to the limiter in neutral."
 
"catch the flu bug and stay aw

"catch the flu bug and stay away from the computer for a couple days and you'll never know what to expect when you return.....

On a slightly serious note, our kids will always be at a slight disadvantage due to "modern technology"; if a device's 'program' prevents them from doing something stupid (and learning from it) they may think all devices are 'smart' and then they'll come home and borrow the........on the other hand, looks like the need for competent mechanics will continue to grow for the next decade or two."
 
".."looks like the need fo

".."looks like the need for competent mechanics will continue to grow for the next decade or two."

You are oh so right! If I was a kid (hah!) nowadays, I'd sign up for all kinds of courses on fixing mechanical things 'cause I'd be in need BIG TIME in a few years, and I'd charge plenty for it!

Jeff"
 
"I agree that mechanics of all

"I agree that mechanics of all types will be in demand over the next few years. A few years ago I was in Costa Rica during a time when the economy was really bad. There were small repair shops all over San Jose repairing everything imaginable. One shop was fabricating a muffler for a car instead of buying one at the local parts store.

Our economy is getting in the condition that will drive people to run their cars and boats longer which means more maintenance. When I was in high school I wanted to be a diesel mechanic. My dad talked me in to going to college for two years so I would be an “educated” diesel mechanic. I kept going to school and became a Chemical Engineer. I am going to retire at the end of this month. Who knows, I may fulfill my life long dream and become a mechanic after all these years.

Relative to boats, my feeling is that all boat owners need to understand the basics so they can get back to the marina.

Chuck Hanson"
 
"..."Relative to boats, my

"..."Relative to boats, my feeling is that all boat owners need to understand the basics so they can get back to the marina. "

You said it!

Jeff

PS: I started out as a Chem E, then switched in the first semester to a Mech E."
 
"Chuck:

your story reminded

"Chuck:

your story reminded me of one I rx'd from a guy I used to work with. He retired early, sold his woodshop, vacation property, and the house. Took the wife to the miami boat show and came back three weeks later owning a 50' sailboat. He retired to 'live the dream'; sailing the carribean...

One of those 'how've ya been' emails described the 'generator repair' he experienced on one of those little islands down there. He said they repaired EVERYTHING as 'spare parts' were in very short supply. The guy from the marina took him and the cylinder head to the otherside of the island to a jewerly store. They went into the back room, out of the back door, and then back into the jeweler's "shop".

He said the owner was a true sheet metal artist and proceeded to laminate some head gasket stock. put the cylinder head down on it, scribed the bolt holes and then punched them out. He said the coolant passages were done by hand. An hour later, he was $20 lighter with gasket in hand. That was 18 months ago and he hasn't mentioned that gasket failing so far. He said the gent was a pretty good jeweler, too."
 
"Being a Cheapskate, I make my

"Being a Cheapskate, I make my own gaskets all the time. Not that hard to do.

Jeff"
 
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