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 Proper RPM Range for a 427 Gasser?
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Jared
Top Member

USA
1865 Posts

Posted - 06/24/2014 :  08:07:04 AM  Show Profile  Visit Jared's Homepage  Reply with Quote
So I replaced my old worn out 366 with a 427 in my bus and I also installed a factory tachometer. The bus drives great now but I have a question on the RPM side of things. If I drive 55 mph I am at 3200 rpms. At what RPM is too much load for the engine? I noticed there really isnt a redline or anything.


dwight
Active Member

USA
42 Posts

Posted - 06/24/2014 :  3:28:02 PM  Show Profile  Reply with Quote
Jared
The 427 low compression regular gas develops maximum torque at 3200 to 3600 RPM depending on year and carburetor. The Allison at full throttle will up-shift with-in 200 RPM of recommended max RPM for school bus use (not a speed demon).

20 SCHOOL BUS FLEET OWNER/OPERATOR (Retired)
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Jared
Top Member

USA
1865 Posts

Posted - 06/24/2014 :  6:04:24 PM  Show Profile  Visit Jared's Homepage  Reply with Quote
Thank you Dwight. If I drive on the highway at 3500 rpm an the trans isnt upshifting am I ok? Would the engine be ok at this rpm for a long period of time?

http://www.flickr.com/photos/jaredg21/sets/
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C.HARDY
Advanced Member

354 Posts

Posted - 06/26/2014 :  6:35:03 PM  Show Profile  Click to see C.HARDY's MSN Messenger address  Reply with Quote
Jared do you know what gear ratio that thing is? 3500rpm isn't that bad for a gasser but I wouldnt push it much harder. That bus was probably geared for max 55 mph.

"Hardybusman"
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C.HARDY
Advanced Member

354 Posts

Posted - 06/26/2014 :  6:37:23 PM  Show Profile  Click to see C.HARDY's MSN Messenger address  Reply with Quote
Jared do you know what gear ratio that thing is? 3500rpm isn't that bad for a gasser but I wouldnt push it much harder. That bus was probably geared for max 55 mph. I know the bus have from Baltimore was geared that way although it is a diesel.

"Hardybusman"
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Jared
Top Member

USA
1865 Posts

Posted - 06/27/2014 :  7:18:11 PM  Show Profile  Visit Jared's Homepage  Reply with Quote
I am thinking its a high 6 - like 6.83 or something. One day I'm gonna jack the rear end up and do the old ratio test.

http://www.flickr.com/photos/jaredg21/sets/
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C.HARDY
Advanced Member

354 Posts

Posted - 06/28/2014 :  09:58:41 AM  Show Profile  Click to see C.HARDY's MSN Messenger address  Reply with Quote
There should also be a tag on there somewhere. I'm thinking that's an Eaton rear. A lot of older Va. gassers were a 7.11 ratio. Back then top speed was 45 and they want the engines lugging all of the time, I guess Baltimore was the same way. That engine should have an overspeed I would think if you pushed it too hard. 3600rpm should be tops but I could be wrong.

"Hardybusman"
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Cal Mc
Advanced Member

256 Posts

Posted - 07/05/2014 :  1:09:21 PM  Show Profile  Visit Cal Mc's Homepage  Reply with Quote
Sounds about the same as we were running. governor should cut in at 3800 RPM (if it is still hooked up) Axle ratio 7.17, top speed depending on tires 60 to 65 MPH The engine if in good condition will run at 3500 RPM day in and day out without a glitch.
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Jared
Top Member

USA
1865 Posts

Posted - 07/06/2014 :  4:39:03 PM  Show Profile  Visit Jared's Homepage  Reply with Quote
quote:
Originally posted by Cal Mc

Sounds about the same as we were running. governor should cut in at 3800 RPM (if it is still hooked up) Axle ratio 7.17, top speed depending on tires 60 to 65 MPH The engine if in good condition will run at 3500 RPM day in and day out without a glitch.



Thanks for the reply guys. Nope the governor is disconnected and the holley on this 427 isnt a governed model. I'm betting it you are right and it is a 7.17. As long as 3500 isnt killing the engine i'm ok with that. Maybe one day down the road I'll swap the entire rear end and also ditch the Dayton spokes.

http://www.flickr.com/photos/jaredg21/sets/
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