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vajrabolt
New Member

1 Posts

Posted - 05/03/2018 :  12:37:24 PM  Show Profile  Visit vajrabolt's Homepage  Reply with Quote
Hi everyone!

I recently purchased a Thomas 1990 C60 School bus with a 366 engine.

The bus accelerates just fine in first and second gears, and the first half of third. In third and fourth, though, the speed maxes out at around 40 miles per hour.

The timing has been adjusted and that didn't make any difference. I am thinking of changing out the throttle body on the bus. Does that sound like it would help?

Could it be a governor on the bus limiting its speed to 40?

The first owner didn't drive their bus regularly, only about 20 miles a year. The next owners did some thorough work on it to clean it out afterwards, and the bus ran well except for the speed limitations.

Any help would be most appreciated, and I will document my progress as I move towards fixing this problem in case someone else runs into it in the future.

bwest
Administrator

United States
3820 Posts

Posted - 05/04/2018 :  06:14:46 AM  Show Profile  Reply with Quote
That's a pretty old bus for those that frequent this forum. If I recall correctly, this would have a holly 4 barrel?

Bryan
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valleybusman
Top Member

USA
798 Posts

Posted - 05/04/2018 :  12:58:01 PM  Show Profile  Send valleybusman an AOL message  Reply with Quote
I had gas bus like that years ago . Mine had a governor on the carb . Designed so when it hit a certain RPM it would pull the throttle plates closed . Couldn't get it over 50 unless you eased into it and gave it 3 miles to accelerate . I think that's your problem .
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flint1
Senior Member

Canada
74 Posts

Posted - 05/06/2018 :  03:53:41 AM  Show Profile  Reply with Quote
http://www.schoolbusfleet.com/forum/topic.asp?TOPIC_ID=23039&SearchTerms=Holley

maybe this is the issue? A little blast from the past..
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bwest
Administrator

United States
3820 Posts

Posted - 05/07/2018 :  05:23:39 AM  Show Profile  Reply with Quote
That certainly was a blast from the past! I have forgotten most of what I knew about those! Ugh, getting old is for the birds! lol

Bryan
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muddywater
Senior Member

USA
50 Posts

Posted - 05/09/2018 :  07:10:21 AM  Show Profile  Send muddywater a Yahoo! Message  Reply with Quote
If indeed your first and second gear acceleration rate is good, I would tend to believe your engine performance isn't your issue. I would be inclined to think of trany issue, maybe. Is this a trany with third and fourth gear torque converter lock up? The torque converter could be malfunctioning. Not saying it is your problem, but maybe it's something that needs to be explored.
Good luck

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Cal Mc
Advanced Member

303 Posts

Posted - 05/28/2018 :  2:00:55 PM  Show Profile  Visit Cal Mc's Homepage  Reply with Quote
That should have a TBI 366,possibly a Tonowanda engine.I believe the vehicle speed is limited by a "DRAC unit inside the bus.(white box about 1 inch thick and 4 inches square)
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bwest
Administrator

United States
3820 Posts

Posted - 05/29/2018 :  06:16:49 AM  Show Profile  Reply with Quote
quote:
Originally posted by muddywater

If indeed your first and second gear acceleration rate is good, I would tend to believe your engine performance isn't your issue. I would be inclined to think of trany issue, maybe. Is this a trany with third and fourth gear torque converter lock up? The torque converter could be malfunctioning. Not saying it is your problem, but maybe it's something that needs to be explored.
Good luck





1990 should be a 545 Allison, no?

Bryan
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