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Old 09-05-2005, 01:09 PM
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Too High RPM?

Guys,

I am currently working on getting my 49 Chevy running. It has a 4.11 rear with 27.5" tires on the rear. At 2750 RPM, this puts it at about 55. I do not drive the highway that much, but my question is that too high an rpm for highway driving? I have rebuilt the engine (307) and it runs well and does mot over heat (new 4 core). Years ago, I used to have an old Mustang II with an old 4 banger that I think the tach used to run 2750 at 60. Am I looking at a short life for this motor. Didn't some of the 60 - 70 something trucks run gearing like this? I almost forgot, it has a rebuilt 350 turbo and I would like to keep the gearing for most of my town driving. Obviously more show than go!!!!! Thanks in advance for the input.

Ron
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Old 09-05-2005, 01:33 PM
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Hi Ron, 2750 is not anything to worry about. My truck runs 2800 at 60 and i've been driving it for 23 years that way! My last engine had 168,000 when I pulled it and it still ran good. In the future, you could put in a GM 700r4 tranny and take advantage of the overdrive and lockup converter and get it WAY down on the highway.

Mark
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Old 09-05-2005, 01:59 PM
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2750 is fine, my Blazer is turning 3000 rpm at a little over 55 mph.
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Old 09-05-2005, 06:46 PM
How fast is fast enough?
 
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My pop's 1 ton Ford work truck pulls a little over 3200 on the highway with about 6000 pounds of crap to pull around. That engine has 240,000 on it- yea its a dog, but it's still turning...
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Old 09-05-2005, 07:55 PM
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I have a customer with a 31 Ford that has a 428, a C-6 and 4.89 gears! He drives it to the Street Rod Nats every year and other shows/cruise-ins all the time. It turns 3800-4000 rpm on the highway and has been doing that for over 10 years.
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Old 09-06-2005, 03:38 PM
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One thing to watch for when building an engine is the cam manufacturers cruise rpm recommendation. You may find your cam likes that rpm. Some of the higher lift cams have very high cruise rpm. I was going to buy a .528 lift roller cam and the cruise rpm was 3400 rpm. With my 3.55 gears and in town driving the car would rarely see 3400 rpm. I had to rethink my cam.
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Old 09-06-2005, 10:53 PM
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Quote:
Originally Posted by Riverman
Guys,

I am currently working on getting my 49 Chevy running. It has a 4.11 rear with 27.5" tires on the rear. At 2750 RPM, this puts it at about 55. I do not drive the highway that much,

.....and I would like to keep the gearing for most of my town driving. Obviously more show than go!!!!! Thanks in advance for the input.

Ron
********
There is some really good input in this thread, but I think you already answered your own question.....
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