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 455 w 4spd rpm question?
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Tribal Scout

13 Posts

Posted - 17 Feb 2014 :  1:48:46 PM  Show Profile  Reply with Quote
This is my first pontiac 455 engine so i'm not familiar with them. I was on Randy's ring and pinion and calculated the rpm range that I thought i was going to run 75mph with a 455 and a 4spd running 3.00-3.25rp 27.5tall tire. My question is? is running a 455 on the freeway at 27-2800rpm's for 40 minutes doable without lots of wear on the bottom end?? I ask because the 455 is a lower rpm engine and is not like a small block chevy or ford right?? Any advice on what nice and comfortable rpm range would be for a 455 going 75 mph for 1 hour?? Thanks.


5438 Posts

Posted - 17 Feb 2014 :  1:56:16 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
I think most would prefer about 2300-2500rpms, not because of durability but because of noise. I am about 2000-2200 rpms and would like to be about 2500rpms because i am right in the "drone zone" of my exhaust system at 2000 rpms. Back before overdrive, people drove these cars from the factory at 3k rpms down the road all day, without upgraded rods and roller rockers or any durability upgrades.
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Bill Boyle
Horse Feathers (Charter Member)

5092 Posts

Posted - 17 Feb 2014 :  2:03:15 PM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
You will not have any wear issue running turnpike speeds with 3.23 type gearing with any traditional Pontiac V8 engine.

The bigger concern would be fuel economy. It would be nice to have an overdrive gear (5th) to drop the rpm 300-400 rpm.

[Note: Increasing the diameter of the rear tires changes the effective ratio. The taller the tire the lower the rpm at every speed. Using a smaller diameter tire increases the rpm; it will also make it more responsive on acceleration to the detriment of fuel economy. ]

"Dedicated to keeping the classic Pontiac engine alive."

400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
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The Great White Buffalo

7284 Posts

Posted - 17 Feb 2014 :  9:01:49 PM  Show Profile  Reply with Quote
Actually most modern overdrives can drop the highway cruising rpms by @1000rpms or @1/3 reduction from the non-OD high gear rpms.

Bowties are for Pee-wee Herman. LS swaps in Pontiacs should only apply to Fieros.

Edited by - Phil on 17 Feb 2014 9:02:54 PM
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209 Posts

Posted - 18 Feb 2014 :  08:37:31 AM  Show Profile  Reply with Quote
I'd say 2200 would be comfortable at highway speeds. Depends on what your going to do with it when you aren't doing the 60 min. on the highway at 70mph. The 455 has more torque than the Chebby small block you mentioned, so you wouldn't need as steep a gear for driving around town as you would with the Chebby. But if it's not going to be just a highway cruiser, you could pick a gear that would get you about 2500 on the highway and still get up and go in the city.
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Mr. P-Body
Running Bear

2258 Posts

Posted - 20 Feb 2014 :  7:32:12 PM  Show Profile  Visit Mr. P-Body's Homepage  Reply with Quote

Funny how time changes one's "view". Mean piston speed is the determining factor as to how long one can "run" at a given RPM. A 455 can run all year at 4,100 RPM. Never hurt it.

In olden times, cars ALWAYS had 3.73 or "stiffer" gears if a performance car. We would drive to L.A. or Van Nuys (60-70 miles)with 4.10 gears and not think twice about it. OD makes things more comfortable, I certainly agree. Stiff gears rattle your teeth... But it won't hurt the engine.

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