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Re: [GMCnet] Engine lubrication [message #355628 is a reply to message #355626] Sat, 13 June 2020 06:35 Go to previous messageGo to previous message
powwerjon is currently offline  powwerjon   United States
Messages: 849
Registered: March 2013
Karma:
Senior Member
Tom,

First of all these guys on these show have no respect for equipment. They probably buzz the 455 in the truck at a high rpm as a guess 4500 +rpm and beat the crap out of it (tech term). Some 455 have be built for racing and that does require special prep on the bottom end and oil system. Oil weight also makes a difference as I have alway run a 15/50 or 20/50 oil over the years starting with dino oil and then as semi synthetic and then a full synthetic in the last few years. Remember that the 455 was originally spec’ed to use a 10/30 or straight 30 weight oil.

The motor in the GMC motorhome depending on the final drive, tire size and speed never goes over 3000 or so RPM for any extended period of time. Typically if you have a 3.07 gear you’re only running 2350 rpm at 70 ish mph. The 3.55 gear runs 2650+/- at 64/65 mph and 3.66 ratio is typically about 2875 +/- at 63/64 mph. I have had experience in all three ratios. I have run all day long with the 3.66 final at 3000 rpm when I needed to make miles for years and have never had an engine issue and or had oil pressure fluctuations ever in the 20+ years and all my engines weather a 403 or 455/461. My oil pressure has run in the motors that I have use has been right at 50 psi at speed. The 455 was used for years to power big irrigation pumps for hours and hours.

J.R. Wright
GMC Great Laker MHC
GMCGL Tech Editor
GMC Eastern States Charter Member
GMCMI
78 GMC Buskirk 29.5’ Stretch
75 GMC Avion (Under Reconstruction)
Michigan



> On Jun 13, 2020, at 6:35 AM, tom geiger via Gmclist wrote:
>
> So was watching a episode of “Roadkill” and they had purchased a old mazda pickup truck with a 455 in the bed of the truck. If you’ve ever watch
> the show, these Frankenstein vehicles are the basis of show. Anyhow one of the host commented that he was not excited about the 455, said it was one
> of the worst engines. Called it a boat anchor. I did some research and found some criticism on the way it leaves the bottom end of the engine dry of
> oil when run at high rpm for duration of time. What do you guys do to help manage this?
>
> Thanks,
> TG
>
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