8.1 Maximum extended rpm?

[Dave Pelletier]

Originally Posted by Bowtie Jim

You can run it at 4000-4500 rpm all day long .
As long as you have plenty of air to cool it down. And fresh oil.
These 8.1 big block Chevys are stout.
The only downside is they like to suck the gas tank dry.

This. As long as you keep an eye on engine temps, tranny temps and oil pressure, I'd have no concerns running at 4-4.5k for extended periods.

Basic design is the same Mark IV big block that's been used since 1965 and it's both proven and stout.




Dave

[yeloduster]

In motorhome applications the 8.1L economy numbers are almost identical to the 6.7L Ford V10.

If you have a Class A motorhome and driver ~62 MPH you will get ~7 MPG towing a car regardless of Ford V10 or GM 8.1L. The frontal area of the motorhome is probably a much bigger factor than the engine.

I have driven my 8.1L motorhome 20K miles and averaged (checked at every fill up and logged in a spreadsheet) 7.1 MPG. It has been as bad as 5.8 MPG and as good as 10.7 MPG. Total miles/total gallons is 7.1 MPG. Most of those miles were towing a Jeep Cherokee. I don't have enough data to claim it but MPG without the toad seems to be about 8.

The blanket statement that the 8.1L GM engine is a gas hog may not be accurate.

[LETMGROW]

Originally Posted by yeloduster

In motorhome applications the 8.1L economy numbers are almost identical to the 6.7L Ford V10.

If you have a Class A motorhome and driver ~62 MPH you will get ~7 MPG towing a car regardless of Ford V10 or GM 8.1L. The frontal area of the motorhome is probably a much bigger factor than the engine.

I have driven my 8.1L motorhome 20K miles and averaged (checked at every fill up and logged in a spreadsheet) 7.1 MPG. It has been as bad as 5.8 MPG and as good as 10.7 MPG. Total miles/total gallons is 7.1 MPG. Most of those miles were towing a Jeep Cherokee. I don't have enough data to claim it but MPG without the toad seems to be about 8.

The blanket statement that the 8.1L GM engine is a gas hog may not be accurate.

Running down the highway with a rig weighing 20,000# or so which is as aerodynamic as a Saltine cracker box isn't going to result in great gas mileage no matter how you drive it. Adding a vehicle to tow around at the same time isn't going to improve the mileage either.
Some folks boast of better mileage driving Diesel RV's. That may be true but the increased price of diesel fuel over gasoline pretty well makes it a wash when it comes to dollars spent per mile.
With proper care the 8.1 engines will have a long life. I had a customer who had two 1 ton. duallys with 8.1's he hauled cattle trailers with. These trucks got beat to death and looked like they spent time in a demolition derby but both trucks lasted nearly 300,000 miles before he bought new trucks and the engines never gave him any major problems.