8V-71 HP?

[5B Steve]

  I have a question, a few months back I had the chance to buy a couple of engines Silver 6V92, (since sold) and

  a 8V-71.  I was told that the 71 was set up at 318 HP. It came out of a truck with a 16spd transmission???

  something double over??, not to sure on the terminology, maybe Tom C. can tune in on this one.  HOW DOES

ONE KNOW IF INDEED IT IS 318 HP?

  Thanks in Advance.

  Steve 5B.......

[RJ]

Steve -

Simply pull a valve cover on this engine and look at the injectors.

N60 = 275 hp

N65 = 304 hp (truckers called this the "318")

FWIW & HTH. . .

[5B Steve]

  RJ,

   Why do they call a 8V-71, 318 If it's only 304 HP?

   Steve 5B......

[TedsBUSted]

Not sure on 304, but GM spec'd and advertised the 8-71 with 65 injectors as 318 HP.

The 16 speed was probably a Spicer 4x4, a big trans.

Ted

[luvrbus]

With the 7E65 injectors a 8v71 na is 318 hp @ 65 degrees and 304 at 85 degrees @ 2100 a 8v71 na with A timing and the N65 injectors stay at around 318 hp @2200 , outside air intake temperature affects the na 2 strokes but I am not going there lol 

good luck

[Geoff]

My DD Field Service book shows you get 318HP with A timing and N65 injectors at 2300 rpm.  The only engines that were set up this high from the factory were fire trucks.  But if you installed N70's you would get close to 318HP @ 2100 rpms.  Back in the day truckers always called 8V71's "318's" and many put way oversize injectors and turned the rpm's up as high as they could.  The cops didn't give out black smoke tickets back then. 

[TomC]

I knew of at least one truck driver friend that turned his 8V-71 up to 2,800rpm-which isn't that much higher then the marine versions at 2,500rpm.  He ran 70 injectors and at 2,800 he would have theoretically been getting 420hp out of it.  Course, engine life would probably dictate rebuilding every year.  My bus engine is turned up to 2500rpm-but have not gone there except to try it.  Normally shifts at around 1900rpm and run it at 1850 going down the road.   Good Luck, TomC

[bevans6]

Here is the torque curve, HP curve and specification of a 318 hp Detroit.  The only way to tell if it's a "318" is to look at the injectors and confirm the engine timing.  If it has brown tag N65's, and advanced timing, it's a 318.  If it has white tag 65's, and standard timing, it's a 318.  per my book, anyway, and all I can do is read the book...   

[bevans6]

A couple more charts.

Note that the HP curve isn't showing any signs of levelling off, it's strictly RPM limited so that's the proof of what Tom suggests about raising the high idle limit on the governor.  Note also the different test specification on the 8V-71N with N65 chart with resulting different HP ratings. 

Brian

[luvrbus]

For years you could just dump fuel to 8v71 for more hp not done that way anymore you have different blowers, gear ratios, liners, pistons,injectors,cams and now days set up right you get more hp on less fuel just like the 92 series.
The C65 does not require A timing it was the beginning of the new style injectors with the timing built in to the injectors you never hear of a 92 series with A timing unless you get way up on hp all done by the injectors


good luck

[Lin]

It is interesting that the first chart shows about the same fuel consumption from 1800-2100 rpm.  It would appear that that is the range to run in.

[bevans6]

I'm not sure how to interpret that line, to be honest.  It's lbs of fuel per HP hour so it takes around the same amount of fuel to make 270 HP at around 1800 rpm as it does to make 304 at 2100, in terms of usage per hour.  That's at full throttle, so presumably you are getting up to where the fueling capability of the injectors is evening out.  But it's interesting to contemplate that full throttle at low RPM is less efficient than full throttle at high RPM, presuming you need full throttle to do whatever you are trying to do.  Part throttle numbers would reflect cruising, full throttle numbers would reflect acceleration and hill climbing.  so I guess shift down climbing the hills.

Brian

[RJ]

Lin said:

It is interesting that the first chart shows about the same fuel consumption from 1800-2100 rpm.  It would appear that that is the range to run in.

With a GM 4106, 4107 or 4108, running the stock powertrain and standard (495 revs/mile) tires, 1800 rpm translates to 65 mph - a real sweet spot with these coaches.

FWIW & HTH. . .

[luvrbus]

That chart changes with different injectors the N65 dumps a lot of fuel at low rpms look at a chart for the 7E65's

good luck

[DaveG]

Hey, let's talk fuel efficiency....the series 60 is the only engine out there (that I am aware of) that the fuel consumption curve dips below .300, so it it no wonder the 60s are capable of such fantastic mpg. And it happens at 1300-1500 rpms

Kinda interesting to see the consumption curve of the 8V71...thanks!