8V71 with 7E55 injector

[OneLapper]

I found a company with several 8V71 LH rotation engines for sale.  I'm intending on buying one of these engines.  I asked what injectors are installed and they have 7E55 injectors.  I am only familiar with the N60s, N65 etc.  My engine has N60 injectors and it's rated for 270 hp.  Do the 7E55 injectors have the 318 hp rating?  The company thinks they are 318 hp rated.

Thanks!

Mark

[TomC]

55 injectors have a 255hp rating with 675lb/ft torque.  Very long lasting with good fuel economy and can be driven all day long with your foot on the floor.  Good Luck, TomC

[HB of CJ]

TomC, would OneLapper be happy with the 7E55 injectors in his Bus Conversion?  I have no idea, but years ago our old American LaFrance fire apparatus had N90 injectors.  8V71N 350hp, 900 tor..

However, they were way too big.  The Engineer (operator) had to quickly learn to "keep his foot out of it" until the mill had revved way up..or...clouds of black smoke was the result.

Anyway, The State of Commiefornia (California) made the shops reduce the injector size to something manageable.  Dunno what size.  Smog laws.  1976 or soss.  Ancient history. 

[OneLapper]

Thanks TomC, I'll have to figure out what it'll take to get the 7E65 or N65 injectors installed.  Found them online for $50 each for rebuilt units.  Waiting to hear back from DD dealer on the differences of the 7E series injectors versus the N series injectors.  I think I'll need a bit more than 255 when pulling my trailer, but who knows what I have for hp now!!!  255 might be a huge improvement!

If I'm going to spend the money and time to install a fresher engine, I may as well build it up to the 318 hp rating.  Now would be the time when it's sitting in a cradle mounted to a pallet.  I'll also advance the cam timing at the same time.

I'm getting 10.8 mpg at 65 mph on a long trip, and 7.8 pulling a 7500# enclosed car trailer.  Actually, hp is fine, I'd like another 5 gears!

Thanks,

Mark
4106

[kyle4501]

More horses require more feeding . . .  Something to keep in mind . . .

[JohnEd]

If you travel at the same speed with all other conditions the same....both size injectors "should: give you the same MPG.  It is only logical as it takes the same amt of fuel to make the same HP in both cases.  If you don't actually use the additional fuel that a larger injector "can" deliver, it should deliver the same efficiency.  Neat logic, huh?  I have been told that it DEFINATELY does not work that way and that no matter how careful the driver is he can't match the efficiency of the two unless he floggs the smaller injector equiped engine and feathers the big injector equiped item. 

Any one care to comment on that?  I accept the "experts' advice...make no mistake.  Still, I got no rationale with the advice.

Thanks,

John

[makemineatwostroke]

Onelapper you will get 318 to 304 HP from the 7E65 injectors in a 8v71 818 ft of torque at 1400 rpm The 7E55 are in the 250 HP range don't think you would be happy with the performance of the 7E55 injectors pulling a trailer

[kyle4501]

Injector size ain't the only thing changed. There are other things that were also changed - timing? power curve? efficiency curve?


If it was so simple, why wouldn't all engines come with the same injectors & simply use throttle stops to limit power?

[OneLapper]

DD just faxed me over the build sheet on the engine I'm interested in.  It originally came with C60 injectors and later had 7E55 injectors installed to save fuel.  Built on 12/17/1981

Does any know how to read these spec sheets?  I'll post the info tonight and hope someone can decipher the data.

Mark

[Jerry Liebler]

Mark,
     I doubt that you really want the 318 hp set up.  To get 318 hp you have to go to 'advanced' timing which has the unfortunate side effect of raising the torque peak from 1200 rpm to 1400 rpm.  The transmissions in the GM buses are designed around the 1200 rpm torque peak and with the 318 setup many small uphills will force you down into a lower gear than you could pull with the lower power setup.  With 'standard' timing n60 injectors are as good as it gets.
Regards
Jerry 4107 1120  (standard timing and n60 injectors)

[OneLapper]

Hi Jerry.  You bring up a good point.  I'm giddy with idea of having a complete engine on the ground, easy to work on, so I figure now is the time to put the engine together the way I "think" I want it.  I know about torque, my TDI Jetta has 100 hp, but 185 tq.

I thought that these coaches came with the 318 hp setup.  I don't really mind the downshift because with the trailer I'm more than likely downshifting to third and holding it at 50-55 mph even if I'm at part throttle.  I wish I had a tach because I have no idea what the governor is set at.  I do know that I had it up to 80 without hitting it.

Is there anyone out there with a 8V71 running N65s with advanced timing?  In a Coach?  I'd love to get some feed back!

[lostagain]

You can get a hand held tach. at Harbor Freight real cheap now, around $60 if I recall. Really good for setting your iddle and no load max. rpm on the governor.

JC

[pvcces]

One of the side effects of going to advanced timing is to narrow the power band a bunch. The "so-called" 318 is really a 304 with standard conditions. The reason that the trucks had this setup is because they had the gears to pick the right ratio.

With a four speed transmission, you need a very wide power band. The standard timed C or N60 provided this. And I don't believe that I've seen a case where the N65 advanced timed bus got the fuel mileage that a standard timed one does.

Ask a trucker if he works his Detroit two stroke much below 1500 RPM. I would be surprised if you don't get told "You don't lug a Detroit".

For what it's worth.

Tom Caffrey

[OneLapper]

Here is some of the data on the "Engine Equipment Record"

Model:  7087=4021  APPL:  332S  Min Idle RPM:  500   MaxNL:  1950   MaxFL:  1800
CamTim:  STD GT-STD CAM   Then a bunch of Customer Spec Info, ship date, sold to, etc.

Equipment                PBT         UPC GROUP

ACC DRIVE               153          06X04 0291
AIR BOX DRAIN          144         06A01A0200
BAL WT COVER          29           06J01 0083
BLO DRV SHAFT         27           ...............
BLOWER                   245
C/S RD TRAIN            89
CONN ROD/PSTN        170
CRANKSHAFT             69
CYL BLOCK                35
CYL HEAD                  91
DIPSTICK                  816
ENG LIFT BRKT           139
EXH MANIFOLD           376
F/HSG ADAPT            40
F/W HOUSING            531
FLYWHEEL                 940
FUEL PUMP               174
GOVERNOR                1484
INJECTOR                 113
INJECTOR CONT         255


It goes on and on, oil cooler oil dist oil filter oil pan oil pressure regulator oil pump, rocker cover, tach drive, thermostat etc.


Does anyone know how to read this info?

Mark

[luvrbus]

Aren't those numbers for a fast parts reference I believe the parts book breaks in down from that number for the engine application.Someone correct me if I am wrong but the model number and block number shows that block can accept a after cooler for a turbo.Sorry I could not be of more help but it takes a master parts book to tell what the group numbers stand for.