8V71 turbo specs

[luvrbus]

The E injector was a federal injector in the 8v71N/A,you differently no not want advanced timing with a 7E65 they smoke and are gutless.When using the 7C65,7C70 or 7C75 you retard the timing on a 8v71NA.
Detroit used the 7E65 with standard timing on the 8v71NA to raise the peak torque from 1200 rpm to 1400 rpm

[windtrader]

Hey, I found a discrepancy in the power figures. Earlier I posted that a 8v71T has 308hp with n65  injectors   865 lbs torque. Later I posted an 8V71N with N65 has 304hp and 800lb/ft. These were cut and pasted from other posts during my research. The thread started out as a turbo question but the latest posts are questions about injector options on a Natural motor.

Is the power increase even worth the time and expense to swap out injectors on an N?

Thanks

[wildbob24]

What is the difference between the PD-4108 and the P8M-4108A I have a buddy that owns a P8M-4108 A

Clifford,

As far as I know, no real difference until 1975, when GM began installing Integral power steering and air throttles and an early version of a split braking system with ABS.

Bob

[Geoff]

I had to get out my Field Service Data book with the 1987 engine specs, my last post was from memory.  By 1987 everybody was using the 92 Series engines and Series 60 so I was not up to date on the 71 Series injectors. In 1987, buses (most likely transits) the only 71 engine available was the 6V71.  Coach listings for that year also had 6V92 and 8V92 engines.  Looking under trucks, the 8V71 used 7E65 injectors for 304HP @ 2100 rpms with advanced timing.  They don't show TA engines except industrial versions.

--Geoff

[Geoff]

I converted my 8V-71N to a turbo. Don Fairchild first looked at the piston rings and determined they were the tight fit rings-as compared to the looser rings that truck engines run. We kept the 18.7 to 1 pistons that were two piece (only difference between turbo and NA two piece pistons is the deck height). I added an air to air intercooler in front of the radiator (luckily had the room). But also had to increase radiator and also add misters. Increased air cleaner from 6" to 7" hose, added auxiliary transmission cooler with thermostatically controlled 12v fan, changed stuffed up muffler to turbo muffler, added by pass valve to blower, added fuel modulator. Was extensive, not cheap, but the performance is truly different. My fuel mileage is the same-mainly because we didn't change the cylinder liners or cam timing. But comparing the N65 injectors at 300hp @ 800lb/ft torque to the now 7G75 injectors at 375hp @ 1125lb/ft torque, you can see the difference in hill climbing with the torque increase. Good Luck, TomC

I had my Data book out and looked up some specs.  The industrial 8V71TA with 7G65 injectors is rated at 330 HP@2100 rpms.  With 7C65 injectors that same engine with the same turbo (TV8501 A/R 123) is rated at 360 HP.  These engines had standard timing with 1.05 or .95 liner ports, and 17:1 compression.  I'm thinking with 1.05 liners and an A/R of 105 you would get 375 HP.

--Geoff

[windtrader]

Geoff,

What does the book show for the N motor with different injectors? Thanks

[Geoff]

Geoff,

What does the book show for the N motor with different injectors? Thanks

8V71N
N55 injectors 265 HP @ 2100rpm
N60.                 280
N65.                 305

[luvrbus]

Last time I counted there was over 60 injectors for the 8v71's even 7E65's can have dozen of fuel calibrations delivery setting plus timing settings,there are so many configurations on a DD that can be done it's not funny.I like getting outside the box on DD's myself  ,fire truck engines used N70's for the full 318 hp on the NA engines that was a factory setting   fwiw    

[bevans6]

They used to call the 8V-71N with the N65's the "318" because that was the gross hp number.  It got so any 8V-71 was called a 318, I think.  I expect 304 is the SAE net hp number, which is a lot truer.

[Geoff]

They used to call the 8V-71N with the N65's the "318" because that was the gross hp number.  It got so any 8V-71 was called a 318, I think.  I expect 304 is the SAE net hp number, which is a lot truer.

Data shows 316 @ 2300 rpm, but It is only factory on a firetruck.  I have also seen other HP ratings that have the above at 318 HP which the truckers used even though they probably had 304 HP.  N70's makes adv. timed 8V71's 318HP @ 2100 rpm's, but they start smoking.  The truckers always used the horsepower rating to identify their engine instead of the model.  I had a trucker call me back in the early eighties and tell me he had a 450.  I replied "You mean an 8V92TA with 9290 injectors?".  He didn't know that but that's how we talked in the DD shop.  Truckers always did the HP and maybe the model engine.  I don't know how they talk these days.  I think it's by engine model number but leave out the brand leaving me to guess all the time.

--Geoff

[windtrader]

The industrial 8V71TA with 7G65 injectors is rated at 330 HP@2100 rpms. 

8V-71N with the N65's the "318" because that was the gross hp number.  It got so any 8V-71 was called a 318, I think.  I expect 304 is the SAE net hp number, which is a lot truer.

fire truck engines used N70's for the full 318 hp on the NA engines that was a factory setting

Based on these statements it seems the difference in HP between a turbo and a Natural with upgraded injectors is not so much. 318hp Natural to 330hp 8V71TA. If so, it seems like a lot of resources to upgrade to the turbo for not much hp gain. The turbo seems to make its difference known in high altitude terrain as the Natural loses a lot of steam.

[bevans6]

When I first installed my 8V-71T ex-NATO engine it had N80 injectors and 405 gross HP.  Smoked pretty decent at full throttle too.  But the difference between it and the 8V-71N with 304 hp that it replaced was frankly astounding.  When I drove the original engine from Toronto to Nova Scotia, the hills on the 401 were mostly third gear and 50 - 55 mph, and the hills in Quebec and New Brunswick were worse, some second gear.  With the turbo engine I didn't shift down on a hill unless I was baulked by traffic.  I would hit the hill at 65 mph, be doing 60 at the top and the engine would just kind of start to grunt a bit as it took up the load.  Really neat. 

Brian

[Geoff]

Based on these statements it seems the difference in HP between a turbo and a Natural with upgraded injectors is not so much. 318hp Natural to 330hp 8V71TA. If so, it seems like a lot of resources to upgrade to the turbo for not much hp gain. The turbo seems to make its difference known in high altitude terrain as the Natural loses a lot of steam.

The 8V71TA can be pumped up to 375 HP.  6V92TA 400 HP, but for no smoke, 8 mpg, and long engine life 350 HP.

--Geoff

[luvrbus]

The last run of the 8v71TA truck engines were 400 HP a nice engine

[windtrader]

Thank you all! This has been a very educational thread, at least for me, and it's much clearer the finer points of injector and timing options and the effect on hp for both natural and turbo motors.