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Author Topic: 8V71 Injectors - What are the different types? (Best pick for 4106 with V730?)  (Read 2167 times)
technomadia
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« on: June 25, 2013, 08:20:00 PM »

I've been reading the forum archives trying to understand the different injector options that have been used on the 8V71 over the years - and so far I haven't found a particularly clear answer that explains the difference between the 7E, C, N, and S prefixes on the various injectors I have seen mentioned.

The number that follows is the sizing - 55, 60, 65, 70, 90 -- this is the amount of fuel injected in each stroke, right?

Looking over an old 4106 GM part book, it indicates that the 4106 originally shipped with S60 injectors. And according to our manual, the engine was governed to 1650 rpm's and 235hp.

That was a long time ago.  I'm curious what the best choice injector setup is today, for a non-turbo 8V71 mated to a V730 transmission (instead of the 4-speed manual). Our engine is governed at 2,100 rpm now.

I've seen a lot of mentions of using an A-timed N65 setup for this configuration, but other threads have mention N60's and even 7E55's as being preferable.

Is the A-timed N65 optimal for fuel efficiency? Hill climbing? Clean exhaust / minimal smoke?  Driving around at altitude?

I did see one old thread say: "BTW the 'A' timing is a disaster in a GM bus because the torque peak is moved from 1200 RPM to 1600 RPM, results very disapointing hill climbing, even though the peak horspower is higher."

But others contradicted this. 

When paired with a V730 automatic, what is the ideal torque peak?

Are there any other injector / tuning options we should be considering during our rebuild?

Cheers,

   - Chris
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« Reply #1 on: June 25, 2013, 08:29:29 PM »

N70 with standard timing since you have a new radiator that will put you in the 300+ hp range if the shop if the shop doesn't know the setting I give it to them  If you use the G's don't advance the the timing when using 4 letter injector it's built in to the injectors
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« Reply #2 on: June 25, 2013, 08:43:38 PM »

If you use the G's don't advance the the timing when using 4 letter injector it's built in to the injectors

G's?  Thats a new one to add to the list.

So just what is the difference between a S, C, N, G, and 7E injector??

Are there any other variants?

Cheers!

  - Chris
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« Reply #3 on: June 25, 2013, 08:45:43 PM »

The guy I used recommend exactly what Clifford recommends;  N70s standard timing, 2300 to 2400 no load RPMs.  From what I understand this setup will smoke a bit in the hills.  How much, I haven't any idea.  The same guy told me use propane in the hills to eliminate the smoke and add horsepower!   I decide to go N65s A timing 2450 RPMs no load.  I get no smoke at all so I wonder if the N70s STD timing would have been acceptable.  

I agonized over this issue for a month btw.  It was horrible.  No one had experience, but the opinions abounded!
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« Reply #4 on: June 25, 2013, 08:58:06 PM »

E's and C's are emission injectors stay away from those Mark I putting a 8v71 together now and I am going to use the 70's I changed his over to a high capacity blower there wont be any smoke the 70's are a fire engine injector they can have a wide range he wants the full 318 hp and that is what he going to get 
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« Reply #5 on: June 26, 2013, 04:34:46 AM »

I have a complete set of N65's that came out of my old engine that were running fine when I took them out.  Let me know if you want them, we can make a deal.  They were installed with A timing.  The book shows timing pin settings for both A and S timing for those injectors.  If you look at the torque curve for the N65 A-timed vs say the 60 with standard timing, yes the torque peak moves to 1600 rpm from 1200 rpm, but the torque at 1200 rpm is still higher for the N65 A-timed engine than it is for the other engine.  More torque is still more torque...

Brian
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« Reply #6 on: June 26, 2013, 05:41:33 AM »

Where's the peak torque on the 70's?  The curious want's to know!
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« Reply #7 on: June 26, 2013, 06:06:15 AM »

You are going to be around 900 lbs  @ 1400 rpm ideal for your gearing the N65 with A timing was for trucks with a 10 speed it's not much good in a bus unless you have more than 4 gears
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« Reply #8 on: June 26, 2013, 06:25:03 AM »

Let me know when you choose which injectors you want, I have a guys number that sold me a great set of rebuilts for 187 shipped and he will give you two weeks to return yours without charging a core. Mine is a 6-71 so only 6 for that price. 
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« Reply #9 on: June 26, 2013, 06:31:50 AM »

I doubt the DD dealer will use anything but a authorized DD injector because of warranty they don't cost that much more  

Chris like others was just trying wrap his head around what all the numbers meant and there is a ton of them and he didn't even mention the tag color 

I am going to PM my injector guys number to Chris that can give him his answers as it all over the map with people on these boards
« Last Edit: June 26, 2013, 06:35:53 AM by luvrbus » Logged

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« Reply #10 on: June 26, 2013, 09:35:11 AM »

I had standard timed N65's in my 8V-71 with V730. Worked well, but would smoke at altitude above 5,000ft. Upgraded to turbo with 7G75's putting out 375hp and 1125lb/ft torque-now it is a pleasure to drive. Good luck, TomC
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« Reply #11 on: June 26, 2013, 11:59:45 AM »

Sorry I assumed that the injectors run about 125.00 each and mine was for a set, I also assumed you where doing the work yourself. My mistake   
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« Reply #12 on: June 26, 2013, 12:01:46 PM »

I still have no idea what the actual difference is between the S, C, N, G, and 7E injectors other than that C and 7E are for better emissions, which Clifford says "stay away from" but which actually sounds like a good thing?!?

What is the downside of these emissions injectors?

Looking over archive threads and talking to some folks - it seems that without a turbo a N70 will be prone to smoking (how much?) - especially at higher elevations, the N65 with standard timing will smoke some, but the N65 with A-timing should have essentially no black smoke at all.

Does this seem to match people's experience?

I certainly don't want to end up with a bus that belches black smoke while driving through National Parks, or while puttering around a campground.

Cheers,

  - Chris

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« Reply #13 on: June 26, 2013, 02:59:22 PM »

 I had N65 Brown tag injectors in mine with "A" timing,, It would not smoke at 10000 feet at 10% grade if your life depended on it. I often wondered if I was getting the horsepower that I should have expected with that combo. I devised a propane mixing system that made a large improvement on grades.>>>Dan (Clifford and I agree on few things, but one thing is agreed, that regardless of the injector size  (within reason) the timing of said injectors will make a major difference in power.
« Last Edit: June 26, 2013, 03:04:56 PM by Utahclaimjumper » Logged

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« Reply #14 on: June 26, 2013, 03:06:40 PM »

Emissions injectors means they are for emission-controlled vehicles. They won't make your engine run "cleaner". Proper maintenance and adjustments will. I say go with the 70's.

Sent from my SCH-I535 using Tapatalk 2
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« Reply #15 on: June 26, 2013, 03:39:13 PM »

[
Emissions injectors means they are for emission-controlled vehicles. They won't make your engine run "cleaner". Proper maintenance and adjustments will. I say go with the 70's.


 They will also "make your engine run like a small dog">>>D
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« Reply #16 on: June 28, 2013, 10:44:55 AM »

Now that we are inside our engine...  We currently have N70's.

No colored tags that I've seen yet.

Cheers,

  - Chris
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« Reply #17 on: June 28, 2013, 11:04:33 AM »

Just a question,  on our Eagle 8V71 what is the horse power of the orange C65 injector? Anything better for more horsepower without toasting it?

Don and Cary
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« Reply #18 on: June 28, 2013, 11:23:45 AM »

 Chris, you will normally see a number imprinted on a colored background, that's the "tag" color. The injectors we recently removed from Red Rider's engine were 70s on a yellow tag.>>>D
« Last Edit: June 28, 2013, 11:26:15 AM by Utahclaimjumper » Logged

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« Reply #19 on: June 28, 2013, 11:25:20 AM »

C65 typically is 304hp and 800lb/ft torque
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #20 on: June 28, 2013, 12:13:15 PM »

  Don Fairchild, hopefully, would be the best to answer this question, since he spent time on developing clean two strokes. I've wanted an answer to this question for a long time, and get the same general answers. I  know some have more smaller spray holes, and there is some differences on fuel ramp up from injector?? I would think that some of the newer design emission type injectors could be beneficial to clean up the exhaust, while making the same power.
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« Reply #21 on: June 28, 2013, 12:40:31 PM »

Injector are easy to understand if you read the book it tells you what each letter and number stands for then the rest you adjust with timing example N stands for needle valve C stands for crown valve the list goes on,

Now the colored tags lol
« Last Edit: June 28, 2013, 01:07:23 PM by luvrbus » Logged

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« Reply #22 on: June 28, 2013, 01:40:37 PM »

Injector are easy to understand if you read the book it tells you what each letter and number stands for then the rest you adjust with timing example N stands for needle valve C stands for crown valve the list goes on,

Our 8V71 book is vintage 1963, and it has both needle and crown valve overhaul procedures described - but the list doesn't go on any further than that. 

In our book the Nxx's are the needle valves, and the crown valves actually have no letter shown as a prefix.  Just "55" and "N55" for example.

No mention in our book about the other letter prefixes, and actually no mention about the practical difference between needle and crown valve, and why / when you would use one or the other.

And no mention at all about color tags.

It would be great if an online reference for this stuff existed somewhere. I imagine a more recent Detroit Diesel book might have more info too.

Cheers,

  - Chris
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« Reply #23 on: June 28, 2013, 02:05:06 PM »

We need a Wiki-Injector section!

The local DD parts manager admitted to me he didn't understand the difference in all the injectors.

Not much hope for us.
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« Reply #24 on: June 28, 2013, 09:38:07 PM »

Why would injectors sizing be a good online source that is only the tip of setting those engines up you have different blowers,valves,pistons,port height,blower gears, compression that goes from 15:1 to 21:1, 5 different sets of cams and different air box pressure DD kept that away from the public for years they only published in their manuals what they wanted you know 

Just now a few of the manuals for different pin setting and injectors to increase the hp have popped up most have been taken from other engines specs

 Who knows some day I may pdf my manuals on the Eagles board if I get some help lol

 I am not trying to be a smart @$# but some things are better left alone people murder those engines every day, I know I killed a 8v92 before by being hell bent no 60 series was going to out do me  Roll Eyes stay with the manual and it will serve one well
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« Reply #25 on: June 29, 2013, 12:32:08 AM »

I am not trying to be a smart @$# but some things are better left alone people murder those engines every day, I know I killed a 8v92 before by being hell bent no 60 series was going to out do me  Roll Eyes stay with the manual and it will serve one well

I love reading manuals - and I especially love reading the deeper level stuff that explains the deep details and the 'whys' and not just the 'whats'.

These engines are beautiful and magnificent pieces of engineering. Understanding the thinking that went into them is very gratifying.

But then...  I am the same why when it comes to computers...  I dig deep to know not just "stick cable A into slot B" -- I love reading the deep details about filesystem and operating systems and network protocols and CPU architecture.

I'm weird - I read documentation for fun...  *grin*

   - Chris
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« Reply #26 on: June 29, 2013, 05:54:15 AM »

Yep it is amazing how much info is on the net for the 60 series and another electronic engines the geeks always find away to copy and pirate the software some know more than the design engineers they cannot do that with a mechanical DD engine ask Don Fairchild lol 35 different injectors for a 8v71 and 30 different setting(configurations) for each add the old HV and S probably over 60  all done by hand no computer  
« Last Edit: June 29, 2013, 07:50:28 AM by luvrbus » Logged

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