HD5 injector question
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Construction and other equipment
Forum Description: everything else with orange (or yellow) paint
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=209051
Printed Date: 09 Jan 2026 at 10:31pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: HD5 injector question
Posted By: random_farmhick
Subject: HD5 injector question
Date Posted: 24 Nov 2025 at 4:34pm
On my HD5 I was doing a bunch of work, and decided since I was so close I would pull the valve cover and check the valve lash and see what's there for injectors. Now I don't know what to do, haha. Valves were pretty close to the book, so fine tuned those, checked injector timing and its WAY off according to the book, BUT still in a spec that is a detroit spec... According to the book it should be 1.484, and it's actually at 1.460, but it also has 70 yellow tag injectors in it, which the book calls for 60 injectors I think. Google search shows 1.460 is what many people set 70 injectors at. So I don't know what to do... It wont get any easier to change it unless I pull them for some reason. It doesn't start TOO bad, but does smoke a little more white than I'd like to see, especially until it warms up. If it was yours, what would you set them at? The only other real detroit experience I've had was a silver 6-71tta in my brigadier dump truck that had 7a77 injectors in it, and that's what it called for so that's what I went back with.
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Replies:
Posted By: DMiller
Date Posted: 24 Nov 2025 at 5:04pm
| Set to 1.460, otherwise will at full throttle overfuel. |
Posted By: random_farmhick
Date Posted: 24 Nov 2025 at 5:22pm
Is that the difference in the 60 to the 70 size injectors? Or just in general? |
DMiller wrote:Posted By: Ray54
Date Posted: 25 Nov 2025 at 11:37am
| Many of the DD engines in the crawler here had bigger injectors for few extra ponys. Have cousin farming with AC HD 9's. They have much newer heads from V8 DD with extra valves, and bigger injectors for major horsepower increase. |
Posted By: SteveM C/IL
Date Posted: 25 Nov 2025 at 2:22pm
| My 8V92TTA was at 1.484 with 9A90's? Think my beginner 6-71 was same with N65's. PO said had later advanced cam. Too much time passed to remember it all. |
Posted By: Coke-in-MN
Date Posted: 27 Nov 2025 at 12:31am
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HV7 is in the 2-71 as stock injectors ------------- Life lesson: If you’re being chased by a lion, you’re on a horse, to the left of you is a giraffe and on the right is a unicorn, what do you do? You stop drinking and get off the carousel. |
Posted By: DMiller
Date Posted: 27 Nov 2025 at 4:06am
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That was a long dormant braincell fire off. Knew that as was taught that in the 1970s and cannot remember who or why. Except was to limit overfuel piston coking in the 71 series smaller engines as opposed to the V or inline six series with larger injectors. Believe came from a mechanic at Western Diesel when I was gaining my DD 71 series overhaul cert. around 1977. Edit: Also had some pertinence of Trunk type vs Crosshead piston styles. Smaller engines tended to be Trunk type. |
Posted By: Eric B
Date Posted: 01 Dec 2025 at 4:18pm
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Smoking white is a sign of over-fuelling. Likely, the 60's or 65's would be a better match for your application and for the type of work it is intended to do. As for injector timing, the factory setting of 1.484 is rather lame (retarded in my opinion) in terms of performance. It's ideal for easier cold starts however. At 1.460 cold starts are more difficult, especially if the engine is worn but you will have really good 'snap' in terms of acceleration and the best 'power-band' is moved up to the higher RPM range. Over the decades I've owned 14 2-cycle Detroits in trucks and other equipment. Some never needed any injector work but on the ones that did, I found the 'sweet spot' to be 1.470. This setting gives good cold starts, a nice 'power-band' and very good acceleration. If you do go with 60's or 65's, you will notice more difficult cold starts in cold weather especially. Trucks are much in need of good and snappy acceleration with a 'good power-band' whereas a bulldozer or other equipment don't need those features as much. ------------- Currently- WD,WC,3WF's,2 D14's B. Previously- I 600,TL745,200,FL9,FR12,H3,816 LBH. Earth has no sorrow that Heaven cannot heal! |