Allis Chalmers HD5 cylinder head cracked
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=161418
Printed Date: 21 Aug 2025 at 2:23pm
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Topic: Allis Chalmers HD5 cylinder head cracked
Posted By: hodaka
Subject: Allis Chalmers HD5 cylinder head cracked
Date Posted: 28 May 2019 at 10:56pm
| While disassembling the engine in my HD5 I was cleaning and inspecting the cylinder head I noticed it is cracked between the exhaust seats and the injector tube. Is this a common problem with these engines? Is it repairable or should I find a different head? |
Replies:
Posted By: DMiller
Date Posted: 29 May 2019 at 6:44am
| 2-71 Detroit I take it? The head can be repaired or exchanged, try Chapin Cyl Head Chapin IL. |
Posted By: hodaka
Date Posted: 29 May 2019 at 1:11pm
|
yes it is a Detroit 2-71. Thanks for the info. Will check them out |
Posted By: DiyDave
Date Posted: 29 May 2019 at 5:52pm
|
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Posted By: Eric B
Date Posted: 29 May 2019 at 7:10pm
|
I take it you've been running this machine yourself? If so, you would know if you've had coolant leaking somewhere? I've had many Detroits over the decades and nearly every time I would pull a head there would be small cracks around the injectors. The first few times I would have the heads repaired or exchanged. After a few years I thought just a minute here... I've never had a coolant leak from these tiny cracks. One time after I had a head repaired and rebuilt spending good money I decided to do a full in-frame. The same head came off after only a few hours and wouldn't you know cracks were present again. Ever after that when I removed a Detroit head and noticed those tiny cracks I just put the heads back on and never had a problem whatsoever. That doesn't mean that any or every crack is problem free but I wasn't going to play the guilt game the machine shop would use to get more work. Unless the the crack or cracks in your situation go all the way to the injector tube or to the valve seat I would re-use the head the way it is. You can take the head in and have it pressure tested and then you will know. ------------- 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! |
Posted By: hodaka
Date Posted: 30 May 2019 at 10:57am
|
Thanks Ive only run this machine from the trailer to my shop. It would barely run. The crack is pretty significant. I can almost get my fingernail in it. It runs all the way from the injector tube to the exhaust seat. |
Posted By: Eric B
Date Posted: 30 May 2019 at 5:55pm
------------- 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! |
hodaka wrote:Posted By: Coke-in-MN
Date Posted: 31 May 2019 at 12:20pm
|
This is a real common flaw it seems in the heads - crack from copper injector seat outward . UNLESS it shows sign of coollant bubbles or loss or overheating - RUN IT . I had my head repaired as the valve seat also showed signs of problem and the shop I had grinding and replacing valve said they would not put new seat in with the crack - also they were not familiar with 71 heads So got a rebuilt head - with new injector tubes and new guides and seats - used 4 new valves and good to go ------------- 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: Coke-in-MN
Date Posted: 31 May 2019 at 12:23pm
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Posted By: Coke-in-MN
Date Posted: 02 Jun 2019 at 11:03am
|
I have a complete 2-71 engine (core) that came with one machine I bought as a extra said low oil pressure so former owner replaced it with a engine from generator - never opened it up myself . Will sell as is . ------------- 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: 02 Jun 2019 at 12:44pm
| Hard for a engine with usually 5-25 lbs oil pressure to have 'Low' oil pressure!!! |
Posted By: Eric B
Date Posted: 03 Jun 2019 at 5:58pm
Years ago I had a 6V53 Detroit that used to come right down to "0" oil pressure at idle in summer heat... did not sit well with me. I was told by knowledgable Detroit people that if you don't reach 30 lbs oil pressure at governed RPM you are playing with trouble and rebuilding is in order. (I guess I'm a little off topic for this thread). ------------- 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! |