Exhaust bosses and manifold questions

This is the place to get help with technical matters concerning your M151 jeep

Moderators: rickf, moose53, Mr. Recovery, raymond

Post Reply
Grasshopper
Corporal
Corporal
Posts: 48
Joined: October 13th, 2016, 9:58 am

Exhaust bosses and manifold questions

Post by Grasshopper » July 5th, 2017, 4:46 am

Hi all,

Rookie question but can anybody post a picture of a new style cylinder head boss and an old style, as I'm not sure which I have? I'm currently removing the exhaust manifold (and all that entails!) due to a leak that worsened over the weekend and badly affected running, and there were no gaskets on the manifold. I'm intending to fit gaskets and have ordered a kit.

After a good soaking, 2 bolts still snapped and they went with minimal force which makes me think that the bolts were hardened but not tempered. A retired tool maker friend of mine said it in not unusual to find stainless bolts where this is the case. One of the bolts drilled through fairly easy, but the other was a right PITA. Still got to finish drilling them, gave up when my arm got tired. Has anybody replaced the bolts with stainless studs, and used brass nuts to secure the exhaust manifold? ALso is it worth installing a new manifold, or just gaskets on the old one?

Thanks in advance,
Vince

Surveyor
2nd Lieutenant
2nd Lieutenant
Posts: 842
Joined: November 13th, 2015, 3:56 pm
Location: Cajun Country

Re: Exhaust bosses and manifold questions

Post by Surveyor » July 5th, 2017, 9:37 am

Newer Style

Image

Old Style

Image
1960 M151 Run #1 (working on it) 60 in 2020!
"There is one nut on a M151 that is very difficult to remove....." - K8icu
"She ain't a Cadillac and she ain't a Rolls, But there ain't nothin' wrong with the radio" - Aaron Tippin
Image

rickf
General
General
Posts: 16275
Joined: November 26th, 2007, 1:28 pm
Location: Pemberton, NJ.

Re: Exhaust bosses and manifold questions

Post by rickf » July 5th, 2017, 9:46 am

The stainless bolts are the ones that break off due to the soft stainless bolt galling the threads. Definitely go with ordinary grade 5 bolts and some never seize. If you have the early head and are using gaskets then you will need to double up on the intake gasket because the exhaust gasket will hold the manifold out on an angle. Use Permatex #3 on the intake gaskets, very thin coats. Pay very close attention to the torque specs in the manual since they are different from gasket to no gasket and they are a lot less than you would think. Also they are a different spec on the center than they are on the ends. If they were tightened too much before then the exhaust manifold will be egg shaped and needs to be replaced.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

Grasshopper
Corporal
Corporal
Posts: 48
Joined: October 13th, 2016, 9:58 am

Re: Exhaust bosses and manifold questions

Post by Grasshopper » July 5th, 2017, 10:13 am

Thanks very much for the clarification, it seems I have an old style head on my A2. I did note the different and low torque settings in the TM, which I intend to follow carefully! I think part of the original problem on mine may be that the exhaust manifold flange cap screw (where the down pipe attaches) was missing, so could have been a contributory factor in the original blow from the centre cylinders.

Husker
Master Sergeant
Master Sergeant
Posts: 312
Joined: August 26th, 2016, 1:52 pm
Location: Fairfax Virginia

Re: Exhaust bosses and manifold questions

Post by Husker » July 5th, 2017, 10:59 am

Is there anyone that has or still sells new style heads?
US Army Fort Rucker

Surveyor
2nd Lieutenant
2nd Lieutenant
Posts: 842
Joined: November 13th, 2015, 3:56 pm
Location: Cajun Country

Re: Exhaust bosses and manifold questions

Post by Surveyor » July 5th, 2017, 6:06 pm

Got one from Blake Callaway at Red River Parts in Texas about a year ago. Back then his prices were $495 for NOS and $125 pulled/used plus shipping. I went with the used and the one I got looked brand new.

Blake Callaway
Red River Parts & Equipment
ph. 903-547-2226
fx. 903-547-2629
bcallaway@redriverparts.com
1960 M151 Run #1 (working on it) 60 in 2020!
"There is one nut on a M151 that is very difficult to remove....." - K8icu
"She ain't a Cadillac and she ain't a Rolls, But there ain't nothin' wrong with the radio" - Aaron Tippin
Image

Grasshopper
Corporal
Corporal
Posts: 48
Joined: October 13th, 2016, 9:58 am

Re: Exhaust bosses and manifold questions

Post by Grasshopper » July 7th, 2017, 6:41 am

Pleased to report that the studs are pretty much all drilled out, having a pack of cobalt drills to hand was most useful! Took my time (which is unusual for me) and completed the operation over a couple of evenings and all went to plan. I'm picking up a set of new UNC taps and drills at the weekend so I can chase the threads, and I'm expecting delivery of new bolts, inlet and exhaust gaskets imminently. I've printed the relevant section of the TM and will follow it careful, having been warned that the torque for the various bolts differs. For a job I was dreading, it's all going to plan which makes me suspicious...

Grasshopper
Corporal
Corporal
Posts: 48
Joined: October 13th, 2016, 9:58 am

Re: Exhaust bosses and manifold questions

Post by Grasshopper » July 21st, 2017, 4:03 am

Update - having chased the threads with taps, I used all the new gaskets, fittings, bolts, nuts and paraphernalia that came in the modification kit. I followed the instructions to the letter. I ran her up, let her cool and then re-torqued the next day. I was surprised at just how much the bolts screwed down on re-torque! (For the record, I purchased a new torque wrench as I didn't have one in the correct range, and set it up on the torque meter at work. I've probably spent 4 times as much on tools for this task as I did parts!). She's all back together and starts better, sounds better and I can now hear that the valves need setting (not too bad though).

Off for a road test this evening as I've not had a chance yet. It will be interesting to see if the flat spot is still there as she now starts and runs (on no load) way better, and I have re-set the mixture screw as she wouldn't entertain running at the previous (rich) setting. Previously I had to have the choke partly out to overcome the flat spot (as seems to be necessary on some MUTTs from what I have read).

Post Reply