exhaust manifold bolts

[68impalass]

Does anyone know the length of the exhaust manifold hold down bolts? Grade 5 or 8? I am installing new head and do not want to use stainless bolts. thanks much

[rickf]

Smart decision on the no stainless! Grade 5 is fine and if you can get the cad plated ones even better. You can go with grade 8 also since a lot of those come plated. It is overkill but we are not talking all that many bolts. Length I do not have right off but if need be I can measure mine tomorrow.

[Surveyor]

The -34P parts manual does not list bolt sizes but the -20P does in this case. Download manual links are at top of this page. The pages you are interested in are PDF page 30 and 31... Figure 10 or actual manual pages 20 & 21. I believe Rick recommends grade 5 because if you ever break the head of an 8 later down the line it's more of a pain to remove. If you ever run across a bolt that does not list length, pitch, etc. you can usually type in the Federal stock number or part number from the manual into a google search and you'll get a number of parts cross-reference websites which will have the information you need.... "teach a man to fish...."

Edit - dang it, he beat me by a minute.

[Hambone]

https://www.ebay.com/itm/HEAD-BOLT-M151 ... 2940788261
Scroll down

[rickf]

Hambone is daydreaming again and not reading the posts. MANIFOLD bolts, to replace the stainless ones.

[Hambone]

I'm practicing for my speed reading class, I have a D-.

[svramselaar]

hi

they have six stripe`s on it so i think grade 8
see below for the type and length

https://www.ebay.com/itm/M151-M151A1-M1 ... 2298877410

george

[rickf]

There you go, 3/8-16 X 1 1/2". If you live near a Tractor Supply you can get them there cheap. I think the grade five there are plated also. I seriously doubt you need grade 8 since there is no shear force on the manifold bolts and if I remember correctly the torque is in the 18-23 lb. range so nowhere near yield breaking force. But like I said before, the grade 8 bolts are usually cad plated so that means no rust.

[m3a1]

Tractor Supply's grade five are not plated. They have a sort of varnish coating on them and they rust quicker than you can say Jackie Robinson. A good fastener supply store will have exactly what you want, however you want it.

[kwb]

Hello friends ! This is my first post on the G838. I have quite a few hours behind the wheel of a M151A1. US Army 1971-1973 but not much time working on them so i'll have a few questions during the rebuild of my A1. Now with the legal stuff out of the way, why should stainless manifold bolts not be used? Thanks, Ken

[rickf]

Stainless steel is soft and when it is screwed into the cast head the threads gall, think tiny fish hooks pointing backwards in the threads. Now, when you try to take them out those tiny fish hooks grab the threads of the head and bind up and the harder you try the tighter they bind and the gall in the other direction. Now it will not go either way. And no amount of penetrating oil is going to work. Regular oil would be better since you need lubrication which most penetrates are not.

[raymond]

My only recommendation here is high heat anti seize.

[m3a1]

Righty-o. Stainless has a lower iron content (so far less chance of corrosion) but as a result, it is far softer metal. There were some good examples of this very problem on youtube. One video shows this fellow simply running a stainless bolt in and out of a nut without obstruction. Eventually it binds up rock solid. So if you use stainless you're trading corrosion resistance for deformation.

Welcome to the G838!

[68impalass]

Great, i appreciate all the replies, went with grade 8's