L34 Head Bolts or Studs?

[tom rider]

I am having to replace head gasket and shave head, was wanting to put in new head bolts, head bolts I took out are 3 1/4" with around 18 threads, according to Kaiser they are 3 1/2" with about 8 threads, I also need the 2 head to block bolts, any input appreciated

[gmwillys]

Tom,

The 1/4" extra bolt length will ensure that you'll have enough thread engagement with the block, so there is no fear there. Somewhere along the line someone used some hardware store fasteners to secure the head. You can go two routes, you can use 15 of the bolts and washers to secure the head, or 15 of the studs, washers, and nuts to secure the head. The F head is similar, except for the pesky short bolt that hides below the carburetor. Studs versus bolts is a pretty close battle. Bmorgil will chime in with his vast high performance engine experience for his thoughts on the matter.

[bmorgil]

Tom, I would not use bolts on the L head. All L 134s came with studs. The amount of thread depth in the block and the thickness of the head and the length of the bolt shoulder, causes most bolts to bottom out on their shoulder before they clamp. The washers are installed to be sure the shoulder doesn't bottom, it must be checked. This causes two issues, first the head gasket will not receive sufficient clamp. Second the shoulder on the bolt usually cracks the head when it bottoms before the head is clamped. Any machine shop that has worked on a 134 will be familiar with cracked blocks at the head bolt threads. The F Head uses bolts. As gm eluded to, someone has used hardware store bolts. If you have an L head, it is important you check the bolt threads in the block for cracks as we spoke of before.

Studs are far superior for heads for a few reasons. They are usually made of a higher strength material. When installing and removing, you are working the fastener threads and not the block threads. The clamp from studs is more consistent. In the case of the L Head, the studs maintain the clamp on the relatively "thin" flat head without bottoming. They do usually cost more and take more time to install.

In high performance, nothing beats a good set of studs on the Heads as well as the main bearings. The fasteners fail in tension. The strength provided by some stud materials can be fantastic. The studs eliminate fastener failure in those locations. Under big horsepower numbers the cylinder pressure is extreme. The head fasteners can and sometimes do stretch and relax. If they are not strong enough they can stretch and fail or stretch and release the gasket seal. In stock rebuilds, if it came with studs use studs and if it came with bolts use bolts.

[tom rider]

thank you for the input, I will order new studs, much appreciated

[gmwillys]

Bmorgil is the man with the right answers.

[tom rider]

When ordering from Kaiser is this the correct stud Part # 349368

[bmorgil]

Two of these, https://www.kaiserwillys.com/products/cylinder-head-to-block-long-stud-2-required-fits-41-53-jeep-willys-with-4-134-l-engine/ for under the oil canister bracket.

And 13 of these, https://www.kaiserwillys.com/products/cylinder-head-to-block-stud-fits-41-53-jeep-willys-with-4-134-l-engine/ for the rest.

The manifold also came with studs and they work much better than bolts. https://www.kaiserwillys.com/products/exhaust-manifold-to-block-stud-kit-8-piece-fits-41-71-jeep-willys-with-4-134-engine/

Use black silicone on any threads that go into the water jacket on the manifold. When installing the studs do not tighten them into the block. Clean the threads in the block well and chase the threads if you have a thread chaser. Leave them very loose so they can "wobble" a bit. Drop the head on and then run the studs down till they bottom. Do not tighten them any further. Finger tight is all they should be.

[tom rider]

Ordering now, very good info on the chasing and how to install studs, I did not know that

Already ordered manifold studs and gasket as it was leaking and had bolts

Thanks

[bmorgil]

You bet Tom! Keep us posted. Take some pic's of the project. We just love the pic's of progress!