Cj5 Exhaust Valve Variations

Hi all,

I'm deep in the middle of a valve job on a '59 CJ5, f-134 engine. I've removed the exhaust valves and have some replacement exhaust valves on hand. When I tried the new valves in the old guides, they won't go in. I've attached a picture below...new valve on left, old valve on the right. It's hard to see in the picture, but the new valve stem is slightly wider than the old. It'll go in the guide about 3/4", but no further. The new valve is Omix Ada, which I know isn't the best quality, but the difference seems more than just poor quality. The new one is longer than the old as well, and the old spring retainer locks won't fit on the new valves. The second picture shows my current parts, retainer lock, retainer, etc. I can't find any new valves like my old ones, and most of the parts suppliers I've spoken to didn't even think there was a different style of valve. Does anyone know anything about my valves? Can replacements be found? Do I possibly have some non-CJ5 valves/guides, and need to replace the guides as well?

thanks!

 

I'm not certain, but the new valve in your picture may be the later style (928342) which used a rotator cap.

The earlier L-head type (637183) might be what you need.

Possibly the one linked below, but please confirm with someone who knows more about it.

Been too many years since I did a rebuild. I recall talking to a machine shop about a similar issue on my 1950 Willys Jeep F-134 pickup forty years ago, but I don't recall the exact answer.

Omix-ADA 17415.01 134CI F-Head Exhaust Valve for 41-53 Willys Models | eBay

Possibly another idea may be to lightly ream the guides and get some rotators. Just guessing.

 

According to the FSM both types (L-head and F-head) should be the same stem diameter for the exhaust. = .371" - .372" Stem to guide clearance .0025" to .0045" in both cases.

However the F-head is 5.909" long, while L-head is 5.797" overall.

 

I'd suggest you get a micrometer and start measuring such things - https://www.amazon.com/gp/product/B0045VKF5K/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

PeteL gave you the diameters, and they will also be in the FSM - another must-have item for this job.

One way that worn valve guides are addressed is by fitting valves with oversize stems. If these valves have slightly larger diameter stems than what came out, it could be to your advantage that the new stems are oversized.

You sure you don't have an intake there instead of an exhaust? I'd expect the intake side could use longer valves, due to the overhead configuration. I'd also guess the L-head and F-head exhaust valves would the same length, but maybe not.

 

I dont think that just throwing in new valves with old guides and seats will work real good without some machining to address the seat and guide wear. Short of a full rebuild, a thorough cleaning, carbon removal, measurement and if good, a lap job might be the most cost effective option. Nothing says you can't use old good valves from another engine if your seats are serviceable either. Aren't the exhaust valves on F134 sodium filled?

I do recall the rotator lifters not being available over 20 years ago. I would not buy a single engine or drive train component from Omix. To spend the money to fit their parts seems counterintuitive.

People have stated otherwise, but I have used old valves in old heads with a good cleaning and a thorough lap job to make leaking old valves seal up and run real good. I am daily driving a jeep that I have done that, spent minimal money, had no professional machine work done and it runs very well for what it is. I love the idea of all new parts to be certain it will run great, but will you notice the difference in power or performance if it just doesnt leak or burn oil and still runs fine?

Old mechanics would fix things and not just replace. Sometimes you need to replace, but often on old engines you can just fix them.

 

Generally - A real head refurbishment needs tools and equipment that the shadetree just can't afford, let alone justify owning. Most people would send the head out to a shop for refurbishment.

The exhaust valves are the ones that see the most abuse, and most often need to be replaced. A valve job means grinding the valves and seats, and this always reduces the thickness of the valve margin. When that margin becomes too thin, the valve must be replaced. If the margin is sufficiently thick, and the valve seals (ie is not eroded by predetonation or exhaust gas - "burnt") there is no reason to replace the valve. So old valves in an old head isn't necessarily forbidden... intake valves are commonly reused. Exhaust valve failure is often the reason for a head rebuild, so exhaust valves get replaced quite frequently.

Just looks to me like you have the wrong part. Even more likely if you had these valves on hand. Walcks sells a lot of these parts - maybe you could give them a call Exhaust Valve F Head 4 Cylinder

 

Here you go-Jeep Willys CJ3B M38A1 Jeepster Station wagon Pick up Truck NOS Exhaust Valve | eBay
Listed for Wagon, Pickup and Jeepster, I only show them listed for M38/M38A1 L and F Head. Part # 800829

 

Wrong part was my initial thought too, but I double-checked everything and this was the part specified for the engine...it's definitely not an intake valve. The picture shows my new exhaust and intake valves together. To add to the story, I took out an intake valve today as well, and my replacement valve wouldn't fit there either! They look identical, but the new valve must be just slightly larger. If anything, I would have thought my valve guides would be worn and the new valves would be loose, not tight. Sounds like I may have gone about as far as I can with my garage tools, and it's time to let the pros take over. I've come this far, might as well ensure it's done 100% correct.

 

That's definitely it. I just don't understand why new valves wouldn't fit in the same guides as the old...everything I've found indicates that the two styles used the same guides.

 

G503 Military Vehicle Message Forums • View topic - M38A1 Exh Valves

Having that part number "800829" made searching for info much easier. Found this thread from someone who had the same question I did, although it sounds like he was able to use either valve style in the same valve guide. That's the thing that has me stumped.

 

Worn guide plus varnish? Part out of spec? Typically the guides are sized to the valves at installation with reamers.

You have not measured the stem to see if the Omix part is in spec. Remember it's an Omix part ...

 

My old parts book, admittedly sketchy, also shows that number as military only.