258 Rebuild/Cam question

[PoliceMonkey161]

Hello All,

So, got my new garage/shop built and everything moved in. I started the rebuild of my 86 CJ and decided not to go with a crate engine this go around, rebuilding the engine myself. Running into a question with the cam, is a cam thrust pin required on the 258? I have not found a direct refference to it in any of the AMC writings, but have read about it on other forums and I see the Chrys/MOPAR books refference it for the 4.0L. The best I can come up with is that "0" lash (end play) is maintained by the dist. and oil pump shaft?


I did some research and AMC did have a part number for it, but no one has one available. It was replaced by a MOPAR part number, or so it seems (MOPAR's part is also very hard to find).

Thanks in advance!

 

[greg92jeepxj]

I regret that any research I am doing does not turn up anything more than you have already found , I am frustrated , and its not even my engine. My older books do not mention a cam thrust pin or spring for the 258 , but a photo in one ( CHILTON ) showing inside cover , shows a pertrusion that is similar to the 4.0 which leads me to expect the 258 will use the same or similar spring and thrust pin ? My 1992 Chrysler shop manual confirms one . Yes, the spring seats into the cam retaining bolt followed by the thrust pin . If I read your post right , I see your beginning the rebuild of the jeep , but , you did tear down the 258 ? My question is , did you find that the cam sprocket retaining bolt is bored for a spring ? Wondering if the timing cover on your 258 has this protrusion and can you use the same as a 4.0 ? I did find also that end play is maintained by distributor/oil pump as well for the 258. I did not find this for the 4.0 . Now wondering as you , do you use the thrust pin or not ? I certainly hope , as you do , someone has better reference to the 258 in terms of disassembly/assembly. Thrust pin/spring or not? Sorry not of better help.

 

[PoliceMonkey161]

Hey Greg...Thanks, I'll need to look at the covers I have at home (have several). I've taken many of 258's from various years apart and can't say I've ever noticed said "pin"? Ran across a thread some that made mention of a cam pin being installed and that got me wondering??????


The engine that I'm using was manchined and rebuilt about 500 miles ago, eventually the owner at the time came across a Corvette engine to swap in it's place. So, I acquired the 258 on the cheap but it had been sitting for a while, needed new paint (well for my taste anyway) and was not truely built correctly (some corners where cut). But the bores, crank and pistions all checked out OK, so I decieded to replaced the rings, bearings, timing set, etc. to be on the safe side.


I will likely install the new cam and check for end-play and go from there..... Unless someone else has a positive answer. Based on what I have seem and read, if I use the heavy (thick) timing cover with the dimple, not sure how the thrust pin would work? Surely the pin would not lineup and ride on the dimple?

 

[greg92jeepxj]

I sure share your confusion . I even found a write up on jeep strokers.com you may have seen regarding installation of a non thrust plate cam into a thrust plate block , just to add more confusion . But you will find the write up interesting regarding the timing covers ( dimple and non-dimple) . I wish I can remember the timing chain job I did with a friends mothers AMC hornet 258 , but I was just a kid and can't recall the details , sorry. My shop manual illistrates the preload bolt ( countersunk) , spring and thrust pin , but no clear picture of inside of cover. I can only assume it lines up on the 4.0 , but has got me guessing on the 258 ? I really hope someone has a AMC shop manual for this engine to confirm , yes or no. I guess if the original type bolt was used on the cam sprocket , it would tell us if it is bored for a spring to go into ? But the 258 was rebuilt and we don't know that . I guess we're praying for a shop manual to help , I know you want it done right and I would not settle for less either . I am hoping for the best for you as I know you do not need this small (but important ) detail to hold up progress. I want you to get that CJ out there too ! Well , I'll keep looking too , hope we find the answer soonest ! Thanks for your reply and best of luck to your CJ build ! You know we would love to see pics of the prize upon completion !

 

[greg92jeepxj]

The thing that bugs me the most too is why if the distributor/oil pump maintain zero end play will it need a thrust pin and spring ? But looking at the CHILTON book I have with regards to chain and sprocket replacement , the picture did show a dimple on the inside cover , assuming it was to use a spring and thrust pin ? The correct bolt , confirmed by a shop manual should confirm if bolt is countersunk for a spring and that a spring and thrust pin was used ? I sure hope so .
I really hope someone on the forum has got an AMC shop manual to help ?

 

[flatie46]

First of all I must say I like your style. Anybody can buy a crate engine, very few rebuild or build their own anymore. It's becoming a lost art and also a lost sense of pride. It's awesome to fire up one you've sweated the details on and built with your own hands.

Now I've never been inside an AMC 6cly and can't answer your question but if you call one of the better performance cam companys they could answer your question. I don't know if Bulltear deals with the sixes but if they do you might want to call or email them. They make excellent perfomance parts for AMC stuff. Good luck with the build.

 

[PoliceMonkey161]

First.....Thank you Sir! You have summed up why I wanted to rebuild this engine, nothing wrong with a crate engine- installed them in the past. It's not just the pride but I also wanted to select my own parts for the build. Since one of those parts was a Comp Cam, I will give them a call (why did I not think of that?).


Thank you again!

 

[greg92jeepxj]

I totally agree . Knowing that the cam selected for the rebuild is a highly reputable company , they will no doubt properly advise their customer proper installation and all parts entailed .
i am quite confident that the rebuild will go just fine and you will be very happy with your jeep .
looking forward to pictures of it on the jeep build !

 

[greg92jeepxj]

Hey , I totally forgot to mention . The jeep strokers.com site has an article that I was unaware of . I don't know if you knew , but I just recently learned myself what hardcore jeep builders have known for ions is to take a 4.0 H.O. head and put it on a 258 block. Just wondering if you would be interested in such a mod ?

 

[PoliceMonkey161]

Hey , I totally forgot to mention . The jeep strokers.com site has an article that I was unaware of . I don't know if you knew , but I just recently learned myself what hardcore jeep builders have known for ions is to take a 4.0 H.O. head and put it on a 258 block. Just wondering if you would be interested in such a mod ?

Yes, I am aware. I just helped another member figure out what he would need. But no, I personally am not interested. I like my Jeeps as they where from the factory (well.....Close to it anyway).

 

[greg92jeepxj]

I hear that . I thought for a minute that I might want to build a CJ/XJ , but I actually am quite fond of the factory CJ personality myself. Well , that might just mean I would have to build two CJ's , wouldn't I ? I better not get any ideas as I don't presently have the cash to build one , let alone two . Before that , my XJ needs rocker panels , some shocks as long as I'm spending money on it again :shades: I could make a list just perusing sites like QUADRATECH , which I blame our forum for turning me on to it . I sure appreciate that ! I figured your up on the 258 hot rod tip , nice to be able to make cheap HP if you need to . If I ever fall into a 258 again , I will jump right in and build one ! Hope your jeep comes together soonest , I know you can't wait either, but I know you got the patience to wait until its built your way , and that's the only way !
Best of luck with it and will look forward to pics when the paint dries ! :welder:

 

[PoliceMonkey161]

After talking many folks (who have actual experience in rebuilding this engine)......... No Cam Thrust Pin is required if using an orginal (heavy) timing gear cover (with dimpable). The thrust pin is only use in the post 86' and 4.0L engines (revised- these covers can be interchanged). If you have an oil bypass check value relief/ bypass (pre- 87' 258) you will not need a Cam Thrust Pin. This is only used in Chrys. blocks....... AMC used the "0" backlash obtained by the the dist./ oil pump shaft and was yelled in place by the dimple (only as a fail safe)! This must be checked prior to start-up!There is confusion about this with regards to the 4 cylinder AMC and GM blocks (2.5/2.4L engine????.......).


I truely want to thank Greag and Flatie for guiding me in the right direction of who to call.......... I will be posting the rebuild in the "How to Section" as I go. Maybe someone else will not have to make all the calls I did??????

 

[greg92jeepxj]

Your very welcome but I know it will be thanks enough to us both to see that jeep on the road again soon .
A man and his jeep , now that's a beautiful thing :shades: