How many you FSJers got running 401s?

fulsizjeep

Just curious. We have 4 that are drivers - 76 Waggy, 77 Waggy, 77 J20 & 88 GW. One running 401 in a 76 Cherokee parts rig is waiting transplant to a 72 J4000 Camper Special.

amcjeepman

Still got it.

jeep_man_401

Still have my '76 401 (modified) powered J10...although it is currently waiting for me to transplant a NP205 and 14 bolt rear end.

dagazio

New to this forum and Jeeps as of this week. I just picked up a slightly worn and battered '74 Cherokee with a 401 body tag (also 5600#GVW, 2dr). I got it to tow my 1972 Glastron. The guy said it was a 360. The side of the block says 401. It kind of looks original, but I'll figure that out later. Originally, I just wanted to replace the bad radiator, but now I'm diving in deeper. When I got this thing home a few days ago, it looked pretty good, but since then, the rear main seal is leaking a little bit. So I was going to change it today, but wanted to check the compression before I bothered. Last night I pulled the plugs and started to check the compression. Evidently, I forgot how to do it, but that's not the problem. Number 2 cyl spark plug was covered in oil or gas and not running like the other cylinders. I saw no compression on #2 either. I put pressure in there and it wasn't leaking through the valves. I took off the valve cover and found a broken intake push rod. I knew it was running one cylinder off at idle and it did sound like one clanking set of rockers, which I think is on the other side of the engine still. Can these loose and worn rockers have bound the push rod causing it to break? So, I'm trying to figure out how much life is left in this motor - mileage unknown. I'm very tempted to change the rockers and push rods. I need to change that main seal and look at the cylinders and main bearing while I'm in there. My question to anyone is: is there a step by step somewhere on changing over to Chevy rockers? I keep reading about milling the stud bosses, but everybody keeps talking about roller rockers. Can I just screw in the 3/8" studs and factory Chevy stamped rockers, with "x" length push rods instead of the factory parts? I'm not sure of this motors future, I want to delay any rebuild. If the Chevy parts add up to less than the AMC parts and I can make them adjustable at the same time, I want to do that. I bought this for $700 and it ran fair enough, shifted good and stopped good. It has very little rust in the body too. There is some hood and fender damage. I do want it running asap and "fine tune" it later.

FuzzFace2

Welcome to the forum. I have to ask would you use Ford rockers on a Chevy or the other way around? If you do and it works then OK but not on an AMC. AMC rockers on an AMC! If you do go for rollers watch out as some say they work with ford & AMC but they do not. The rocker hits the retainer and pops the keepers out and then you know what happens! If using it for towing the stock set up is good no need to spend $$ when not needed. Now if you do want to go roller Harland Sharp makes a bolt on set to replace the bridge set up the head has now. Up till this bolt on set you would need to run push rod guide plates and that’s why the milling of the mounting studs. It could be the cam has a flat lobe and the rod fell out? It sounds like you are going to tear down the motor for a look see? If so you may want to throw a RV cam in it with new timing chain replace rings, bearings seals as needed, stock rockers & push rods and never worry about it again. If you do a new cam make sure you run “break in oil” or Bulltear’s oil because of the zink that is needed. Dave ----

ironman_gq

check the rest of the cylinders and make sure the rest of the valve train is in good shape including the cam and timing set you can get a look at the pistons and cylinders from the bottom when you replace the main seal. watch out for cracked skirts and scored cylinders. crank the motor over by hand so you can look at everything. you might even be able to see the cam from underneath to check for bad lobes or damage.

dagazio

FuzzFace2 wrote
Welcome to the forum. I have to ask would you use Ford rockers on a Chevy or the other way around? If you do and it works then OK but not on an AMC. AMC rockers on an AMC!......It could be the cam has a flat lobe and the rod fell out?
Dave ----

Yes, I would, if there was and improvement and cost less at the same time. Besides, I'm new to this AMC thing - I have no loyalty, but I've heard rumors that AMC may have done this themselves here and there.

...About a flat lobe, is it common for this on the front lobes? I still have to take it apart to find the rest of the push rod, but I would tend to think that the oil pressure is higher on the front of the engine and those parts would have the least wear. I'm assuming the oil pump is up front. Well, this is all pointless until I inspect. Of course, I could have just bought a set of rockers and rods for one cylinder and checked everything after installation!!!

If it makes you feel better, I have a high probability of replacing all of the rockers/parts and push rods with the AMC parts. I just need to check out the inside of the engine before I spend the money on that stuff.

sdf1968

One

rollen dean montoya

as you take things apart make sure you keep everything marked so when you put it back together nothing has been left out or put back in the wrong place. note: do not attempt to use chrysler parts on an AMC . they won't work. use only the AMC or good aftermarket parts specifically for the AMC V-8

FuzzFace2

dagazio wrote
FuzzFace2 wrote
Welcome to the forum. I have to ask would you use Ford rockers on a Chevy or the other way around? If you do and it works then OK but not on an AMC. AMC rockers on an AMC!......It could be the cam has a flat lobe and the rod fell out?
Dave ----

Yes, I would, if there was and improvement and cost less at the same time. Besides, I'm new to this AMC thing - I have no loyalty, but I've heard rumors that AMC may have done this themselves here and there.

...About a flat lobe, is it common for this on the front lobes? I still have to take it apart to find the rest of the push rod, but I would tend to think that the oil pressure is higher on the front of the engine and those parts would have the least wear. I'm assuming the oil pump is up front. Well, this is all pointless until I inspect. Of course, I could have just bought a set of rockers and rods for one cylinder and checked everything after installation!!!

If it makes you feel better, I have a high probability of replacing all of the rockers/parts and push rods with the AMC parts. I just need to check out the inside of the engine before I spend the money on that stuff.

On the “other make” rockers if it added power and was cheaper we all would be doing it 😉
Some Co’s IIRC say the fords will work but when you start to look at the geometry and action it is not right when matched up to a true AMC roller rocker. Some issues just off the top of my head roller tip not centered on valve tip adding side load to valve/guide, retainer hits on under side of rocker and pop the keepers out then dropped valve, rocker bottoms out on studs.
If you are looking at roller rockers and they use the same part number for AMC and any other make walk away (or run). Harland Sharp makes rollers for AMC 1 of them a bolt on with no machine work needed and none of the part #’s are used for any other make motor. I have not looked into Crane but they may be another just for AMC but you need to check first.

As for the flat lobe it could be any where on the shaft, I pull a race cam out of a 304 and had one in the center that was real bad I did not look at any others it went right in the trash can.
As you know till it’s apart it is going to be hard to tell why the rod fell out & broke.
Dave ----

fulsizjeep

Just got home from a 401 road trip to Arizona for 10 days. Here is the ride at Mexican Hat Rock yesterday. She rolled over 100k on Nov 21. It was a great ride with a roaring 401 and cheap gas! :?

tarior

dagazio wrote
...About a flat lobe, is it common for this on the front lobes? I still have to take it apart to find the rest of the push rod, but I would tend to think that the oil pressure is higher on the front of the engine and those parts would have the least wear. I'm assuming the oil pump is up front. Well, this is all pointless until I inspect. Of course, I could have just bought a set of rockers and rods for one cylinder and checked everything after installation!!!

If it makes you feel better, I have a high probability of replacing all of the rockers/parts and push rods with the AMC parts. I just need to check out the inside of the engine before I spend the money on that stuff.

Flat lobes are no more common in AMC V-8s than in any other make. AMC used only AMC parts in their motors.

jarcher401

Just picked up my 401 from the engine shop today for my 79 j10. yeh i know they stopped putting them in, in 78, but the cam took a crap in my 360 and had way too many miles on for just a cam replacement and had this 401 core since 2000 so i figured now was the time, life's too short not to enjoy it. got a 400 turbo with quadra-trac and 3:07 gears. also sprung for the edelbrock shorty headers and performer package. z & m jeeps took care of me with pre bent stainless brake lines and engine wiring harness, nice to see companies reproducing parts for these fsj's

jarcher401

Motor's all in and life is sweet again, no make that sweeter. This thing has loads of torque. The rebuild consisted of Edelbrock intake, cam, carb, timing set and shorty headers, and even shelled out the $280.00 to have it all balanced. This is my first 401 and has far exceeded my expectations. I'm gonna have a lot of fun at the stop lights.

Old Rugged Crosser

Hey, that is one sweet looking Jeep truck. Is the interior as good as the outside? You should be real proud of it. Take good care of it. There are not many around in that condition. :sa:

jarcher401

This is a shot from about a year ago, since I have the antique tags on I dont put alot of miles on but since the 401 install it is more of a blast to drive this year will most likely see more miles. As you can see the tow chain hook is still under the seat so I do still use it to haul and such.

fifesjeep

Better late than never but, :shock: nice truck man!!! :t: