Just rebuilt 258 now it's tapping help!

[djdelee421]

I finished my very first rebuil on a 258 it's got new everything block was magna fluxed bored .030 over and honed. Machine shop rebuilt head It started tapping during my break in 2k rpm for 20 mins. Id appreciate all the help I can get. I'd like to get some opinions on the sound before I pull the motor apart. 
https://youtu.be/4bDBjcIzY2c

[djdelee421]

Well I figured out where I fudged up. I didn't prime my oil pump and then I ran it at 2k for 20 mins I think I smoked the cam but what other damage could there be?? Thanks for any advice

[mudkicker715]

Its hard to tell. Did you use the prelube jelly on the cam?  There is somthing i remember about throwing a 7120 head on my 84 with a 94 4.o that i stroked out. The lifters were different sized between the 2. I also used the cam from the 94 ho. I am just saying more info please

[djdelee421]

I don't know exactly what head I have but I know it's from an 81 I bought the head from my machine shop they said it would fit my block is the original 83 it's a stock cam crank just .030 over and I used assembly lube on lobes and journals so I'm just trying to find out how bad I screwed up not priming the oil pump I also used Lucas zddp in the oil. I also just removed my dizzy and turned the oil pump with a drill and it pumped oil all the way to the rockers like it should. I don't have an oil pressure guage lol another newb mistake but the oil still looks clean so idk how bad I goofed.

[mudkicker715]

Ok, it sounds like you are original to 83 year motor. It to me sounds like a valve train thing. In your utube. Your certain its tight? Most likely you are? Any issues firing it up, like bad backfires, or wrong id of number 1 on the dissy. I am maybe thinking a bent pushrod or all cause of a bad firing order. Idk that is cheaper. How hard to fire it up after the build? Is it harder to start now than the first time? I have built many 258's but its been years since i have done so.

[mudkicker715]

I just noticed you have a aluminum valve cover from a jeep maybe. Why? That will not fit a 81 or 83 amc 258.  Different bolt patterns on the valve cover iirc. Maybe i am wrong, maybe i seen wrong? But that dont look right to me. Meaning you might have a head that needs different lifters. Idk. But i see somthing wrong in that split second of viewing your head.

[mudkicker715]

I was actually able to pause it to see your valve cover, you have one from an 87 to who knows when. So i maybe go back to what head do you have. I could always be wrong but that is not a valve cover for your year motor. Meaning you have a head for a newer motor, and maybe you have short lifters? Anyway thats my diagnosis from your video. I am almost certain your hed is 87 and up.

[djdelee421]

I will take pictures of my head with the valve cover off I'm just assuming the head is off of an 81 something because there is a stamp that says 81 under valve cover I bought the valve cover online so Idk what it's off of but the machine shop bought all my lifters and said everything is a match I'm guessing that I should just go ahead and pull the head and see what's going on

[djdelee421]

I also torqued everything to spec and have re checked and everything is tight on the head

[djdelee421]

Last time I fired it when I took that video it fired right up. First time I went to fire it I was 180 degrees off on the dizzy and when I switched the wires around it fired right up started holding it at 2k and bout 5 mins in the tapping started but I didn't think it was that bad so I kept goin

[amcfool1]

hi, that is the correct valve cover for 81-86 258s. Its an aftermarket type sold by the Jeep places like 4wd hdwr, etc. I have two of them. good luck, gz

[djdelee421]

I can never seem to get pictures to work but I realized that the machine shop decked my block could this mean my pushrods are too long? Also I got the casting number for my head is 3235480 and from what I read online that is a head from a jeep? Could that be the issue?

[eaglefreek]

Did you check lifter preload when assembling it? That's when you would have known if the pushrod length was correct. I would remove the valve cover and check for a bent pushrod as mentioned. I did a cam change on my dad's Oldsmobile 307 about a year ago and when priming the oil pump with a drill, I had him in the car looking at the oil pressure gauge and it took quite a while to build pressure even though a lot of oil was getting up to the heads. I thought I had screwed something up, but it just took like 3-4 minutes. Also, I didn't do the 2k RPM thing. I somehow stumbled on to the link below and used 5W30 Valvoline Full Synthetic High Mileage with MaxLife and didn't use any zinc additive for break in. That was a year ago and the car is still running great.

https://540ratblog.wordpress.com/

[djdelee421]

Didn't know anything about pre load but I will check for bent push rods and if they are bent do I replace them with shorter ones or something? That would be great if it was that easy.

[eaglefreek]

You'll have to search the net for checking lifter preload and read a few different sources. It took me a bit to figure it out, but it's pretty basic. IN my opinion it's tougher on the 250 since the lifters are in the block and you can't see them. On a V8, with the manifold removed, you can see when the lifter plunger starts to move.