hello and 258 question

[wildmanwayneo]

hi im wildmanwayneo i have a AMC 258 i6 / 4.2l 6cylinder with roller rockers it was just built before i got it, so they said but ive driven maybe 3,000 miles and it wore a hole through a lifter block and the cam was worn pretty bad on one of the lobes. When i took it apart the timing chain was wore out and i found in some of the paper work they gave me when i bought the jeep( it is a 1987 yj with a 1977 motor ) a list that said take timing chain and gears back to part store, now why you would put a used timing chain back in when rebuilding your motor is beyond me, the timing chain was really wore out. The question i have if anyone can help is the length of the pushrods will they be longer since there are roller rockers? they are 9" 15/16 long and i think stock ones are about a half inch shorter, now the 1977 AMC 258 i6 / 4.2l is a little differant then the others it has the temp sending unit on the back of the head not in the front and the catalog from quadratec shows a differant part number for the pushrods. Another problem is im not sure what kind of roller rockers they are think there comp cams but i think there not made for this motor because the guide plates are welded which i think means they were wider so they cut them and welded them back together. So if anyone knows anything about this kind of set up i could use some help, thanks

 

[thiswontbetooexpensive]

Re: hello

First off; hello and welcome to the site from Texas.

I would also recommend that you try and put your questions as they come up in the appropriate section of the forum. Electrical, drive train, etc.

I can't answer your question personally, but someone will be along shortly who can at least get you pointed in the right direction. This is a great site that is a wealth of information and collective intelligence.

I would also suggest adding some pictures of the rocker set-up you have going on there. Pictures are always helpful!

 

[0822]

Re: hello

:ww:from Missouri

 

[tjmons]

Re: hello

:ww: from Michigan

 

[JR74CJ5]

I seen push rod lengths being discussed in a few AMC 258 i6 / 4.2l thhreads before, but am having a hard time finding them right now...

I'll keep looking.

I know Tarry99 and coldair may have some info on this subject...

I'll shoot them a message to see if they can help out a little in the right direction.

out of curiosity, did the "builder / seller" of this engine have anything to say about this? Any kind of warranty? 3000 miles is a small number for a freshly rebuilt engine... (as I am sure you know) to be having these types of issues...


~ Jr

 

[tarry99]

hi im wildmanwayneo i have a AMC 258 i6 / 4.2l 6cylinder with roller rockers it was just built before i got it, so they said but ive driven maybe 3,000 miles and it wore a hole through a lifter block and the cam was worn pretty bad on one of the lobes. When i took it apart the timing chain was wore out and i found in some of the paper work they gave me when i bought the jeep( it is a 1987 yj with a 1977 motor ) a list that said take timing chain and gears back to part store, now why you would put a used timing chain back in when rebuilding your motor is beyond me, the timing chain was really wore out. The question i have if anyone can help is the length of the pushrods will they be longer since there are roller rockers? they are 9" 15/16 long and i think stock ones are about a half inch shorter, now the 1977 AMC 258 i6 / 4.2l is a little differant then the others it has the temp sending unit on the back of the head not in the front and the catalog from quadratec shows a differant part number for the pushrods. Another problem is im not sure what kind of roller rockers they are think there comp cams but i think there not made for this motor because the guide plates are welded which i think means they were wider so they cut them and welded them back together. So if anyone knows anything about this kind of set up i could use some help, thanks

Wildman..............Looks like you have a big Mess!......Next to impossible for anyone over the internet to answer all those questions without being there first hand..........Yes and no on the pushrod length...........meaning you already know you have a problem. Are the rockers standard for that application? Perhaps, but you mentioned there was some welding done to the guide plates. Is the Cam Hydraulic or solid lifter? What's up with the timing chain is anyone's guess? Pushrod lengths are the last thing you measure and make after all the geometry is correct in the overhead.

Just from the sound of things you just have to go back to square 1 and start over meaning the motor has to come apart and things need to be verified and measured.

I see motors all the time that some novice spent a bunch of money on buying useless parts from a person or company like Summit or Jegs that may fit but do not complement the motor in any way....................here is what I suggest:

Get someone local there that will tear it apart and sort out the problems and tell you what it is going to take to fix it...........trying to diagnose this over the internet is just a waste of time. Sorry

 

[johnnyreb]

I agree on finding a local reputable builder, then do a full tear down.
If th PO shorted on a timing, then what else is screwed up.