258 4.0 Head Upgrade cam swap - JeepForum.com
 
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post #1 of 13 Old 09-10-2013, 08:20 AM Thread Starter
Mjjbk
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258 4.0 Head Upgrade cam swap

I have a 76 258 4.2 that i am doing the 4.0 head swap on now i need to know what cam to use. Some have said the 4x4 medium comp cam but i also need to know what push rods, lifters, springs, ect to use. Some say the 258 rods will work but change out the springs ect. Some say it will all work but im worried about valve springs binding or bending a push rod...and what about valve lash.? Any help would be appreciated and no not all the engine shops know it all.

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post #2 of 13 Old 09-12-2013, 07:46 PM
jsawduste
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One place to call Hesco. http://www.hesco.us/

Jeep contracted Hesco for all there racing endeavors back in the day. Bennie and Leee (yes 3 e`s) have forgotten more then most others will ever know.
Give Hesco a call and talk to Bennie. He will be able to answer all your questions and provide proven parts so you only do it once.

Did you know the Comp Cam springs and retainers they sell in the kit don`t fit the 4.0 head ?
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post #3 of 13 Old 09-12-2013, 09:01 PM
supersport126
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What head are you planning to use, stock 7120 or a clearwater conversion head? I just did this upgrade
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post #4 of 13 Old 09-20-2013, 11:17 AM Thread Starter
Mjjbk
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I went with the 7120 and i bought the comp cam 68-235-4. Now i need to know what oil pump will work or if i can use my stock oil pump with that cam. The comp cam guy didnt know..but he did know how to sell it to me..
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post #5 of 13 Old 09-20-2013, 11:20 AM
supersport126
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Quote:
Originally Posted by Mjjbk
I went with the 7120 and i bought the comp cam 68-235-4. Now i need to know what oil pump will work or if i can use my stock oil pump with that cam. The comp cam guy didnt know..but he did know how to sell it to me..
Stock oil pump in fine. I used the original with 80k in it. You got lifters with the cam right ?
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post #6 of 13 Old 09-20-2013, 11:31 AM
supersport126
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Quote:
Originally Posted by supersport126
Stock oil pump in fine. I used the original with 80k in it. You got lifters with the cam right ?
Also if your block is tapped 1/2 you'll be ok but if it's tapped 7/16 you will need centering washers from Hesco. I have a set brand new if you need them
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post #7 of 13 Old 09-20-2013, 11:32 AM Thread Starter
Mjjbk
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Yes sir i got the lifters and that is awesome i was trying to find that answer for a week. Now this is tough but i know i need different springs on my head which are being installed but how do i know what push rods to use.? Can i use the 4.2 or the 4.0 or go with a different size...the machine shop is not installing the head i am so i cant measure for them...? Any hints.?
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post #8 of 13 Old 09-20-2013, 11:48 AM
supersport126
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Quote:
Originally Posted by Mjjbk
Yes sir i got the lifters and that is awesome i was trying to find that answer for a week. Now this is tough but i know i need different springs on my head which are being installed but how do i know what push rods to use.? Can i use the 4.2 or the 4.0 or go with a different size...the machine shop is not installing the head i am so i cant measure for them...? Any hints.?
Oh boy , I think I have the springs you need also (made a few mistakes during my build) I'll sent you a pic and part number later on tonight or in the morning but they are dodge 318 springs I think?
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post #9 of 13 Old 09-20-2013, 11:51 AM
supersport126
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Quote:
Originally Posted by supersport126
Oh boy , I think I have the springs you need also (made a few mistakes during my build) I'll sent you a pic and part number later on tonight or in the morning but they are dodge 318 springs I think?
Stock push rods from your 4.2 block
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post #10 of 13 Old 09-20-2013, 11:52 AM
supersport126
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Stock push rods from your 4.2
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post #11 of 13 Old 09-20-2013, 11:53 AM
supersport126
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Quote:
Originally Posted by supersport126
Stock push rods from your 4.2
I'm driving so my responses are kinda all over the place
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post #12 of 13 Old 09-20-2013, 05:06 PM Thread Starter
Mjjbk
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Thanks for all the info i appreciate it...
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post #13 of 13 Old 09-20-2013, 08:21 PM
jsawduste
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Chevy LS springs are another good option.

I am not convinced that the 4.2 pushrods are correct. Little known fact but there are actually 3 different pushrod lengths that were offered by Jeep. Another consideration is whether the base circle of your cam is machined differently then a factory grind. That alone would dictate a different length pushrod. To be safe I would do a bit more research and even incur the expense of a pushrod length measuring tool to make sure you are setting the engine up correctly. http://www.summitracing.com/search/p...pushrod%20tool or your machine shop may be able to help.

Don`t forget the break in oil and proper cam break in procedure. The use of Brad Penn or Joe Gibbs ZDDP fortified oils will help ensure your engine runs long and stays healthy.
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