Another engine tapping question.

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01-02-2018, 07:48 AM

#16

97grand4.0

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Join Date: Nov 2015

Location: syracuse ny

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Year: 1997

Model: Grand Cherokee (ZJ)

Engine: 4.0, new lifters valve job with new springs and exhaust valves, preload set with shims

Quote:

Originally Posted by Bugout4x4

The pushrods I replaced mine with were only a few thousands longer. But realigning the rockers along with these slightly longer pushrods did the trick. Twisting the rockers and alignment bridges back where they belong was the main improvement though. Changing out the pushrods cured most of them but I had a few that were still rattling, I then noticed these few rockers were twisted out of alignment with the pushrods and valve stems. So I twisted them and the bridges back into line with the "push". The rattle completely stopped and has been gone since I did this.

Yes the misalignment of the rockers is a quite common occurrence. Some are REALLY out. Mine weren't too bad but they were dead on when I got done. Like I say what happens is people crank down on one valve, say the intake, and if the other is slightly open, the bridge gets pulled 'down' from the pressure of the spring on the other side. good find.
I would be curious to know what pushrods you used. I would be afraid of hanging a valve a little bit open thus ...burning an exhaust valve or not completely seating for instance. Not saying it maybe isn't a good idea, I would like to look at it myself and decide. A sort of solution to not replacing the pita lifters maybe? lol

I would add that a buddy of mine did a head and lifters, and he said the lifters made a huge difference. Back in the day, we always replaced lifters and chain right away with a new used engine for instant performance reinstatement.

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01-02-2018, 08:17 AM

#17

Bugout4x4

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Year: 97

Model: Cherokee

Engine: 4.0

Quote:

Originally Posted by 97grand4.0

Oh absolutely, depending on how worn the lifters are, they could make a huge difference. As the plunger and check valve spring wear the high pressure area under the plunger can get weaker. After doing some homework about lengths I probably ended up with the same sealed power rods you may have used, # SLP-RP-3275 and these are listed as "universal". But they ended up being slightly longer than factory on these. I think more than anything they helped account for what wear I had on my rockers and lifters even though they were low mileage and fairly new when I found the cracked head.

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01-02-2018, 09:06 AM

#18

Bugout4x4

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Join Date: May 2015

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Year: 97

Model: Cherokee

Engine: 4.0

Quote:

Originally Posted by 97grand4.0

There is something else I noticed on these concerning the bridge twisting. I was following the discussion you and Dave had about this awhile back and it sent me looking. What I found was the same bridges seemed to be twisted in every picture I saw of these with the valve cover off. Know what I think? I think these few particular rocker/pushrod locations were not actually inline from the factory to begin with. I think these were off from the drawing board and over time and miles they just get pushed even farther out of line.

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