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Mild Thunder

Jake And Valve Adjustment

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I have a 1998 CH613. I bought the truck a few years back. Bought it with 570k miles, and now it has about 690k. Runs very well. Power is good. Pulls 32lbs of boost. Engine is labeled 355-380HP, but previous owner says he had it turned into a 427HP?? Is that possible? I drove a stock 2000 year 355-380, and it felt like a slug compared to mine. That truck empty felt like mine loaded.

Anyhow, I noticed my jake doesnt seem to be strong at all. it engages ok, but slowing/stopping power is minimal, unlike the other truck. I have not had the engine touched since i bought it. Someone told me i should have the valves adjusted. Is this the cause of a weak jake?? Thanks!

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The Jake might need a tune up kit. I'm not sure what is involved or how much it is but after a while they wear.

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It wouldn't hurt to have the valves done. Did mine at 500k and made a big difference in power and mileage. Should help the Jake too. BTW, I wouldn't doubt the previous owner, 32PSI boost is about right for a 427HP.

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A $100.00 and an hour should tune up your Jake.

While your at it, adjust both the valves and the Jakes.

A Rebuild kit is just some pistons and 'O' rings.

You'll need a set of valve cover gaskets and some 'O' ring lube to finish the job.

AND DON"T DROP ANY OF THOSE TINY PARTS DOWN IN THE ENGINE!!!!!! LMAO

It will happen!!

Packer

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Not sure how much experience you've had with E7/E-Tech engines and Jakes, but you will NEVER feel the same stopping power as an ASET with Powerleash or MP series with VCB. In any case, if you do decide to run the overhead yourself, be sure to adjust the brake loosely at .017". When I say loosely, only MINIMAL drag is required. Otherwise you could end up with a broken guide pin and possibly replacing a head.

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Is this something I should just let the Mack dealer do?? Have them adjust valves and rebuild jake? About how many hours labor would it cost? Im only a few miles from the dealer but dealer prices scare me sometimes, but so does the idea of screwig up my motor trying to save a few bucks! lol

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Is this something I should just let the Mack dealer do?? Have them adjust valves and rebuild jake? About how many hours labor would it cost? Im only a few miles from the dealer but dealer prices scare me sometimes, but so does the idea of screwig up my motor trying to save a few bucks! lol

I had mine done a year ago...valves adjusted and jake. They replaced the solenoids, adjusted the valves and had to replace a worn out set screw thingermajigger...around $450 altogether. The biggest deal was finding the time, as the truck has to sit almost over-night to allow the motor to cool to 'room' temperature.

And tech_j is right...my engine brake (the "stealth" brake) is a tiny step above worthless. I think they call it stealth because you don't even know it's on.

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Just out of a curiosity can you install a pac brake on Mack engines?

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