Engine/Transmission (1994 - 1998) Power & Mileage Problem?

[PDPhillips]

My '97 2500 4X4 after about 225k blew the head off of one of the head bolts toward the rear of the engine, resulting in removing the head to get the remaining piece of bolt out, planning the head and a valve job. When they put it back together it was right at tolerance for the stock head gasket. Therefore to be on the safe side the mechanic put in a 50mm over gasket sent from Cummins. It now sure seems to me the truck's power and mileage have noticably dropped. Has it dropped or am I imagining it and if not should I have the stock size head gasket put back in? Thanks.

 

[snappy]

Welcome PDPhillips. I deliberately installed a thicker than stock head gasket in order to run more boost. This was years ago but one characteristic is harder starting especially in cold weather. You can add more fuel to get the power back up. Mileage is best controlled with judicious use of the right foot.

 

[Missouri Mule]

Cummins upgraded the stock gasket to a thicker gasket because of it blowing before they did that members would use a marine head gasket that was thicker than stock. With the thicker gasket you loose some compression ratio(larger compression area).

 

[JMcCoy]

It couldn't hurt to check the rubber fuel return line behind the fuel pump. It may have cracked a little during the head removal. Just a thought. Good luck.

 

[surfbeetle]

Stock 12valve max boost is around 20 psi, get a gauge and see what your boost is. You should check your intercooler, piping and clamps to make sure you don't have a boost leak. If you need more boost and fuel, the TST kit will help you. My max boost now is around 35 psi.



It's possible that your boost levels may have been low from leaks and then worsened by the thicker head gasket and resulting lower compression ratio.



There's a back issue, maybe 50 or 52 (can't remember) that illustrated how to check for boost leaks with the engine off using an air compressor and plumbing fittings to pressurize the system. Good luck.

 

[PDPhillips]

Thanks to you all for the info. Will check out all before considering tearing it down again! P

 

[JMcCoy]

Good Idea. I "borrowed" that trick to test mine, before I deturmined it was the fuel return line. It called for two 3" rubber plumbing caps and a valve stem. I used QWIK-CAPS from Home Dept and a metal valve stem. I think I spent $8. 00 total. It was very easy. Don't over inflate. A few pounds of air will do. 125 lbs from your compressor will blow your intercooler apart. I'm sure you know that. I'm not trying to insult anyones intelligence. I just don't want to receive hate mail later. LOL. Was the pump tampered with? Low power can also be attributed to pump timing, cam plate setting, star wheel adjustment, bad injector, dirt in the fuel injector line. If the cam plate is set all the way back, It will reduce the power. Full forward should increase power. Let us know how it turns out. Good luck.