Cylinder Head studs vs bolts universal m25xp

[TimTimmeh]

Just took the head off my m25xp but noticing differences between it and the manual which indicates 2 studs 12 bolts, where mine is 14 bolts. Any insights as to why this would be?

 

[Stuphoto]

Every engine manufacturer makes minor changes like that in a production run.
It could have been an update, they may have run out of studs or it may have been a mistake.

Either way, it didn't harm your engine, so I would think you could do the same or get a couple studs and nuts if you wanted to.

If you decide to run with the 2 studs it will be easier lining everything up and holding it in place.

Just in case you didn't know, some manufacturers recommend replacing the head bolts and studs every time.
I would think the manual should tell you if yours are like that.

 

[TimTimmeh]

I guess it doesn't really matter, doesn't say anything about replacing the bolts. It turns out there is a hole in the head so waiting on replacement now. No other damage done though so should be easy once I get the parts.

 

[Greg J]

Hi Tim. I spent a number of years as a diesel mechanic, and like Stuphoto said, it's usually recommended to replace all the bolts/studs when replacing a head/gasket. The reason for this is that properly torqueing bolts generally calls for "stretching" of the bolts. But this would mean that any attempt at reuse would place the bolts beyond acceptable fatigue levels. Also, I would prefer bolts anyway, as I've had some "lovely" experiences trying to remove studs in the past. Most heads usually have some sort of locating dowel anyway.

 

[footrope]

Hi Tim. I spent a number of years as a diesel mechanic, and like Stuphoto said, it's usually recommended to replace all the bolts/studs when replacing a head/gasket. The reason for this is that properly torqueing bolts generally calls for "stretching" of the bolts. But this would mean that any attempt at reuse would place the bolts beyond acceptable fatigue levels. Also, I would prefer bolts anyway, as I've had some "lovely" experiences trying to remove studs in the past. Most heads usually have some sort of locating dowel anyway.

I got this advice also, when I had the head off of my 5432. And it is highly recommended to clean the threads in the block to ensure that torquing to the required value allows all the force to go into holding the head to the block, not into drag from dirty threads. I couldn't find a thread cleaning tap so I cut grooves in the threads of an old head bolt and was able to capture quite a bit of junk. I hope the re-assembly goes well.

Craig