Cylinder head bolts - Have to be replaced?

[pamlicopanther]

My 150 says on the head not to use old bolts when replacing cylinder heads. Is this common? How important is it to replace them if nothing is wrong with them?

 

[BaileysBoat]

Re: Cylinder head bolts - Have to be replaced?

Very common requirement on many engines to replace head bolts during assembly. In many cases the bolts designed as torque to yield and stretch to give the correct force on the head.

The service manual will tell you how.

 

[j_martin]

Re: Cylinder head bolts - Have to be replaced?

If you do cheap out and re-use them, don't re-stretch them, just torque them.

 

[pamlicopanther]

Re: Cylinder head bolts - Have to be replaced?

If you do cheap out and re-use them, don't re-stretch them, just torque them.

How do you know you won't restretch them? Do you just torque to the recommnded 30 ft/lbs and then not add the 90 degree turn?

 

[Faztbullet]

Re: Cylinder head bolts - Have to be replaced?

Use a torque angle guage to get the 90 offset....

 

[j_martin]

Re: Cylinder head bolts - Have to be replaced?

How do you know you won't restretch them? Do you just torque to the recommnded 30 ft/lbs and then not add the 90 degree turn?

You torque them to just below the torque that it took to stretch them in the first place. It's more than 30, but it's not much and I don't know just exactly how much.

Go ask T-Rex on Screamandfly.com. If anybody knows how to recycle the bolts, he would. He could also give you the statistics on how many stay together.

 

[j_martin]

Re: Cylinder head bolts - Have to be replaced?

Use a torque angle guage to get the 90 offset....

The question is can you and how to re-use stretch bolts. I don't think you'd re-stretch them. There has to be an elastic limit you'd likely exceed doing that.

 

[pamlicopanther]

Re: Cylinder head bolts - Have to be replaced?

You torque them to just below the torque that it took to stretch them in the first place. It's more than 30, but it's not much and I don't know just exactly how much.

Go ask T-Rex on Screamandfly.com. If anybody knows how to recycle the bolts, he would. He could also give you the statistics on how many stay together.

Thanks - I will check that out.

 

[pamlicopanther]

Re: Cylinder head bolts - Have to be replaced?

Thanks for all the responses.

This is a great forum.

 

[j_martin]

Re: Cylinder head bolts - Have to be replaced?

Thanks for all the responses.

This is a great forum.

I think 40 lbs would be appropriate. You won't find a formal declaration of the torque spec because you're not supposed to re-use them.

 

[sschefer]

Re: Cylinder head bolts - Have to be replaced?

My 150 says on the head not to use old bolts when replacing cylinder heads. Is this common? How important is it to replace them if nothing is wrong with them?

What is wrong is that they are one time use bolts as was explained before.

As per the head, torque specs on the head and the manual, you must replace them.

Only buy genuine Merc replacements. Aftermarket head bolt marketers are less likely to stand behind their product.

Just for info, the 30lbs + 90 degrees eliminates the need to retorque the head bolts after break-in.

 

[pamlicopanther]

Re: Cylinder head bolts - Have to be replaced?

What is wrong is that they are one time use bolts as was explained before.

As per the head, torque specs on the head and the manual, you must replace them.

Only buy genuine Merc replacements. Aftermarket head bolt marketers are less likely to stand behind their product.

Just for info, the 30lbs + 90 degrees eliminates the need to retorque the head bolts after break-in.

I will make sure I replace them. I am taking the time to do it all right so I will certainly get that part right too.