head bolts

[andy]

I am in the process of renewing the head gasket on my 71SL U.S.,I ordered the parts from sls, inc new head bolts,according to their info on their site the lenths of the six shorter bolts for this head are 105cm,so thats what i ordered,when i took out my old ones they are 110cm.
What is the correct size,?should i use the smaller ones?
thanks,
Andy Spain.

[andy]

One more thing,am i being a bit over the top changing the bolts,and washers?
cheers,
Andy.

[Ricardo]

Hi Andy
On newer Benzes, well even on '84 190e's for example, MB requires replacement of the headbolts. I think  Dr. Dan told me that it was because the bolts stretch ever so slightly when torqued to specs and that they are also going into blind holes, so will bottom before reaching proper torque if reused. I don't think that applies to our vintage  cars though and my headbolts were certainly reused when I had my head rebuilt several years ago. Hopefully Dan or Joe will confirm this, but I haven't had any problem with leaky headgaskets.
Hope that helps

[andy]

Thanks Ricardo for your advice,since been in contact with sls,who tell me two bolts for this head,140mm and 105mm,so why were my smaller headbolts 110mm?
Any more advice as to use the 105mm will be appricated.
Andy, 1971 280sl U.S.

[ja17]

Hello,

These head bolts on the older engines can be re-used. The length of the headbolts sometimes is a result of the thickness of the "foot" on the cam supports. Some of these headbolts go through this foot, so if the thickness of these cam supports is different, the length of the head bolt is also different.
All cylinder heads are the same depth more or less (within 2mm). So if your engine block is the same and your cam supports are the same thickness, you should use the same length head bolts.

Joe Alexander
Blacklick, Ohio

[enochbell]

Andy,

You probably already know this but just in case:  be very careful to evacuate completely any oil or coolant from the blind holes before you reinstall, otherwise you won't get proper torque (best case) or you will overstress the block and...(worse case)

Best,
g

'64 230sl, fully sorted out...ooops, spoke too soon

[andy]

Thanks guys,
Joe,i understand about the bolts(X8) that pass through the cam supports,these are 140mm,and so were the new ones,its the smaller headbolts(X6),sls say they should be 105mm,and the ones i took out are 110mm,now that ive bought the new 105mm,is it safe to use them,if not i will just reuse the original 110mm.
Thanks again,
Andy Spain.

[TheEngineer]

I re-used my head bolts. I'm also real paranoid about what salesmen say (anyone who sells parts) If you had 110 m/m bolts in there, consult the BBB. It may be that a P.O. installed the wrong bolts. Check it out by screwing the 110 m/m bolts all the way in (without the head installed) and measure how much clamp-up you have. If the bolts are too long they will bottom out, if they are too short, you will have less thread engaged. So, use the right size. And:-Very important!- retorque the headbolts after running the engine 10 minutes. Just run it until warm. You will be surprised how much torque you have lost. Then, re-torque again after running it for a few hours. Also, check if the cam shaft binds after the head bolts are torqued. You have to remove all rocker arms. You should be able to turn the cam shaft by hand. I had to take off .005 inch on the bottom of two cam shaft towers to get there. Also, put a dial indicator on one valve and measure the opening timing: It's described in the BBB. When the chain stretches, or the head is thin, you must use an offset key to bring the valve timing back.

'69 280SL,Signal Red,Automatic,retired engineer, West-Seattle,WA