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Head Bolts And Carb


robjob0

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Hi all

I've just put my cylinder head back on with new bolts but need to remove it again do I need to use new bolts again when I replace it or should the other be ok. I haven't run the engine yet so only tightened to first stage. Also I've got a 32/34 DTML weber carb has any one got a picture of where the pipes go to on the front and back

many thanks Robin

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Hi all

I've just put my cylinder head back on with new bolts but need to remove it again do I need to use new bolts again when I replace it or should the other be ok. I haven't run the engine yet so only tightened to first stage. Also I've got a 32/34 DTML weber carb has any one got a picture of where the pipes go to on the front and back

many thanks Robin

 

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I would say that if you have not fully torqued down the bolts to the final setting then you should be able to remove and refit the head without any problems. The general point of using new bolts is that the old bolts have been stretched so if reused then could break.

Regards

Martin

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not sure about the pinto but alot of engines use stretch bolts. They can be reused as long as they don't exceed a cetain length ie stretched. You'll need to find the measurement if that is the case from a haynes manual. i probably do things incorrectly but ive reused head bolts for all 4 heads ive taken off various engines. mainly because the bolts would probably cost more than the cars ^_^ so it didn't matter if i broke them. Iam always very nervous when tighening them up. Normally put a bit of grease on the underside of the bolt head and make sure you don't have excess oil down the bolt holes. hopefully someone will have more definitive info. hth

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Guest mcramsay

for the sake of a tenner change them, if you wanting to do it propperly then just change the bolts. ive had a head go on a pinto before because i reused bolts. and just a small warning putting grease on a bolt will majorly affect the torque you put on it. so worst case scenario, if you reuse a bolt thats been streached (when you have tightened it) and its passed its elastic limit and is now in its plastic limit, (meaning its not going to shrink back down to its normal size once its undone) its going to strech more and more. then if you stick grease on it and torque it up it might say you have torqued it to 80N/M (just a random figure) but belive me with grease on it, it will tighten much more. and never mind that the guage on most torque wrenches is completley innacurate, you have no idea how much torque you are sticking on that bolt. i know i sound majorly over the top here, but in the worst case scenario i would rather pay a tenner for new bolts, rather than trying to drill out a sheared off head bolt. :) change the bolts, do it once, jobs a goodun ;)

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Hi Robin,

From what I have been told there are two types of head bolts.

Early type bolts are normal bolts.

Later type bolts are strech with Torx (symbol of the Devil) heads.

I did renew mine.

John

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and just a small warning putting grease on a bolt will majorly affect the torque you put on it. so worst case scenario, if you reuse a bolt thats been streached (when you have tightened it) and its passed its elastic limit and is now in its plastic limit, (meaning its not going to shrink back down to its normal size once its undone) its going to strech more and more. then if you stick grease on it and torque it up it might say you have torqued it to 80N/M (just a random figure) but belive me with grease on it, it will tighten much more. and never mind that the guage on most torque wrenches is completley innacurate, you have no idea how much torque you are sticking on that bolt.

 

True but if you are angle tightening them rather than torqueing them them it won't be so much of a problem as 90 degrees is 90 degrees and won't be affected by the oil/grease. as long as they aren't past the specified stretch limits.

 

although i had a look in the haynes manual which shows four stages of tightening to specified torque so i guess that must be for normal bolts, which i would agree could be affected by grease/bad torque wrench.

 

Is tightening different for stretch bolts on a pinto? ive always done angle tightening on other engines which i think must have used stretch bolts. Would be worth double checking which bolts you have to make sure you tighten them as intended. If indeed there is a different way.

 

who knew bolts could be so exciting :D

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True but if you are angle tightening them rather than torqueing them them it won't be so much of a problem as 90 degrees is 90 degrees and won't be affected by the oil/grease.

 

Sorry Zed, but that's wrong.

The 90 degrees will differ because its based on the resistance of the threads being felt at the bolt head.

 

Follow the manufacturers or part suppliers recommendations to the letter. EG ARP supply their own lubricant, and specify two different settings depending on whether you use that or a single weight oil.

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