Head bolts too tight, so what?

[scot]

Hi, after being generally dumb today, I realised that I have tightened the head bolts to a higher torque than specified. I was interupted mid flight and in the haze I camly read off the FT Lbs scale. So bsically I took em to about 78Ft lbs and then 90 degrees "TWICE" must admit they did seem to still be tightening.

This is possibly my dumbest moment for a while, but alas it happened and I was 4 hrs down the line (manifolds on) by time it dawned on me.

Basic question is thus: Given that I torqued them down regularly and in the correct pattern, what is the expected net result of the bolts being to tight?

Scot

[fatfires]

Hi, after being generally dumb today, I realised that I have tightened the head bolts to a higher torque than specified. I was interupted mid flight and in the haze I camly read off the FT Lbs scale. So bsically I took em to about 78Ft lbs and then 90 degrees "TWICE" must admit they did seem to still be tightening.

This is possibly my dumbest moment for a while, but alas it happened and I was 4 hrs down the line (manifolds on) by time it dawned on me.

Basic question is thus: Given that I torqued them down regularly and in the correct pattern, what is the expected net result of the bolts being to tight?

Scot

your sump might be a bit higher!!!!

[NiftyNev]

You have gone over by about 25% with the bolts. I would personally be worried about this. I would be inclined to remove the bolts and replace them with new ones. Not sure what overtorquing would do to the head gasket though.

Nev

[kitesurf_phil]

As they are stretch bolts I would imagine that over torquing by 25% could result in one or more shearing, which could at best, result in a blown head gasket. Personally I would be cautious about running it up until the bolts have been replaced, especially with diesels being such high compression engines.

[scot]

As they are stretch bolts I would imagine that over torquing by 25% could result in one or more shearing, which could at best, result in a blown head gasket. Personally I would be cautious about running it up until the bolts have been replaced, especially with diesels being such high compression engines.

In the light of day, I have to feel inclined to agree. I think one knows the truth but just don't wanna face it... The gasket is the interesting bit. Looking at the construction it would be fair to deduce that it does not compress over a certain point I think (though Im altogether not sure!!). The bolts were originals in very good condition, my guess is the would stretch before anything was hurt during the torquing down process. If this could be relied upon then I guess that removing the bolts once the engine is built up and replacing them would not hurt.

I should have finsihed her today, I think I will be firing it up just to see if it starts and then waiting till tuesday to replace the bolts when they arrive. If anyine has conclusive proof tht the gasket will not cope with "re-torquing" in the meantime, then I suppose this must be considered and I have to decide whether it has to be stripped down again to replace the gasket again.

Thanks for your advice.



For the general info of the readers, we are discussing a 92 2.4 Surf with 122,000KM on the clock, hammered for the last 2 years 40,000 miles. The head went cracked accross inlet to exhaust on all 4 cylinders, although I deduce that the head has been cracked slightly for a while causing sporadic water pressuriztion. In my opininon this was brought about by poor cooling system and the odd radiator leak which resulted in a BAD overheat last week. After replacing the radiator a few days ago, the head lasted just 9 miles before going spectacularly with white/blue smoke. Untill then (even after the overheat) she has run very cleanly with no smoke at all.



Scot

[NiftyNev]

I think I will be firing it up just to see if it starts and then waiting till tuesday to replace the bolts when they arrive.
Scot

If you do start it then I would say do not let it get too hot. Heat = expansion and this may cause head problems or snap a bolt or two. Maybe I'm being over cautious but better to be safe than sorry.

Nev

[spans]

One Question, if the bolts needed to be replaced, would the gasket be ok as well, after it has been compressed between the head and block?

I don't know really, the gasket that I put in mine looked like layers of metal with some raised bits, but the gaskets from my distant past were like asbestos kinda stuff, and those had to be replaced if they were compressed, and un-tightened.

shows how much I know huh

[andrewlee31]

if you release them now you risk losing seal on gasket, personally, i wouldnt bother at all, made bolts for many years, and a few ibs ft wil make no difference to the bolt, it will take many tonnes of pressure to shear the head off.

[scot]

All ok

if you release them now you risk losing seal on gasket, personally, i wouldnt bother at all, made bolts for many years, and a few ibs ft wil make no difference to the bolt, it will take many tonnes of pressure to shear the head off.

Well, in the end you have to do what you have to do... I was loosing £££ having the car off the road and with it almost complete, I decided to leave the bolts alone, else risk snapping the taking them out and possibly duffing the head gasket.

Verdict.
Well, 600 miles later and all is fine. Not a drop of water usage at all and she's running fine. Thanks to all of you for your advice. I may pay in the long run, but I really just could not afford anymore time that week to re strip it and pull the gasket to replace the bolts.

Oh yeah one tip!!! Heads from Milner offroad do not come with the wierd metal half moon blanking plate thingy at the back of the cylinder head. I found this out first time i started it as oil literally p##### out of the back of the head. Gave me a fright I can say. So when rebuilding the head make sure you take it off your old one and re -instert it.


Scot

[dirtydog]

Oh yeah one tip!!! Heads from Milner offroad do not come with the wierd metal half moon blanking plate thingy at the back of the cylinder head. I found this out first time i started it as oil literally p##### out of the back of the head. Gave me a fright I can say. So when rebuilding the head make sure you take it off your old one and re -instert it.


Scot

LOL i did the same thing when i took the rocker cover off and lost the plug. drove 4 miles before i realised but tony sorted me one in the post! hoorah.