(Home) Head bolts, replace? Sources.

hi all do you realy have to fit new head bolts when fitting new head gasket thanks jason k

- (#9669) jason k, 29 Mar 04 07:01

Hi Jason.
I believe that you can re use the bolts, but they are stretch bolts, so for the sake of £40 its worth going for new.

- (#9669) dave Bright (Bournemouth), 29 Mar 04 07:06

jason,

you have 18 cylinder head bolts so you are 18 times more likely to have a bolt break and as dave said they are stretch bolts and have they been off before ? if you do use them inspect each bolt and look for any damage or deform apply a light coat of engine oil on the treads and under the cylinder head bolts.

play it safe and get new bolts fitted,let face it you will only pay for the materials as they have to be fitted anyway.

- (#9669) dennis, 29 Mar 04 10:36

The bolts are designed to be tightened the limit of their elasticity, that is they reach their elastic limit, they can only tighten down by that amount once, after that they are liable to stretch to failure, also they cannot be relied upon to stretch uniformly at this time ie when it gets hot.
They are 40ish quids, get some and a genuine gasket, consider these insurance for the job.

- (#9669) Master Simon, 29 Mar 04 14:06

2 things try FaB engineering for headbolts they specialise in head reconditioning but can supply other bits including headbolts .Also do the headbolts from the Camray model fit as these are cheaper still ,my guess is there no different if the engines a 2ct
FAB ENGINEERING TEL 01594 860450
cheers Paul
ps I ve no connection with fab but they have given excellent service to me on numirous occasions

- (#9669) Paul Absalom, 30 Mar 04 03:04

I tested my bolts in a laboratory and have found that if used for the second time they are capable of withstanding more than 30% of their recommended maximum torque value based on the recommended tightening procedure defined in the 2ct engine repair manual.
That's very significant !
Based on these findings I would recommend you use them again - I did !, as long as you can assure this is only their second torque time and the head of the bolts are not damaged.

- (#9669) stephen judge, 30 Mar 04 14:54

Why not just do what it says in the manual. Measure overall length, and reject/ replace any that don't tighten correctly. I reused the set in mine three times, although I did replace one or two from a secondhand set on the final occasion...

- (#9669) david miller, 30 Mar 04 23:20

2 things are the headbolts on the toyota camry deseil the same as the one s on the townie and I get my bits from Fab engineering in the forest of dean for alot less than £40

- (#9669) Paul, 1 Apr 04 01:29

Should be the same providing the Camry you are quoting is the 2C engine

- (#9669) Ian Dunse (Derbs), 1 Apr 04 03:46

Quote"I tested my bolts in a laboratory and have found that if used for the second time they are capable of withstanding more than 30% of their recommended maximum torque value based on the recommended tightening procedure defined in the 2ct engine repair manual.
That's very significant !
Based on these findings I would recommend you use them again - I did !, as long as you can assure this is only their second torque time and the head of the bolts are not damaged. /quote

If i read this correctly you say they are capable of withstanding 30% more torque?
So you are saying that you would apply that amount more torque whilst tightening down your C.Head??
It is my understanding that a material will appear to withstand more pressure up to the point it yields, in this case it would be catastrophic, the reason such a material is selected is because of the different rates of expansion, what you are advocating will cause the bolts to be under excess tension, no bolt will stop that amount of silicon alloy from expanding without it distorting, which is maybe why there is an incidence of repeated failure.

I feel this an insurance item , if you can get them cheaper do it but you'll be spoiling a good ship for a hap'orth of tar if you don't put new ones in.

- (#9669) Master_Simon, 1 Apr 04 16:17

I'm not advocating that you tighten the head bolts up any different than the manual indicates.

What I am saying is the the torque value obtained by the manual procedure (85-90 ft-lbs), is well within the failure limit of the bolts.
So in theory, using them again is low risk.

- (#9669) stephen judge, 2 Apr 04 13:07

A short search on google and I found this, it is for a seller of bolts granted but the technical bit makes sense.
http://www.robbos.com.au/myweb/Tech_Bolts.htm
I note you say about a torque figure but this is not the case with my engine, they are pretightened then are tightened in sequence as described in the article.

- (#9669) Master_Simon, 2 Apr 04 13:52

Yes, but a torque + angle = a specific tensile loading. Remember that the angular figure is just an indicator of the degree of stretch of the bolt- based on the pitch of the thread. New or old, a GOOD bolt will provide the same tensile strength at that loading. A failing bolt will edge from elastic to plastic transformation around that point, hence the recommendation in the manual to replace any bolt that doesn't feel just right during the tightening process.

- (#9669) david miller, 2 Apr 04 15:07

It's your cylinder head if you want to risk it for 40 quid then so be it, on my engine it recommends swapping them , my mechanic agreed, as did the cylinderhead centre who were providing the warranty for the head.
- (#9669) Master_Simon, 2 Apr 04 23:34