Torqueing Up Cylinder Heads

[sujitroy]

OK. I searched a bit in the forum but dont have the patients to sift through. I plan to reinstall two heads. ROM says to torque to 55 in a particular order. Should I say torque to say 40 in the sequence and then down to 55 in the sequence or should I go straight to 55 in one go?
On a side note,
I spoke to the folks at ARP who make the head bolts I'm using. They say their bolts don't stretch so no need to retorque however, they say the gasket can compress so retorque for reason.

Sujit

[Seaking]

https://socforum.com/forum/forum/sta...quing-sequence take a look at the link in first post

[flying farmer]

Oh dear, there are about a hundred combinations of ways to torque the heads.
Certainly they want going up in stages, not straight to 55.

I don't like the way suggested in the manual which IIRC (can't be bothered to look) was all the studs first, then the bolts afterwards.
I think this was because the second head had the inlet manifold bolted to it before being tightened down so it made sense to squeeze the heads together by tightening the angled bolts first.

However, if the heads or block have been skimmed, the inlet manifold will be too wide for the resulting gap between the heads. To my way of thinking this can only prevent the heads from clamping down properly.
I prefer to bolt both heads on first then fettle the inlet manifold to fit the resulting gap. If doing this it is important to fit the little bolts that go into the front cover as well, as it is possible you will not be able to fit them after the heads have been torqued up. I will leave you to guess how I found this out

To avoid over-compressing the gasket on the stud side due to tightening them all up first, I prefer to go stud then bolt, radiating out from the centre. One of the big problems on Rover V8s was the outer part of the heads had an extra row of studs which tended to tip the heads due to the extra clamping pressure causing the gasket to fail on the inside of the V. Rover later deleted the outer row of studs to prevent this happening. This is why I don't like the idea of over-compressing the head gasket by tightening all the studs up first.

Doing things this way round means non of the components will fighting each other, and by fettling the inlet manifold to fit the gap between the heads you stand a reasonable chance of actually keeping the water inside the engine which I failed to do with the first engine I built following the manual

No doubt Motorsport Mickey will be along shortly explaining why he uses different torque settings on the different length bolts

Neil

[flying farmer]

That link from Seaking shows the order I torque things in.
Effectively I am bolting the heads on two 1850 dolomite engines then fitting the inlet manifold between them

[Matt Cook]

If you are using the lubricant that comes with the arp studs then you will need to reduce the torque. This should be covered by the instructions for the lube.

[Tdm]

I am no expert on the subject, and defer to those far more knowledable than I.
The last time I did my heads was in 2005 after a head gasket failure, and first I had the Heads skimmed locally

I followed the Haynes Workshop Manual for torqueing them up first, then re-torqued them about 6 months later.
14 years on I have not had another problem with the Heads, and the car runs really well, except for the oil leak problem I currently have since fitting a Weber carburretor.

Just my twopenny worth.

[Motorsport Micky]

No doubt Motorsport Mickey will be along shortly explaining why he uses different torque settings on the different length bolts

Neil[/QUOTE]

No I'm trying to resist Neil, however I'd like to know from Sujit have ARP supplied a mixed set of studs with nuts and two different length bolts ?

Micky

[sujitroy]

if i recall corectly i have 5 same length studs. with 3 bolts one size and two shorter . I like the ideal of clamping down as Neil suggested and install the inlet manifold after.

[Motorsport Micky]

I share the same system with Neil as regards the torqueing sequence across the head and I tighten to 20/35/55/65 (long studs only see below) to try and get the head to compress equally across and along the length in sequence to avoid wrinkling the gasket.

Your decision regarding the ARP fastenings is whether to follow the ARP instructions and use their lube (if supplied by them), or another lubrication system if not or fit dry as per the Triumph system. There is no doubt a lubricated thread will more reliably achieve an even torque and clamp across the head, however the lube will remove a proportion of the "stiction" (sticking friction) which you get when the two threads (nut and stud or bolt and cylinder block thread, this will then increase the clamp actually imposed upon the threads and then the block surface.
If ARP has enclosed a sheet showing the torque applied for the fastening, once lubed I think you'll find it about 15% increased over the standard 55 lb ft (depends upon the lubricant), it pays to check because there is not always a large envelope of spare torque capacity in the threads in the various blocks that ARP supply their studs and bolts for.. Also the point regarding the Rover V8 engine block tilting by Neil is well made, this has been theorised by myself happening in just the same way with the Stag engine. The bolts (and especially the short bolts) clamp the head very firmly and again are used down the length of the block on one side, the shorter bolts not having very much head under them indeed, I think they do tilt the head by overcompressing the gasket on that side which is why Neil is teasing me regarding my torqueing system used.

With the standard studs ( with two threads which deform and corrupt the torque achieved) and nuts and the studs being considerably longer than the long set bolts, (one thread) which themselves are longer again than the shortest set bolt I believe applying the same torque to all does not apply the same clamping force to the head and gasket. To compensate for that and fitting them dry I set the studs and nuts at 65lb ft and the long set bolts at 55 lb ft (standard torque level) and the short set bolts (with not much head thickness under them) at 35 lb ft I have no method of measuring it but I believe the clamping force is more evenly applied to the gasket.
Although Gareth Thomas is regarded poorly on a number of forums he posted that the shorter setbolts apply more clamp (see some of the posts on cylinder head work where this is mentioned). My car has been together for 15 years now with over 13,000 miles on the engine and so far shows no problems, (retorqued 6 times by undoing one flat and retorquing up to these figures given). I don't know whether this method is better, there are other cars torqued up exactly as per manual and appear to be ok also, so your choice on whatever you would use, maybe the important thing is the retorquing at regular intervals which keeps an even clamp on the gasket. At the last retorque (last year) I was unable to see any difference in the amount the nuts and studs tightened to how they were fixed by myself previously so I assume they did not tighten up any more.

Micky

[mole42]

I used Mickey’s torque settings on my recent head job, but kept the long studs to 55. Previously I had used 65 as per the Sprint heads but only managed about 30,000 miles before the gaskets leaked.

agreed that GT knows what he’s talking about and that he doesn’t suffer fools …

Richard

[Motorsport Micky]

he doesn’t suffer fools …

Richard[/QUOTE]

Unfortunately he doesn't suffer anybody if they have a different opinion to himself, and that includes Graham Chapman and Enzio Ferrari ! which is why many people just discount what he says without examining it for it's worth. A different opinion doesn't necessarily mean a wrong opinion, "pearls cast before swine" can be rescued and used if you think they have a value.

Micky

[Tdm]

I share the same system with Neil as regards the torqueing sequence across the head and I tighten to 20/35/55/65 (long studs only see below) to try and get the head to compress equally across and along the length in sequence to avoid wrinkling the gasket.
My car has been together for 15 years now with over 13,000 miles on the engine and so far shows no problems, (retorqued 6 times by undoing one flat and retorquing up to these figures given). I don't know whether this method is better, there are other cars torqued up exactly as per manual and appear to be ok also, so your choice on whatever you would use, maybe the important thing is the retorquing at regular intervals which keeps an even clamp on the gasket. At the last retorque (last year) I was unable to see any difference in the amount the nuts and studs tightened to how they were fixed by myself previously so I assume they did not tighten up any more.
Micky

I bow to your superior knowledge (and Neil's) and find the comment about regularly retorquing very interesting. While my Inlet Manifold etc., is off I will try retorquing mine as haven't done so since 2006 (when I torqued them up to 55). When I originally torqued them up, as I said before, I followed the Haynes Workshop Manual sequence, starting in the midlle and working outwards.
Not done as many miles in the car since doing so as you have though, only about 7,000+, and not had problems with the Heads - just numerous other things..

[trunt]

My engine was assembled almost a year ago and will be installed in the next few months, I used the conventional torque pattern(spiral) and fettled the inlet manifold but did them all to 55, I kinda wish I had seen Neil's comments on the differing torques but probably too late now.

My question is weather it’s advantageous to re-torque again prior to installing the engine? obviously no heat cycle but the gasket may have compressed a bit..

terry

[flying farmer]

Put it this way, re-torquing takes a matter of minutes and is far simpler with the engine out.

If the nuts/bolts go up to exactly the same position all you have lost is a bit of time, if they go further then the gasket has compressed and it was well worth doing.

I have always done all the head bolts to the same torque (55lb). I have not bothered going any higher as I have looked inside a sectioned head and the internal structure between the studs is fairly thin.

The way that the different fasteners arrive at that torque is very different. The short bolts have very little stretch in them and although I have never measured it I reckon the number of degrees you have to turn the fastener to get from say 40-55 lbs is much less on the shortest studs compared to the longest ones,

This lack of stretch must, in my mind, increase the clamping force so Mickeys theory about reducing the torque makes sense.

However, my first Stag engine did about 70,000 miles before head gasket failure, and both gaskets had failed at the rear of the back cylinder on both sides of the block. One fire ring had formed a V into the bore, the other had formed a V into the waterway at the back of the head.

I have no idea which was causing the cooling system pressurisation problem that I was able to ignore for about 8000 miles due to a header tank being fitted, but I suspect the cause of the problem is the differential expansion between the alloy heads and cast iron block. Both the block and the head were still perfectly flat and a new pair of gaskets cured the problem (that engine was in my TR but has been in the Estate for the last 10 years)

This area at the back of the block often seems to sink, but it might just be wear caused by gasket shuffling through thermal cycling. In this case the relative clamping pressures of the short bolts don't really have any effect

Neil

[dasadrew]

Here the difference in position of the long bolts before and after a re-torque after a couple of hundred miles. Short bolts didn't show a measurable difference; can't recall what the stud nuts returned. (actual tightening done with Norbar, but positions photographed with normal wrench with unchanged ratchet position before/after)

Drew

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