Head to water pump bolt

[The Veg]

The head has not been dropped.

[alan.barker]

Good i'm pleased for you.
It's a strange problem and difficult to imagine what's happened.
Around the Bolt holes in the Head are there any Burrs caused by the Bolts being tightened in the past. So now with the Studs tight in the holes in the Head there is no moment possible.
I know when Dowels are used to position Head and Gasket it can be difficult to remove dowels, due to Burrs.
Maybe just lift off Head to check for Burrs pushed into top of Bolt holes.
Good luck
Alan

[2cams70]

Note that Tony Ingram stocks the ARP bolts. Ideally you need to have the heads turned down slightly on three of the bolts (intake side front and rear) for cam cap clearance and also exhaust side rear for cam cover and gasket clearance. 2 of the ARP washers need to have flats machined on them for cam cap clearance and in the right hand side rear position use a smaller OD diameter ARP washer than the one supplied in the kit. All the bolts fit to perfection then.
Did you use just one thin paper gasket for the front timing cover?Some people also use an unessessary second gasket on the backplate to front cover joint. If you have this combined with use of larger diameter studs will also contribute to the situation you describe.

[rgh0]

Measured up some bolts and studs to see how different they really are.

Bottom to top in the photo

ARP Studs - 11.05 mm shank 10.90 mm threads

Original Lotus later large shank bolts - middle shank 9.80mm, threads and upper shank 10.85mm

Original Lotus early small shank bolts - middle shank 8.65mm, top and bottom shank and threads 10.90 mm

My only set of ARP bolts is in an engine so cant measure those.

So the studs are around 0.15 mm to 0.20 mm larger diameter. So they may limit moving the head by around 0.1mm or 4 thou compared to bolts. Maybe making it hard to get the front cover bolts in but it seems a small amount and suggests some other issue. Maybe try grinding a taper on the first couple of threads on the bolt to help get it started if the difference in alignment is this order of magnitude.

By the way I always place the head in position and then fit the front bolts and studs - the studs have a hex socket in the top to do this makes pulling the head much easier also if you remove the studs first also.

cheers
Rohan

[2cams70]

That's interesting. If Veg can temporarily try refitting the head with the old bolts and report the results that will give us some more information to work with. There can't be that many possibilities as to what's changed

[The Veg]

I've already discarded the old bolts as the head had been off for a couple of months.

[2cams70]

Note the ARP head stud clearance issue has been discussed here before. I prefer to still not use them though for reasons already stated. See link below

viewtopic.php?f=39&t=32893&start=

In this link it refers to stepped holes in the head - i.e ones at top are different in diameter to ones at bottom hence the problem with the studs.

I've just measured my ARP bolts. They are 11.05mm just below the head and 9.3mm along the main length.

[rgh0]

Yes - the old post is what I said then and it does not appear to be different now ! Lotus heads are living beings and were never particularly accurately machined when new and change over time in various dimensions with temperature and bolt loads and creep of the metal plus all sorts of other abuse. So its hard to be definite about anything. Yes studs are slightly bigger in diameter and you may have problems fitting them but the different is small and in general they have fitted on the heads I have used them on.

Personally I prefer studs for a racing engine as you can get higher gasket clamping loads. For a road engine the original Lotus bolts ( if you have them, I dont think I would trust modern no name brand replacements) or ARP bolts are fine.

cheers
Rohan

[The Veg]

A couple more thoughts:

Potentially the front cover assembly is not seated properly or the gaskets / sealant used is too thick or the cover and back plate dimensions just wrong. I would try to understand the root cause of the misalignment as it may be affecting other things such as chain clearance.

Same old back plate too. The new gasket for it is paper-thin, pretty sure the old one was too.

Going back to this point, I'm not sure I expressed it clearly: it's not the front cover being too far toward the front of the car, but rather being too far toward the block, as if the gasket behind the back-plates was too THIN rather than too thick. Pushing the head back would seem the easy solution but the holes are already against the studs at this point and it still didn't make enough difference.

If the amount of misalignment is small and its just due to the hole location in the front cover being a little wrong I would look at reaming out the hole in the head to allow the bolt to align or getting another front cover

That's sounding more and more tempting, much more so than taking apart the front of the engine again.

In any case, since I've un-fastened the head I may as well pull it back off at this point and see what's going on down at the bottom of it and see if that hole can be reamed or something. Will probe it again first to see if I can determine with any certainty how much off it is, since the hole is too long and narrow to see down it.

[alan.barker]

Maybe the Front Cover has been skimmed because it was warped in the past.
This could be a moment to convert to Water Pump Module.
Alan
Ps. I think i would rather redrill the hole in the Front Cover further forward and fit a stainless keyed insert. Better than touching the Head

[2cams70]

For reference previous owner of my engine did this bodge. Probably they tightened up the head bolts before loosely installing the three timing cover to head bolts to align things first. Not a bodge I'd recommend though.
I replaced this bolt with a new one prior to assembly and used ARP head bolts (not studs) and had no issues with the alignment.

[The Veg]

Yes the studs aren't needed for a road engine. Too thick and therefore not enough "springiness" to accommodate head to block movement at reasonable bolt torques.

I'm not familiar with this- please fill me in on the details. Does potential harm lay ahead?

[rgh0]

When designing bolted gasketed joints like the head to block join, that are required to contain pressure you generally want the bolts and the metal structure they hold together to be as stiff as practical and the gasket to be flexible. This minimises the bolt deflection under pressure loads and keeps the gasket compression load as constant as possible. It is not clear to me why the original Lotus bolts had reduced shanks of two different sizes. The ARP studs look a better design to me and the finer thread and nut give a much better control of clamping load versus torque


This type of design is different from designing a clamped metal to metal joint under cyclic mechanical loads, such as with a con rod bolted main bearing cap. The aim in this type of design is to hold the bolt stress as constant as possible to avoid fatigue failures. Thus the bolt needs to be less stiff the the compressed metal to metal join so small deflections in the join dont change the bolt tension. In these applications reduced shank bolts are common.

Apart from the potential problems that some may have fitting ARP studs due to the tighter tolerances on fit in the head holes, I see no problem using them in a road car. However they are not really needed either versus conventional bolts in a road car

cheers
Rohan

[2cams70]

Sorry but I don't entirely agree with Rohan's explanation.
Aluminium's thermal expansion rate is around 2.5 times that of cast iron. Consider an Aluminium head bolted onto a cast iron block using "dumb bolts" - i.e very rigid and stiff bolts (eg. ARP studs). Under running conditions when the head heats up because the bolts are so stiff the head will have no where to go when it expands relative to the block. It will therefore have to compress the head gasket in order to make room for itself. This happens every cool down and heat up thermal cycle. The gasket is not made of rubber with infinite elasticity. Every time a head gasket is compressed and relaxed it looses some of its elasticity to recover and it will eventually fail.
Smarter bolts are ones having adequate "springiness" to allow the head to rise slightly when it expands under heat thereby relieving the head gasket from some of the stresses of having to compress and relax during every thermal cycle. The smartest head bolts are the "torque to yield" type as used by virtually every modern OEM manufacturer these days. These bolts can maintain a constant clamping force over their entire stretch range so the head gasket is best protected over many load cycles.
The Lotus head and the Ford block were originally designed to be used with bolts having a certain clamping load. If you increase that you risk causing distortion of either the block or the head face. If you overtighten any flange bolt it bows inward right? Think the same effect when you overtighten your cylinder head.
I'm not saying your cylinder head gasket will fail if you use ARP studs but I can see from an engineering perspective that they aren't ideal. It may be ok on a hobby engine where cylinder head bolt tension is checked on a regular basis, it's not expected to run reliably over many hundreds of thousand kms with many heat up and cool down cycles, not expected to survive full RPM excursions from cold, etc. I won't be rushing to use them in my engine however.

[alan.barker]

+1
I have always reused the original Lotus Bolts on 5 different Elans +Copper original spec Head Gaskets over 46 Years.
Never retorqued a Head. Always torqued on assembly in 4 stages to sequence
Only had 1 Head Gasket blow after several thousand miles.
I must be a very lucky person
Alan