Fanalone restoration

[ncundy]

We move on a few steps. After considering the options and much reading of BSI and EN standards for bolt and stud design, referring to my university books and my dads brain ( ). the route we have chosen is studs with reduced shank diameters.

Any thoughts welcome particularly if anyone thinks we have missed something out

Why studs ?

Well, the use of inserts in aluminium is not because aluminium is not strong enough (in terms of UTS) but because it has poor fatigue properties. The use of bolts means that the threads in the aluminium would very quickly become damaged after only a few removal and refits of the bolts. By using studs you no longer need inserts as you will no longer have to disturb that part of the joint.

Why reduced shank diameter?

The point of highest stress in a bolt is at the inner root diameter of the first thread on the shank. This dictates the load you can put into a bolt before it breaks - so there is no point in having a shank diameter larger than the thread root diameter. Because of the way standard bolts are made the shank diameter is always the same as the outer thread diameter not the root diameter. This also brings another problem (particularly for our aluminium bits). Because the shank diameter is now greater than required its extension vs load profile means that as the engine heats up (and bolted joint expands) the increase in load across the joint is higher than need be. This manifests itself as damage to the bolted face on the aluminium (where the face has effectively been crushed). On cooling this can lead to a reduction in tension in the bolt and it comes loose. So reducing the shank diameter to that of the inner root diameter increases the relative extension of the bolt vs a given temperature rise, resulting in a lower stress at the aluminium face; so reducing the crushing of the head. It is very important that good spreader washers are used on aluminium faces - standard ones will not do.

In actual fact you can reduce the shank diameter to less than the root diameter as the stress in the first thread is a notch stress and has a load factor of greater than 1. Some books suggest you can go as low as 70% of the thread root diameter.

The work below is that of my dad.

The starting point is an M12x1.75 cap bolt (grade 12).

This is turned down to the treading diameter for an M8x1.25 (the original bolt size) at one end.

The shank is then turned down to the inner root diameter of the M8 thread.

M12 is used for the stud end because it is the smallest you can go for when drilling out the original M10 thread in the aluminium, and still have enough metal for the tapping diameter required.

The second photo shows roughly what they will look like installed (this one is not screwed in nor does it have the hollow dowels)

The third photo shows crush damage on the head.

Next job is to prepare the head for them. To be continued...........

There is some excellent technical advise on the ARP site (well worth reading):
http://www.arp-bolts.com/Tech/Tech.html

[lancialulu]

Neil

You may remeber I had a similar problem on my HF head (ex Paul LeClerq). quite a number of threads had gone soft. Indeed I had one stud with an M12 end that had also gone soft! and one insert inside another.

I went down the timesert route (from Wurth v expensive) and used Aurelia cap studs (from Omicron).

One thread had to be welded up and re drilled and tadded/inserted as the previous repair had breached a water way. Done several 1000 miles since and still touching wood!

The guy who did my head expressed concern on the tourque values (2.5kgm) for the caps as he felt this was 25% over the helicoil in aluminium specification. I can only assume the while the studs have to hold the cams in place with the valve spring effort on the cam caps, the caps also perfom the function of holding the rocker cover on which has the effect of pulling the cam caps off the head!!!

I agree studs are the best esp if like me you want to play around with different cams from time to time.

Tim

Re Time serts these are prone to fail as well on the smaller sizes (due to wall thickness) but you can get a stronger one called "Bigsert"!

Tim

[angelorange]

I had this problem after the engine builder in 2006 fitted wrong caps and worn out camshafts.

ARP were helpful but could not make studs from standard stock:

"We have looked at the head sheet you sent us. The closest we have in a stock part is 5.175” and the ideal length should be 4.46”, so they’re .715” too long. I think they’re wont be enough thread left for the nut, so It would not work. I've spoken with Vere-Lanca and the part they had purchased from a dealer that said they would fit are in fact to long. So this could be the same stud that has been tried and will not work.
 
I am sorry we are unable to help further. We can make them as a special. However for one set the cost is going to be very high. Like I said we have made the rod bolts for Omicrom."

In the end Peter Gerrish fitted better cam caps, had the head machined and special inserts installed.  After head gasket blew in winter 2009, I went with new head bolts M8 12.9 grade and competition copper head gasket.

No problems there after.

Studs make life difficult when you want to take head off - whole engine must come out first

best


 
 

[ncundy]

I should have said that the studs are only for the cam caps, not to replace the head bolts. I don't have a problem with the.....thankfully 

[lancialulu]

Lukas/Neil

I too was only refering to the cam caps. On a 1600 I cannot remember but I think there is still clearance to remove the cam caps with the head in place.

On head bolts I would always recommend the use of 12.9 cap bolts and the thick washer as supplied by Omicron and others. and progressively tourque down to c 25ftlb as opposed to 14ftlb (?) for the fiat bolts.

[DavidLaver]

For anyone else wondering "what's a time-sert" here's the FAQ with a nice little demo movie up the top.

http://www.timesert.com/html/faq.html

David

[fay66]

Thanks David,
Well worth watching.

Brian
8227

[ncundy]

Very good ! What was the spray he was using - I could do with a bit of that!

[ncundy]

With my dad back from his holidays we start again 

Now into drilling and preparing the head.

First the faces of the head bolt holes were refaced level as they were all crushed because the spreader washers were not big enough. This was done with a cutter mounted on a dowel guide in a vertical drill (first photo). The refaced hole surfaces  can be seen in the second photo.

Then the cam cap holes were drilled out. A guide was made out of aluminium with a hollow dowel in to locate in the dowel hole of the holes, to keep everything square (3rd photo). Then the holes were drilled down to the stop (4th photo).

Next step is to tap the threads.

[DavidLaver]

Took me a couple of times to re-read and fathom photo 3.  Have you got a picture of the upper gubbins (cam bearing) that locates in the "dowl hole of the holes".

David

[ncundy]

Yes - not the most lucid post I have ever posted  

I haven't got any photos and all the parts are at my dads but reply 124 shows the caps from the top view, reply 128 shows the hollow dowels. The cam caps have a female drilled that takes the male (visible) part of the dowel. I have done a quick drawing in lieu.

What we did was to pop the dowels out (reply 128) of the head and put one of the dowels in the drill guide, so that it would locate exactly (from whence it had come) in the head. Then we could drill out the hole with confidence. With the hole now the correct size, the dowels can be put back in the head (the diameter we need for the studs is less that the diameter of the dowel rebates) and the cam caps assembled as before, nice and true (we hope   )

[DavidLaver]

I'd not noticed that the posts were numbered - handy!!

After a reread and looking at the other photos it makes sense again...  Odd how two of the caps have three not two bolts. 

David

[ncundy]

Well, after a day a day at the NEC, an afternoon in the workshop has got me back on track after 3 months. All the studs are now in (photo 1 & 2) new washers are fitted (photo 3) and still time to make a nifty little attachment to the drop hammer to help remove the cam caps without having to resort to levering the of with a hammer and scewdriver (photo 4)

[ncundy]

Head is now finished - just waiting a final torque, so after getting some new rings from Omicron I've assembled the pistons and installed them.

Plenty of oil and use fingers not piston ring compressors and they are pretty easy to install.

Has anyone ever found a source for the water pump seals or an equivalent (even if it required some machining of the housing?). My pump is in super condition and I'm loath to just replace it with a new one. And the kids would have to go without Christmas presents if I did anyway 

[chugga boom]

hi neal, i've sent you a pm with an offer , if there was enough interest in getting replacement seals made i'd have a couple, food for thought, get a batch of say 40>50 made?? would it be worth it??