Cylinder head

[mcclelland]

Hi all,

Help and advice needed:

I have a standard twin cam head that I would like some work done on, that is converting to big valve spec; new valves, seats, guides, skimming and porting. I am aiming for something in the region of the old QED 360 head, its going into my plus 2.

I have spoken with "Autosprint" whose details I gleaned from this forum, they are prepared to do the work, but will NOT replace the valve seats, state they have had lots of problems with them falling out of Lotus twin cams ????

So.. can anyone recommend a firm that could competently carry out the above at a reasonable cost. I live in the N. West, but travel isn't a problem as its not going to be a regular thing... I hope.

Best regards, George...

[DavidLB]

Paul exon, exon engines at coalville did mine very pleased and he was a QED

[rgh0]

The seats falls out for 3 reasons

1. The engine has been very overheated- you usually know about this!
2. The interference fit with the new seats was not correct- you may not know about this but it would be a rare mistake for an experienced machine shop to make.
3. The head was too soft to retain the seats interference fit - you need to test the head hardness to know if this will be a potential problem

Any machine shop that knows twin cams will hardness test the head first before doing any major work on it as many heads these days are to soft to be reliably rebuilt which may be the source of your shops concern

cheers
Rohan

[patrics]

Hello George,

You could go to John Smirthwaite at JS Motorsport 01827 830096

Regards
Steve

[pwhitehouse]

I have recently had my cylinder head refurbished by Cylinder Head Services in Bilston (outside Wolverhampton) 01902 895590 (Colin or Carl). They replaced the exhaust valve seats which appear to have suffered from the recession associated with the use of unleaded fuel. Also the valve guides (in iron rather than phosphor bronze), recut all valve seats and refaced the valves and fitted and reshimmed the camshafts and refaced the head. They also bored and decked the block for me (+40 for Omega pistons) and plateau honed it. Sadly I am unable to reassemble the engine at present because I have now discovered two bent con rods! I am having a great deal of difficulty sourcing replacements for these, any help would be appreciated.

I have used this company previously and would recommend them. A couple of friends who are Clubmans rally men use them regularly also.

[GrUmPyBoDgEr]

I have recently had my cylinder head refurbished by Cylinder Head Services in Bilston (outside Wolverhampton) 01902 895590 (Colin or Carl). They replaced the exhaust valve seats which appear to have suffered from the recession associated with the use of unleaded fuel. Also the valve guides (in iron rather than phosphor bronze), recut all valve seats and refaced the valves and fitted and reshimmed the camshafts and refaced the head. They also bored and decked the block for me (+40 for Omega pistons) and plateau honed it. Sadly I am unable to reassemble the engine at present because I have now discovered two bent con rods! I am having a great deal of difficulty sourcing replacements for these, any help would be appreciated.

I have used this company previously and would recommend them. A couple of friends who are Clubmans rally men use them regularly also.

Hi,

I have to admit to having never hearing of cast iron being used for replacement valve guides.
In the old cast iron cylinder heads the valves often ran directly in the iron but that was a cost thing.
Can you tell me the theory about the use of cast iron in the Twinc' please?

Cheers
John

[reb53]

I have to admit to having never hearing of cast iron being used for replacement valve guides.
In the old cast iron cylinder heads the valves often ran directly in the iron but that was a cost thing.
Can you tell me the theory about the use of cast iron in the Twinc' please?

Cheers
John

The only time I've replaced mine, the originals, and the replacements, were cast iron. Certainly not bronze.

Ralph.

[512BB]

This is a very interesting topic, to me at least.

It would appear that there is more than one company called Cylinder Head Services, as I was recommended to a company of the same name, at Moulton, Northants. who come with high regard.

As far as valve guides go, what are the advantages, if any, of using bronze guides over the original steel? Is it that bronze has a self lubricating element, and therefore the tolerances can be run tighter, therefore less oil runs down the valve stem/guide than it did with the original steel guides?

If that is all there is to it, I shall continue to use the bag full of original steel guides that I have collected over the years, when I come to replace the next lot, and ream carefully to size, as those have been used for decades in twin cam engines, with no issues, if done properly.

And are you sure chaps, that you are not confusing cast iron with steel?

Leslie

[elj221c]

I can't find reference to guide material except in David Vizard's tuning book. He says that the standard guides are cast iron. It would explain why I have heard of them shattering if (incorrectly) trying to remove them cold.

He also says that bronze guides offer less friction and better heat transfer which is apparently a good thing on the exhaust valve side.

[512BB]

Hmm, interesting Roy. Perhaps the bag of original guides I have are cast iron, and not steel, as I thought. How does one tell the difference?

Roy wrote:
He also says [VISARD] that bronze guides offer less friction and better heat transfer which is apparently a good thing on the exhaust valve side.

Thats as maybe, but as I have already said, twincam heads have run happily for 3 decades, before bronze guides were ever thought of.

And chatting to Peter, above, this afternoon, his engine people say they will not put in bronze guides in a twink head, unless you want them replaced again, in very short order.

No, I will take a lot of convincing on the bronze guide debate, I will stick with original.

Leslie

[AHM]

Leslie,

Most likely cast iron - By sight Iron is greyer and will rust evenly in a matter of minutes, by sound it is duller and doesn't ring as much.

I think the Bronze Age came before the Iron Age.... and bronze was used for valve guides before the twincam was thought of.

I too would stick with Iron - cheaper and easier to fit, longer life, and for a road car you are unlikely to need the properties of bronze.

[512BB]

AHM wrote:
Most likely cast iron - By sight Iron is greyer and will rust evenly in a matter of minutes, by sound it is duller and doesn't ring as much. I understand that Simon, easy to check on a block, but on a little lose unfitted valve guide? Weren't they EVER made in steel for the twink?

I think the Bronze Age came before the Iron Age.... and was used for valve guides before the twincam was thought of. I did not know that, but call me a philistine, I am only interested in early Lotus, and the red cars of course!

I too would stick with Iron - cheaper and easier to fit, longer life, and for a road car you are unlikely to need the properties of bronze. You are right there, I don't drive like an idiot anymore, although her indoors might disagree.

Thanks for your thoughts,

Leslie

[AHM]

I'll prefix this - There are many alloys of , Bonze, Steel, and Iron.

The material would be chosen for amongst other things its resistance to wear and galling.

Bronze and Iron have self lubricating properties.

Bronze has better heat transfer than Iron, and a similar coefficient of thermal expansion to aluminium

The use of steel would be unlikely where Iron exhibits better properties.

[Spyder fan]

Perhaps the bag of original guides I have are cast iron, and not steel, as I thought. How does one tell the difference?

Leslie

Leslie,
Place one on an anvil and hit it sharply with a large hammer, if it shatters it's cast iron, if it flattens, it's steel..... simples

BTW: you seem to have a collecting fetish?


Kindest regards, see you at Donington no doubt.

[512BB]

Spyder Fan wrote:
Place one on an anvil and hit it sharply with a large hammer, if it shatters it's cast iron, if it flattens, it's steel..... simples

Strangely, I did think of something along those lines, but thought that if oil ran down the guides before..................

Spyder Fan also wrote:
BTW: you seem to have a collecting fetish?

Yeeeees. You see, I bought my first Elan, ie car, when I was 21, still have it. And I loved, love, that car, so much, I knew I would I would own it for life. At least, that is the plan.

So over the years, I have amassed a small collection of parts, that, I am sure, will come in handy one day. Or, are you talking about the collection in my cellar? You better PM me about that collection Alan!

Sorry for the thread hijack George, but I have certainly learnt something on this one.

Leslie

PS. If I cannot take my parts collection with me when I go, I will bequeath it to Gary. That guy is a mensch.