Puzzling head feature

[davep]

I've had new valve guides installed recently and I've noticed that an area around each combustion chamber is recessed a few thou, each area corresponds to the cylinder/piston circumference:



Does anyone have any idea why the recesses are there? They are 4.3 BV heads (1.69"/1.46") and have been extensively worked on so my initial thought was CR adjustment maybe.

[Chilliman]

Do you have standard pistons? Or maybe the heads have been skimmed then recessed to retain original CR? Someone cleverer than wot I am will be along I'm sure

[Ant.]

They would/should have compression rings fitted.
It is a ring of wire that presses into the copper headgaskets, to ensure a good seal.

[Alexdaredevilz]

I think Spend is the expert on these, send him a PM

[Simon says]

They are similar in design to 'Will rings' as fitted to the likes of tuned Hillman Imp engines back in the day to deal with higher cylinder pressures in performance high CR engines

Edited by Simon says on Saturday 25th August 14:58

[davep]

Thanks for the responses guys. Where is Spend these days?

If I fit composite gaskets am I going to hit problems?

[Pupp]

I'm a bit puzzled. Is this some machining that whoever did the valve guides has done or was it there when you pulled the heads for that job? If it has been done by the guide installer then you need to be asking him why etc...(maybe WTF) if it as there previously then what gaskets were fitted when it was stripped?

The composite gaskets I'm used to won't seal properly with that recess as there is a compression ring around each aperture that is intended to squash down to the thickness of the main gasket material and be gripped by both faces. If copper fire rings are intended to be used, I'd be careful to try and ensure they dont protrude into the cylinder/combustion chamber void as that's asking for trouble from a det/pre-ign point of view if they start glowing or collect carbon that does...

[carsy]

I cant belive someone has managed to get them out. When i rebuilt mine i quiried them with V8D and they said the only way to get them out would be to skim the heads.

They stated they would be fine with Composites so i left alone. If it was me i think i would give them a go with composites.

Could you not get new rings put back in.

[davep]

The recesses or groves where there before the valve guides where done. Composite gaskets came off and the block face has no corresponding grove, the gaskets where in good order.

Read some info on Wills Rings and high CR on the V8 Owners Forum, blimey you learn something new everyday!

[TVR Beaver]

Looking at the pics, they are not recesses or groves... more one big reliefe into the head?...
So the groves where there before and now they have machined them to this?...
As said above... you need to measure the compresion ring on the composite gasket to see if they will compress them... if the ring is small than the counter bore you have in the head, then it won't work... the compression band will be exposed?

If it was like that before.. I can only guess its been done to lower compression?... has the block been skimmed that much that the pistons stand proude of the top LOL...

[Simon says]

It almost looks like the groove as been machined away with head skimming/facing.

[rev-erend]

If you can feel the grove with your finger nail then as others have said it's there to seal the area.

You just need to put the correct grade/size of copper wire in the grove and use a copper gasket not composite.

It's an old racing trick for extreme compression ratios but I doubt you really need it.

[davep]

An optical illusion in the pic, it's a 2-3 thou groove and like the guys said above I now know they're there to locate wire compression rings. There were no rings in place when the heads were taken off and no gasket problems. The heads have a casting number ERC 0216 and no injector notches in the inlet ports but the ports have been enlarged.

[rev-erend]

That might actually be the receiver ring .. the main one being in the block.

Do a search on O ring block / head..

Not really necessary unless using scary CR or boost.

[carsy]

All 4.3`s came out of the factory with these rings fitted into the heads. The head gaskets used with them by the factory were 1.2mm all copper ones.

Obviously at some point in the past, for some strange reason, someone has managed to take the rings out of yours. If yours ran ok with the rings removed on composites, i would just re fit with composites. Only other option is to find someone to re fit the rings.

[davep]

Thanks for the advice carsy. Like I said earlier there are no corresponding grooves in the block face.

The engine was rebuilt due to slipped liners ten years ago using a V8 Dev 4.6 performance short engine and the original BV heads, but, interestingly, the car came from the factory as a standard 4.3. I've read a previous post by Spend on TVR BV heads and I must agree there has been extensive porting and flow work done, however I cannot be sure that this was originally done by TVR Power or as part of an upgrade between 1992 - 2001.

[carsy]

The heads will have been ported by Power from the start. Having rebuilt mine I know mine also has had a lot of porting work done. I think it was Spend that has commented in the past saying the 4.3 heads were ported about as far as you can go and generally Power did a good job on them.

I would imagine your conversion involved just fitting the slightly larger valves.

[griffter]

V8D sell the wire to make new Wills rings. Listen to their advice on cutting the wire with a chamfer so that when compressed the ring is still complete.

[davep]

Grifter, thanks for the advice. When you did your engine upgrade did you do the head assembly and wire work yourself. If so, what gaskets did you use and did you do any before and after compression checks?

How's that B9 of yours, missing the Griff yet?

[blitzracing]

The wills rings I had on a highly tuned Imp engine where gas filled tubes (i think it was Argon) - not wires and the slot was about 2mm from memory. Never had a leak at 10.5:1 CR, but the head used to crack instead.