4.2 Valve clearances

[Tanguero]

Prior to having a remap at TCS and being fairly close to a 12k service I thought I had better check and hopefully not adjust my valve clearances, however this is what I found when I measured them (in thou");

Left Bank
Cyl Inlet Exhaust
1 10 14
3 9 16
5 9 20
7 9 18


Right Bank
Cyl Inlet Exhaust
2 6 19
4 6 20
6 8 18
8 4 20

I know that the clearances tend to close up with time but all the exhaust clearances are huge compared with the TVR spec 12thou!! I can only assume that they were set to at least this clearance at the last 12k service (before my ownership!)

In the temporay absence of TVR Power does anyone have any Idea where I can get suitable shims?

Edited by Tanguero on Sunday 17th August 11:07

[Tanguero]

10 thou inlet and 12 thou exhaust was what trackcar suggested (in a thread I can't now find!!)
8 & 10 thou is the factory setting.

What puzzles me is that the clearances are meant to close up with wear, which mean my exhaust valves must have been massively out when it was last done.

[Tanguero]

Ummm - I dont think so. I have exhaust valve gaps in the region of 18 - 20 thou at the moment which is far to big. If they close up with time then the must have started out even bigger.

Edited by Tanguero on Monday 18th August 12:47

[Tanguero]

trackcar said:

The inlets close up, but you never usually have any problems with the exhausts .. if they're 18thou or thereabouts they've been like that for a very very long time.

Very interesting! What sort of effect on running do you think excessive exhaust clearances would have?

[Tanguero]

trackcar said:

Has very little effect on top end but makes the low speed trapping efficiency of the cam better as you're effectively reducing the lift on overlap and the overlap period, so it will actually run very nicely indeed with large clearances and much improved idle exhaust emissions! If there's no sign of wear and they're not excessively noisy you might want to leave them as is.

Would the exhaust clearances have much bearing on the remap you are going to do for me? It has always sounded a little "Massey Ferguson" especialy when cold, but I guess whether I leave the exhaust clearances on the large side will depend on if I can find some shims.

Unfortunately TVR Power's stock of shims was one of the few parts affected by the fire - most other parts are fine but no shims for the time being.

[Tanguero]

The O.D. is 10mm and the I.D. of the cup is 7.8mm and the sides are 2.54mm (100 thou) deep. The ones on my car ranged from 60 - 120 thou effective thickness.

I did find these http://www.bighealey.co.uk/search.php?keyword=shim... for an unspecified Jaguar engine - although I havn't been able to work out which one or what size valves they are for. I have asked them but no response yet.

Edited by Tanguero on Tuesday 19th August 13:11

[Tanguero]

trackcar said:

I have shims if youre struggling .. not a complete set by any means though so will depend if youre lucky or not on sizes, or contact andy at APM he must have some ?

Thanks for the offer Joo - I have just got the ones I need from Racing Green, but much appreciated anyway!

[Tanguero]

cupra20v.t said:

sorry to dig this back up again but what clearances are recomended then.

I wouldn't mind the car runing nicely with low idle emmissions (i could accept a loss on top end speed)

tvr service manual says 0.010 on exhaust and 0.008 on inlet.
someone saying trackcar suggesting 0.010 on inlet and 0.012 on exhaust
and tanguero saying his exhaust between 0.018 and 0.020

what do people advise for smooth low speed driving, nice idling etc.

are shims readily available now?

I cant help with availability of shims, but I went with trackcar's recomendation of 0.010 inlet and just evened up the exhaust to 0.018

He remapped it shortly afterwards and produced a very decent 350bph. No huge power gains for a 4.2 but most importantly smoothed out the bottom end and improved drivability massively. It is running beautifully now 6 months later.