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

[clive f]

I`d be interested to know the answer to this one myself, if no one else replies I`d call a few people who advertise servicing in Sprint, also try giving Joo a call at track car solutions.

[jbvipercerb]

When I adjusted mine I only needed 2 shims, and really could have got away without any. I swapped them around to other valves. Though your clearances are quite away out you could try this?

[HarryW]

Forgive my ignorance, is there two sets of values for valve clearances, one of the the 4.5 and one for the 4.2 . My understanding was the 4.5 clearances were 8 and 10 thou (+/-2 before having to adjust), does the 4.2 use 12 thou for both then.

I'm sure someone who actually does this, as opposed to just read it like me, will be along shortly to clarify

[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.

[HarryW]

Tanguero said:

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.

If they close up over time then 10 & 12 would make sense, you are already at the +2 allowed on setting up. Giving you -4 for them to close up before they hit the -2 tolerance.

[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

[The AJP Griff]

The way i understand it is that initially,from new,the gaps will close up due to valve stretch until they are fully 'bedded in' or whatever.Then after this initial period comes to an end,surely it is only fair to expect the gaps to increase with wear?

[trackcar]

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.

[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?

[trackcar]

Tanguero said:

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?

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.

[The AJP Griff]

It's interesting stuff,this.Joo,is it the difference in temps placed on the valves,that makes them behave differently regarding the stretching etc?Have you ever experimented with tighter clearances than std to see what the effects are?

[trackcar]

The AJP Griff said:

It's interesting stuff,this.Joo,is it the difference in temps placed on the valves,that makes them behave differently regarding the stretching etc?Have you ever experimented with tighter clearances than std to see what the effects are?

it's the waisted inlets stretching i think. You dont have to experiment with closing the gaps up, they do that themselves and they drive like a pile of poo To be fair once you get to about 30k on the engine they tend to settle and not need to much tweaking after that.

[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.

[trackcar]

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 ?

[RichV6]

Just a thought, are AJP shims unique to that engine?
If not what are they from. Also without pulling
one from the engine what diameter are they and what
is the thickness range.

On other engines, not AJP, I have on occasion had the
odd shim surface ground to size when shims were in short
supply.

[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

[RichV6]

The shims are not what I expected at all!
Thanks all the same, may well run a little longer
towards the year end before tackling this one.

rgds

Richard

[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!

[cupra20v.t]

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?