Spark plugs

Whilst I'm getting a new HG fitted they also want to change the plugs.  The standard plugs are BKR6EP-11.

I've looked in the archives and the consensus seems to be that :-

a) Don't bother with platinum, the only advantage is they MAY last longer

b) Use heat 7 instead of 6.

I need to let them know tomorrow, any thoughs?

Sorry for following up my own so qucikly, but gapping.

NGK says 44 thou

MKIV-NZ says about 0.7-0.8mm (about 33 thou)

Thoughts?

Why are you getting the HG changed? Toyota built the mkiv so that in the event of a serious engine explosion you would be able to retrieve the HG and use it again (well not really that good but they had to make sure it didnt do a mkiii and blow the HG on a regular basis).

So whats happened to make the HG go?

JB

Head gasket????

This is a new one on me. Some MKIII bod slipped the net surely.

Yours,

J

Doesn't running a thicker head gasket lower the compressions and allow you to run higher boost?

Have a look on NGK's web site for their top of th range spark plugs...can't remeber the name/number off hand.

The plugs to use are stock Toyota gapped to 1.1mm. Or if you are running higher boost than stock then go one grade colder and gap to 0.85mm. SHOP!! sells the NGK plugs at around £20 a set of six.

Still intrigued as to why a new head gasket.

Yours,

J

Hi, I've posted a few times about the BHG on the UKSUPRAS list.  I've copied my latest update below.

Do you think I'll need the colder plugs given my spec?  I haven't got a boost guage yet so can't tell what I'm actually running.  I also think I don't have the second cat in.  I've hit fuel cut twice - both after LONG WOT runs up hills at about 130MPHish.  I guess the SHOP!! plugs arn't Platinum tipped at that price, they will be the BKR7E-11.

==== Start story ====

AS some may remember back in June I was talking about my car maybe having a BHG.  I would

drive 100 miles to work and after the engine had cooled down the expansion tank was empty and

you usually couldn't see any water in the rad.  Top it up and drive home and the same thing

happened.  Take it for a 15 minute WOT run and the same thing happened.

There was no detectable leak, no problems with a pressure test and an analysis of the coolant

didn't show any exhaust gasses.

It had been to two places, and the second time in at one of them they managed to crash it on a

road test.  Not too bad, but due to a combination of errors I got it back last week after three months.

Needless to say, despite having a new rad the problem was still there.

They finally decided that it must be either a BHG or cracked head.  ( I'd originally told them it was

probably a BHG, but they naturally wanted to diagnose it themselves.)

They took the head off today and sure enough the gasket has gone.  The strange thing is the head

bolts on the inlet side were all 75lbs and the ones on the exhaust side were all 45lbs; probable

cause of BHG.

He said  he'd seen this before on Integralies, apparently due to the heat off the turbos.

So, perhaps a warning here - mine was built June 93 - chassis  number in the low 6000 range with

100,000 KMs ( 60K miles ) this may be something to watch out for.

Hopefully getting it back next Friday (how many time have I heard that before) so am looking forward

to becoming a proper member and actually turning up to events and track days etc etc.  I guess

Oakington if there as still spaces, but I don't want to book it until I've got a reliable car under my

feet!

==== End Story ====

that is strange, I have seen engines which have physically melted pistons, destroyed valves and blown turbos apart due to too much heat and boost, but none of them ever took the headgasket out.

I have also seen a few UK specs experiencing compression problems once they have put some very high miles on, normally over 130,000 or so. It may not affect all UK specs but certainly I know of 3 that have had the problem.

JB

There's another aspect to this, surely. I reckon someone has played around with the car before you owned it.

Because Branners is right: MKIV engines destroy valves and seats, melt pistons, blow turbos... but never, to my knowledge, has a MKIV *ever* blown a head gasket.

Take Justin's car, as an example. Number 1 turbo was totally shot. His valve faces had been severely eroded by detonation. The mating surfaces of the valves and seats had more craters on them than the surface of the moon... but the head gasket? Absolutely perfect.  

And all this about the torque of the bolts... ah, that's just nonsense.

For a start, the head-bolts do not have a final torque setting. Not only that, you cannot tell the torque a bolt was tightened to by the amount of torque needed to undo it.

On the basis that more torque is needed to crack loose a bolt than it was tightened to in the first place, your head bolts were mighty loose!

Yours,

J  

BTW, when, on the UK spec, will the turbos start coming to the end of their lives?

Ash and Branners,  I've had another chat with them today about it.

1) The HG looked original when they took it off.

2) It also looked like it had been loose down one side.  There were few impressions of it on the head and block.

3) It had blown across to one of the water channels

4) They took the bolts off in reverse sequence.  After the mechanic had taken the first two off (one each side) and noticed a big difference in them, he called the boss in to have a look.  They then checked the torque on the others.

5) The head was warped and ha had to be skimmed.

6) The rest of the engine looks in good condition apart from one bore has been washed out and a couple of the plugs were spotted.  They said this would be due to the coolant getting into the cylinder.

I've not seen it yet, may go down there tomorrow if I can make it, so all I can say is what they've told me.

As for the plugs, NGK don't make a BKR7EP-11.  The do it non platinum, or they do the PF7B - split fire.  I've decided to stick to the stock ones, certanly for the moment.

Still, should work OK when I get it back :-))))

Well, Steve, you appear to be the first person in the world to suffer a BHG on a MKIV. And, by all acounts, you will no-doubt be the last.

Either you were darned unlucky, or someone has been fiddling with the car before you bought it.

Either way I hope all comes right for you in the end.

Yours,

J

If you are hitting fuel cut you should consider cooler plugs. You may have a problem with missfire at high boost if you stick with the stock plugs

Ash, I think this may be one of those cursed cars ;->, I'm just waiting for it's next unfortunate episode.  Not neceseraly just the cars problem, but things happeneing around it, like the garage crashing it and the problems getting it fixed.

I'll try and get some pictures of the gaskit and post them on my members area.

By someone may have been fiddeling, what do you think?  Loosened the bolts for some reason?

Phil - I assume you mean that by hitting fuel-cut I'm running sufficient boost to warrant the cooler plugs in addition to fitting an FCD?

I'm going to be fitting a boost guage shortly so will be able to tell what it is actually running.

That is exactly what I mean.

Andy took me out in his car he had std plugs. At high boost, still got one cat, I think,  he gets a power sapping misfire.  I will have to pop and see him to see if he has fixed  it.

Misfire could be lots of things, but yes bad plugs could do it.  I didn't have any misfire problems before and the old plugs looked OK, so I recon I should be ok with the platinum 6's.  Chatting to a Evo VI owner who was running est 400BHP, he moved to 7's and started getting cold running problems, ran like a dog until it was hot then was OK.

Maybe there could be a table of members cars with columns for things like exhaust, cats, filter, plugs, boost etc.  Not sure how managable that would be thought.

I changed my plugs after taking advice from Leon.

From what I recall the plug-induced misfire does not happen in all cars despite similar mods.

I just did it as a precaution.

With NGK plugs it is not a cost issue either, it is a different matter with HKS or Blitz plugs.