Do you have #6 cylinder failure experiences

[JonRB]

Hi folks

Following on from an earlier thread on the subject, I'm trying to gather experiences and evidence as to whether the Speed 6 engine has an inherent weakness in #6 cylinder and, by inference, what can be done to improve matters.

So if you have had a failure on #6, or have direct experience of one, I'd very much like to hear from you either in the thread or by email (via my profile) if you prefer to be discreet.

Thanks!
Jon

[andyoleary]

Interesting question. I think it's been looked at before but, from my experience and understanding, the linear oil flow (from front to back of the head) compromises the #6 cylinder and, couple that with (perhaps) a poor level of attention when servicing (it's hard to get to) "might" lead to this being perceived as a common weak point. Perhaps there are other factors involved though.

There are options out there for oil-way mods to improve flow in that area, especially for the exhaust valve. Racing Green fitted a new feed to my engine which effectively gives a closed-loop oil flow circuit so there is no imbalance in the oil pressure anywhere in the head.

Just my tuppence....

Andy

[Whitey]

I understood it was not cooled as well as the other cylinders hence leading to problems

[Barry Ashcroft]

My thoughts is it's due to poor oil flow to the rear of the engine

[icraigmy]

Barry Ashcroft said:

My thoughts is it's due to poor oil flow to the rear of the engine

Absolutely correct. When I had my engine rebuild/upgrade at Dulfords, Richard modified the oil ways to make sure that cyclinder #6 got oil first.

[Whitey]

The Leman cars had water cooling mods done to the block to keep #6 cooler, but I understand this mod is too expensive to make sense on a road engine.

[TVR_owner]

I had also heard, not sure how true, but from quite a good source - that there was a problematic map from the factory.

With this map, when the radiator fans were running at above 3500 rpm engine speed, no 6 injector was starved of fuel causing that cylinder to run lean.

[Barry Ashcroft]

icraigmy said:

Barry Ashcroft said:

My thoughts is it's due to poor oil flow to the rear of the engine

Absolutely correct. When I had my engine rebuild/upgrade at Dulfords, Richard modified the oil ways to make sure that cyclinder #6 got oil first.

Yep mines going in next Month for the follower shaft extra oil feed mod

[andyoleary]

TVR_owner said:

I had also heard, not sure how true, but from quite a good source - that there was a problematic map from the factory.

With this map, when the radiator fans were running at above 3500 rpm engine speed, no 6 injector was starved of fuel causing that cylinder to run lean.

I've not heard that one before, very curious. Is that due to a software "glitch" or is there some other reason for the injector being starved?

Andy

[supercopa]

I had a head gasket failure between cyl 5 and 6, caused by misfire in Cyl6.

this cyl runs too hot and after a measure of compression ratio, it revealed that the ratio on 1st and 6th cyl was a lot more than others, above 12.5:1.

I was told it's because when the head gets cold after a run, it bends at the extremities. Thus progressivly slighty modifying the volume in chambers 1 and 6. No problem with the 1st chamber even with a high compression ratio because it gets fresh air from the outside and fresh oil. that's not the case with the 6th which is the hottest, with less oil...

[Barry Ashcroft]

TVR_owner said:

I had also heard, not sure how true, but from quite a good source - that there was a problematic map from the factory.

With this map, when the radiator fans were running at above 3500 rpm engine speed, no 6 injector was starved of fuel causing that cylinder to run lean.

Not sure this is correct as the injectors bank fire and are not sequential

[VARLEYHYD]

Barry Ashcroft said:

TVR_owner said:

I had also heard, not sure how true, but from quite a good source - that there was a problematic map from the factory.

With this map, when the radiator fans were running at above 3500 rpm engine speed, no 6 injector was starved of fuel causing that cylinder to run lean.

Not sure this is correct as the injectors bank fire and are not sequential

Again not sure if true, but I understood that there was an issue with the factory map, that when the fans were running the ignition timing advanced further, so no.6 suffers from detonation.



G

[TVR_owner]

VARLEYHYD said:

Barry Ashcroft said:

TVR_owner said:

I had also heard, not sure how true, but from quite a good source - that there was a problematic map from the factory.

With this map, when the radiator fans were running at above 3500 rpm engine speed, no 6 injector was starved of fuel causing that cylinder to run lean.

Not sure this is correct as the injectors bank fire and are not sequential

Again not sure if true, but I understood that there was an issue with the factory map, that when the fans were running the ignition timing advanced further, so no.6 suffers from detonation.



G

That may be it Graham, I new it was something to do with maps, fans and detonation of no 6.

Luckily, what I know first hand about S6 failures you can write on a postage stamp.

[boardinscotland]

Barry Ashcroft said:

icraigmy said:

Barry Ashcroft said:

My thoughts is it's due to poor oil flow to the rear of the engine

Absolutely correct. When I had my engine rebuild/upgrade at Dulfords, Richard modified the oil ways to make sure that cyclinder #6 got oil first.

Yep mines going in next Month for the follower shaft extra oil feed mod

Mines at Dulfords now for upgrades as well as some de cats etc. cant wait.

[tail slide]

Though the oil flow can be usefully improved throughout the engine by various means (and was on mine, after some initial problems with my modified 4-litre, inc. gasket blow on no.6 ) I understand that it's the relatively low flow of coolant around the rear cylinder, plus ignition that's rather too close to the limit of advance (ie. can often go over it if anything is not at optimum) that can cause overheating & detonation problems on 6.

Not too difficult to improve a fair amount though

Edited by tail slide on Monday 22 December 14:49

[icraigmy]

boardinscotland said:

Barry Ashcroft said:

icraigmy said:

Barry Ashcroft said:

My thoughts is it's due to poor oil flow to the rear of the engine

Absolutely correct. When I had my engine rebuild/upgrade at Dulfords, Richard modified the oil ways to make sure that cyclinder #6 got oil first.

Yep mines going in next Month for the follower shaft extra oil feed mod

Mines at Dulfords now for upgrades as well as some de cats etc. cant wait.

You will not be disappointed. Just done 12,000(and service) since my 4.0L upgrade/rebuild done at Dulfords by Richard(top man).

The engine is running absolutely fantastic and lots of power. Best thing I did to my Tamora

[Jediworrier]

Not having any knowledge of the engine before deciding to pull mine apart (less than 1000 miles from a dealer service that apparently included tappet adjustment, not payed for myself) I have to agree with neglect on servicing at the back. 12 inlet finger follower was very badly worn and had been reshimmed to shut it up without addressing the real issue, the knackered follower. Also, the blown head gasket between 5 and 6 because of a leaky injector is interesting. Before I decided the head needed to come off, I reshimmed it (12 inlet felt wrong, difficult to insert gauge but showing acceptable gap) and upon cranking/firing up fuel was spraying back from cylinder 5. Upon removal of head the gasket was showing signs of starting to blow between 4 and 5 and had a leaky injector on 5.
Head mods were apparently done at just under 9K by, from reading this forum, a pretty good garage but it's just a scribble on the back of a page in the log book with a signature so not really to sure what's been done - apart from less than 10,000miles since.


ETA, sorry if techno jargon's wrong, I'm not a mechanic.

Edited by Jediworrier on Monday 22 December 21:42