Rate my spark plugs (newly acquired Pre-cat Griffith)

[EddieJT]

Clocked up something like 400miles in the last 10 years; only been driven to the MOT station and back for the last 10 years. Car has no history so don't know how many of those years these plugs have been on the car.

I should add, I’m new to V8s but it does sound to me like a missfire when cruising. Drives smoothly though, and doesn’t misbehave when accelerating hard….doesn’t sound like a misfire when idling either



Worst offender:

Edited by EddieJT on Sunday 19th November 12:59

Edited by EddieJT on Sunday 19th November 14:04

[GreenV8S]

Those three are obviously contaminated - perhaps due to worn valve stem seals. Since you don't really know the history of those particular plugs, I assume you'll fit new B7ECS and check the condition again at the next service.

[Panamax]

GreenV8S said:

Those three are obviously contaminated - perhaps due to worn valve stem seals. Since you don't really know the history of those particular plugs, I assume you'll fit new B7ECS and check the condition again at the next service.

Yes indeed.

Or if you're a cheapskate and know which plug came from which cylinder, just clean them up, put them back in (swapping fouled plugs with the cleaner ones) and continue driving. Obviously you'll keep a careful note and photos of what came from each cylinder and what was put back in. Then next time you check the plugs from the three potentially problem cylinders you'll know exactly where you are.

Keep an eye on oil consumption as well. You could always do a compression test while the plugs are out if you're feeling keen.

[EddieJT]

GreenV8S said:

Those three are obviously contaminated - perhaps due to worn valve stem seals. Since you don't really know the history of those particular plugs, I assume you'll fit new B7ECS and check the condition again at the next service.

Oh, do you reckon?

That’s was the original plan yes, though I read the B6ECS are better suited?

[EddieJT]

Panamax said:

Yes indeed.

Or if you're a cheapskate and know which plug came from which cylinder, just clean them up, put them back in (swapping fouled plugs with the cleaner ones) and continue driving. Obviously you'll keep a careful note and photos of what came from each cylinder and what was put back in. Then next time you check the plugs from the three potentially problem cylinders you'll know exactly where you are.

Keep an eye on oil consumption as well. You could always do a compression test while the plugs are out if you're feeling keen.

Good ideas. Interestingly it doesn’t smoke (other than a puff on first start-up).

[sixor8]

Many owners have fitted BPR6 instead of 7s, mine has them fitted by a TVR specialist. They burn slightly hotter and improve combustion. Unless you do a lot of high speed driving, or trackdays, BPR7s don't work all that well.

[Panamax]

EddieJT said:

Good ideas. Interestingly it doesn’t smoke (other than a puff on first start-up).

Smoke on start-up is generally valve guides. Oil drains down the leaking guides into the cylinders while the engine is off.
Oil consumption is often piston rings and might be valve guides.

I reckon if you keep a careful eye on things you'll be able to work out what's going on without starting to dismantle anything. I'm a significant believer in "if it ain't broke, don't fix it".

On the subject of plugs I know all sorts of people have all sorts of ideas. I generally try to stick with what the manufacturer recommended in the first place.

[eliot]

sixor8 said:

Many owners have fitted BPR6 instead of 7s, mine has them fitted by a TVR specialist. They burn slightly hotter and improve combustion. Unless you do a lot of high speed driving, or trackdays, BPR7s don't work all that well.

Agreed - colder (higher number) is more suitable for high performance/ forced induction engines and can have a propensity to foul on repeated cold starts if it’s running rich.

Op - car needs a new set of plugs as a starting point, but I don’t think that’s your primary issue

[EddieJT]

EddieJT said:

I should add, I’m new to V8s but it does sound to me like a missfire when cruising. Drives smoothly though, and doesn’t misbehave when accelerating hard….doesn’t sound like a misfire when idling either

Thanks guys; do you guys reckon the fouled plugs are causing the above?

[eliot]

EddieJT said:

EddieJT said:

I should add, I’m new to V8s but it does sound to me like a missfire when cruising. Drives smoothly though, and doesn’t misbehave when accelerating hard….doesn’t sound like a misfire when idling either

Thanks guys; do you guys reckon the fouled plugs are causing the above?

Change the plugs - three of them are shagged. Then monitor, if he same three get oily then it’s head or ring problems

[EddieJT]

Will do.

If it continues let's hope it's the head.....really can't be bothered with the hassle of removing another engine.

[Belle427]

The ignition system needs to be in tip top condition on these, plugs and leads suffer a bit as do the extenders if still fitted which are normally the source of most misfire problems.
Most change the plugs as mentioned to BPR6ES or BP6ES but this is another grey area as the R stands for resistive and its not clear which you should use.
Original extenders and leads are resistive i believe so some use the BP6ES with them and BPR6ES if the extenders are removed and aftermarket leads used.
The science being you need some resistance in the circuit for the system to work efficiently.
Happy to be corrected.

Edited by Belle427 on Monday 20th November 07:10

[Byker28i]

Isn't there also an issue with some chinese knock off plug extenders that have been around, causing misfire issues. I think some local owners found problems

[Belle427]

Yes they are better off removed tbh and the appropriate leads used with some heat protection socks for belt and braces

[EddieJT]

I have what I presume are the original Beru extenders (so not cheap Chinese), and new looking Magnecor leads. Not seeing any arcing in the dark.

I presume the misfire I suspect I'm hearing is a plug too fouled up to fire; so if I replace/clean the plugs and the fouling soon returns, how do I diagnose valve stem seals for sure?

[Belle427]

If its not being used and just started now and again that's probably your issue.
Pop a new set in it and take it for a good drive.

[EddieJT]

Let's hope so.

[Panamax]

EddieJT said:

how do I diagnose valve stem seals for sure?

The usual clue for valve seals is blue smoke out the tail pipe on start-up or when you let off the throttle and go to engine braking. Worn piston rings is low compression and oil fouled spark plugs, blue smoke on acceleration.