non French - spark plugs

jgra1 · Unread post by **jgra1** » 03 Sep 2009, 20:10

http://2.bp.blogspot.com/_2fj8MH_LeQ0/S ... plugs2.jpg

one pic with flash one without...
the plugs went back in wirebrushed.. so all the new black on the ceramic has only been there since the 220 mile blast.. it could be leaky rich exhaust gas..

also as before some threads are oily... even though they were clean before..

addo · Unread post by **addo** » 03 Sep 2009, 21:37

They look pretty good to me. Oil could have been on the threads in your heads, or possibly seeped into the recesses by leaky rocker cover gaskets.

Mike - MMT is an additive that colours plugs (thus affecting readings), and in greater concentrations builds up a crust. Not so good! Traditionally "readings" reflected the condition of the lead oxide coating upon the plug; it's why the modern lead-free fuels are less reliable indicators of motor health.

As to wideband vs plug readings - I'll take the wideband every time. One plug being "off" will give a clue about motor problems in a particular cylinder, or cooling issues, but overall hard data is preferred to subjective observation.

jgra1 · Unread post by **jgra1** » 03 Sep 2009, 22:06

I agree addo.. they look ok.. the van is almost nippy when on song and catches up slower cars with suprising ease.. it's only 190 horse I think, but
maybe there is some torque there...

its more the WOT and the other end, the idleing that seem off.. got plenty of ideas and things to do

see what you mean re: engine mounts, they are not far from the manifolds....

I have been told off tonight for not checking the timing.. 36° BTDC with vac advance unplugged I believe..
I didn't even know I could rotate the dizzy! as for seeing a mark on the main crank pulley, looks a nightmare

MikeT · Unread post by **MikeT** » 04 Sep 2009, 09:47

They do look a bit better than before but it's almost impossible to tell from a photo of that quality. I do think addo is right about the oil coming from above rather than within.

Addo, the overall colour tells us little more than the average mixture being burnt, pretty much as a wideband in the exhaust tells us. If you're happy with that, that's fine by me but there's far more to reading plugs than just looking at the colour. The information proper plug reading tells us is factual, not subjective, not average and not inaccurate. However, for this application and at this stage, proper plug reading is probably overkill so I won't comment any more on the matter, I just wanted to get a better understanding of what you were advising.

jgra, you're right, V8's have bucket loads of torque (you should know that, owning a V4 motorcylce 8) ) and if you're running on the lean side, there's even more available if you want it

jgra1 · Unread post by **jgra1** » 04 Sep 2009, 10:35

the planning for trip2, Cornwall, in early October is underway

this time, I will need to connect the LPG up... that will bring a whole new set of mixture issues (although it was running on LPG fine a couple of years ago) - if anything, LPG simplifies things..

Think I need to go see my friendly MOT man and check emmissions on both systems and see...

how does the carb idle on lpg? presumably the idle circuits are doing nothing... in fact, the only part of the carb that allows the engine to run must be the butterflies?
and vacuum to measure the amount of gas leaving the vapouriser...

addo · Unread post by **addo** » 04 Sep 2009, 10:56

The carb should be doing nothing on idle with LPG on - the shutoff solenoid stopping fuel supply to the bowl.

Have you looked at an exclusively LPG conversion, using aftermarket throttle body and single plane manifolding? Here's one company.

Were you to use the vehicle a lot, updating the motor to a modern aftermarket EFI would probably offer good return on investment, but it's that bit dearer and more involved when compared to a gas-only setup.

jgra1 · Unread post by **jgra1** » 04 Sep 2009, 14:19

hmm..

its an old vehicle Addo. with plenty of issues and areas to spend money, solar panels being one possibility...

it got us away and was fun.. and for the most part was powerful enough.. so part of me wants to leave well alone and enjoy it really..
get the carb running right, reconnect the LPG and throw my 250 on the back

KP · Unread post by KP » 04 Sep 2009, 15:17

LPG would be much better for the thirsty V8 you have addo

And solar panels?? why not bin the engine and get an electric motor? in that RV you could have more than enough batteries to power you to pitch site and back and charge up on their electric when you get there, just have to find a site that charges a flat rate for daily electric as i think some charge for what you use don't they

jgra1 · Unread post by **jgra1** » 04 Sep 2009, 15:59

hi Will, they are starting to do this..
although re-selling electrickery is a minefield I think

nice idea though, but would miss the sound of the 8 cylinders, each one has the capacity of a small car

jgra1 · Unread post by **jgra1** » 10 Sep 2009, 09:30

I have brought 8 new plugs for £8 inc post on ebay

apparently the chevy engines dont use sealing washers as the plugs are a taper fit.

I checked the resistance of the leads, the chevy blog has them, all fine.

I brought a new dizzy cap and rotor arm, and also will fit new centrifugal advance springs, but need to test these..

set the timing then go back to the carb ..

my 'modern engine tuning' book contains some interesting stuff about plug gaps.. the chevy has about 0.5mm at moment and 1.2m is specified, although I am not sure whether to widen the gaps now.

addo · Unread post by **addo** » 10 Sep 2009, 10:09

LPG uses smaller gaps; if you have the Delco module (that little squashed hexagon plastic ignition module with five terminals) then you can probably widen gaps more than if you are just running points and a hot coil.

You could try widening the gaps until it starts misfiring under load.

jgra1 · Unread post by **jgra1** » 10 Sep 2009, 10:20

thanks Addo

I think I will leave them as they are.. hoping to reconnect the LPG up soon...