Wedge TR8 plug reading - my read is time for head job

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Just pulled, re-gapped to .30, and photographed the TR8 plugs in an attempt to determine why she is still not running right.

I've found the TR8 hard to troubleshoot, since it will ring just fine on 7 or even 6 cylinders. The base motor is just so strong that she'll shrug off a lot of issues.

Several of these plugs seem to be indicating a too lean condition, but others seem pretty dark.

Plug #1

Plug #3

Plug #5

Plug #7

Plug #2

Plug #4

Plug #6

Plug #8

 

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Several of these plugs have a light tan color, which I thought was too lean but might actually be correct.

#1,3,7, 4,6 are all the same light tan.

The others seem pretty dark, especially #5

 

[Mickey Richaud]

Just to muddy the water, are you sure those are the right plugs? Woody recommended BPR5EY11 (at least I THINK that's the right number) for mine. Probably will make little difference, but just some fodder for the mill...

 

[tdskip]

I'll have to double check Mickey - I did research them when I put them in - but you make a good point.

 

[tdskip]

I should have added that #5 was dry, dark, but not wet. Several of the plugs had some oil at the base where the plug meets the cylinder head, but none was actually damp.

 

[Mickey Richaud]

The light-colored ones look pretty close - maybe slightly lean. Others are rich. Wires in good shape?

 

[tdskip]

The wires have less than 1000 miles on them. #3 was iffy, so I replaced it.

The plugs I have in there are a cooler version of plugs that NGK recommends for the car, gaped to .30 based on factory specs. NGK recommends .35 as an FYI.

 

[PeterK]

I always shoot for turkey-turd brown, just a little browner that what you have. You can always step down a heat range and try to see if it's better. But check for the correct plugs first.

I've not had good luck (ever) with NGKs and would recommend Bosch first. ymmv of course.

 

[Geo Hahn]

...I've found the TR8 hard to troubleshoot, since it will ring just fine on 7 or even 6 cylinders. The base motor is just so strong that she'll shrug off a lot of issues...

There is a trick that is useful on the 4 cylinder TRs if you suspect a miss -- might be helpful on an 8 where it is even harder to hear.

Just after starting a cold engine (carefully) feel the temp of the exhaust manifold at each cylinder and see if any are noticeably cooler than their neighbors.

Could also be done with an infrared thermometer if you have one but the difference in a cylinder that isn't firing well is pretty easy to tell by feel.

 

[tdskip]

...I've found the TR8 hard to troubleshoot, since it will ring just fine on 7 or even 6 cylinders. The base motor is just so strong that she'll shrug off a lot of issues...

Just after starting a cold engine (carefully) feel the temp of the exhaust manifold at each cylinder and see if any are noticeably cooler than their neighbors.

Could also be done with an infrared thermometer if you have one but the difference in a cylinder that isn't firing well is pretty easy to tell by feel.

Oh, what a practical idea. Never thought of it. I'll - carefully - give that a go next time I have doubts about if a cylinder is firing Geo.

I think I've ruled out a full miss at this point. The black plug is what has me most concerned at this point.

Is a bit of oil at the base considered an issue?

 

[RonMacPherson]

Another way, is to use a squirt gun, or water spritzer, to see which cylinder doesn't "vaporize" the water.

 

[BobbyD]

Re: TR8 plug reading - my read is time for head jo

Guys, I can't read plugs well at all but I found a couple of good info sources about it. The first one is on my site https://tr6.danielsonfamily.org/spark_plug_heat_range.htm and provides lots of good info on plug types, heat ranges, applications, old vs new models etc and was compiled with the help of some Triumph "experts". Then there's this place https://www.4secondsflat.com/Spark_plug_reading.html which is all about reading plugs. I had no idea that the color of the ground strap is a timing indicator.....but again.....I can't read plugs.
Maybe this will help someone.

 

[tom628]

Re: TR8 plug reading - my read is time for head jo

The only thing I would add is, don't try to correct a really rich or lean mixture condition by changing plug heat ranges. If the plugs are anywhere near the spec. range, correct the mixture first; and timing, if necessary.

Tom

 

[tdskip]

Re: TR8 plug reading - my read is time for head jo

Thanks guys.

So with a dual carb set up how do you correct the mixture if some of the plugs on the same bank are OK and some are carbon fouled?

 

[Brosky]

Re: TR8 plug reading - my read is time for head jo

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]So with a dual carb set up how do you correct the mixture if some of the plugs on the same bank are OK and some are carbon fouled?[/QUOTE]

Tom,

Make sure the plug wires are firing on those cylinders. If they are old and heat damaged, you may not be getting a good spark, which can mask itself as an internal issue. Just because it doesn't skip or miss badly, doesn't mean that it's getting full voltage.

 

[tdskip]

Re: TR8 plug reading - my read is time for head jo

Hi Paul - sounds like you are suggesting that if some f the plugs are good on the same bank then that suggests I have a power not mixture issue.

She has new plug wires with the last 500 +/- miles. I did find a wire that had an iffy connection from the wire to the spark plug boot which I replaced.

I checked for leaks along the wires and connections with a testing light - didn't find anything.

 

[Brosky]

Re: TR8 plug reading - my read is time for head jo

How about an ohm meter/resistance reading for each wire?

Distributor cap connections inside at the towers and inside where the rotor sends the voltage? I've seen corrosion build down inside the cap towers and inside on the electrodes. It doesn't take much to cut power down enough to give you funny readings.

 

[tdskip]

Re: TR8 plug reading - my read is time for head jo

Good point - I'll have to get a proper meter.

In theory (yeah, I know) the distributor and cap and rotor should be OK since they are almost brand new units from Woody.

Before I bought her the engine was rebuilt but the distributor they reinstalled was trash. I wonder if the heads were damaged by poor firing prior to fixing (I hope) the distributor issues?

 

[Brosky]

Re: TR8 plug reading - my read is time for head jo

This may or not be your problem. Reading plugs is part art and part science, especially with the current mixes of fuel on the market compared to years ago when all hot cars ran Sunoco 260 or Shell High Test.

If you can eliminate any possible outside influences, before taking the inside path, you will be much better off.

Remember the order of diagnosis:

1. Good compression (includes checking of lift for cam lobe wear which may have an affect on fuel volume on the intake Worn rings or leaky valves must be evaluated

2. Good Spark (Distributor points or electronic, cap, rotor, wires, coil, plugs)

3. Proper Fuel/Air Mixture (carb adjustment and internal conditions)

If you follow this path, you will be less likely to miss anything or confound yourself with hidden issues.

JMHO

 

[RobT]

Re: TR8 plug reading - my read is time for head jo

So here is my dumb question for the day:

What is the difference between a "hot" spark plug and a "cold" one (other than the obvious!) and what is the best "tempraature" plug for any given engine/tune?

Have often seen folks refer to hot vs. cold plugs but was always a bit clueless about what this all meant.

Thanks,

Rob.