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MG TD TF 1500 - Sparking plug..AGAIN!

Gene...hope your out there!
From another post tried the "shut down under load & coast into the garage.
Bosch Platinum WR7CPX
Gap @ .032
Think I have it ...but maybe a bit lean?
What do you think.
Also I did re-gap the plugs ..had a friend tell me "don't do that with the BP plugs..just install with factory gap"
Any feelings on that?
That is what I have done in the past and had good luck with it...but these got reset when I was trying to figure out why car was running so poorly.

Other info:
Running pertronix neg grnd with Lucas sports coil & bumblebee wire.
Timing advanced 30degrees @ 3000 RPM
Stage III tunned

First shot:
Plug # 1
Shut down under load @ 50MPHG

Cheers
David 55 TF 1500 #7427


David Sheward

Next pic:
same plug after idle for 10/15 mins


David Sheward

one more..
same plug after leasurly 20 mile drive...normal turn off:


David Sheward

Dave....

It might be a little lean but it's hard to tell without having the plug in my hand...but it's definitely not running too rich. I'd be happy with it unless your engine's supercharged...then it might be a bit lean. It sure makes a difference in what your plugs looks like when you check them after driving and not after just idling, doesn't it?

I've got the earlier XPAG head (modified for the larger valves like the MK2 and TF) but I run the 1/2" reach plugs so I can't comment on the BP's. I have a Mallory dual point with Pertronix guts and the Lucas sports coil but even then I don't gap my plugs as wide as you. You may be able to get away with it with your set-up (if it's not missing obviously you can) but you might want to close it up a bit to .028. That's still considerable wider than stock and will give you plenty of spark.
Gene Gillam

David,

It is hard to tell from the photographs, but it does not look too far off, at least in the second photo.
Ignore the black soot inside the steel shell and look at the color of the porcelain insulator. Ideally this should be light to dark brown, about the color of a Starbucks Mocha, black is rich, white is lean.
The Bosch platinum plugs work great in a fuel injected car, but not so in a carburated one as the small center electrode can carbon up easily in less than ideal mixture situations. Bosch claims that the platinum plugs are self cleaning, but a sloppy SU can crud one up pretty fast!

Good luck, Ben Travato
Benito Travato

I'm with Benny on this one. I've found that the platinum plugs are not ideally suited for carburated applications. They foul to easily. Stick with a regular tip and you will be better off in the long run.
LED DOWNEY

"It sure makes a difference in what your plugs looks like when you check them after driving and not after just idling, doesn't it?"
Gene, and how ...can't thank you enough for bringing that to my attention. It is so common sense can't believe I never heard or thought of doing this before!
Might just have to try this in my Mit's, run Bosch it it also maybe that will give me a better idea what their Platinum's should look like.
Going to try this tomorrow with some NGK's. I have a better idea what those should look like in a LBC as I have been looking at those for years...just never "shut down on load".
If nothing else gives me a good excuse to play with the TF all day again! Much more fun than drywall.
Cheers, and thanks again,
David 55 TF1500 #7427
OBTW all the above ran to operating temp of 75/80 degrees C.
David Sheward

Funny thing is I had switched to the platinum a few years ago because regular plugs were fouling sooner.
Me thinks it will take a few hundred miles to sort this out tomorrow!
David
David Sheward

Forget about the plug information, what carburators are you using 1 1/4" or 1 1/2" SU's? & what needles are you using?, Jet height?
Float level? & float level at the jet?
Also what drivability problems are you having?
Sport coil should be good to about .032" or so plug gap.
Max total advance should be about 34-26 degrees all in at 3,000 for a normaly aspirated engine or 32 or so degrees for a blower app;ication. Running poorly, please give us more info, replace the pertronix with a known good set of iginiton points, & condensor.
Len Fanelli

Len ,
You must have missed the rest....was on other threads.
Izzy sat unstated for a couple years due to auto accident. Car ran great when parked with current set-up. Always started on 1st pull and did so again after a bit of prep (fresh gas, MMO down the plug holes,ect). Then out of the blue started running poorly VERY RICH, as in enough to gag you & was hard to start. Izzy did not appear to like the "new" gas additives as discussed on another thread! Carbs removed and cleaned but believe part of problem was I reset floats at 5/16 not 7/16 (as Mr. Twist did?) 1 1/2" su's of course (TF) and all seems fine there now so just getting the mix reset. Only about 600M on the 2nd rebuild and don't want to burn a piston. Have been running the Bosch for about 8 years (prior to rebuild) and have had good luck with them. Mechanic friend told me I should never change the factory "gap" on those??
I did close these down to .032. Gene had mentioned "shut down under power" on another thread and I gave that a try. Took my carbs "up" four full flats but wondering if might be best to back off 1. As I said, main concern is to NOT burn a piston this time. Melted down 2 after fist rebuild (wrong size freeze plug "popped" at speed after about 250 miles..no fun!)
Cheers,
David 55 TF1500 #7427
David Sheward

David, you should have a GJ needle in the carbs. I have burned 2 pistons at 2 different times using GJ needles! Change to a #5 needle.
Len Fanelli

Len,
To be honest I am not sure on needles!
Carbs were re-built by John Twist years ago and had never been a problem. Out of the box , on the car and were perfect...why mess with something done by someone with far greater skills than mine!I was suspect of "crap" in them from the "new gas" problem and because they had sat dry so long gaskets had dried out. The floats were very dirty (even though I run a clear filter ahead of fuel pump) , so was glad I cleaned them. I went by the book setting floats @ 5/16 and Dave (on BBS) mentioned that John might have used "widely accepted" 7/16 instead. so leaned out the mix. At least she's no longer dripping fuel from the tail pipe now! LOL
Going to put in a set of NGK's and do the same I did with the Bosch the other day. Been around LBC's for many years and would just feel more comfortable seeing what a set of "old school" plugs look like. I have just been getting some mixed reviews from mechanics around here....but they are also mostly Chevy & Mopar guys.
Cheers,
David
David Sheward

Len, Dave,

Good thought about the needles being used but not sure that it's pertinent with the issue Dave was having.

I have found a great comparison (visual) chart for the needles: http://www.mintylamb.co.uk/suneedle/

Before I put on the supercharger I was running a #6 needle...compare that to the Moss GJ, H1 and GL. My plugs were always clean but I was probably running wayyyy to lean.

Gene
Gene Gillam

This thread was discussed between 07/08/2009 and 09/08/2009

MG TD TF 1500 index

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