Spark plugs/wires help

[penciltester]

Hi everybody

You guys have been a great help, now for another question.

How do you change the spark plug wires? I mean just getting to them at the back of the engine looks like an interesting procedure.

Dave at DMC Midwest suggested to remove the idle motor and fuel injection lines, which makes sense, but does anyone else have any other suggestions or tricks?

Thanks again!

[DeLorean03]

Some people say you can just "loosen" the air plenum/fuel mixture unit (the piece consisting of the throttle butterfly plates back to the fuel distributor [FD]), and you can get to the distributor cap to change the plug wires.

Personally, I would just remove it. The 6 fuel lines don't need to go in any one order, so as long as you keep track of where the other lines go on the FD, you'll be good. It just makes life much easier to me.

An excellent How-To for removing the intake manifold is here: http://dmctalk.org/showthread.php?429-How-to-Removing-intake-manifold&highlight=intake

Obviously, you don't need to do THAT...follow up to the end of Step 8.

Once again, you do NOT have to remove the fuel mixture unit, but to me, it's just easier to do it - provides me more room to move around and much better visibility on the distributor cap. YMMV.

[Gfrank]

Going to jump in here, slightly off topic if that's ok, I'm doing the same job shortly,
Recomended plug gap? Thanks

[NightFlyer]

Going to jump in here, slightly off topic if that's ok, I'm doing the same job shortly,
Recomended plug gap? Thanks

If your ignition system is stock, then run the stock plug gap = .024"

If you're running some kind of HEI, then you'll want to open up the plug gap, usually to around double the stock spec = .048"

[DMCMW Dave]

If you're running some kind of HEI, then you'll want to open up the plug gap, usually to around double the stock spec = .048"

And then start frying the distributor cap and rotor.

The system is designed around the smaller gap which electrically sets the system voltage (it takes a certain amount of voltage to jump a specific plug gap under specific circumstances). When you raise the gap the voltage required goes up as well. The stock coil may not keep up (and the car would run poorly under load), but a high output coil will keep up. Unfortunately the distributor cap /rotor is engineered for the lower voltage (there is a resistor in the rotor for RFI purposes) and when you raise the voltage in there, bad things can happen, minimally lower life of the components. And I've never seen any proof that raising the spark gap has any impact at all on how well the fuel mixture explodes in a stock engine. So - why? [If you are going high pressure, i.e. compression, turbo, blower etc., you are changing everything and it may make sense).

When you start modifying parts of the car, you need to understand whole systems and not just individual pieces of it. I have not seen a performance version of the cap and rotor yet, it's the weak link in the high voltage part of the system.

This is another potential advantage of an EFI system that has the capability of operating coil packs, now you've eliminated the cap and rotor.

[NightFlyer]

And then start frying the distributor cap and rotor.

The system is designed around the smaller gap which electrically sets the system voltage (it takes a certain amount of voltage to jump a specific plug gap under specific circumstances). When you raise the gap the voltage required goes up as well. The stock coil may not keep up (and the car would run poorly under load), but a high output coil will keep up. Unfortunately the distributor cap /rotor is engineered for the lower voltage (there is a resistor in the rotor for RFI purposes) and when you raise the voltage in there, bad things can happen, minimally lower life of the components. And I've never seen any proof that raising the spark gap has any impact at all on how well the fuel mixture explodes in a stock engine. So - why? [If you are going high pressure, i.e. compression, turbo, blower etc., you are changing everything and it may make sense).

When you start modifying parts of the car, you need to understand whole systems and not just individual pieces of it. I have not seen a performance version of the cap and rotor yet, it's the weak link in the high voltage part of the system.

This is another potential advantage of an EFI system that has the capability of operating coil packs, now you've eliminated the cap and rotor.

I agree 100% with you on the theory/engineering and especially on the WHY - but as you know, Bill R. and several others are running what Bill refers to as HEI:

1) Suitable coil (Bosch blue coil is not suitable)
2) Increased voltage into the coil
3) Widened spark plug gap

As far as I'm personally aware, no one running such a set up has any issues with frying the cap/rotor (though that could explain what happened to Farrar's car, but that remains to be seen).

I just thought I'd mention it, as you never know what kind of stuff people are running for whatever reasons.

[NightFlyer]

BTW - If Bill were here, he would have used the term 'nonsense' and the phrase 'thank you very much,' so I just thought I'd throw those into the thread for good measure :biggrin:

Bill and others have and continue to prove that you can run stronger voltage into the cap/rotor without experiencing meltdowns.

[penciltester]

Thanks for the help everybody. The process has begun. The repeated phrase from my father and uncle is "Why the hell would they put it there/make it that way?" :hmm:

[David T]

Thanks for the help everybody. The process has begun. The repeated phrase from my father and uncle is "Why the hell would they put it there/make it that way?" :hmm:

Over the years on this forum there have been several instances of no start. Eventually the trouble was diagnosed to be a none-OEM coil. For whatever reason the system does not tolerate "High Performance" type coils. As Dave S points out, you cannot bolt on a few parts and expect an improvement in performance. The motor was engineered as a system and unless you approach improvement from a systems point if view, adding a few random parts can't make any difference. Of course there is the psychological effect. In fact, my car seems to run better right after I clean it or change the oil! The other effect is if you replace an old, worn out part with a "performance" part you may notice an improvement just because the newer part replaced and old, worn out part. Not a very objective way to measure improvement.

[Chris4099]

In regards to the OP, I've swapped the plugs and wires without disconnecting a single fuel line. First remove the idle speed motor and "pipe of agony". Next disconnect the linkage between the throttle spool and butterfly valves at the air metering unit. Now remove the 4 bolts holding the W pipe to the intake manifold. Finally, remove the bolts that hold the air meter brackets in place. You can now move the whole air metering unit (with W pipe) up and towards you which will expose the distributor. It's still tight, but at least you don't have to disconnect any fuel lines. However, if you do decide to remove the whole air meter for even easier access, make sure to order new copper O-rings. You can't reuse the ones currently on the fuel banjo bolts.

When reinstalling, here's a trick to turn the "pipe of agony" into the "pipe of minor inconvenience". Put a bright light on the side of the engine. Now push the air metering flap all the way down and look inside. Adjust the light until you see it shining through the hole. Now when you start to reinsert the pipe, you can see when it's close and will help guide you through. First time I tried it this way, took me about a minute to do.

[NightFlyer]

However, if you do decide to remove the whole air meter for even easier access, make sure to order new copper O-rings. You can't reuse the ones currently on the fuel banjo bolts.

I'm still using the stock/OEM copper washers that came with my car from Dunmurry and have had the fuel lines off several times. Never had an issue with reusing them.

[DMCMW Dave]

Once you are done carefully monitor the fuel injection lines for leaks when you restart the car. If you do the "leave them all connected and move the whole assembly" method you are stressing the 30+ year old fuel lines a bit.

[NightFlyer]

Once you are done carefully monitor the fuel injection lines for leaks when you restart the car. If you do the "leave them all connected and move the whole assembly" method you are stressing the 30+ year old fuel lines a bit.

Stressing the lines (whether 33 years old or new) is definitely a greater concern than re-using the copper sealing washers is, at least IMHO.

[penciltester]

Got back from a business trip and plan to finish this up. How much torque is applied to the banjo bolts?


Thanks again

[NightFlyer]

7-9 ft/lb on the M8 hollow bolts.

9-11 ft/lb on the M10 hollow bolt.

14-17 ft/lb on the M12 hollow bolts.

I usually just tighten them down without over-tightening them (you get pretty good at it after a while). When removing them, you should've gotten a good idea of how tight they need to be.

[David T]

7-9 ft/lb on the M8 hollow bolts.

9-11 ft/lb on the M10 hollow bolt.

14-17 ft/lb on the M12 hollow bolts.

I usually just tighten them down without over-tightening them (you get pretty good at it after a while). When removing them, you should've gotten a good idea of how tight they need to be.

Although the copper washers can be reused it is not a good idea. The seals become work hardened from use and are no longer soft so it takes a lot more pressure to deform them to make them seal. When the fittings leak the temptation is to tighten the banjo bolt a little more. The banjo bolts can't take all that much torque and break. If you must reuse the seals you can anneal (heat) them up to soften them. The seals are not expensive so the best advice is to replace them. You really should have some extras anyway just in case you drop or lose any. And you can't find and pick them up with a magnet!

[penciltester]

Thanks for the help guys. I was able to get this finished today.