Big block plug wire difference?

[Mike E.]

Looking at my 1971 AIM, I notice that part numbers for spark plug wires between LS5 and LS6 are different. Then the listing under the U69 section lists different numbers for LS5 (braided), but no listing at all for LS6. Really curious why there would be a difference between the non-radio wires, and if there would be a similar difference between LS5 and LS6 braided wires.

[James G.]

Re: Big block plug wire difference?

I would be interested to know the difference as well as there doesn't appear to be a reason for a different wire between the two engines.
Have you tried searching the part numbers?
In GM PArts wiki? to determine if there is a reference to something in the parts books?

[Joe L.]

Re: Big block plug wire difference?

Looking at my 1971 AIM, I notice that part numbers for spark plug wires between LS5 and LS6 are different. Then the listing under the U69 section lists different numbers for LS5 (braided), but no listing at all for LS6. Really curious why there would be a difference between the non-radio wires, and if there would be a similar difference between LS5 and LS6 braided wires.

Mike------


There were different wires for LS-6 with and without radio although the wires for "with radio" were not shown in the AIM.

In PRODUCTION specific individual wires were used for each position although some positions used the same wire. In SERVICE individual wires were once available but only two of the original wires were available (one for the first 2 cylinders on each side and one for the last two cylinders on each side). Wire SETS were not used in PRODUCTION but were available in SERVICE. These sets may or may not have included the same wires used in PRODUCTION.

The wires for LS-6 with radio (i.e shielded) available in SERVICE were GM #6295124 (34") and GM #6295128 (28"). I am VERY confident that these two wires were among those used in PRODUCTION for the LS-6 with radio.

LS-6 without radio (non shielded) available in SERVICE were GM #2989400 (34") and GM #2989404 (28"). These are among the wires shown in the AIM for the LS-6 without radio (except that the AIM has the the 2989404 incorrectly shown with transposed 4th and 5th digits).

So, why did LS-5 and LS-6 use different spark plug wires? I know not. I can tell you that according to GM all of the wires were of the glass interbraid ("carbon core") type. I can't imagine that the shielding would have been different for LS-6 and LS-5. The only POSSIBILITY I've come up with is that the distributor end terminals for the LS-5 were straight and the LS-6 were 90 degree. If so, I have no idea why.

[Mike E.]

[Joe L.]

Re: Big block plug wire difference?

Joe, thanks for the response. There is, as you know, a paucity of original-wire big blocks out there, whether LS5 or LS6. While the LS6 used the older style plugs with gaskets and the LS5 used the “peanut plug” with tapered seats, I can’t imagine that would necessitate any difference in plug wires, nor a difference in boot angle. But who knows?

Mike------

I think you've hit on it. I had not considered that the difference in plugs could have resulted in, at least, the GM engineering perceived need for different spark plug end boots. I can say that the spark plug end boot angle was the same for all----135 degrees.

This theory is also supported by the plug wires for small blocks. The wires for gasketed plug Corvette small blocks were different than those for the tapered seat plugs.