273 Commando Spark Plug Wire Options?

-
I have a hard time believing that the fins are attached with RTV. That product cures flexible, not rigid. While it is not susceptible to many solvents, it's not rigid and not for solid, unsupported adhesion. I would have guessed some sort of epoxy.
Read through this thread. Post #6 is Leanna's post.

 
I just ordered a set of wires from Summit, made by Denso, 7mm black with red/orange boots. All made up for an LA small block. Cost just a bit over $40 delivered to my door.

Before I forget, Summit #DNP-671-8118
 
Last edited:
I just ordered a set of wires from Summit, made by Denso, 7mm black with red/orange boots. All made up for an LA small block. Cost just a bit over $40 delivered to my door.
Let us know how they are.Denso should be top notch stuff.
 
I've been really impressed with Magnecor wires. I had been working on an ignition kit for the import market years ago and we tried wires from a half dozen sources. We ended up going with Magnecor even though they were one of the pricier options on the basis of their quality.
 

I just ordered a set of wires from Summit, made by Denso, 7mm black with red/orange boots. All made up for an LA small block. Cost just a bit over $40 delivered to my door.

Before I forget, Summit #DNP-671-8118
How do they fit?
It says on Summit that they won't fit a 67 273 Barracuda
Can you please post a picture of the wires installed?
Thanks

Denso Products 671-8118 Denso Ignition Wire Sets | Summit Racing

20251114_142618.jpg
 
Last edited:
I'm glad to post a review, bit it may be a week or so until I can. They won't show up until tomorrow and I'm on the road most of next week. I really don't see how they can fit a 70 318 routing, and wouldn't fit a 273. I had 273 commando valve covers on my 340 for years and the same LA wires worked just fine. I will install them and let folks know/ take pictures. If they work, I'm gonna stock pile a few sets (I have 3 LA small blocks).
 
Read through this thread. Post #6 is Leanna's post.

Fair enough and we are going to have to agree to disagree. From a materials science standpoint in 1966 (my Barracuda's year) a black RTV Silicone used by a US automaker was like finding a Ipod that year .... you can't because it was not available yet. Available sources say stuff like this:

The factory adhesive Chrysler used was a black, hard-setting epoxy-type mastic Chrysler called it, generically, a “thermal setting black epoxy adhesive.” Internally it was a resin-based mastic manufactured by:
  • United Technologies / Dexter-Hysol precursors, or
  • 3M’s early Scotch-Weld equivalents
Why it's not what we now call RTV silicone because RTV Silicone:
  • Didn’t exist in the needed oil/heat-resistant black formulation until the late 1970s
  • Stayed flexible—not good for bonded trim
  • Was too expensive for mass production in the 60s
Epoxy, on the other hand:
  • Cured rigid and glass-hard
  • Withstood 250–300°F easily
  • Stuck well to aluminum + painted steel
  • Could be heat-accelerated on the assembly line
  • Was dirt cheap
This was the standard trim adhesive of the era.

Modern equivalents are things like:
  • 3M 08115 Panel Bond (structural, overkill, permanent)
  • JB Weld Original (steel-filled epoxy)
  • 3M Scotch-Weld DP190 or DP100 (closest to the old Chrysler adhesive)
  • Hysol EA-934NA (a nearly perfect period match, rock-hard when cured)

Feel free to vote me off the island, but the story is not checking out. Based on available records of the era, in 1965–67:
  • Silicone RTV wasn’t oil-safe
  • It wasn’t heat-stable enough
  • Black RTV didn’t exist
  • Urethane RTV hadn’t entered automotive use
  • Polysulfide RTV was toxic, expensive, and aerospace-only
  • Epoxy-RTV didn’t exist yet (epoxy adhesives cured via chemical hardener, not “RTV” vulcanization)
 
Last edited:
Fair enough and we are going to have to agree to disagree. From a materials science standpoint in 1966 (my Barracuda's year) a black RTV Silicone used by a US automaker was like finding a Ipod that year .... you can't because it was not available yet. Available sources say stuff like this:

The factory adhesive Chrysler used was a black, hard-setting epoxy-type mastic Chrysler called it, generically, a “thermal setting black epoxy adhesive.” Internally it was a resin-based mastic manufactured by:
  • United Technologies / Dexter-Hysol precursors, or
  • 3M’s early Scotch-Weld equivalents
Why it's not what we now call RTV silicone because RTV Silicone:
  • Didn’t exist in the needed oil/heat-resistant black formulation until the late 1970s
  • Stayed flexible—not good for bonded trim
  • Was too expensive for mass production in the 60s
Epoxy, on the other hand:
  • Cured rigid and glass-hard
  • Withstood 250–300°F easily
  • Stuck well to aluminum + painted steel
  • Could be heat-accelerated on the assembly line
  • Was dirt cheap
This was the standard trim adhesive of the era.

Modern equivalents are things like:
  • 3M 08115 Panel Bond (structural, overkill, permanent)
  • JB Weld Original (steel-filled epoxy)
  • 3M Scotch-Weld DP190 or DP100 (closest to the old Chrysler adhesive)
  • Hysol EA-934NA (a nearly perfect period match, rock-hard when cured)

Feel free to vote me off the island, but the story is not checking out. Based on available records of the era, in 1965–67:
  • Silicone RTV wasn’t oil-safe
  • It wasn’t heat-stable enough
  • Black RTV didn’t exist
  • Urethane RTV hadn’t entered automotive use
  • Polysulfide RTV was toxic, expensive, and aerospace-only
  • Epoxy-RTV didn’t exist yet (epoxy adhesives cured via chemical hardener, not “RTV” vulcanization)
Makes sense. I was just going by what Leanna said and she knows more about it that I do.
 
Fair enough and we are going to have to agree to disagree. From a materials science standpoint in 1966 (my Barracuda's year) a black RTV Silicone used by a US automaker was like finding a Ipod that year .... you can't because it was not available yet. Available sources say stuff like this:

The factory adhesive Chrysler used was a black, hard-setting epoxy-type mastic Chrysler called it, generically, a “thermal setting black epoxy adhesive.” Internally it was a resin-based mastic manufactured by:
  • United Technologies / Dexter-Hysol precursors, or
  • 3M’s early Scotch-Weld equivalents
Why it's not what we now call RTV silicone because RTV Silicone:
  • Didn’t exist in the needed oil/heat-resistant black formulation until the late 1970s
  • Stayed flexible—not good for bonded trim
  • Was too expensive for mass production in the 60s
Epoxy, on the other hand:
  • Cured rigid and glass-hard
  • Withstood 250–300°F easily
  • Stuck well to aluminum + painted steel
  • Could be heat-accelerated on the assembly line
  • Was dirt cheap
This was the standard trim adhesive of the era.

Modern equivalents are things like:
  • 3M 08115 Panel Bond (structural, overkill, permanent)
  • JB Weld Original (steel-filled epoxy)
  • 3M Scotch-Weld DP190 or DP100 (closest to the old Chrysler adhesive)
  • Hysol EA-934NA (a nearly perfect period match, rock-hard when cured)

Feel free to vote me off the island, but the story is not checking out. Based on available records of the era, in 1965–67:
  • Silicone RTV wasn’t oil-safe
  • It wasn’t heat-stable enough
  • Black RTV didn’t exist
  • Urethane RTV hadn’t entered automotive use
  • Polysulfide RTV was toxic, expensive, and aerospace-only
  • Epoxy-RTV didn’t exist yet (epoxy adhesives cured via chemical hardener, not “RTV” vulcanization)

Black RTV is what I have used with good results, I have done more than a few. The original adhesive is not rock hard and there are only 2 round spots, about a 1" diameter, that adheres each fin to the valve covers. It is relatively easy to remove the fins with the original adhesive and can be cleaned completely off with a wire wheel. I would not want them permanently attached. I have to throw the BS flag on the not oil-safe claim and the not heat stable. RTV is used on many joints to seal oil pans, intake manifolds, and other places as well such as exhaust manifolds and exhaust joints. It will however dissolve in gasoline. Besides, my engines do not leak oil, and I use stove pipe valve covers. Of course, what do I know. Maybe the RTV will weaken and fall off in the next 50 years that my engines will last. So far I can't tell the difference between the original adhesive and the "new" RTV in function.
 
Last edited:
I had mine black wrinkle powder coated about 5 years ago and had the fined pieces clear powder coated.
Just used a couple of dabs of clear silicone on each and their still on solid like new.
 
so the Denso wires arrived and I just installed them. Box says they were made in Mexico. They are black radio suppression wires with black boots at the cap and red/orange boots at the plugs. I worked them around to hide the Denso writing on the wires. The boots are the same color as stock boots, but are longer than stock. I'm not a numbers kind of guy and don't know when they went from black wires to orange wires at the factory. At first glance these look pretty close to stock black wires. When I put them on I tried to set them up like the early LA wires in pairs using a set of factory clips used on those years and there is no doubt that they will fit fine. They even seem a bit long, notably for the back two plugs on the drivers side. There is no issue reaching any of the plugs after you kind of test fit wires around to get the best match. Here are some pics of the mock up on my 70 Dart LA motor. By the way they also fit great on the factory 1970 LA looms on the motor, which are completely different - 4 wire loom in the back and a two wire loom on the side of the valve cover toward the front.

The wire set from Summit cost $26.99 + $11.99 shipping and handling. If you were buying enough stuff anyway to get free shipping it would be a particularly good deal.

DSC04771.JPG
DSC04772.JPG
DSC04773.JPG
DSC04774.JPG
 
-
Back
Top Bottom