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Discussion Starter #1
When I bought my car('67 396-375)it had the small tapered plug (Bosch Super R6). I replaced them with what was called for, which is the large plug with the gasket. Both are the same length and seem to work fine. What would be the difference, if any?

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Gary
1967 Camaro SS/RS 396-375 4sp.

http://community.webshots.com/user/amike95
 

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Gary, the smaller plugs were used in later model heads like 70/71(?) and up. They went to a taper seat on the plug instead of using a gasket for a seal.
If you have GM heads you can check the casting #'s at www.mortec.com and verify what you have.

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Drew

69' X-11 350, Turbo 350, Factory Air, PS, PB, 12 Bolt (410 gear) & NOT AN SS
 

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Drew,
Thanks for the reponse. I'll take the valve covers off and check the casting #'s. So, am I hearing you say that as long as you obtain a seal and the thread length is the same, either one is OK?


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Gary
1967 Camaro SS/RS 396-375 4sp.

http://community.webshots.com/user/amike95
 

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Gary, no I wouldn't say they interchange the head using a plug with a gasket will have a flat surface area where the plug screws in vs. the tapered seat plug head having a countersink surface at the plug hole.
 

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They are definately not interchangeable or their would not be 2 different part numbers.

The plug style is dictated by the cylinder heads, not the year model of the car. As was said above, the factory went to different style plugs in 71/72 and you should check the plug sealing area for either a tapered seat or a flat gasket sealing surface. If you knew the date code from the head it would also help.

-Mark.
 

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Discussion Starter #6
OK, I got ya now. Thanks!
 

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I just posted this in another thread...

<BLOCKQUOTE>quote:</font><HR>Originally posted by DjD:
...Pull a plug and look at the hole. You can tell if the seat is square or tapered and get the correct plug for your heads. There have been threads on the chevelle site and here that support guys running the wrong plugs without problems but I feel it's the little details that help in the long run...
<HR></BLOCKQUOTE>



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...Dennis
"The '69, the '96 & the club"
 

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Dennis is da "man"! He has a good way with words and getting a point across.

Are you a service "advisor" ???



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Drew

69' X-11 350, Turbo 350, Factory Air, PS, PB, 12 Bolt (410 gear) & NOT AN SS
 

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?
huh
If you have a head with a squared off plug hole you need the "gasket" large plug.
If you have a head with a tapered plug hole use the tapered plug.
The plugs will cross fit as the are both 14mm, but that is it, they will fit and not work properly.
If you put a tapered seat plug in an older square seat hole you may run the risk of contact between the piston and the plug as the tapered plug may extend further in the cylinder.

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Tim
67 ss/rs,
My slice of the web!!
 

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Tim, I agree with what your saying but if they are using the small plugs without the extended reach (i.e. R46T) the clearance would be OK without hitting the piston/valves.
I would run the correct plug for the heads on my car, regardless.
 
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