I have a 472 out of a 74. It is in a 70 deville and was wondering if anybody knows what size the plugs are to block off the smog pump inlets in the heads? I'm getting pretty pissed at this thing lately and have not been able to search and find anything usefull. Please let me know if I have missed it or if someone knows from experience.

Thanks
Charlie

I think they are 1/2".

I was at my shop when they installed them in the 500 I built. They cleaned out the holes with a drill, smeared some sealant on the plugs and pushed them in with a brass punch and hammer. As mentioned, I think they are 1/2", I'd clean up the holes first, and see if you can get a rough measurement.

Come to think of it, my engine builder commenting on using a sharp bit, and it was a heavy duty drill, not some pip-squeak 3/8" cordless. I had to hold the engine on the stand when he was doing this, so I'd recommend having a friend around to keep the engine steady. He paid special attention to how clean the holes where too. In the end, it did not take very long to do.

If you have the smog rail you could measure the ends to confirm the size, they are a press fit if I remember correctly.

If you can wait until June 14th, I can measure the ones I used, if you like.

If all else fails, just call Cad Company or MTS, I bet they know off the top of their head.

Cheers,
Bovey

I installed these yesterday in my 74 Talisman and they are 11/16". Now I'm waiting for the bottom pulley to finish the job of removing the air pump.
Regards
Alan.

The eazy thing to do is use dimes, yes 10 cent peices...Just take a socket a little smaller round and hit them in...

Hey guys.

Just measured the heads on our 500 and the smog rail we took off. And yes, they are 11/16s.

Happy Father's Day to all the dad's out there.

Cheers,
Bovey

thanks for the info. I am going to plug them tomorrow with a dime (atleast no the motor is actually worth something) and hope it helps with some of the problem.

Thanks
Charlie

I think I used a 3/8 NPT pipe tap and tapped the existing hole, then just plugged it with a pipe plug that took an allen wrench. Going by memory of several years ago but I don't remember it being too much of a chore whatever I did.
Joe

Er, um, don't use dimes, get a freeze plug and be sure to tack weld it in place. You don't need the things coming out later... I had this done on my 68, and it presents a much cleaner simpler engine compartment with one less belt to boot!