Datsun Roadster Forum-311s.org

So I am installing some smog pump insert plugs on my 1970 SRL311 and the 3rd one back only goes in halfway at the most. It seems as if the shaft on the plug is larger than the hole in the head. I've switched with other plugs and other holes and the issue stays at the #3 hole. Any ideas on how to proceed ? Maybe this is from years of carbon buildup in there ?

Maybe put some ATF in the hole, let it soak, and put a drill bit in there (turning by hand only) to remove any buildup. Start turning counter clockwise first, so you don't do any cutting.

Alternatively you could turn down the OD of the insert shaft(put into a drill and file it down, then polish). The sealing is at the threads, not on the shaft, so this would not cause any leakage.

Finally, you could cut off appx. 3/16" of the shaft length. This would still fill the cavity.

Mine all went in and seated so they were all pretty much flush to the outer surface. I would say you probably have some buildup for sure. Also make sure you don't have some messed up threads...I chased all mine first before putting in the plugs.

Pipe thread tap

They are not pipe threads. They are not tapered plugs.

I believe they are 14mm-1.5...someone correct me if I'm wrong.

Yes, that is the correct size. Threads are fine, I chased it prior to installing and it went all the way in. So the issue is beyond the threads and has something to do with the shaft portion of the insert plug into the head. So it's either try to clear out the hole, or cut down the diameter of the insert shaft.

Clear the hole. You don't want the clucking chicken, the insert portion prevents that. Pat

a rifle bore brush will help

Upon closer inspection, I see some kind of sleeve still in there from smog pump days. Not sure how to proceed at this point. Any ideas ?

Did the other holes have that? If not, maybe a big EZ out, turned counter clockwise? Do you have the old inserts? I'll dig up my old ones, and see what that could be. Pat

No the other holes did not have it. It definitely is some sort of sleeve off the old smog inserts. I'm thinking of just leaving it since it's been there for the last 20 years. EZ out scares me in that I may drop metal shavings into the head. Also, If I try to really tighten the heck out of the new insert, it may push that sleeve into the head as well. Snug it up with Loctite and check it every once in awhile ?

I'd get a le ft hand drill coat it with axle grease and drill only far enough to seat you new insert.
Dan

Left hand EZ out shouldn't make any shavings. I think the problem is the shoulder height, on the plugs. Unless you eliminate that "sleeve", your plug won't seat. I'd try PB blaster, and a large EZ out, both styles, and get it out of there. Pat

not sure if this is necessarily a practical idea, but a suggestion - use the tool that one uses to extract broken pipe from a sprinkler system - comes in 1/2 and 3/4 (i think) sizes by default. It's metal with anti-clockwise 'biting' teeth!

FWIW