What size threads are these? M18x1.5 or M20x1.5 ?

 

According to the Earl's Performance Plumbing catalog I have with me right now, it's M20 x 1.5.

 

"Here at Earl's Performance Plumbing, we'll shoot the s*** clean out of your house! After adding more horsepower to your throne, you'll want to be at least 6 feet away before flushing to avoid bodily injury. Not responsible for small children and pet loss due to failure to follow safety instructions"

Seconds later, at the sewage treatment plant

Steve: Hey Bob, did you hear that weird whistling sound? Kinda like a jet running loose in the pipes?
Bob: Did a turd shoot out of the inlet pipe and make a 15 foot splash?
Steve: Yeah, yeah it did!
Bob: That's Earl's performance plumbing then, they've been supercharging toilet bowls since 1968! I've got one of their big block commodes in my house. Did a courtesy flush one time and sucked my nads clean off!
Steve: Ah, that'd be about the time you put a v8 in your RX7, wouldn't it? That makes a lot of sense now.



This Earl, he is a reputable source? I'm going to order a pedestal adapter and I wanted to be sure before I ordered it.

 

Earl's Performance, as in Holley...Smart ***...

I tried to double-check with Transdapt as they have a good cross reference, but their site just tried to load a huge PDF and crashed my browser (stupid Firefox). Since Earls does not list M18x1.5 as a size in thier Mazda chart I have to assume it is M20.

 

Gotcha - I didn't realize that Earl's was Holley - if it were me, I'd go back to Holley if my other choice was Earl.

 

Oh, for reference for everyone else, M20 fits like a dream.