smokinggun

I have what looks to be a genuine Mugen oil cap. It however doesn't thread into my JDM B16B valve cover. Does anyone know if the threading on any of the B series valve covers differs from others? Is the threading on the JDM cover different than the USDM cover? I went to Autozone just now and the oil cap they had for the 1999 DOHC Civic fits just fine. The Autozone cap has a longer threaded area than the mugen one has...

Any input is much appreciated.

Thanks!
Anthony

JRCivic1

They should all be the same... maybe it isn't so genuine.

NVturbo

Even a cheap OEM style one should fit. The one you got is a MUUGEN.

DumpdEJ6

Fugen.

Pro-SeriesFab

What is the outside width of the threads?

The M32-3.5 thread for most any oil cap is "special", I assume due to them being injection molded.

The dimensions I get out of threadpal/machinist handbook for M32-3.5 aren't that close to what the CNC machine has to cut them to for the cap to thread in a normal valve cover . . . the minor diameter is considerably smaller than it is "supposed" to be.

My guess is whatever chinese outfit machined them, the print said M32-3.5 and they cut them without checking the threads on an actual part. Either that or you have a thread or two that is damaged.

Vtec04

Why will the stock cap not work fine? My oil cap was stock for the last 225K miles. It didn't cause any problems yet. Or do you just want this one for the looks? Just curious.

smokinggun

Nope, it's authentic.

Thanks for the reply Pro-SeriesFab, the machining on this oil cap is very well done. I believe because it's a billet cap (machined) the tolerances are much less than with an OEM threading. Recently I had this valve cover coated and even the minuscule amount of powder that reached the top threading was the culprit.

I didn't have a stock cap, and was trying to figure out if my problem was the actual oil cap itself or the valve cover. The cap itself ended up threading into another valve cover. My problem ended up being a very tiny bit of powder coat in the threading.

smokinggun

Vtec04

Glad it was something simple,

JRCivic1

Sharing that you had your valve cover POWDER COATED would have been very useful information from the beginning... this would have likely eliminated the vast majority of the "Genuine Mugen" bashing in this thread. Remember, the more information you can provide, the better chance the community can help.

Glad you got it figured out.