Cam Cap O-ring
 

Hey so..was having issues with vtec, checked everything and everything checked out..was suggested to replace the o-ring under the cam cap as it can leak and prevent enough pressure.

so I got the part from honda 91302-ge0-000, and it's close to the right size, and I even verified online that it is DEFINITELY the right part..there is two part numbers listed but both are for a 8.8x1.9 o-ring

now..BOTH of my stock heads (I actually will be trying with the second head now anyway) have PLASTIC, flat o-rings in that spot..wider than the new rubber one and fits around the dowel looser..

I'm assuming perhaps there was issues with the plastic ring and was replaced w/rubber but I'd like some confirmation from the community or a tech note or something, just seems odd the replacement is as loose as it is but it's definitely the right part #.

engine is b17a BTW...pr3 head

Re: Cam Cap O-ring
 

I'm betting that the old o-rings aren't plastic, they are just old enough to feel like plastic. It should definitely be a rubber o-ring there.

Re: Cam Cap O-ring
 

its an o ring they look like that from the heat and age turn them to hard plastic

Re: Cam Cap O-ring
 

I thought that too. But it's not. It's ACTUALLY plastic and its sized to fit EXACTLY in the hole..

I have two b17a heads and they BOTH had the same PLASTIC ones.

it's height is the same height as the new rubber - it hasn't been flattened.

I'm assuming Honda changed the design but..

let's see if I can get good pics..

https://cimg4.ibsrv.net/gimg/honda-t...bcf1b25298.jpg
https://cimg9.ibsrv.net/gimg/honda-t...2dc6598497.jpg
https://cimg3.ibsrv.net/gimg/honda-t...1b59435d4d.jpg
https://cimg6.ibsrv.net/gimg/honda-t...4a2761a685.jpg

it's definitely plastic
​​​​​​!!!

both are pr3 heads from b17a engines from 92 gsr

one of the engines is #1700024 and came with a factory chipped ecu (wondering if the ecu was finalized at this early point in this engines production)
the other is #1700484 and came with a non chipped p61.

I would guess that most newer vtec heads indeed have rubber, and that indeed after a while it would look flattened and hard..but..even so it wouldn't *perfectly* fit the whole as if it were machined for it if this were the case..they're obviously different sizes and the material is obviously different even from the pics.

I'm guessing that they eventually replaced it with rubber in all the new motors..I'm sure the rubber probably seals better than plastic anyway..but..I wanted to confirm..see a tech note or something, especially since this is TWO heads I've seen this on and I had read before about them getting "flattened" and thought that was all it was until I actually compared new vs old..?

Re: Cam Cap O-ring
 

At least at this point I'm confident the o-ring I got is the correct replacement but..it's just weird to see something change and usually when it does there's a "part #x replaces part #y" or a tech note or..

Perhaps some of the people who thought they had a flattened rubber one actually had plastic..although I'm sure a lot of them indeed had a flattened rubber.

curious if first Gen b16s are the same..again both my b17a's were like this..

the actual parts site does show two part ##s for that spot but again BOTH are 8.8x1.9 orings, so it's not as if one was an older different style, at least from what I saw in the parts lookup..

Re: Cam Cap O-ring
 

how much do you want to bet? I could use some easy cash ;) 😈

Re: Cam Cap O-ring
 

Looking at the two side by side, the rubber is taller (thicker). The cap is going to compress the rubber, and in 20 years that rubber will be as hard as plastic and flat and leaking.

I don't know how many PCV tubes I've messed with, that snap just like plastic, look and feel just like plastic and then the new one is a pliable rubber. I would never had believed it wasn't plastic had I not bought a brand new one from Honda.

Your "plastic" ring was once a rubber o-ring that's been compressed and heated to what you found today, a plastic washer.

Re: Cam Cap O-ring
 

Still don't believe it.. and this is after reading like 20 white papers on rubber seals and washers in the last few weeks.

if it was just squished, there would be varience between the two I found..they measured identical and perfectly fit the hole and perfectly fit around the dowel while the washer does not.

I've seen flattened, hardened rubber ones but this seems totally different. You can see the difference in the material just from the reflection.

Re: Cam Cap O-ring
 

Why would it be variance, the metal parts are machined to exact specifications to within .001" or closer. They should fit the same and create the same result to the naked eye.

Also look at your picture where you did the side profile of both the rubber and plasticized rubber. The hardened one doesn't have equal thickness. Even in your picture you can see the left side is thinner than the right. That is from the rubber o-ring not being perfectly centered when compressed on assembly.

If Honda originally made plastic washers, I can assure you the thickness of the washer would be uniform throughout.

Re: Cam Cap O-ring
 

because your eyes and a photo on the interweave > a micrometer?

I found the other plastic one today...both measure 0.500" in diameter, exactly, taken at 5 measurement points around the circumference. The ring itself has more varience, which if it was compressed rubber, it shouldn't be as the washer is equal all the way around but the average width of the ring is less than 0.001 varience. The height has zero varience all the way around on both rings at 0.060"

the rubber ring is about 0.0070x0.0070 = 0.49 area cross section.

the plastic ring is 0.00565x0.0094= 0.5311 area cross section

so for something that squished over 20 years..how did I end up with MORE material?

I can't find my sub gram scale atm to compare weights but yeah..

​​

Re: Cam Cap O-ring
 

My oh my, so touchy. Interesting you claim it has more material when you can't weigh it at this time, guess your hands are > than a scale? =)

It would be interesting if you could put a small ring of oven bankable clay in the spot, assemble and bake it in the oven and take it apart to see the results.

Re: Cam Cap O-ring
 

The dark blue O-ring that you have pictured above IS the correct part... and although you firmly believe that your original parts were plastic, you would be incorrect. The only way we are going to be able to convince you is to have you install the new O-ring you have now, torque down the cam caps properly, and then in 25 years, pull it back apart and check it. What you will find is that it has miraculously transformed from a dark blue rubber O-ring into a perfectly form fitting, thinner, wider black plastic washer.

The next issue is that this passage way doesn't feed the VTEC circuit... it is for lubricating the camshaft lobes and rocker arm pads. In order for it to affect the VTEC circuit, it would have to leak internally so bad that the oil pressure would drop low enough all across the block and head to either fail to close the VTP switch and/or supply enough oil volume to mechanically lock up the rocker arms.

Re: Cam Cap O-ring
 

No ones being touchy. Trying to establish truth - regardless of whether you're right or I am right.

No one has come out and said, oh yeah, I took apart a super rare b17 20 years ago & it was rubber.

I would never be able to duplicate the exact shape and mass w/clay as you suggest so this appears an exercise in futility.

As for it having to do with VTEC, I've seen posted in several places on the interweb that it could affect things as well as supposed reports of it fixing problems - I wondered about this myself but hadn't traced the oil path.. And people wonder why I don't take their word @ face value and call me touchy?

Again..just trying to get to the truth here and I've pulled countless o-rings out of old cars..including THIS one on b16 etc..seen hardened and flattened but this is still different.

Re: Cam Cap O-ring
 

I had thought about not being able to get the same physical dimesnions however, I figured if you could get it relatively close and it turned out totally different than what you are seeing it would be fairly strong evidence supporting your theory. If on the other hand it came out pretty close to the same it would be weighing in on the other end.

Is it exact, no, but it can emulate pretty closely.

I suspect it would not be close enough to satisfy you either way but was a thought I'd toss out there.

Re: Cam Cap O-ring
 

I looked up a '93 Integra GS-R on an Acura Parts online search... and the part number for the O-ring that you need is the same as you have purchased. It is 91302-GE0-000. Here is a link to what I discovered for you:

https://www.oemacuraparts.com/auto-p...er-head-2-scat

Item/Part #25

So, even IF the part you have described was a plastic disc 25 years ago, the part number you have purchased will work perfectly in this application.

Re: Cam Cap O-ring
 

That's how I found the replacement in the first place and my question was never whether it was the correct part, just IF it had been changed.

Re: Cam Cap O-ring
 

I am reasonably confident that it has not been changed from a plastic washer to a rubber o-ring... but since I am unaware of a way to go back in history and search through the parts catalog and part numbers available in the mid 90's... there may not be a definitive answer for you on this issue. I know that the current part number has been in use (and not superseded) since 2002 because I have a package of one with that date on it. :)

Re: Cam Cap O-ring
 

I had the plastic disc in my 2000 b16 head as well. Great work on getting it out without cracking, mine cracked in half.. I put in a harbor freight o ring from the pack I had (good luck o ring) and it hits vtec fine. I ordered a honda oem o ring just in case and it did arrive like a regular o ring.

They had to change the part number a rubber o ring does not take that exact plastic shape over time, calling bullshit.

Re: Cam Cap O-ring
 

crazy..at least someone doesn't think I'm nuts? I have two early b17 engines, #1700024 and #1700484, both had the plastic both came out pretty easy too.

I found my scale but not sure it's accurate enough.

Re: Cam Cap O-ring
 

Oh boy... you both do understand that a plastic washer wouldn't completely seal... especially after it got REALLY HOT a few times... and then cooled and shrank... right ?!?

Rubber loses it's elasticity over time. Heat exposure alters the structure. So over the years, the rubber gets hard (and feels like plastic) and the shape morphs from O-ring round to flat washer shape... and it turns into the EXACT shape of the recess that it is supposed to fit in. Weird.

In short: Even IF you could pick between a flat plastic washer and a round rubber O-ring... you want the O-ring. ;)

Re: Cam Cap O-ring
 

I can assure you that when an o-ring is placed in a machined receptacle and has a flat machined surface torqued down against it, it will compress to fill the available space of the machined receptacle. I've worked on an old Honda motorcycle engine that used quite a few o-rings, and the vast majority, if not all of them, exhibited the same attributes that you are describing. I can't fault you for thinking that the o-ring was actually a plastic disk, because if I didn't know it was rubber, I'd swear it was plastic too.

Re: Cam Cap O-ring
 

Of course we would want rubber.

Read my post again on the measurements. It's not the exact shape. And I never said it wasn't a possibility just, odd.