So, I built an sr20det bottom end, and am now starting to overhaul the redtop head to go with it. I brought it to the machine shop to have the valve stem seals replaced. I bought the seals from Enjuku. They are supertech seals, 6mm intake, 7mm exhaust. I was under the impression that these seals were correct for the sr20det head. However, the machine shop tells me that the seals do not fit the exhaust valves. The intake valves are fine. To my knowledge, the valves are stock. Why on earth wouldn't they fit? I looked at the valve stem seals before handing them over to the machine shop, and they were correctly packaged as 6mm 7mm valve stem seals. Springs and retainers look stock if that means anything to anyone. Are these not the right seals? What's going on here.

Call enjuku

You're kidding??!!! Well, why on earth didn't I think of that!?!? Wish I was smart like you!!!

Is there any reason why the previous owner would put exhaust valves with smaller stems into the head? Possibly from a DE head for some bizzar reason? But I'd imagine they probably wouldn't be compatible with stock retainers or springs. My dilemma is, enjuku confirmed that they sent the correct seals, the box that came from enjuku had the right part numbers and the bags the seals came in had the right part nubers. So, the only option is that the valves are simply different than stock DET valves. Unless I'm not fully understanding the issue from what the machine shop is telling me.

I'm glad your smart like me and double checked... Anyways, have the machine shop measured the o.d. Of the valve stems? If they are 6mm than somewhere along the line it sounds like someone got valve guides done with the smaller de valves. When I got machine work done on my sr head they were also confused as to why the valves were.”different” and figured out to just use ka valve seals on there own. Maybe when the work was done previously, the machine shops only logical solution was to ”put it back to stock”. I just wanted to see what enjuku would say first, they are good guys and are very helpful.... No need to get bent.

I apologize for being confrontational, I (wrongly) figured you were trying to be a smart a**. Anyway, I just don't understand why someone would replce the stock SR valves with smaller DE valves (assuming that is the case). It just seems counterproductive to me.

Totally counterproductive! But for a machine shop that doesn't really know there shizz wouldn't surprise me at all.... Probably told the customer something was wrong with it and ”it will cost this much to fix it”

Well, I kinda figured it out. I had the machine shop take measurements of valve stem and the seals. verdict is, the seals are correct for an DET head. The exhaust valve stems are 6mm (where as they should be 7mm). However, the shop says they fit properly and shouldn't create any issues. I think this was either a mistake, or someone had a brilliant idea. As I understand it, a thinner exhaust valve stem will equate to better flow and less turbulence through the exhaust port. Might be minimal, but that's my story and I'm sticking to it haha

I guess the take home message here is: I have a set of brand new valve stem seals for a DET head if anyone wants them haha