Replacement valves
 

I'm rebuilding a VVT head, and the exhaust valves on cyl 4 are pretty eroded and need to be replaced. Mazda OE run $38 each. Supertechs are about half that, but there are a bunch of sizes and I'm confused as to whether I can mix them with OE valves. There's also brand X valves for about $10 ea.

Any recommendations?

Not from my car. This was a Japanese take-off. Kinda looks like det.
https://cimg7.ibsrv.net/gimg/www.mia...9b16e2cb34.jpg

If it helps any, I have valves from a na head in my vvt head. Pretty sure they're all interchangeable between 1.8s, if you're not going big, go stock. I just measured them and did a visual inspection. I would say any would work.

Interesting. I have an old BP05 head. The valves are cast with "05" whereas the VVT head exhaust valves are cast with "4W". They went from HLA lifters to solid lifters when they went to the 4W head. If it fits, what's different enough to justify a new part number? Maybe length? Did you have to shim them funny? I guess I could measure them, ya know, for science.

intriguing, i have an 00, and 01 engine here. both have same markings and same lifters. Australia.

I think the 01 should have "6D" intake valves, but "4W" exhaust.

Funny shimming? No, i just shimmed it like normal. When i measured them they were the same height and diameter. I thought for sure they would be different. As is the story of the rest of my car as far as my vvt swap, they were just conveniently available, seemed to work and they did.

Edit, I looked at a parts site and it showed the same dimenions other than overall length. It showed 102mm for the vvt and 101.4mm for the 95. The valves I used on the 03 engine were from a 94-97 head. I did measure them 6 or 7 years ago, and i remember them being the same. I only had to order a few shims when I set clearance. Ill research more when i get back to work.

Ah! 949's description of supertech valves says something like "oversized .6mm". Starting to look suspiciously like oversized for a BP05, but the correct size for a 4W or 6D.

I just found my build thread, which I hadn't updated in 6 years, and yes. I wrote that I measured them exactly the same. So it beats the hell out of me.

https://www.miataturbo.net/build-thr...e-57217/page2/

Now 949 didn't list the lengths of the supertechs that I saw, but 5x did (all I did was google miata valve diminsions) and I found this:

Looks like they are all calling all 94-05 valve stem lengths 102mm.

The only measurements I found on my phone, partsology, claimed that the earlier models had a 101.4mm height.

Then I found this, which lists 102mm (101.89mm, close enough).

https://sites.google.com/a/philb.us/...Specifications

So I would say that they will all interchange fairly easily. I know mine did. As long as they measure up, use ones from the old BP05 head and lap them up and roll with it. Free valves!

No clue why they are different part numbers, unless they are somehow treated differently. I suspect what makes the part numbers different is that they have different numbers cast on them. I have had absolutely zero issues running the BP05 valves in my VVT head. I took the good valves out of my blown engine, and the valves out of the donor kia engine I had, and measured/eyeballed them and used the ones which looked best. That was my strategy.

Dimensions seem almost identical (my BP05 valves are about .004" shorter- avg 102.01mm vs 102.115mm). The only obvious difference is that the BP05 valves are magnetic while the BPW4 valves aren't, which suggests a different alloy.

https://cimg6.ibsrv.net/gimg/www.mia...9290d2183a.jpg

Well, holy shit. I never checked that. Way to science. Wonder what the alloy difference is?

I do believe it is safe to say they arent a weak point. The vvt head i got had huge pits in the valves. The abused kia engine i got looked pretty great. Is it possible the older ones are beefier? (Not magnetic means stainless, right?) While i cant directly make any comparisons running mismatched valves (all my valves are na valves) i dont see how it would be an issue.

If you mix, cross streams, or whatever be sure to remember which valves are where, so you can tell us which ones are where and which ones broke first.

Non-magnetic usually means stainless, yes.

Also most factory exhaust valves will have a friction welded wear tip on them

also most are of a 2 piece manufacture, where the head is welded to the stem

So when you check with a magnet, you have to check all 3 spots

The .6mm is extra length. It means when you do your valve job there is plenty if extra material to grind off when you are setting your valve clearances. I just went through this with my supertechs, thankfully i have a friend with a valve grinder!