Bent valves
 

So the other day I changed my water pump, belts, etc. Well I screwed up and didn't tighten the intake cam gear. The gear slipped today, bending all 8 intake valves. Now, I am not trying to be cheap, I am just curious. I was running Supertech valves on both intake and exhaust, but I have a nice set of OE intake valves. Can I use those with my boostz?

Why not?

I don't know why not, that's why I am asking. Just curious, I really don't want to pull this turd back apart.

Sorry. I see many here make a reliable 250whp on the street with stock motors. It depends on your application. I don't know if all the track guys upgrade em (Some do, obviously), but for street use at 250whp, I personally don't see any reason not to just throw the OEM valves in. Will you be tracking your boostz?

How exactly did the valves get bent?

he's at 360+, so nowhere near 250, but IMO the stockers would still probably be fine for you Ryan.

Like Vlad said, when dynod it made 360whp, currently its just north of that. The car does get auto-x'd, track days, drag strips, and some freeway runs. And my general everyday abuse on it.

If you get some time check out the build thread, there are some videos in the last couple of pages.
https://www.miataturbo.net/build-thr...o-build-67816/

When the cam gear slipped it jumped time and they hit the pistons.

That's what I am leaning towards. If it was the exhaust side, then without a doubt I would be buying and sticking the stainless steel ones back in it. I'm just not sure if the intakes are seeing that much abuse/heat to put the stainless steel ones back in.

My biggest concern is when this car starts seeing more and more track time at the same level of power if its going to cause an issue down the road.

I guess if it does I will address it then. So for now, I will order a new headgasket, throw these in it and get back to it.

I put 275-350whp through a stock head with stock valves for quite a while (multiple track seasons). No issues.

This ^^^^


Remember, Soviet is making more than 360 with stock valves and NASTY timing table. If I were to upgrade only one side it would be the exhaust on a turbo car and intake on NA.

I would quickly hand lap them in though, and by hand I mean with a cordless drill.

So it's decked enough to an interference engine? Or is that the forged piston's fault?

The entire head has to obviously be rebuilt, or at least that side. I'd just do the supertechs while I'm at it. No point in half assing it now. Although it sounds like we're questioning the benefit of "upgraded" valves.

Cool, thanks Andrew, it's good to hear solid evidence. Now I don't worry so much, not that it is a dedicated track car, but it has been seeing that a lot more lately. Thanks again for the input.

I will lap them in and call it good.

Curly, I think it was a combination of things. The block has been decked, the head has been surfaced, higher lift cams and the forged pistons. The pistons do have relief cuts though, but not enough lol I don't really think the head needs to be rebuilt, but I am going to check the guides to be sure. When I say bent, I don't mean they are bent like a pretzel, they just barely kissed the pistons, bending them just enough that they don't seal all the way around.

If you are putting in the stock valves, at least get the valves resurfaced first, to make sure they are round. When lapping, (not my recommended procedure) make sure the lap is not too close to the outside of the valve seat. (or too close to the center, I doubt that) With all the other work done, I am wondering if the valves were perhaps +1mm? If so the stockers wont work.

No they weren't oversized, just standard sized Supertech stainless steel valves.

What do you mean by this? I don't understand when you infer that you don't recommend lapping the valves? I WOULD NEVER install a head that didn't have the valves lapped in. Well, maybe on an engine I don't care about. But not a FI engine and certainly not this one! Sure, a full valve grind and lap would be better......but I don't see a problem if the seats are in good shape and you get a good seal when lapped then you will be fine in my opinion.

If a valve grind is done correctly, the only reason to lap the valves is to see where the valve to seat relationship is. I was recommending not just lapping to the existing seat, do it right the first time.

If anything, stock valves will be stronger at the point where the stem meets the valve.

The reason most people get valves in the first place is because performance valves are undercut for added flow. The undercutting process makes valves more fragile to collisions. It is a trade off between flow and strength.

You sir are correct, for the intakes I am not going to worry about it. The valves I had look great, they are installed and now I am just waiting on a head gasket. Does anyone have a new Cometic MLS headgasket for a 1.6? :rofl:

Here is a sample lol
https://www.miataturbo.net/attachmen...ine=1382283285

ERMAHGERD THIS IS A 1.6?

Much love. Bigger engines, pfft. Why bother, amirite?

lol yeah dude, 1.6 358whp/306 ft/tq @21 psi.