Valves too long. What can I do?
 

A few months ago I dropped my '99 head off at a machine shop. The valves on cylinder 1 had collided with the piston, after the rod had let go.

So I bought a set of new Supertech +1mm valves and springs from another member here. The machine shop took ages to do the job and then at first they didn't realize the valves were 1mm bigger. I explained everything when I dropped off the head. So after they've done all the work for stock sized valves they were going to install the valves and realized it doesn't work.

I finally got the head back with everything installed and guess what? There is no valve lash, because the Supertechs are 0.6mm longer. I'd told them that too when I dropped off the head.

I have given them the opportunity to fix the problem, but at this point, I'd rather do it myself.

Here are my options:
- Take it all apart and grind down the valve stems (for that I need a machine shop which will take months again)
- Install shorter shims (expensive - a shim is almost $4 and I need 16 of them. Also I can't tell right away, what size I need, since I have 0 lash right now, so I would need to buy a complete set with different sizes!)
- OR: I have a set of hydraulic lifters off a '97 engine. Can I install those? Does the '99 head have what it takes to feed them with oil?

BTW: Emilio from 949 said in an email to me that the longer valves will work with the stock cams.

I'm only planning on running the engine like that for maybe 6-12 months, so it needn't be the super-best solution, just something to work for a while.

Find a machine shop that isn't staffed with hackjob imbeciles and it will take them a couple of hours at most to tip the valves and bring the lash back into a serviceable range.

Did they machine the seats? Maybe they were cut too deep?

Yeah - they machined the seats. I don't think they're cut too deep. I saw the head with just the valves in and they looked nice and flush.
But the Supertech valves are 0.6mm longer. If you don't adjust for that somehow, you're not going to get the valves to seat!

Savington: From a purely theoretical standpoint wouldn't it be better to go with thinner shims instead? That would keep the valvetrain weight down. If I can't do the quick & easy fix (hydraulic lifters), then i would like to do what's best for performance, if it's not too expensive.

Supertech Cam Follower Lifter Miata
Supertech Lash Caps Miata

Probably to expensive, but its what I did.

^ Yupp. That's a little more than I can afford to spend right now.
Just the lash caps are more expensive than the stock shims anyway. And I'd still have the problem of not knowing what size I'd need.

With those I ordered larger than needed, and grinding them the way you do valve tips.

do they make a valve that will fit the head with out mods? i bought a set of Manley valves, i never thought they would be any different in length?

Does anybody know if I can just use the HLAs from the '97 head?

MS SUBs and 6mm generic lash caps in another option.
Yet another; Zetec Shimless (Ford YS4Z-6500-...), if the needed thickness is in the range 17.145-17.655mm.

I'm far from a valvetrain guru, however it's been my experiance (on other engines such as the ACVW) that cam manufacturers seem to specify different cam grinds for use with hydraulic vs. solid lifters, insofar as that they use slightly different lobe profiles for the two.

I've utterly no idea what, if any, practical ramifications this might have in the real world of B engines.

HLA cams don't have to have a initial ramp to take out the lash, they can stomp directly to the real ramp without damaging the valvetrain.

I don't know if there are oil feeds for the HLAs in the NB heads (position, volume etc). Looking at some old post by FM-Keith, it seems like the VVT head lacks the feed but the earlier NBs have it.

Just checked - the '99 head has the oil-feeds. So... the verdict on the HLAs is?

no go on the HLA's as the 99 cams are ground for soild lifters.

in this situation, get the valves ground down.

i have to say that supertech did a dick move by making the valves .6 longer in the stem and not above the keepers.


find a different machine shop to do the work in a timely manner. its simple basic work that doesnt even take that long.

Come to think of it, I also have the cams for the HLAs. Not the perfect solution- I understand. But workable?

workable, probably, but its stupid. you might as well have a 94 head on your car with that setup. the HLA cams have much less lift than the NB soild lifter cams.

The issue you're going to have is that 0.6mm is ~.024". Most Miata OEM shims are in the .125-.132 range, so even if the seat cut didn't lose you any distance at all (it did), the 0.6mm longer valves are going to put you outside of the usable range of any available shimset, and probably outside the safe range for the factory HLAs too.

You really need to find a competent machinist to finish the job. Give him all the lifters and he should be able to get everything set up correctly. It's the only correct way to do this.

If the valves are sitting flush to the chamber that means the machine shop sunk the valves. This kills flow, screws with valve spring install height/seat pressure and lash etc. I suggest you correct the real problem and take it to a competent machinist, you may need to have new valve seats installed.

Sav

Would you be ok with tipping the valves .080" to get clearance?
I am working on this exact problem with an MSM head, and that is what we need to get clearance.

Find a machinist who knows more than me, which is sad. You need to call it a loss and move on because this engine will not live a happy life. Think of all the time and money you're going to continue putting in and around the engine, when it will certainly puke it's guts through your turbonator.