+1. The couple of times this happened to me, it was the machining.

 

My local shop has been doing a lot of K20-24 stuff lately. he said they are up to 200-250lb valve springs to keep those things together. food for thought cause in a miata, 90 lbs sounds big. not so much.

 

I don’t think spring pressure is the issue (running the Supertech double hive springs from 949) and my RPM is set to 7k.

Taking my head to a different shop tomorrow, will keep you posted

 

Your confused i went to their site and literally scrolled through their catalogue and it has no mention. Its all about the Chevy basically.

Thank you though.

 

I think you are confused, or just missed it. It's in the sport compact catalog on the main page. His link takes you right to it.

 

I couldn't find Chevy; maybe I'm missing something:

http://manleyperformance.com/sc/Manley_SportCompact.pdf






Just kidding around. The main page isn't really that intuitive because the links up top look the same, but point differently depending on whether you're using the sport compact part of the site.

 

Lots of talk about intake valves. Are there recommendations for exhaust as well?

 

inconel you cheap turds. Or have those failed?

 

I got a full set of Manley SS +1 intake and exhaust. Good price at Sport Compact Warehouse. Haven't really run it yet though I'll get back to you in a year!

 

I have never had an issue with any exhaust valves.

 

interesting.

 

Likely a combination of a few factors there. Exhaust seat widths are cut wider, the cam profile is not nearly as aggressive in the Miata, and (in turbo applications) you don't have the net-negative force of the air actively pushing the valve/lifter away from the camshaft. Thus, even with the same valve, they fail on the intake side and not the exhaust side.

 

ill be interested to monitor my engines health. OEM intake valves, OE seat width, double heavies, boost.

 

so to update anyone who's following this. I sent my valves, springs, retainers, keepers etc off to Supertech. Below are their findings.

 

If they wouldn't make the ******* things too long in the first place, there would be no need to cut them down, which would negate any potential interference issues.

 

So basically the keeper groove is too far up the stem of the valve?

--Ian

 

Standard Supertech answer. "The issue is clearly the fault of everyone but us even though all our parts break all the time."

I wouldn't put their parts on my lawnmower.

 

FYI I just did a comp. test and all were 200 across the board. The leak down was 1 1/2 to 2% . This is the 3rd season on this engine with the supertech inconel intake +1mm valves from Flyin Miata. I am now a believer as I used to cup the seat faces and loose lash in less then a season with the SS intakes no matter what brand. They ain't cheap, but neither is rebuilding a head a couple time a year, not to mention the time and machining.