I am working on a ~300whp VVT motor build. I already have all the other supporting parts ordered and am now looking at new valves. I am sold on +1mm Supertech stainless intake valves. I was about to order +1mm Supertech Inconel exhaust valves when I noticed that they also carry an +2mm Inconel exhaust valve option. I have seen +2mm exhaust valves on the Supermiata CNC head and some serious builds, but I did not find lot of discussion on when +2mm exhaust valves are needed or what is needed to install them.
When should the +2mm exhaust valves be used over the seemingly standard +1mm exhaust valve upgrade? Do these +2mm cause issues with OEM valve seats and/or piston interference? Are there special machining requirements to fit the +2mm valves?

Lastly, I have read too many threads to count about keeping or removing the oil squirters on my forged VVT build. I will be using Supertech forged pistons. There seems to be a lot of discussion surrounding the Wiseco forged pistons being a different alloy with increased temperature resistance which removes the need for oil cooling on the bottom of the pistons. Also Flyinmiata's fancy Wiseco pistons force you to remove the squirters. It doesn't sound like you need squirters for most N/A builds. I did read some comments about Supertech pistons not being the best candidates for oil squirter removal (not clear why) and some claims that people are running without squirters on Supertechs with no issues. The Supertechs do appear to have similar oil draining holes under the oil control rings like the Wiseco pistons do, which has been presented as a reason for not using squirters. I have not been able to get a nice clear write-up on what to do with oil squirters on my higher HP turbo build using Supertech pistons.

I understand that the OEM cast pistons have much greater need for the cooling effect of the oil squirter compared to any forged piston. Has anyone tried to modify the oil squirters to reduce the opening and reduce the oil flow? It would seem that you could still benefit from the additional cooling and lubrication, but reduce oil flow diverted to squirters and limit oil burning by not overloading the oil control rings.

 

Has anyone install the +2mm exhaust valves in their own heads (not CNC'ed off the shelf head)?

 

I don't have any experience to add but have a question. Would using over-sized valves with stock valve seats (meaning same diameter hole) not have any difference flow? It seems like there's really nothing that is actually improved

 

I’ve built both with and without them. This last build is with them following the theory you state and some long discussions and agreement with my dyno tuner. Our warm oil pressure is about 12-15 psi lower, and not surprising, with them as compared to before and it doesn’t burn a single drop of oil even on the hard beating days.

I’ll also put a plug in for doing all the cooling mods you can afford - big intercooler and oil cooler, hood vents, ducting, etc. there’s a significantly greater amount of heat with a big HP build.

 

You should consider using the Manley oversize valves instead of Supertech based on their failures.

 

currently installing 300zx inconel exhaust valves into my Miata. you'll need a keeper from a Toyota if you wish to use the Miata retainer. also shimming the springs will be needed for this solution.

also fab9 sometimes has 30mm exhaust valves in stock.

 

I have not seen issues with Supertech valve failures as of late. Some info on issues with Supertech valve seals though. What kind of valve failures are happening?

 

I am planning on running the big RX-7 oil cooler for additional cooling on track so it should take care of the additional heat going into the oil from the bottom of the pistons.

 

Id bet you if you did a quick search you could find an abundance of info on the site.... just sayin

 

Just searched again and found issues with springs and seals. Not a single post about valves failing. Even did some google searching all the threads point to other issues like springs causing valves to fail, not valve quality issues leading to failures.

 

Looking around real quick it appears that the 34mm Manley valves are only about $30 more for the intake side. Any down side to the Manley 34mm valves?

I did finally find some concerns about premature wear on specific batches of SS Supertech intake valves, but that the Inconel exhaust valves should be fine.

 

Welp. Good luck fam.

 

HaHa! Found https://www.miataturbo.net/engine-pe...-fixed-102062/ while browsing. I wasn't searching for "soft" Supertech valves.

I remember reading this thread years ago, but I though it was just a bad batch that was fixed in later years. https://www.miataturbo.net/race-prep...t-82462/page5/

While it isn't 100% clear what is causing these valve issues, it is making me doubt the Supertech intake valves enough that I am not willing to risk it. I will definitely be looking at the Manley 34mm valves. Found the FM Inconel valves, but that's a little spendy for my budget right now.

Why are so many of our main vendors still selling these stainless Supertech intake valves if they are still producing crap results?

 

Because they work - initially - and then they fail. And the failures can be attributed to any number of things done on the engine builders side even though it's pretty clear that the issues revolve around the use of supertech.

 

Has anyone had any issues with the Manley SS intake valves? While I have not found issues related to the Manley SS intake valves, I am now debating on just getting the FM Inconel intake valves since those seem to be bullet proof, even at $33 per valve!

 

Just to verify, the correct Manley intake valves part number is 11104-8, right? https://www.summitracing.com/parts/man-11104-8

Most places seem to list these for all but VVT motors, but from what I can tell all 1.8l should use the same valves VVT or not.

 

Do I need to replace all valve guides with Bronze valve guides to be compatible with the new valves?
In the past I have ready that stainless valves needed to be used with Bronze guides to prevent galling with cast guides used on most OEM guides. I have also read that this is no longer an issue with chrome plated valves like the Manley SS and Supertech Inconel valves that I am using.

My intake valve guides all measured good, but the exhaust guides need to be replaced. I would like to just replace the 8 exhaust guides with a OEM replacement guide. Just want to make sure all guides do not need to be replaced with Bronze in order to work with the new SS and Inconel valves.

 

if the head is 100k miles old or more, replace the guides. or suffer oil consumption and smoke issues. knurling is a band aid and wont last long.

 

Bronze or cast guides?

 

Manganese bronze is your best option.