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I may regret this, but...I've ordered and received those "lash caps" (I couldn't help myself
Anyway, these puppies will fit between the valve stem and the post of the SOB and will take up the gap (measured at 0.071 in) between the shim and the base circle of the cams. Of course, at .085 in, that makes these caps too thick, so I'm going to VERY SLOWLY and carefully "face the caps bit by bit until I get the valve lash that I want. Is that going to be tedious? Absolutely! Will I regret that decision halfway through? Probably. Will I fly against all wisdom and common sense just to fell smug about having SS valves and solving a stupid problem (hopefully without trashing my top-end)? You betcha!
It wont be the first time, and it probably won't be the last time.
Here's some "Valve Cap" pics showing my first test fit. Here's a cap, pre-installation Seating on the valve step. It's a slight interference fit so it seats with a satisfying "snap" Left side is w/ the cap, right side is w/o
Do not try to hand lap the shims, it won't go well. You need a precision grinding table to do it. Take the head off, bring it to a machine shop, and have them properly grind the tips of the valves to fit your shims.
Do not try to hand lap the shims, it won't go well. You need a precision grinding table to do it. Take the head off, bring it to a machine shop, and have them properly grind the tips of the valves to fit your shims.
I appreciate the input, but the valve stems are too short, not too long. Right now I have a .070" air-gap between the SOB and the cam base circle.
I doubt this is what you wanna hear. But if you're pulling the head, and removing the valves to grind the stems... Just replace the valves with parts that are correct and avoid adding all the extra mass to your valvetrain. That's my thought.
Supertech makes stainless and inconel valves that fit just fine!
Question to the general community; A few years ago (2020-ish?) there was a lot of discussion about ST valves being "soft". I'm just wondering if that has been resolved.
My machine shop’s comment was that there are a lot of factors that can contribute to accelerated wear on the valves. How was the valve seat cut? I.e. How much contact area the valve has to transfer heat. Did the valve faces get ground or lapped, removing the harder treated layer? What was the engines tune like, EGT, usage, etc. is the rest of the valve train setup correctly for the use case? Then, of course, there could’ve been bad production runs of the valves themselves.
I ended up doing stainless intake, and inconel exhaust. I asked for a conservative wide valve seat profile, which may hurt flow a little bit, but who cares. No lapping or grinding of the valve faces. I will swap to Inconel intake valves if it becomes an issue.
If the normal retailers do not have stock of the valves you need, reach out to Supertech. They will sell direct if you’re in a jam.
I replaced the ageing RX7 alternator with a "new" reman (because the old one has been running at ~16 volts continuously for years and the internal regulator has ceased to function). Now, I'm running at a more reasonable 14.4 volts and I'm loving life.
Clutch was slipping badly so I replaced the single-disk Xclutch package with a new twin-dick clutch from Clutch Master.
The new clutch is "substantial" - in that it hooks up like nothing else I have ever experienced and pulls whatever the engine throws at it..
UNFORTUNATELY it hooks up too good, to the point that I can barely drive it without it grabbing so fiercely that I stall the engine or put tremendous shock loads through the drivetrain. I think that I've ruined the synchros in the transmission because I can barely get the trans into ANY gear unless the car is rolling, or the engine is shut off. No amount of adjustment at the pedal will allow the trans to engage with the engine running. If I didn't know any better, I would say that the clutch isn't fully disengaging with the pedal to the floor and the shifter in neutral.
Right now, I'm pissed (mostly at my inability to drive this twin-disk clutch) and disheartened...
Coming from a 4 Puck Competition Clutch Stage 4, which was just as horrible as your experience with the twin disk (but it went into gears no problem, just super grabby), I hated to drive my car in town and threw a Bofi Racing Hybrid Clutch into my car and since then, I love driving it again.
These race clutches simply suck on the street, so do super light flywheels. Aint no 19 years old anymore, YO.
I had a FM Happy Meal and it couldn't hold what I was puttin' down. The XClutch ceramic "Stage 2" clutch kit was a dream to drive but it started slipping after a year of abuse. I've had Exedy clutch kits in the car in past years and was not terribly impressed with them. I haven't used an ACT clutch (yet) but I'll try ANYTHING that can hold 300WHP reliably.
Doing research...My experience with the FM2 was not the most positive; adjustment was a bit wonky, slipped after a year of (admittedly) hard use at about a 300whp power range. I think that the BOFI - while attractive - would take too long to get here (I'd like to get the car moving by this weekend). So I think the field has narrowed down to the ACT.
I'm thinking that the ZM2-XTSS ("extreme" organic street sprung) package will suit my needs. I'm a bit concerned about their 315hp (crank) rating might be overwhelmed by my car, and I almost contemplated the "XTG6" (6-puck ceramic) option. But I don't need any more grabby clutches to have to deal with. Does anyone have any readily available clutch kit options? I'm all ears.
Beyond that I found a local shop that claims to be able to rebuild a NB 6-speed, so I'll let them take a whack at repairing. I'll put my "spare" 5-speed in for the short term and see what happens.
PS - If anyone wants a slightly-used Clutch Master twin-disc for their race car, PM me and I can give a fair price for it.
Here is a thought experiment; You have a 6-speed transmission - original to the car - that has suffered multiple abuses over it's 25 year life. But after a "traumatic relationship" with a harsh (twin-disc) clutch, it has finally succumbed to horrible indignities and refuses to shift properly or smoothly. So, you remove the 6-speed and the offending twin-disc and send the transmission out for "rehabilitation", and the clutch off to the "shelf of shame". In their place you have a brand-new ACT clutch kit and a 5-speed trans that has been lurking around the garage for at least a decade.
So, the question/decision is, do you;
Put in the 5-speed and new clutch and drive off into the sunset (waiting for the inevitable damage that 300+ WHP might do to the glass-like internals of the 5-speed). while waiting for the 6-speed to be repaired. Or...
Suffer through the "driving-drought" until the 6-speed is repaired and ride off into glory (until the next thing breaks).
Wha say you denizens of MT.net? Ride now and pay later, or be stoic and wait.
I used the XTSS for years on track and street until I swapped to the BMW transmission. Loved it. Never slipped, never failed. Easy to modulate for trailer loading and street driving. It even survived a trip to the drag strip and launching.
My vote - Turn down the boost to something the 5 speed can handle reliably. I don't see the point in doing all that work just to destroy the transmission in short order.
I'm also so mechanically sympathetic it's bordering on cowardice, and drive a naturally aspirated Miata with a 5 speed. I don't have the boost addiction, my vote means next to nothing.
I'm with Option. Did the same thing when my 6 speed grenaded. Turned down the boost from 300whp to 240whp and found that the car in fact did not suck to drive in the interim.
Also surprised nobody's mentioned the SuperMiata clutch options yet? My SM sport 4 puck clutch wasn't SUPER EASY to drive, but it was streetable and could hold enough torque to kill a 6 speed (which it did eventually).
Thanks for the inputs. Yeah, turning down the boost to achieve longevity of the 5-speed is the smart (albeit blasphemous) choice.
I did seriously consider the SM clutch but I weighed it's advantages regarding superior torque handling capacity over the "immediate availability" of the ACT clutch kit. Yeah, short-term gratification over long-term usability - probably a poor decision. But seeing as how I bought an unusable (to me) twin disc system - I'm all about poor decisions!
Shameless plug again - that twin-disc is on the chopping block to a better driver than me.
09-29-2023, 08:11 PM
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