Sunshine Guy

Clutch adjustment has been an Achilles heel on many of these Ford V8 conversions. Unless a person does a fair amount of tinkering, it can be difficult to get sufficient release travel for optimum clutch disengagement without starting with undue preloading of the release bearing.

To avoid the possible, unpleasant surprise of fast-wearing transmission synchros, after "loosening" your clutch adjustment, you might want to double check actual disengagement. If a clutch disc is dragging just slightly against the pressure plate at full release, the gears may not grind when shifted normally but the synchros are being overworked from the necessity to slow part of the mass of the clutch as well as the mass of the gears rotating at different speeds. If the drag is considerable, the synchros can overheat and fail in a tiny fraction of their expected service life.

If you can sneak a feeler gauge blade in between the clutch disc and pressure plate face with the pedal fully depressed, around .060" clearance should ensure smooth shifting on most clutch disc/pressure plate combos.

What if you can't measure actual clutch gap? If you know your synchros were good when installed and still at low mileage, if gears engage smoothly when shifted leisurely but "grunch" when shifted more quickly, you can suspect the possibility of inadequate clutch disengagement. Also, at slow idle with the trans in neutral, press in the clutch, wait a full 10 seconds, and cautiously try to engage reverse without going to any other gear first. Reverse is unsynchronized, so any clutch plate drag due to inadequate engagement with cause it to grind badly trying to engage. A tiny bit of clash doesn't necessarily mean your disengagement is unacceptable, but if there is enough clutch plate drag to abnormally wear the synchros, that reverse gear will complain loudly when attempting to engage it from neutral.

If you've already worked out all the gremlins from your clutch system and are confident your disengagement is fine, feel free to ignore this well-meaning but unneeded advice... : )

MX-Brad

I’ll never turn up free advice from people who know more than me about this. I thank both you guys.
I had wife pedal the clutch while I looked at the fork. It appears good, but I’ll have a better idea in a few days.
I had to stop for the day now, but plan on checking the rockers on Wed. Should I loosen the nuts and let the lifters ‘pump up’ overnight, or do they only need a few minutes?
Thanks again for all the help guys.

Sunshine Guy

A hydraulic lifter has a spring inside between the main body and the internal plunger/piston where the pushrod rides. Assuming the lifters are clean and in good condition (so nothing is "sticking"), the internal plunger should come to full height immediately when releasing tension on the pushrods.

I assume you are undertaking rocker arm adjustment in hopes of quieting the valve train. Without re-reading this long thread I don't remember whether you've already done this, but if not, this is the perfect time to double check your rocker arm geometry. Make sure the push rod lengths you are using, when the lifter is adjusted to the correct preload, creates the correct angularity between rocker arm and valve stem. You should select a pushrod length so that a line drawn between the two pivot points on the rocker (the trunion and roller tip shaft) will be at 90 degrees to the valve stem when the valve is at half lift. That way, there is minimal variance from that ideal, 90 degree relationship between rocker arm and valve stem as the rocker rises and falls from the half-lift point. This is really what is important to avoid side loading the valves, and also for getting the maximum, full, advertised lift range from the rockers. Variance from this 90 degree relationship at half lift will cause both diminished performance and increased wear in the valve train.

With the proper angular relationship between rocker arm and valve stem thus established, you should also see a "contact pattern" of the roller tip that is both NARROW and close to CENTERED on the valve stem. If rocker angularity is the correct 90 degrees at half lift and the roller does not contact the valve stem near the center in a narrow band, unfortunately the dimensions of the rocker arms you have are not ideal for the dimensions of that particular head (rocker stud holes to valve guide dimensions, in particular). This rarely happens on factory parts, but it's certainly possible if you have both aftermarket heads and aftermarket rocker arms (more potential variables).

If you haven't done this before, there should be some good youtube videos that detail the process. Here's a good one:
It takes some time and patience, but is not actually all that difficult. For "special tools" you can get by with a magic marker to determine current geometry, and a less-than-$20 adjustable pushrod and 99 cent springs from the hardware to determine the correct pushrod length needed to correct any geometry problems you may discover. A dial indicator is nice for measuring valve lift, but you can get by with a ruler, some patience, and some extra care if necessary.

It's nearly impossible to predict what length pushrods will be needed on any particular engine combination. Many engine parameters affect the pushrod length required: base circle dimensions of the cam, block deck height, cylinder head castings, rocker arm design, valve stem length, depth of valve seat cuts, head gasket thickness, etc. etc. There are so many variables affecting rocker arm geometry that it is easier to just check it, and if not satisfactory use that adjustable pushrod to determine the alternate pushrod length needed. Numerous different pushrod lengths can be found "in stock" ready to ship, and if needed, custom length pushrods are not much, if any, more expensive than good quality, in-stock items.

Anything other than the correct pushrod length will result in a less-than-ideal rocker arm geometry which not only can cause noise, but also numerous functional issues like oil consumption through the valve seals, fast valve guide wear (from side loading the stems) as well as early valve float due to the additional drag that side loading causes. You'll also get less than full advertised lift at the valve.

Few other engine "blueprinting" steps can be so successfully undertaken by the average home mechanic for so little cost while producing such great benefits in performance and longevity.

MX-Brad

Thanks. I’m familiar with that video. I may have to revisit this, but for now now I may have yet another issue.
When I took off the upper plenum I saw some leakage of some type that could possibly be contributing to my bucking issues.
I’m not sure if it’s oil or gas ...it smells like either. I put a straightedge on both the upper and the lower mating surfaces. Both were dead straight . Can I use a thicker gasket or something to make this seal better? I’ve been using the 5 packs of FMS gaskets, but maybe there is something better. I recall seeing something similar last time I had the upper off.

Sunshine Guy

To join manifold halves with clean, unwarped surfaces, I personally would either use a gasket with no sealer (FelPro or OEM Ford brand), or I would be likely to consider Hylomar Universal Blue Sealant by itself (no gasket). Either must be applied to very clean surfaces with all traces of former gasketing gone. Just before assembling, do a final surface cleaning with acetone, MEK, or maybe brake cleaner. Watch out, the good, chlorinated brake cleaner will remove any paint in the vincinity and is nasty on your skin and respiratory system , so take precautions.

Hylomar must be applied so you have a very thin film; probably only a couple thousandths when joined and torqued in place. It is an anaerobic sealer that does not dry out or harden, so it must not be trapped between parts in thick "sheets" or "globs." Hylomar Blue is a great choice as a sealant in this application because it is temperature resistant to almost 500 degrees F., and is resistant to gasoline, alcohols, water and antifreeze...all the stuff one might find in the vicinity of an intake manifold. Hylomar can be applied to one or both surfaces to be joined (but remember, it must be very thin). After applying a thin film and before joining the parts. you must let the sealant be exposed to air long enough to flash off all its solvent. It has an almost unlimited working time, so you can be patient before joining.

If you suspect something isn't joining up properly here, there are videos on youtube on how to make up a simple smoke generator which should help locate any manifold vacuum leaks, as well as help you confirm when you have them fixed.

engineer

Hi Brad,

I can provide some additional info to the already great info posted by Sunshine guy.

1) Thrust bearing: Your measured thrust clearance of 5 thou on assembly and now 6 thou in the car is normal. It takes a few thrusts to properly seat the thrust bearing and crank faces. The additional 1 thou is the bearing now being properly seated and slightly worn in with the crank surface. I have measured many new bearing sets on thrust and they normally measure 5-5.5 thou. After running in it usually measures around 6 thou...I think you are good

2) Clutch: I am very happy that you released the preload off the clutch adjuster, the monster miata kit has a clutch master that provides barely adequate fluid displacement to the slave to properly disengage the clutch, without excessive preload. Upgrade to the Tilton clutch master if you have not already done so. Then you can back off the preload all the way. Technically the thrust bearing should barely touch the clutch fingers, that is all the preload you really need. butt up against it but without "pushing" it.

3) Upper Intake gasket. The upper intake gaskets can and do get oily wet. The PCV valve vent on the upper intake is likely the main culprit in your case. I would use a catch can ( I recommend the Mishimoto small can) to remove the bulk of the oil. The other thing I can recommend is that you check that the intake manifold surfaces are flat and that they meet up well WITHOUT a gasket in place (i.e. no gap and cant see light through the gap) and there is no other interference which may cause them not to mate properly (i.e. hose fittings or rubber lines). Either bad machining or slight vacuum hose interference can make the upper intake not properly clamp to the lower intake. I would advise that you use a little bit (not too much as it get squeezed out!) of silicone sealer on the gasket mating surfaces upon install. If everything is machined perfectly this will normally not be necessary, but should you have and surface irregularities in the machining, this will ensure a 100% seal. I had the same issue as you with a wet upper gasket, it was solved by using the silicone as the surfaces were not machined perfectly. I then added the catch can to the PCV hose line, which prevented the bulk of the oil getting in there in the first place. It is all good now and the catch can seems to pick up almost all of the misty oil that comes out of the PCV vent nicely. I empty it out at each oil change

3) Lifter preload: Sunshine Guys post sums it up very nicely. Not a lot to add, just make sure the wear witness mark on the valve stem is centered on the valve stem. I use a marker to colour the tip, install the rocker gear with correct preload. Rotate the engine through 2 full revs, then remove the rocker arm and check the wear pattern. If wear line is offset toward the exhaust manifold...pushrod is too long, if its offset towards the intake manifold its too short. Also the valve stem wear line should ideally be less than 80 thou and centered on the valve stem.

MX-Brad

Alright, I have a good game plan for my day tomorrow.
1 Check and reset my rockers. May sound silly, but I’m actually just using roller tip rockers. They’re the PRW sportsman rockers. A few engine builders told me they would be quieter and more durable than a full roller. I may change them out at some point.
2 Retorque lower intake bolts....oh ya, the intake stud that holds the heater tubes- do I just loosen off the nut and tighten down the stud with an open end wrench to get it close? I won’t be able to get a torque wrench on the stud without removing the tube.
3 Reinstall the upper gasket. I’ll smear a light coat of RTV black on both sides. I had noticed this issue before and considered using RTV, but the thought of having to clean the mess everytime the upper comes off made me rethink. And I’ll make some ‘ temporary install studs’ to help guide the upper into place so the gasket doesn’t slide around when I drop it on.

engineer

Hi Brad,

Ok each in turn..

1) The rockers you have will be fine, no need to change them if the tip alignment on the valve stem is OK (centered wear mark and no more than 80 thou thick wear pattern)
2) The lower intake is 23-25 ft lb...which is pretty much hand tight with an open end spanner, so that will be OK to do. Just make sure you torque them in the right sequence....and do it 3-4 times all round to make sure its seated. The intake wiggles itself down slowly...so make sure that every bolt does not budge at 23-25ft lb. You will be surprised how many times you need to go round until its locked in place...its usually about 3-4...but just keep going until there is no more give.
3) Yep, agreed...some install studs do help if you are doing it by yourself....I sort of do the same thing...I just put the bolts through the holes in the lower intake and then lower it slowly whilst watching the bolts drop into the holes in the heads. Not too much sealer on the intake gaskets (upper and lower) as it will squeeze out and make a mess if you get trigger happy with the goo . But the RTV does ensure its a good seal.

MX-Brad

Quick question on O2 sensors. Attached pic shows where Martin locates his O2’s. Mine are about another foot aft of that. Would that be enough to have bucking issues? Trying to find pics of where they’re located on a foxbody.

engineer

Hi Brad,

The O2 sensors should be as close as possible to the engine, the further away they are from the engine the more time lag there is to correct the fuel. You can adjust the O2 sensor delay parameters in the EECIV to counter for longer time differences due to 02 sensor placement in correcting the fuel curve.

I have mine roughly in the same area as yours and I don't get any bucking...

MX-Brad

Hi Sunshine Guy,
I got everything back together, car is still on jackstands. This is what I’ve done regarding clutch adjustment:
I’ve loosened the master pushrod all the way, tightened back to snug, then gave about a half turn preload to the master. then de pressurized the slave to retract the slave pushrod all the way. While retracted I loosened the adjuster nut to have basically no preload on the TOB. When I press the clutch pedal it seems to give good range but the rod doesn’t retract 100%. I guess this is the ‘self adjusting’ nature of a hydraulic slave.
To this point things seem good, but when I start the car and press the clutch pedal- the rear wheels spin maybe one revolution as I slide the gearshift into first. Just while I’m shifting from neutral into gear, and then the wheels stop. I’m guessing I need just a tad more preload on the TOB which will also give a bit more throw.
I may switch to the 7/8” master at some point as Engineer as suggested, but I do like the light feel of this setup if I can get adjusted 100%.
Thanks for any insight you can share.

engineer

Hi Brad,

The light feel of the martin clutch master is nice I must admit, but I had to load the TOB with too much preload to get the required throw, additionally the TOB was toasted after 25000 kms. Only upgrading to the larger clutch master allowed me to adjust the clutch with ease. The amount of preload that I took out of the slave adjuster was crazy when i upgraded my clutch master. Its great now with the Tilton master..but the pedal is definitely heavier..

Sunshine Guy

I agree with what Engineer said. The larger clutch master is probably the surest and simplest bet for adequate disengagement with minimal wear on the throw-out bearing. It will almost certainly be easier on your synchros and your T.O.B., and equally certainly a bit harder on your leg. No free lunch, it seems.

I haven't had mine running long enough to decide which way I will ultimately go on this. Martin has built a lot of cars with the smaller master, and while he admits the adjustment has to be "just right," a lot of people seem to feel it is satisfactory. (I drove Martin's shop car some years back and it seemed fine). Others have reported frustrations with achieving/maintaining adjustment and have subsequently made changes.

If you decide to stay with the master you currently have, a couple things might help.

First, look closely at the clutch pedal stops and the travel allowed. See if there is anything you can do or modify to allow the clutch pedal to come up just a bit higher and/or travel just a bit lower into the floor. A bit of extra pedal travel might move that master cylinder just enough extra to allow both a reasonable bearing preload as well as sufficient clutch plate disengagement.

Second, if you search on the forums you will find some people have rigged up a brace to support the mounting of the slave cylinder, to remove any flex in the bracket that would effectively sacrifice slave travel by allowing the slave to move slightly under pressure. Some seem to feel this helped the situation. Final thought, moving the connection point of the slave cylinder inboard on the pivot arm effectively increases travel, but if memory serves you've already done that.

Finally, FWIW, I am interested in investigating hydraulic throw-out bearing systems before I make a final decision. These used to be quite expensive but in recent years a lot more companies are making them and the prices have come down substantially. I have read where different brands and setups have been tried but I don't recall anyone finding what they felt was a "perfect combination." These are mechanically quite efficient, so with the right match between master and hydraulic bearing it should theoretically provide the required travel with the minimal possible pedal effort. Some people don't like these because if a hydraulic T.O.B. leaks you have to pull the transmission to fix it. My thought, if your clutch operating system isn't working up to par, you are going to end up pulling that transmission anyway to fix synchros or a worn T.O.B.

Wish I could offer more help on this, but since I haven't sorted out my own yet I can't offer first hand experience or a definitive solution. I will say, on both this forum and the "Engine Conversions" section of Miata.net you will find many threads where this exact issue has been discussed over the years and people have tried different things. There's a lot of previous experience out there if you are interested in pursuing it.

MX-Brad

Cool. Thank you both.
I’ll play with it a bit. When I first got it on the road 5 years ago, I really didn’t have any trouble setting it up.
Most of the issue I see other folks having is either the clutch not disengaging completely, or too much preload resulting in slipping. In my case I may have had too much preload, but had no slipping at all....but I’m sure the excessive preload contributed greatly to my failed thrust bearing.
Anyways, will post back tomorrow with my findings and other issues.
Thanks again.

MX-Brad

Quick update on everything.
First off, I think I have the clutch system figured out. Nice engagement with no grinds, and barely any preload on the TOB. Taking the little rubber off the bottom pedal stop gave a slight bit more travel, and every time I made an adjustment I made sure to completely retract the slave rod.

My other work was adjusting my rockers and addressing the plenum gasket leak.
The rockers are tricky. I remember on initial assembly over the winter that the pushrods ended up having to be quite short to get the roller to center over the valve. I actually had to order some Manley 6.050. Any longer and they would drift over to the outside of the valve. I have them pretty much centered, but the line is quite wide. I know this is either an issue with poor castings or the incorrect size of rocker. Gonna have to live with it for now. Maybe check into better heads over the winter. I can always sell these ones.
A few of the guideplates were out of kelter so I straightened those out. Snugged the nuts to 2/3 to 3/4 of a turn after zero lash on the base circle. The result is slightly quieter, so I’ll call it a win for now. I can live with it I think.
eta: now that I’ve driven it a bit I can hear it’s noticeably quieter. Yay.

On the plenum gasket, I still had reservations about using rtv on that....it’ll be such a bear to clean whenever the upper has to come off. So I compromised and applied a couple good coats of copper gasket spray. It’s supposed to to fill small imperfections and come off clean. I probably won’t know if it worked until the upper comes off again. Oh, and I do run a catch can off the PCV. Always have. I also used to use a small glass inline filter on the tube running from the oil fill to the TB. I wonder if I should put that back on. Maybe with the engine sucking in more air, the oil could be coming from the valve cover. I modified the baffle rather than completely removing it.

I ran smoke through the system and found no leaks other than around the TB shaft (normal). Vacuum checks out at a solid 17”, so I’m pretty sure no vacuum leaks.

On the bucking- I unplugged the O2’s. No change, still have a 2k rpm bucking. it’s not horrible but very annoying. Will keep working with my tuner on that.
So there you have it. Seems I’m cautiously in good shape. Assuming I can get this bucking fixed, and my thrust clearances stick, I’m golden.
Thanks guys for the great advice and positivity.
Cheers. Brad

engineer

Hi Brad,

Great work my friend. That sounds great. The upper sealer you used will be perfectly fine, you just need that little bit of extra insurance. RTV can indeed be a pest to get off, but my philosophy on that is I hope to not have to take the upper intake off for a few years at least (never preferably)

Great news on the clutch adjustment. I am sure you will be Ok from now on in.

PCV catch can is great...the inline breather to the TB with a filter on it is good as well. I stuff thick stainless steel wool into the oil filler neck where the breather tube starts. That seems to keep the majority of oil at bay before it gets in the breather tube...my TB is pretty clean. I just remove the steel wool when I do the oil change to fill it up and then I stuffed it back in.

On the valve tip wear line did you measure how thick it is ? It should not be over 80 thou thick..if its a lot over that then that means the sweep over the valve stem is too great. It could be the type of rocker that is used (assuming pushrod length is OK...should be close if you are centred on the valve) that is causing that. If its close to 80 thou it will be Ok. But if its too wide there will be issues later on.

17 inch of vacuum is perfect on the Xe264..thats is great news..that is perfect

Ok for the bucking I believe that's likely in the base tune. I would advise that you make sure that the AFM is in good condition (or get anew one). That is the most critical element to the A/F metering. With that new you can be assured that the tune will be accurate and the car will respond well. Also I trust that you serviced (cleaned, flowed and new filter baskets) the fuel injectors before installing them. Same for the ignition system (coils, plugs, ignition modules and ignition wires) they really need to be new to make sure you have no hardware anomalies in the system.

Also I am not sure if you have checked the fuel pressure at the rail. There is a port to tap a gauge into to make sure that you are getting stable fuel pressure. Any anomalies can be a pump issue (not hard to change and a walbro gss 342 upgrade is cheap and worthwhile).

But I assume form your description that the pump and pressure is OK, but its worth a pressure test to be sure.

I think this buking is in the tune. I assume the bucking is somewhat an abrupt forward/backward motion (like towing a trailer) and is NOT a surge. From the O2 sensor test you did its likely not fuel related. I also assume it does the same thing hot and cold (thereby implhign its not affected by fuelling). This may point to an ignition table gremlin. I would check to see if you you have too much ignition timing at the low TPS % opening angle being used when you cruise.

Your tuner will be able to see this in the data logs...and sort it through. Many times tuners get overly focused on full power runs and spend little time on the "transients" i.e. tipping in from coast to light throttle, backing off throttle to idle, idle return behavior, part throttle to full, etc etc. There is a lot to do to get the map as good as oem under all conditions..a good tuner should get you very very close to OEM levels

I am so happy you are motoring again...keep up the great work and keep us posted

regards,

MX-Brad

As usual, you bring up some good points.

Valve stem marks are way more than .080.....I didn’t measure but guestimate about .120 or more. I know it’s an issue with the wrong rockers, but I also had some Summit brand Scorpion knockoffs that were exactly the same.....not sure what to do there as not too many folks have these heads and are able to suggest what rockers work best. I’ll live with it for now, but am really hoping to go for some better heads and rockers next year. Gotta make sure they’re no taller than what I have or I open another can of worms regarding valve cover clearance to the upper intake. At least the mark is centered.

MAF is a brand new SN95 unit. I still have a ‘93 MAF but it bucks with it too.
I didn’t send the injectors out for cleaning. That would have been a great idea. I don’t think they’re the issue though....the bucking is at that specific rpm regardless of gear. As you suggest, it doesn’t seem like a fuel or load issue when the rpm is so specific. I’d gladly buy wideband if I thought it was a fuel issue. Plugs are new, wires and coil are around 10k km. Same as the distributor. Could a faulty coil do that? It’s a Blue Streak or something like that from rockauto. Maybe should try a Motorcraft one.
I should check fuel pressure. Planning to do an upgraded pump over the winter as I’m still running the stock one.

jrmotorsports55

Brad, just a heads up, I had the same bucking in the 1500-2000 ish range (tach was not exactly accurate) and my tuner spent hours trying to tun it out and could not completely get rid of it. My car had lopey TF Stage 2 cam, and aluminum flywheel/driveshaft, and we chalked it up to the combination of parts on engine with the touchy throttle. The car ran great otherwise, just had to keep it in the 2000 and up range. Just a little input on my experience.

MX-Brad

Hey Jason,
Congrats on the sale of your car. Thanks for your posts over the years. Always interested in other peoples builds.

This engine is such a mild, close to stock build I can’t imagine I won’t get a handle on the bucking eventually.
I paid Decipha for remote tunes for life, and he’s not that old lol, so we’ll get it figured out sooner or later. In the meantime I’ll keep throwing the occassional part at it to appease the car gods.
It is strange that some folks can do tons of mods and have a perfectly running engine, and others buck right out of the gate.

engineer

Hi Brad,

Ok, leave valve train alone for now. There is little you can do to fix it without changing rockers and or heads if the pattern is centred. It will likely be Ok for normal street duties...different story if you were racing at 7000+ rpm all day.

Glad to hear that AFM is new but an injector clean would have been nice. Next time the upper is off...take them out and have them services. They will pick up a lot of flow and improve the spray pattern immensely if they are old enough. I always do them for any engine i build, for my latest one I purchased a new set form ford racing...not that much more than having an old set cleaned and checked.

Also coils can be faulty and cause grief...but this will be more a "miss"..a hesitation or momentary drop in rpm as opposed to a "buck" which is a rocking motion back and forth.

A new coil is always a good thing if the Blue Streak one is a little old or suspect. And a motorcraft coil is a good option..they are very very stable and will last forever...a lot of aftermarket coils can crap out earlier than expected.

If the bucking is always at the same RPM no matter what load, temp or fuel enrichment level then its likely the tune, but a new coil will make sure that everything in the ignition system is almost new...as this is a tune, ignition or timing issue from what I can tell. Also has the ignition module been changed as well ??? if not..these do let go from time to time so changing that is a good thing too.

If you do the pump upgrade a Walbro GSS342 is a an easy fit....but its noisier than std...so you will hear it if you tune your ear in...

Sunshine Guy

Jason might be on to something here. While one would hope to tune out as much of that low rpm roughness as possible as their primary effort, whatever engine surge or lope remains after best-effort tuning might be exacerbated or amplified elsewhere in the drivetrain. Especially if experiencing significant wheel hop when the tires break loose, this effect might be indicated.

When tires are "clawing" for traction they successively hook more or less to the pavement, sending shock waves that load and unload the various drivetrain mounts. If anything is "winding up," i.e. flexing to absorb those forces it acts like a spring that loads and unloads, to the detriment of maintaining consistent tire contact and traction. Most common is the nose of the differential flexing upward against its springs or bushings (however its mounted). A rear transmission mount that flexes may add to the problem. Engine surging would apply similar, intermittent shocks to the drivetrain (from the other end) which could reasonably amplify the "bucking" felt due to wind-up and release of components acting like a spring.

So if wheel hop is observed, anything you do to chase that gremlin may also help reduce the "felt effect" of any remaining engine surge. Obviously it won't change what the engine is actually doing but rather might make it somewhat less noticeable to the driver. Some have found the Monster Miata rear transmission mount (cross member) to be a bit too flexible in their particular application. Adding two additional mounting points part way towards the center of that cross member, up through the mount and floorboard with bolts and backing plates above, seems to remedy that flex for those who experienced it. Making sure the differential is very securely and solidly mounted with firm, new bushings should eliminate any excess movement there.

I would certainly focus first on getting the engine to run as smoothly as possible at low rpm. "Tightening up" the drivetrain would be a secondary effort to mitigate any remaining effects of this issue. Although, if such stiffening is needed the worst outcome is probably a minimal reduction in felt surging but a significant improvement in putting down the power smoothly. So not a wasted effort in any case.

MX-Brad

Well, this happened today...

The devil help me, is anyone familiar with this sound? Is sounds like a rattle or some sort of interference. I immediately assumed a loose rocker and tore to top end off. They were all tight and no signs of interference on the valve cover. Someone give me a match please.

It beat me today. Tomorrow night it goes up on jackstands and I see if I can isolate the noise.

engineer

Hi Brad,

I think I may cry...but I need to stay focussed.

Please use a rubber hose (some 3/8 or 5/16 fuel line works well...or a garden hose) as a stethoscope to isolate the noise.
From the hollowness of the sound on the video it seems to be coming from the bottom end ?? Generally a rocker noise or valve spring noise is more "Ticky" this is more "drummy". The hose trick will reveal if its under a rocker cover, lifter gallery or coming from the oil pan.

This engine really does not want to play in your car...maybe time for a new one ..just to teach it a lesson

MX-Brad

The knock was coming from the pan. Ran it last night for a bit and it wouldn't make any noise...then had a hunch. I pressed down the clutch and a few moments later it started.
Seems I've toasted yet another thrust bearing. I was a little frustrated about this, but better today.
Since I measured, had clearance, and was able to move the crank with everything but the slave/TOB connected, it seems that it must have been that excessive preload that I didn't discover until recently. It HAS to be that, right?
I'll pull the engine this weekend and get the shop to do bearings and cleanup one more time. I kinda owe them that since they were good to me last time. And if it is excessive TOB preload that did it, then it's totally my fault.
What I don't get is the people who say they have too much preload and their clutch slips, and if not enough preload they have grindey shifts. My clutch wasn't slipping. Not sure what I'm missing here.

engineer

Hi Brad,

Good news its a TOB...thats an easy fix (relatively speaking...),

To fix these gremlins, I would strongly advise that you replace the clutch master withthe Tilton unit. It will give you all the throw you need to make the clutch adjustment easy. The monster miata clutch master just does NOT have enough throw for my liking...even though it feels nice and light under foot. You will battle with it almost every time not matter what you do. Some people get it to work, but for me without excessive preload i could not change gears. After I changed my clutch master I backed off the adjuster, I would say about an INCH...and then I got the TOB to just touch the clutch pressure plate. When I pressed the clutch the slave move so much further forward I had to grind a little more metal off the tip of the adjuster as it touch the pressure plate.

For the $80 it will stop all the clutch adjustment issue nonsense..but the pedal will be heavier...its a small price to pay and you will get used to it in 1 day.

Keep us all posted my good sir..you are almost there..!

Regards,