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Finally at a point where my hair won't grow... I have a 1995 with a 94 block and head, 95 cams, ST heavy double valve spring kit, and ST solid lifter (SUBs-5.5mmm shims) and for the life of me can't find anything related to proper lash or a good start for lash specs for this set up. I tried the OEM lash for NBs and at first it was loud. Then I went as tight to the low side as possible (.007 intake and .011 exhaust) the second time around, and it definitely quieted down. It still has a tick, at both cold idle and warm, and louder when warm. I assume it's loud when warm due to oil temps/pressure. At idle, you can also tell that one or more exhaust valves are not opening enough Engine runs great otherwise, good vacuum, boost... My current setup.
Any help in which direction to go would be greatly appreciated.
I know you all are more knowledgeable than I, so please go easy on me, "I'm a virgin"...
Update, they shrink from heat, not expand... First pic is from when I first set the lash and had every cap bolted down to spec. Second is where I measured today after a few runs and up to full temp (195-200f). It was fun playing in hot oil, but worth it to get measurements. So I'm planning to set all around .002-.004" tighter cold I guess. I'll update again when I can.
I don't understand much of what you have written. A little valve train noise is ok. Increased clearance would be considered looser. It is true that the clearance will be greater when the head casting is warm. Although under load when the exhaust valve increases in temp the clearance will decrease. If a valve runs out of clearance it will burn. Set the clearance to +- minus .001" of the nominal value. I have know idea what you mean about the idle and exhaust valve not opening enough.
I don't understand much of what you have written. A little valve train noise is ok. Increased clearance would be considered looser. It is true that the clearance will be greater when the head casting is warm. Although under load when the exhaust valve increases in temp the clearance will decrease. If a valve runs out of clearance it will burn. Set the clearance to +- minus .001" of the nominal value. I have know idea what you mean about the idle and exhaust valve not opening enough.
OK, so hear me out... When it's hot, the clearances open up. Maybe I'm misunderstanding how the lash is really supposed to work, but never in the 20 years of building engines have I ran into this issue. Lash is normally set so that when it's hot, the clearances get tighter from expansion, allowing valves to open more and generating better flow at higher rpm. I used to set them in other cars so that when it's at full boost, high rpm, that the buckets almost ride the cam profile. Again, this isn't just a little valvetrain noise... its a lot. Almost like the lift of the lobes were smacking the buckets hard, but everything looks OK.
How will valve burn from being out of clearance? I've burnt a few valves before, never from lift, but from injectors or pump going dead mid pass.
How will valve burn from being out of clearance? I've burnt a few valves before, never from lift, but from injectors or pump going dead mid pass.
If you run out of clearance/lash, the valve is not touching the seat (by definition). The valve will quickly 'burn' as alllll the heat in the valve goes out of the valve thru the seat when on base circle. Horray thermally conductive valve seat materials.
If you run out of clearance/lash, the valve is not touching the seat (by definition). The valve will quickly 'burn' as alllll the heat in the valve goes out of the valve thru the seat when on base circle. Horray thermally conductive valve seat materials.
Ah, that makes sense. Zero lash is always bad, and I understand that even too tight of a clearance at high RPM could cause ramping, or a valve not seating to transfer the heat. Thanks for chiming in Tim! Would you have an idea why these are looser when warm though? I'm at a stand still after measuring since I'm not 100% on where to go with clearance.
I have 3, and absolutely. I used one initially to verify it's the valves and knock or a bearing. I ended up using a very expensive borescope to check each cylinder and in the oil pan for any kind of debris or scarring. All looks almost new still with the usual wear and built this engine over 2 years ago.
That is a nice clean engine bay modified by a master.
You may be new to Miatas but you've been ******* with stuff for a while now.
You've changed to SUBs by yourself.
You, Sir, are NOT a virgin...
One possible issue is you have changed to solid lifters with a cam that started with HLAs.
Sometimes that causes issues.
Might not matter with the cam profiles that Mazda uses.
The guy I'd want involved with this is Turbo Tim and he already is...
I'm interested in what this turns out to be.
I expect valve clearance to decrease with warm up as well, but your VC sheet looks like mine (tight/loose notations) so I'm betting you're checking them correctly.
Because of this thread I'm going to do both hot and cold valve clearance checks to see if I can duplicate your findings when I get my MSM back up.
It works pretty well but I'm looking at the super tiny ones that work with a smart phone now.
I was running HLAs but had many issues with collapsed lifters, ITM lifters, and more. Best I can describe is one lifter was stuck open, or all the way out. OP in the head was perfect, according to all the info I've read on here. In the last couple months I added the light double valve springs and SUBs, which the first set of shims were too small and too high of lash clearance. The valvetrain noise was louder than the exhaust and my neighbor's hood dumped S2000. Second time a week or so later, I set them at the same as in one of the pics before buttoning everything back up. The noise is way less then previous, but still louder than it should be and hasn't changed at all.
I've had this car since early 2015, it was all stock except for wheels and janky horn button the second owner messed up. Original 89k miles, $4,500. I've done quite a bit to polish it up... This is only one of my engines, built with "ebay" rods from Maxspeedingrods, CP pistons, ACL bearings, ARP everything, OEM gaskets, OEM OP pump with a peterson external PR valve, oil pan baffle... For just the block, it works way better than my last JE piston + Eagle rod rset up. Eagle rods suck IMO, they never come balanced, not even close, and one was out of round that slipped by me and my machine shop. Wore a bearing out, destroyed a rod journal and head from oil issues. Maybe I'm not a virgin to cars and mechanical/fabrication/welding stuff, but I am to posting stuff anywhere.
I hope yours runs good again soon. If your VCs are close to mine, I would set them like I used to do 2J, Evo and Ferrari Solids. Make em tight enough when cold so they are in spec at hot.
I'm also very interested in the Peterson external PR valve.
How do you like that?
Nice builds!
I didn't mind the pistons, nearly zero slap on a cold day starting up. They were for my overbore (2.0L) block and seamed great at first. I don't think I would run them again though in a BP engine. Hard to tell much as the rods ate that crank up within 1,000 miles after break-in.
Lol, the good ole Peterson valve... I got the idea from a guy "down unda" on this forum, I love it. I welded an OE cast OP housing relief shut with a full aluminum plug, then added some new BE pump gears. Once it was on, I made a bracket to hold the valve itself right on the frame rail, made my own 10AN PTFE lines, used a Mishimoto sandwitch plate for the feed and return, then lastly welded a 10AN bung to the front of the oil pan (under the alternator) for the relived oil. I can adjust it on the fly should I ever need to, but it's set for 65psi max cold and a solid 20psi hot at 900rpm. I see the average OP when cruising, and peaks at 65psi when on it. I referenced many sources before hand to get it dialed in. Paired with an ATI damper, I think it's all good for higher RPM. My limiting factor is cams and maybe head flow, but I'm not worried about that.
Oh, thanks btw!
The cylinder head casting is made from aluminum which has twice the thermal expansion of steel. The valves are made from steel so as the head warms up it moves the cams away from the valves and lifters. There is some expansion of the valves/lifters at the operating temp but it is only half of the head casting. Under load when the engine is making moderate to high levels of power the exhaust valve will have a much higher operating temp which will decrease the clearance. The clearance is determined by the service interval and based on an acceptable amount of noise. Over time the valve seats wear and the valves move upward decreasing the clearance which dictates the valve lash preset clearance/service interval. Thousandths of an inch in lift will not have an appreciable effect on output. Mechanical/solid lifters make noise and HLA's don't. The most common cause for a lone tick is an exhaust leak.
The cylinder head casting is made from aluminum which has twice the thermal expansion of steel. The valves are made from steel so as the head warms up it moves the cams away from the valves and lifters. There is some expansion of the valves/lifters at the operating temp but it is only half of the head casting. Under load when the engine is making moderate to high levels of power the exhaust valve will have a much higher operating temp which will decrease the clearance. The clearance is determined by the service interval and based on an acceptable amount of noise. Over time the valve seats wear and the valves move upward decreasing the clearance which dictates the valve lash preset clearance/service interval. Thousandths of an inch in lift will not have an appreciable effect on output. Mechanical/solid lifters make noise and HLA's don't. The most common cause for a lone tick is an exhaust leak.
Yep pretty much this.
My limited experience: some engines loose lash, some gain. It depends on material (engine/head & valvetrain), geometry, and temps. Best to just accurately measure your actual engine hot and set your lash accordingly. And yeah, a few thou valve lift isn't going to affect power to the degree that every other variable in the world combined will affect power.
My limited experience: some engines loose lash, some gain. It depends on material (engine/head & valvetrain), geometry, and temps. Best to just accurately measure your actual engine hot and set your lash accordingly. And yeah, a few thou valve lift isn't going to affect power to the degree that every other variable in the world combined will affect power.
Thank you and LeoNA! You both gave me the sanity check I needed. I did exactly that, still grinding the shims to what's needed. Once everything is back together, I'll gladly give an update.
10-07-2022, 09:49 AM
SUBs with NA Cam Lash
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