R&D thread for shim-under-bucket conversion!
 

OK I know Mazda Comp sells this but I want other options. Because. :) Ok because i'm not a member. fine.

Anyone (Brian you have my head... got calipers?) know the OD and length of the buckets?

The valve stems are 5.96mm for intake or 5.94 for exhaust. Supertech sells a 6mm lash cap which I assume will work.

I remember hearing rumors that the 4AGE buckets were the right size, but rumors aren't guaranteed to open valves.

Here's the part info:
one of those is bound to be our size. or close. or close enough ;)

Also: at what point do the dual springs become necessary? The Supertech duals are about 50% more seat pressure (74lb) and about 30% higher rate overall.


notes:
Mazda Motorsports "solid lifter" p/n? B6N7-12-183
From a protege site the bucket p/n is: BP2Y-12-183
http://www.maruhamotors.co.jp/miata/...camfornb8.html


thanks guys.

I guess I should put mine up for sale.

errr, your what???

No idea if this is relevant or not, but I ran across this post over an mnutter regarding potential interchange between Miata, Zetec, Duratec (MZR), and Honduh springs (and lifters).

http://forum.miata.net/vb/showpost.p...9&postcount=24

Scroll about halfway down the post for the details, including "graded" solid lifters that don't require shims.

Any 6mm shims will work. I used a set of 16 off ebay made for a chevy. Cost $30 shipped.

You can get teh mazdaspeed lifters through MiataRoadster.com for only $200. For that price I wouldn't bother searching for other methods.

Glad to be of service.

200? well sheeit.

I've got an entire mazdacomp shim under bucket valve train from 99 cylinder head (springs and cams). They're stuff we ran in the motorola/grandam cup. I put them up on miatanet classifieds but got nothing but wieners.

Rob--we were discussing your cams, but never really got to terms. If you have a price in mind for the whole set up, shoot it my way. Honestly, all my spare change is going to the block right now, but maybe...

I'd assume that setup is too hard core for a street car?

Randy Stocker was telling me it would be pretty bad ass for a boosted street car actually. :dunno:

brian (neogensis "i've awaken the beast") has a good description of what it's like trying to get cams like this to idle - a lot can be tuned out, tho still lumpy compared to a stock cam. BUT with a turbo car and reduced overlap it shouldn't be as bad. I never ran these on the street, but on the track way up in the rpm they were just badass.

Without the cams, the valvetrain would be fine IMO. It's far lighter than the stock setup and will spin way easier.

Sorry about that Ben - totally forgot. I'll hang on to that stuff for your engine, just totally spaced.

i already sent the money to billwilner for the buckets. just need to find brian-neo's source for the cheap lash caps.

Brian, did you get all one size or custom sizes to fit your specific application?

I had to grind them manually to fit. I used a diamond coated knife sharpened. Takes forever but its worth it. Just search ebay for 6mm caps.

^Totally gonna show my ass here. I understand how shim under bucket works... but exactly what is the advantage over the current configuration of the valvetrain. What is this gonna buy you? What is the advantage?

I can deal with grinding my own caps I guess... I've got the sharpeners :)

Sam, the benefits are mostly reduced weight and the ability to run higher lift cams with less liklihood of destruction...

Normal shims are big quarter-sized things that are kinda heavy compared to the pea-sized lash caps used with shim-under-bucket. Plus at high rpm with big cams, if you float the valves, those standard shims are no longer captured by anything and can slip out from under the valves and do bad things.

but mostly the lower reciprocating mass means the valvetrain can handle higher speeds.

You dont risk spitting the tiddly-wing stock shims at high RPM, wich could damage the head. Its also lighter, which is a big deal at those RPM's.

What does this type of benefit does this modification produce, sorry to hi jack.

.

and less mass means you don't need stiff springs: less spring rate = less pressure on the cam lobes and less effort to rotate the cams

:rly:

so would stock springs handle a .400 lift cam at 8500 rpm or is that just silly...