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Old 05-27-2008, 12:36 AM   #1
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Default Head Rebuild

I have a fully built 1.6 bottom end recently finished and am ready to tackle the head. I have the valves, valve stem seals, and have some cams picked out but cant decide on either the FM valve spring kit or the belfab valve spring kit. They both have the same specs just FM is a little more expensive and requires the valve keepers from a 99-05. I was just wondering which one is just better as I know next to nothing on engine heads.
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Old 05-27-2008, 03:22 AM   #2
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Im not much of a Guru here on heads but I can pass this info on... If your looking for a cam that is more aggressive and no valve float, AND be able to rev higher(providing other things are balanced like the crank and a harmonizer) you could go for a cam-over-bucket sollution and forget about the springs. Takes a little more time, but if you know your way around an engine shouldn't take you more than a day and a half (solo) to measure up the correct spaces and all. (Considering I built my first complete engine in 5 days from scratch and it was out of a 62 Jaguar XKE with solid lifters..


But if you just want advise on which spring kit to go with... I will throw my 2 cents in. I have bought a lot of FM parts, they havent steered me wrong yet and they have excellent support. I dont know anyone who can say that about any aftermarket car company. So if it was me. I would buy FM valve springs and "spring" for the extra cash
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Old 05-27-2008, 02:19 PM   #3
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Thats kinda what I was thinking I just wanted to see if anybody had any experience with either set. What is cam over bucket and how does it work?
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Old 05-27-2008, 03:22 PM   #4
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Quote:
Originally Posted by highroller101 View Post
you could go for a cam-over-bucket sollution and forget about the springs.
I am not following you here...
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Old 05-28-2008, 02:57 AM   #5
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Are you familiar with older engines? They have solid lifters no valve springs. They have shimms to adjust the bucket height (the bucket slips over the valves and the cam turns on the flat). No springs
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Old 05-28-2008, 03:12 AM   #6
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Uhm, Lowballer, you still need springs. They're what pull the valve closed. And technically all Miatas are, as you say, "cam over bucket." The cam sits atop the lifter, which sits atop the valve stem. No rockers.

What you're describing are solid lifters, which the Miata switched to in '99. The only difference between the two systems is that rather than being self-adjusting, they require shimming as you indicate. Otherwise, the basic components are the same, springs and all.

Here's a picture. I even labeled each part for you. Notice, it has a shim, then the tappet, and under that (drumroll) a spring.





Yada, I assume you're speaking of the Belfab single spring kit (SPRK-MM16S) and not one of the dual kits. At $180 less than the FM solution and given the identical specs, it would seem a winner to me.
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Old 05-28-2008, 03:44 AM   #7
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My bad on that one. Sorry it was one hell of a build complete engine in a few days! I dont remember all of it unfortunately.... ps the shimm goes under the tapet... doesnt it?
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Old 05-28-2008, 02:27 PM   #8
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yeah that's the ones. Would I have to get the keepers from the 1.8 with those still?
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Old 05-28-2008, 02:39 PM   #9
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Quote:
Originally Posted by highroller101 View Post
I dont remember all of it unfortunately.... ps the shimm goes under the tapet... doesnt it?
Not according to either the Mazda parts catalog (above) or the Mazda Factory Service Manual:





To adjust the clearance, the tappet is depressed with a SST, and then the shim is prised up from the bore with a screwdriver.



I'm going to have to ask that you stop trying to give advice about NB cylinder heads until you have seen one, preferably with the valve cover removed.



Quote:
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yeah that's the ones. Would I have to get the keepers from the 1.8 with those still?
I honestly don't know. A call to Belfab would be in order here.

Just out of curiosity, why do you require aftermarket springs?
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Old 05-28-2008, 03:59 PM   #10
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not really needed bit will let me get a little bit more rpm with a good cam correct?
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