Mazda MX-6 Forum banner

1 - 13 of 13 Posts

·
Registered
Joined
·
197 Posts
Discussion Starter · #1 ·
Well the idea stuck me while looking at my 12v head and my 8v head side by side..... so here is the results. the 12v rocker shaft is larger in diameter than the 8v but its nothing a little machine work couldn't fix. Not really sure if the benifits out weigh the work but just wanted everyone else's opinion.









 

·
Premium Member
Joined
·
1,032 Posts
interesting but i would worry about structural integrity of the "bored out" rocker
 

·
Premium Member
Joined
·
3,355 Posts
All very interesting....

I would not have thought the 8v rockers would have fitted, but nice idea tho. would have been a nice easy mod. Maybe its a case of looking for rockers of another Mazda engine....maybe an old MA, I have a feeling the rocker shafts in that a bigger diameter....

I was thinking more along the lines of drilling out the 12v ones and replacing them with solid.....I never saw that original article by adamturbo....was alot more work that I thought it would be....one of these days I might get around to it, but its a lowish priority.

Still, thats one thing I prefer about the old 8v heads, I was never that concerned about occasionally setting the valve clearances.....HLAs are installed by the manufacturers to make the engine low maintenance, performance is a second priority.
 

·
Premium Member
Joined
·
1,032 Posts
... idk it appears to be a much bigger hole and i would just be concerned about weakening the metal... im assuming the reason to do this would be for a large boost type application and high revs on something you have just bored the piss out of would concern me if it was my engine...
 

·
Registered
Joined
·
4,171 Posts
... idk it appears to be a much bigger hole and i would just be concerned about weakening the metal... im assuming the reason to do this would be for a large boost type application and high revs on something you have just bored the piss out of would concern me if it was my engine...
its a rocker, why will boring it out concern you, the purpose is to mive up and down, it will have the same aluminum left when bored as the stock rocker since they are the exact same dimension except for the center bore, its like saying boring your motor .040 over scares you. when most people on a simple rebuilt bore there motor at least .020 over if the cyl is severely scar..if anybody have 12 of those bad boy, sent it my way, i will be the guinea pig and will install it withing a week with pic and video. im not scared to try new things, i actually think it will work and work great. it will be great for a higher reving f2.
 

·
Premium Member
Joined
·
2,999 Posts
it will have the same aluminum left when bored as the stock rocker since they are the exact same dimension except for the center bore
ademan, take a closer look at the pictures. There wont be the same aluminum left if bored and they arent the same dimensions.

Gavin
 

·
Premium Member
Joined
·
1,032 Posts
also are they made of the exact same stuff? or are they made of different grades of aluminum?
 

·
Registered
Joined
·
2,246 Posts
Different ratio rockers wont work on these motors. The reason pushrod motors can use different ratio rockers is that the ratio is determined by the distance between the pushrod cup and fulcrum center. It's the pushrods ability to acomodate different angles, with out this you would have a misalignment that will likely destroy the motor.

If the critical dimentions are the same or can be corrected when boring out the fulcrum then it should work well enough.

I dont see any issues with stregnth after the machining. There looks to be plenty of material.
 

·
Registered
Joined
·
89 Posts
lol, doesn't anybody own a simple set of calipers? I don't seem to have any 12 valve rocker arms with me but have a crap load of the 8-valve ones (since I own Mazdatruckin.com, lol)

8 Valve Mechanical Rocker Specs
The Rocker Arm Ratio is 1.72
Bore Diameter is .635" tol: +/- .005"
Diameter of the casting around the rocker shaft in the horizontal position: .900"
Diameter of the casting around the rocker shaft in the vertical position: 1.040"

Casting thicknesses are referenced with the rocker arm in the full valve lift position. The thickest part of the casting is parallel with the load at it's maximum.

Not to sound rude but I found all the chatter about if there was enough meat or not annoying. I'm sure someone can get the 12 valve bore, measure the wall thickness and determine if the remaining wall thickness on the 8-valve rocker would be more or less after machining. I'm pretty sure both of the cast alloys are the same.
 
1 - 13 of 13 Posts
Top