[ctrench]

So i picked up a rebuilt head with a shaved deck a while back and just installed it, i was told that the shaved deck messes with the timing, is this true?? and is there any way to get around it without aftermarket cam gears??

 

[wajalama]

What year is your Miata?

You can adjust the timing on the NA's with the CAS, or use a standalone ECU.

 

[ctrench]

i have a 93, and yes i know i can adjust the ignition timing with the cas, but i heard the shaved head would cause mechanical timing to be off

 

[wajalama]

Oh, for mechanical timing, I'm pretty sure that cam gears are the only way to adjust it :/

 

[ctrench]

damn, do you know how much the mechanical timing being off, would affect performance? because the head being shaved raises compression, so i dont want to screw myself even more by hurting the engine

 

[wajalama]

It depends on how much the head was shaved. Got any numbers?

 

[irish mx5]

i skimmed my head 20 thou and i think i remember reading that it would also advance the timing just enough.
a little advanced isnt a bad thing but too much is.
adjustable cam gears or adjust the cas is the only way i can think of adjusting it

 

[ctrench]

no, thats the thing... i picked up the head, tb, and water pump after a customer at a shop skipped out on paying for the job. So for $170 i snatched it up without asking for any paperwork specs

 

[irish mx5]

well if it was just skimmed for a head gasket job then it will be nowhere near 20 thou.
but if it was skimmed a lot just for compression then youve got a problem

 

[3MiataFamily]

No issues with mine after a skim for a valve job...mechanical timing is just fine...topped off by the EX/Intake cam swap..

 

[ctrench]

I think it was a basic leveling type of shave but im not 100% sure... i guess ill find out when i redo my ignition timing tomorrow

 

[1vicissitude]

It RETARDS the cam timing, does not advance it. Unless a serious amount of material was removed, don't worry about it. You'll have bigger problems if that's the case anyways like piston to valves hitting.

It can be advantageous to retard the intake cam 6-8* according to solo miata. The exhaust side shouldn't do too much. Each tooth is 12* for reference.

If this was a head shaved just to straighten it out, I doubt anymore than .010" was removed. Unless this is a performance shop building for compression I wouldn't worry, even .010" is past manufacturer spec (.008 for 1.6 .004 for 1.8). I know you can shave .030" without any worries on a 1.6, although I have read as high as .045". Their engines might be interference now though.

 

[ctrench]

ok, i dont think they took off much. i just wanted to know if i can get away without having to get aftermarket cam gears

 

[1vicissitude]

Worst case scenario you can take a caliper to it if you really need to know when both heads are out. More than likely a 99% chance you have nothing to worry about but the install itself.

Even if it does run funny, just try it out first and buy cam gears if you need them. A little cam retard isn't going to kill you.

I don't get why people are accidentally giving you wrong information. With technical stuff like this, if you aren't sure don't comment. Would suck if misinformation ruined this guys stuff.

 

[irish mx5]

^ sorry about that i meant to say retard,s timing.
youve explained it perfectly there

 

[NAautoxer]

all spec miatas are running shaved heads with OE cam gears. you will be fine. they make plenty of power..

 

[ctrench]

ok thanks guys for your input i really appreciate it!! and it not the power im worried about i just want to get her running good, then later worry about more power