Questions about valves and valve clearance

G

Gavin

Member
I have a spare head for my FS 2.0 thats been sitting in my basement for some time now waiting to become a part of larger long term plans for the Pro. Im planning to install mazdaspeed intake and exhaust cams into it, and had also considered skimming the head down (maybe 0.020- 0.030) and using a 20 thow head gasket to up compression (without having to break open the bottom end).

My questions are as follows:
1. Considering the increased lift and duration of the mazdaspeed cams, at what point are my valves going to start hitting pistons (that is to say, should I skim the head/ utilize a thinner gasket at all?)?

2. Along wit the cams I had also planned to add; adjustable cam gears, and upgraded valve springs, but was hoping to avoid the expense of upgrading my valves. Is it really necessary to move to SS or titanium valves when using more aggressive cams (i.e. revving to moderately higher RPM)? I realize its a good idea, but is it necessary in the case of the FS?
 
just get the thinner head gasket. less troubles. it's not so much the valves hitting the pistons as that'll take increased lift AND the valves not closing with the piston goes up - not very likely to happen...but they problem may be the piston hitting parts of the head that shouldnt be so close to the piston.

upping the valves isnt required, but new valve springs probably are if you're going agressive cams (i really should get new springs)
 
I definitely agree, better valve springs are a real plus (if not a must) when moving to more aggressive cams; and I am fully intending to install a proper set at the same time I upgrade the cams.

Does anyone know for certain how close the piston actually gets to the top of the combustion chamber at TDC? I want to avoid causing myself any clearance problems as a top priority (of course). But, Id also like to increase compression as much as is possible so as to loose less low RPM power when I mess with the timing, to take full advantage of the cams.

Are there any other members here that have successfully decked their cylinder head?
 
i'm running about 0.340" lift now and there is no bang when the valves are fully opened and the pistons are at tdc. no real point in going bigger than 0.350" lift on our engines
 
Mazdaspeed cams aren't really considered "aggressive" cams though, are they? I mean, I have them and I have no problems revving to fuel cut.

I agree with twighlight on the gasket, much easier - shaving the head could get ugly and it's not going to increase your CR that much anyway.
 
Where are you considering getting the headgasket from? Cometic makes one, but only down as low as .027". =) Milling the head true wouldn't be a bad thing, though. But that's generally never in excess of .010. Always a good idea if you're using a new (to your engine) head, too.
 
I was planning to get the Cometic, but I had thought the Cometic gasket was .020 thick? Oh well, I guess I wont be improving my CR with the gasket as much as I was expecting. Are there other thin head gasket alternatives out there for our cars?
 
In spring-steel, the Cometic gaskets can be had as thin as .010", but to retain any degree of the stock strength, you'll want to get an MLS gasket. The stock one is MLS at .040" thick. Dropping down your headgasket thickness to .027" would bring you up to 9.3:1. Shaving another .010" from the head would bring you up to 9.5:1. .020" would by 9.7:1. Changing the volume of the combustion chamber by having the quenches welded up, let's say by... I dunno... 5cc, or so, would bring the CR up to about 10.3:1, if you shaved the .010" off the deck.
 
Even with Mazdaspeed cams, you won't have to upgrade your valve springs. The FS doesn't support the RPM needed to necessitate it, and I'm sure even the JDM Mazdaspeed engine didn't have stiffer springs anyway.
 
Alright, my thinking at this point is to go with a .020 head gasket and deck the head .010 (just to true it up) thanks for your opinions guys.

Now, I had planed on purchasing my Mazdaspeed cams from SR, but after a quick search I see that several members have been less than impressed with them. So now Im taking a second look at buying blank cams and having them ground to custom specs. The only problem is Ive never done that before so Im not sure where to do my shopping. I had thought that AWR sold blank cams for our cars but they dont seem to be offered on their web page. Can anyone point me in the right direction to find an appropriate set of blanks?

Also, if anyone would like to share their custom cam specs, and/or can recommend a reliable shop to do the grinding, Id be happy to hear about it.
 
Gavin said:
Alright, my thinking at this point is to go with a .020 head gasket and deck the head .010 (just to true it up) thanks for your opinions guys.

Now, I had planed on purchasing my Mazdaspeed cams from SR, but after a quick search I see that several members have been less than impressed with them. So now Im taking a second look at buying blank cams and having them ground to custom specs. The only problem is Ive never done that before so Im not sure where to do my shopping. I had thought that AWR sold blank cams for our cars but they dont seem to be offered on their web page. Can anyone point me in the right direction to find an appropriate set of blanks?

Also, if anyone would like to share their custom cam specs, and/or can recommend a reliable shop to do the grinding, Id be happy to hear about it.
Click to expand...

Can you even get blanks for the FS? Hard-welding is an option. I'm sure somebody has a spare set of cams laying around you can buy for cheap.

The best way to engineer cam specs, is to have your cylinder head flow benched. Utilizing flow patterns at various amounts of lift, a cam profile can be optimized to suit those flow patterns. I know that Elgin Cams can do this, but I believe they may no longer be in business. Comp or Cat Cams also do custom cams.
 
i was under the impression that the cams from the MSP were no different from the regular protege cams. Am I wrong on that one?
-Mateo
 
Yes, you can get the cams hardwelded, or buy new billets. New billets are 99$ a piece, and can be ground to basically any spec. Regrinds of your stock cams, which will require re-shimming the head, cost about $150-200. J-Spec/Mazdaspeed cams will run you some number I'm not familiar with, since I'm not really interested in purchasing them, and hardwelds will run you in the range of 400-500 dollars.

http://www.crower.com/ <-- Regrinds
http://www.webcamshafts.com/ <-- Hard welds
 
Thanks for the links flat_black

Brian, Boston, & Yeller as far as I know you are very correct. I've picked up a bad habit of referring to the J-spec cams that I was looking to buy as Mazdaspeed parts; only because there are several retailers that use the terms interchangeably, misrepresenting themselves to a certain degree as selling Mazdaspeed parts, when they are actually offering JDM parts.

But Im thinking custom may be a better way to go now anyway. I just need to figure out what I want my specs to be.
 
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