AbeFM

iTrader: (3)

Ok, well, after having several deals fall through, I've finally got a collection of awesome parts, but I have so many, I can't decide what to do - so I thought I'd ask you all for advice.

The big question: Would I rather have a VVT head, or a MSM head?

The MSM is supposed to have bigger valves, higher temp (and stiffness?) springs, and longer duration intake came (lift too, maybe?) while the VVT head has, well, VVT. I think the lift is high on it, too, but I don't know.

As to the state of them, the VVT head has "63k miles" which I believe, the whole motor looks pretty much perfect, broken in, but it doesn't look beat at all. The MSM head just came out of a machine shop. The cams turned a little hard, so I pulled the cams, cleaned it up, and I'm going to pull the tappets and see how they look.

AbeFM

iTrader: (3)

Second part of it:
I have two utterly fine short blocks - a '00 and a '03. The '00 has a balanced crank, carillo h-beams, '97 OEM pistons with their low compression (9.0:1).

The '03 is bone stock, which means OEM just-itching-to-bend rods, the awesome MBSP, high compression pistons (10:1 I think?)....

Right now my guess is I'll put "my" '00 crank, the oil pump I'm getting from the group buy, and my rods into the '03 block and tray, and get it punched out to 20 (0.40?) over and put in wiesco "turbo" pistons (8.6:1 I believe).

I have another spare '01 oil pan... I was thinking of putting the '97 pistons on stock rods and whatever head I don't use on the "race" motor, and keep the whole thing as a spare. Then if I have engine problems (or, a engine doubt) I can swap motors, turn down the boost, and be running in 1-2 days.

One advantage to this, I could put together the spare motor right now with what I have on hand, and when I get all the parts and machining done on the 'race' motor, I could swap them out (ideally, I've finished rebuilding my 6 speed by then, swap them both together)

One more question: Is there any sense to putting the MBSP on a motor with OEM rods? Seems like a joke to me, the rods will go long before the MBSP can make a difference. On the other hand, if I put it together with the '03 pistons, head, it'll be shitty for turbo but I could just sell it as a complete, running motor.

AbeFM

iTrader: (3)

Lastly, on the heads... Should I do any head work? I'm looking at the MSM head, and it's kinda nasty - factory bumps from the casting marks.. I think with the oversized pistons, a touch of deshrouding, polishing, and port matching, and I'll have a head (along with the OEM big cam) which will take me where I want to go.

Now I'm just curious what all is a good idea. I'm open to suggestions, that's for sure.

patsmx5

iTrader: (16)

Depends. I'm pretty sure the intake cam is the only difference between a regular 99-00 head and a MSM head. And FWIW the difference in cam specs between a MSM intake cam and a 99-05 exhaust cam (which can be installed in place of the intake cam) are very minute. Bigger valves are heavier valves and the head doesn't need bigger ones anyway.

If you can figure out how to control it, don't mind the extra work up front to get it all figured out and working properly, and would appreciate the power band possible with VVT, I say I say VVT all the way.

If you just want to get the car running and make good power, regular 99' head worked.

EDIT: And I agree the MBSP is probably a joke. Maybe it does something to help fight harmonics or something like that, but I doubt it. It does very little for added "strength".

AbeFM

iTrader: (3)

True up to a point. I've been thinking, if I could put the MSM cam in the VVT head, yeah, it would work - but right now I'm thinking the VVT cam is shorter duration (perhaps I'm wrong here) and hence needs to be moved around to get what you can out of it. Using OEM specs as a guide, I think VVT set right over VVT set wrong will make you some gains, but VVT set right over a non-VVT cam... the gains might not be what you think when comparing improperly and properly set VVT.

I believe the castings are mostly the same in the heads.

Do you have the specs on these cams? That would be awesome to know... How the intake and ex cams from the three heads ('00, MSM, VVT) actually compare. Would be an awesome table to have.

Also, I wonder how much to punch out the block (i.e. which pistons to order)

patsmx5

iTrader: (16)

Bore it till ya hit the watter jackets, then back off a hair. You know my opinion with regard to bore, build, and head work.

The cam specs can be found on the mazdaspeed forum. The MSM intake cam is better than a stock intake cam. Exhaust cams for 99-05 are ALL the same.

y8s

iTrader: (8)

everyone tells me the front of the VVT intake cam is vastly different from the rest of them... am I misled?

I say use the built bottom end. Slap the MBSP and oil pan on it.

then make the most of what you can with the VVT head. mild headwork and call it a day.

AbeFM

iTrader: (3)

Hmm, interesting. Well, I do have like 57 heads. I could pull the VVT off the junk head, see which cams fit where.



So, why, in your unbiased opinion, should I run the VVT head? :-)

y8s

iTrader: (8)

Lets assume you can make the VVT head components equal to the MSM head components (valves, springs, cam grind)...

plus it has VVT.


actually, I'd like to see pics of the VVT/non-VVT cams side by side. if you can do that.

AbeFM

iTrader: (3)

Can-and-will.

I think I'd have to buy valves for the VVT head, though.... And springs. or use the MSM head for parts and toss it's shell. :-(

I'm still sort of looking for "best power" with a loose correlation to "lowest cost & effort". If I can get the MSM cam in the VVT head, I guess I'm done thinking about it though. Somehow, I doubt it.

patsmx5

iTrader: (16)

VVT cam has a thingy built on the back of it to trigger the CPS located on the valve cover above the cam. MSM intake cam isn't gonna have this.

AbeFM

iTrader: (3)

I was looking/thinking about that - when I looked,I saw it was just a ring, probably press fit on, possibly easy enough to retrofit.

The issue seems to be the front, again I'm not sure I can't modify it, but it would be some work. The cam-gear bolt hole has a hole drilled (I guess to let air out?). Also, the head of the cam is longer (but the same diameter), with four holes for oil (one for each "chamber" (or vane) of the VVT), which I think wouldn't be too hard to recreate. Then the front cap for the oil passage woud be tough, so I think you're only hope would be to make a ring with the right holes on it, and attach it to the cam. I actually don't think it would be that hard, but I think you would have to use the VVT head.

Which means you're back to small valves. I guess I could bring the MSM springs over, but at that might, I'm breaking up a MSM head for nothing - better to just buy a set of aftermarket springs for $200.

So I think I'm back to the original idea, run one head or the other. I'm not seeing a lot of love for the MSM head, it seems, odd, since I was thinking it was the better choice. I'm still not sure I'd see actual horsepower gains with the VVT head.

patsmx5

iTrader: (16)

Grr, lost everything I typed.

In short:

Intake cam for VVT is wayyyy different than any other intake cam. Retroffiting a different cam is about impossible and 100% impracticale. If you want a different profile, get it reground.

If you wanna play, dyno the car at different levels or advance and retard. You'll likely find full advance helps low end, full retard helps high end. Furthermore, you may find that more retard = more HP until you reach max retard. Then since you wanna play, figure out how to expand the range of the pulley to take advantage of this. That, or offset the cam a tooth to gain that much more retard by sacrificing that much advance.

AbeFM

iTrader: (3)

It I just wanted to get more range, I could simply grind down the stops in the VVT mechanism. It's really not complicated at all. There's a chamber with what's basically an apex seal, and they pump oil in which leaves out a drain. That force against the two sides expands it. There's a bump that stops the travel in at least one direction, I suspect on two.

What worried me is the VVT cam is so peaky. It looks to have zero duration. It's like they took a high HP system, and shortened the duration until it didn't pollute. You'd think you could advance the cam to cut overlap on the bottom end and still control pollution.

patsmx5

iTrader: (16)

Advancing the cam would mean it opens sooner, and close sooner. It would open sooner increasing overlap.

Did you measure the duration of the camshaft? Or do you have numbers for the duration? What are you looking at?

AbeFM

iTrader: (3)

Here's a "junk" 2001 head I got some pics of.

CPS:

You can see how it mounts in the full sized version


The second set of teeth is just in focus on the far side.


VVT Mechanism:
Cover plate off:

One could envision thinning those up to get more travel. I think Matt's earlier dynos showed that the coverage is already more than is needed?


Slightly cleaned mechanism. Is just rotates, it's that simple.


Most of the way "on", you can see the holes where the oil feed in on the central shaft.


Cam Belt Gear:

VVT mech off, this is basically a flat plate, gear mounting holes. You can see it uses an extra-large 17mm head mounting bolt.


You can see the back of the VVT gear. Different, but not special. I have no idea why there's such a nice bearing surface in there, it should only move a few degrees, once per travel through the revs.


CamShaft:

Within the error of my rushed measurement, they are the same diameter



While the ex cam is normal, the intake....

..is some 19.5mm longer.

The hole on the left, just to the right of the cam oil seal is a through hole intersecting the main cam bolt. It's not an oil passage as best I can tell, it's only there to let air out from behind the bolt? That doesn't make a lot of sense, but it's what I see. If it did spit oil, it would get everywhere?

Perhaps it's an oil return for the VVT system, but I don't see it. Actually, perhaps the four holes in the face of the cam, I thought they were all oil feeds, but maybe some are returns? Doesn't make sense given the 4-fold symetery of the of the VVT mechanism.

AbeFM

iTrader: (3)

No I didn't measure it. They just LOOK peaky. So much so, I'm not sure you could grind a wide profile on it, without getting shims that are 5mm oversized.

You're right, I got my cams confused. :-) The point remains, you could shift them out of the way of crossflow and make the durration longer.

patsmx5

iTrader: (16)

You know you can use a caliper as a depth guage right? Use the other end Abe.

You can not separately control the intake valves opening and closing with respect to position of the piston with VVT. You can only move the two in a pair. When the intake valve close is more important than overlap. Faster the engine spins, the higher the velocities in the intake ports. Faster velocities means that the cylinder continues to fill with air as the piston reaches BDC of the intake stroke and begins the compression stroke. That's because the moving air has mass and a velocity, so it has momentum which increases with the square of velocity IIRC. So the faster the engine turns, the faster the air moves, the longer the intake valve needs to stay open before closing to maximize cylinder filling.

When I do the exintake swap I'm not drilling the cam gear. I'll do the math and figure out where the "correct" spot on the gear is to align with the alignment mark, then retard the cam to the closest tooth of the gear. More HP.

AbeFM

iTrader: (3)

What the heck do I need a depth gauge for?

All I'm trying to figure out is which head will buy me more HP, ideally with less work.

patsmx5

iTrader: (16)

To measure how far the cam sticks out? The depth that is.

There is no clean cut answer Abe. It all depends what you want and what you're willing to do/spend. I'd venture to say both heads have the exact same "potential" to make the same peak HP numbers on a dyno. That is, if both were built to the hill and everything was perfect, the heads would perform very similar. They're very similar.

Only difference being the VVT cam has the ability to to make more in the lower RPMs where the non VVT head will suffer. But the benefits of VVT come with the complexities associated with controlling it.

Are you really asking a question? I mean, which is better is quite objective if you don't have constraints. Maybe a budget, time frame, and your definition "better" are needed?

Hell I'll say this. My head will flow better than either of those heads no matter what you do to them. Send it to FM with a blank check. My setup was labor intensive, but only costed ~200 bucks. Well worth it. The cliche "knowledge is power" would have a whole new meaning. Money HP all the time.