Cam Specs - Help

[twilightprotege]

Hey,

I have a really simple question (well a few actually), but I'd like to know the reasoning behind answers and something that points to proof for those questions (if possible).

I have an MP5 with an Injen Cold Air Intake. I want to change the cams for something a little more wild, for immediate performance, but also want the cams to be appropriate for when I turbo the car (after warranty runs out). From reading the hundreds of threads etc, I have come up with these specs :

Intake : 0.350@0.050 225deg
Exhaust : 0.340@0.050 215deg

What does everyone think???

I know it's not wild, but I would think of it as a mild cam. Would anyone change these specs and why? What overlap would you say? 10 deg? 15?

To help with your decision, when the car is turbo'd, I will be raising redline to 8000rpm (through strong and lightweight internals and new ECU etc), and be running around 14psi boost.

So, I'd love some help...........bring it on!!!!!

Twilight Protege (Andrew)

 

[njaremka]

if you plan on going turbo, leave the cams alone. IMHO, waste of money.

now, if you want to stay NA, take the head off, get it polished up and flow tested, then get some custom cams. tell your grinder your flow numbers and what you want, and they will really get you some serious power.

 

[Zeus]

Those durations are good for FI, as long as you don't dial in any overlap. I'd go with more lift though, and plan on reworking the head at the same time like the man said. You will need higher rate springs, and it would be good to loose some bucket and retainer weight too. Otherwise stick with the MS and J-spec bump sticks.

I had picked close to the same numbers for a mild NA -

In - .437@226 deg
Ex - .423@221 deg with 6-8 deg overlap.

I have the blanks on a shelf in the garage, but I'm holding off till I can throw in a stand alone. I'm going with the Tech3, and am just waiting till I have the time. Basically you'll need to do that first, with adjustable pulleys, or the those cams will be a real let down.

My advise is go all the way or just swap for the MS and J-spec sticks.

 

[twilightprotege]

Thanks for replying guys, more thoughts from others would be greatly appreciated too.

A few more questions...

What lift can the stock springs handle?

If I were to say put 6 deg overlap on the cams while it is NA, is that easily changable once i go FI?

And finally (well for the moment anyway), would I expect to see any problems with the cylinder and the valve having a meeting and screwing my engine???

Thanks again,

Twilight Protege (Andrew)

 

[Zeus]

The only way to find out how much lift they'll take is to tear it down or find blue prints, neither of which I've done yet. I'm sure the valves will float at higher revs anyway, so I've resolved to do the cams, pulleys, valve train, head and ECU all at once. That is if I get to it before the RX-8 comes out.

If you use adjustable pulleys with the cams, you can dial overlap in and out as you like. But I'm not sure how the stock ECU will respond with the ex cam position sensor moving around. Anybody else know?

Most aftermarket pulleys I've used before can do +/- 4 to 6 degrees. So yes, you can dial it out when you install a spool.

As for checking the valve/piston clearance for valve lift, my guess is that with the relatively low compression of the motor there's ample room. But to be sure, you'd either need to find someone who's looked already, or tear it down, put clay on the piston, reassemble it, turn it over and tear it down again to see. This is especially importent if you deck the head or change pistons too. But if you plan on doing a turbo, I'm sure you won't be raising the C/R. A very good idea none the less if you raise lift by more than about 20 mils.

The whole deal makes the MS cams look pretty good huh? Like I said it's all or nothing. Makes the prospect of a new side port roto look pretty good too. I'm already talking myself into giving up on the Pro, and saving for the RX-8. Zoom zoom my ass.

 

[twilightprotege]

Zeus, So with the cam specs you've chosen, you havent actually checked to see if they would be ok yet?

With the engine we get here in Australia, we get a higher compression piston, 9.7:1 to be precise, what you you think about clearance on that?

Further to both of statements, HAS ANYONE CHECKED EITHER OF THEM????????????????

 

[twilightprotege]

Oh Zeus, I should ask as well, has Tech3 given you any indication on these points????

Oh, and (gee I like the questions) how much would valves, valve springs and head polishing be???? Considering I want the engine to rev to 8000rpm on completion, would titanium be the go? I want the engine to be ultra strong and reliable.

Thanks again,

Twilight Protege (Andrew)

 

[njaremka]

Twilight Protege (Andrew):

sounds to me like you want a Speed World Chalange Protege engine. those suckers cost upwards of $25,000.