XR400,Port/Polish,Titanium valves????

[frogburner]

I am very much considering some motor work this winter to my 400... Right now All I really have is a K&N filter W pre- charger, 170 main jet, and a Mega Max II slip on.... What I would like to do is ,, drop in a XR400 Cam, Port and polish with Titanium valves, and a DMC full exhaust... Do I need to have more compression?? If so What piston should I go with??? How much roughly do you think this would run me in price???? Would there be a big difference in power??? please write back if you can help me out

Go ahead and add a stock bore high comp piston if u want to fully notice it.

[JhallettEX]

Do not go with the xr400 cam, I went with this exact cam my first time, along with alot others on this site. I was not happy with it at all. I have since switched to the HotCams stage 2 and I am very pleased with it. I recieved alot more power and throttle responce with it. It is also a straight drop in cam so you will not have to hard face your rockers, etc. This cam ussally runs in the $120-130 price range with NO core charge. C&D Racing has 7 of these cams in stock now and could also get you a package deal with everything you need cheap. Give them a call there number is in my sig.

[Matt Fisher]

Using Ti valves with an Xr cam would be a waste. Ti valves are worthwhile if you are running a very large cam at very high RPM's. Decreases the odds of having the valves float.

The XR cam is really mild, not a good choice if you want to make big power, but great for a small and easy power increase. Also not worth doing port work with the XR cam.

If you're going to increase the displacement or at least raise the compression, then running a larger cam than the XR would be worthwhile, as well as the port work.

IF you're willing to run race fuel- the easiest way I've seen yet to make more power is with a 12.5:1 piston, and a good sized cam. Just a thought.

[MIKE400EX]

Hey MATT! Did you get your 440 running yet?

[Matt Fisher]

Nope, I go to the machine shop on Monday to have the cylinder decked and the piston shaved. The Ross 89mm piston assembly will end up being lighter than the stock one. :)

We did finish my friend's 440, and it hauls butt. He has the 479 cam vs the 450/451 I have, so it will be interesting to see the difference between the two when mine's complete.

I posted pictures of the custom oil cooler on the Yahoo 400EX list, it's pretty cool (pun intended).

[MIKE400EX]

I did a little "creative machining" on the Wiseco piston I used, it ended up only 6 grams (pin, rings, locks,piston) heavier than stock. Funny thing is, it's much smoother at all RPM levels than than stock low comp. piston. I chalk that up to a better skirt design - or a little better Q/C! I've been planning on swapping the 450/451 cam for the 479 this winter - so I'm anxious to hear your results. Good Luck!

What do the #'s mean? Is that the lift, duration or what?:confused:

[MIKE400EX]

That's the Web Cams designation for their cam which is similar/same as the White Bros. Track, GTC, HRC......

[Texan32]

port/polish is going to run up a heafty bill. I can't speak on personal experience, but from what i have been told, and p+p job only really helps when you do a big bore kit. From what i've heard, for the money you spend on it, it makes very little differnce on standard bore (including 405,416 and 425).

Also, it IS suggested that you bump you compression when you go with a bigger cam. You already have the motor apart, a JE 11:1 piston kit is only like 120 bucks. And with 11:1, you can still run pump gas.

One last thing, i'm not a jetting expert, but a 170 main sounds a little rich for a stock motor and a MMII...

this is just my .02...take it for what its worth...

[Matt Fisher]

Mike-

Got the cylinder decked tonight and the piston shaved- only 291 grams now. Parts to get coated this week. My friend went nuts on coating everything- I'm being a bit more reserved.

Frogburner (great name :D ),

A bigger and/or higher compression piston will move more air (as will higher RPMs). The more air (the bigger and/or higher the compression) you move, the more things like port/polish, really big cams, bigger carbs, etc, etc. matter.

What's your goal, and your budget?

Speed costs money- how fast do you want to spend?