would this give me a good increase in power

[Nick110]

a stock 400ex head, full port and polish, titanium valves, and hardened springs.also any suggestion that r different are appricated. thanks. its for a 2004 400ex

[6858-400ex]

THE PORT AND POLISH WOULD BUT I DONT THINK THE OTHER WOULD

[bwamos]

The titainum valves and hardened springs should allow him to run a more agressive cam though. And, rev up a little faster.

[wilkin250r]

Why are you asking? Do you know somebody that is selling a 400EX head with those modifications? As it sits, those mods alone are not going to give a significant gain on an otherwise stock motor.

Porting will allow more airflow, but with the stock bore and camshaft, you are not pulling a significant amount of air, so it won't do much. However, if you have a big bore or stroker, with an aggressive camshaft, the porting will really have an effect.

Likewise with the titanium valves and stiffer springs. By themselves with a stock camshaft, absolutely no difference. But they will allow you to run a very aggressive, high-rev camshaft, which will create more power.

By themselves on a stock motor, those mods won't do anything. But when they are part of a complete motor package, they will allow significant gains.

[Nick110]

what if i drop in a cam and a high comp. piston. will that wake it up

[400exredrider]

yes and a FCR

[wilkin250r]

The porting will help a bit if you're using a high-rev camshaft, however, some people don't like the high-rev camshafts. True, you gain power in the upper RPMs, but you LOSE power in the lower RPMs. They make the motor "peaky", and can be a handful in tight sections.

The porting will be most effective if you also increase the bore, like a 416, or better yet a 440.

A high-compression piston is a big power boost on a 400EX. 11:1 is about the max you can go with pump gas, any higher and you will need race gas. However, a true 11:1 is tricky to get on the 400EX, and if you don't know why or how, I suggest you do some major research, or you let a pro handle it. By "pro", I don't mean your local dealership.

[400exredrider]

what wilkin said is exactly true, i have a hard time harnessing the 416 in the trails because it has the torq there, just dont get all power until its on the top end.

[frosti108]

im with you 400exredrider. i sorta wish i had gotten the stage 2 WEB cam because the the high rpm cam, stage 3, is pretty damn weak on the lower revs and very powerful only in the very top of the repm range

dont wanna blow it up now without a rev limiter all :devil:

[chadmel]

If you've already done a full exhaust, rejetted, and aftermarket filter with lid off then the next step would probably be a cam and high-comp. piston. It will be a noticeable difference. Hope this helps.