newbies first rebuild... UH OH lol

[redrider311]

alright my motor is starting a little bit of a knocking sound that i dont really like and i talked to rich hetrick and we decided i need to just rebuild my engine... now im pretty mechanically inclined and ive rebuilt many top ends and other motors.. but this is my 400 :( .. so im a little concerned...

basically when i rebuild my 400.. what all do i need to do to make it perform better.. im hoping to keep most of the same parts i have in it right now.. but i would just like to make it run better.. any help from you real gear-heads would definataly raise my confidence.. lol thanks guys

[Cody_300ex]

Shave the head or jug/cylinder down .020 -.050 or just use one layer of the head gasket. That will bump your compression up a lil. Lap the valves good, do a nice clean valve seat cut(3,4 or 5 angle valve job), make sure you file the rings before you put them in, theres thousands of lil tricks. Good luck!

[wilkin250r]

I wouldn't recommend shaving your jug just yet. If you've rebuilt other motors, then you already know all the basic aspects like deck height, squish, valve clearance, cam timing, ring gap, blah blah blah. The same applies to your 400.

Unfortunately, for maximum performance, there's not a whole lot of modifications that you can do yourself, unless you're a competent machinist. Porting the head, larger valves, possibly machining the cylinder, all those things you'll have to send out. However, you can still get an increase in performance without these things. A simple high compression piston and an aftermarket camshaft will have dramatic effects.

One aspect to pay very close attention to is deck height and squish band. Many of the aftermarket pistons have had problems in this area for the 400EX. I'm not sure if they have been corrected or not. Measure your base gasket thickness, the head gasket thickness, and take all that into account when measuring or calculating the deck height. If you decide to go with thinner gaskets, or shave the cylinder, be sure to double and triple-check your valve clearance.

[Cody_300ex]

Originally posted by wilkin250r
I wouldn't recommend shaving your jug just yet. If you've rebuilt other motors, then you already know all the basic aspects like deck height, squish, valve clearance, cam timing, ring gap, blah blah blah. The same applies to your 400.

Unfortunately, for maximum performance, there's not a whole lot of modifications that you can do yourself, unless you're a competent machinist. Porting the head, larger valves, possibly machining the cylinder, all those things you'll have to send out. However, you can still get an increase in performance without these things. A simple high compression piston and an aftermarket camshaft will have dramatic effects.

One aspect to pay very close attention to is deck height and squish band. Many of the aftermarket pistons have had problems in this area for the 400EX. I'm not sure if they have been corrected or not. Measure your base gasket thickness, the head gasket thickness, and take all that into account when measuring or calculating the deck height. If you decide to go with thinner gaskets, or shave the cylinder, be sure to double and triple-check your valve clearance.

wilkin if im not mistaken I am pretty sure that his base gasket will be .020. The base gasket on mine was. The head gasket, im not to sure about.