Resolved 420a Valve Size

[nboyd2002]

So, first time poster. I've looked online and through the forums. I could be missing something. I have a 1997 Mitsubishi Eclipse RS with the 420a engine.

It's just a toy project for me but I am completely rebuilding the motor. I have already ordered a vast amount of new parts including forged rods. I have not ordered any pistons yet until I've broken the motor down and sent it off to be hot tanked, cleaned and bore size checked and evaluated to be bored 20 over if need be, end goal once engine is completely rebuilt to add a turbo kit to the engine.

My question is, what size valves should I be looking for? Will standard OEM valves handle the 8-15 psi or what particular type should I be searching for.

Thanks for any help and answers in advance.

 

[BLACK'98DSM]

Standard OE size valves would be fine. You can go with a +1mm oversize for a slight performance increase, but is not necessary. You could just save those funds and turn up the boost if you want more. I always oversize for my N/A builds because options for extra power are limited. You really don't need any different valve material for a street build. Just make sure they are properly lapped/sealed and you are good to go.

 

[nboyd2002]

Standard OE size valves would be fine. You can go with a +1mm oversize for a slight performance increase, but is not necessary. You could just save those funds and turn up the boost if you want more. I always oversize for my N/A builds because options for extra power are limited. You really don't need any different valve material for a street build. Just make sure they are properly lapped/sealed and you are good to go.

Alright sounds good. I appreciate the response back. I had seen a few different sets of +1mm when it came to the valves so wasn't for sure if it meant I needed to adjust anything else to make those work. I'll grab a set of the +1mm over size then just for the extra bit of increase to add to the build since I'm already doing the engine rebuild.

 

[Canadian_CD9A]

The +1 valves won't do anything for you; I've seen them lose power before when the setup didn't warrant them. Stick with stock size.