Having a lot of mixed answers/feelings reading these 5.3 build threads.

I am swapping to a 5.3L iron block shortly. I have 243s sitting at shop right now and am leary about having them milled or not. I've read it will drop compression down if I stick those on.

I also plan on running nitrous, up to 150. Should I have the heads milled down .030 like everyone states or just leave as is? I plan on boosting the motor during the summer as a long term goal.

I know this has been covered 1000s of times already, but I need definite answers...

Thanks all!

 

if you are going to give the engine boost then leave the heads OE, maybe just a shave .010

 

Two reasons for a .030" cut on the 243s.
First it will allow you to run a 7.4" pushrod as the base circle of a higher lift camshaft is smaller.
Second it will help the smaller engine maintain approximately 9.5 compression which will keep it more responsive for a boosted application.