How much difference from a stock 243 head from a stage 3 243 head? Just want to know whats the hp difference is.

 

maybe 20 hp.you need a 4" bore to run most stage 3 243s heads because of valve size.

 

agreed, 20ish horsepower is a good generalization.

The gain in power depends a lot on who is doing it the work on them though and how much time they invest.

 

Moving from External to Internal III.

 

if u r stock motor use 2.5 stage heads

 

JRz28 I have a stock bore LS1 and 243's with 2.055 intake valves and have no issues.

 

He may have no clearance issues, but the cylinder is shrouding the valve.

 

LubeLizard,,, So I guess the the Impala and truck 5.3 engines that come with 243 heads from the factory are having valve shrouding problems also because they have a 3.78 bore with 2.00 intake valves.

I guess the 20 extra horsepower the 5.3 engines picked up going to the 243 heads with 2.00 intake valves is thanks to valve shrouding.