VTEC Intake Valve V. LS Intake Valve

[brian11to1]

VTEC Intake Valve = 33mm
LS/B20 Intake Valve = 31mm

Im getting all my research finished up so I can start accumulating parts for my 11.5:1 B20B All Motor Build. This far I've decided on:

84mm IB Spec 11.5:1 Pistons
IB Spec I Beam Rods
Line bored GSR Main Girdle
Crower 62404 Cams
Crower Dual Valve Springs w/Titanium Retainers
this is just a simple list the real list is much longer

My question is... would I benefit from cutting new valve seats to seat a VTEC valve (33mm) into my LS Head (31mm I. Valve)? If I had my "porter" do this would it be beneficial to me. What would be the pro's and con's of having larger Intake Valves. Are they better for higher RPM's or what? Thanks

Brian

 

[erebunicrx]

i think its going to shift the whole powerband up. you may have a better peak hp but alittle less bottom end. you might be better off looking for a p8r head. im not sure how much your going to pay for the new valves but the p8r comes with the 33mm intake valves anyway.

 

[brian11to1]

How hard is it to find a P8R head?

 

[erebunicrx]

my motor came with one. but on h-t there are people selling them. the problem with the p8r head is noone has built one that i know of and i had problems with my 404 cams. the valve spring was coilbound on the intake side at a 440 lift. so i had to get 8 ret from crower from a h22. idk if this is going to work but thats what brian crower said would work. i will find out very soon though.

 

[erebunicrx]

also the p8r head has a 84mm combustion chamber

 

[brian11to1]

What was the deal with the Spring? I didnt understand that. It cant have an 84mm comb. Chamber... thats more than double the size of any B series.

 

[erebunicrx]

your combustion chamber now is 81 with the regular b20 head. the p8r is only 3mm bigger and makes it the same bore as the block. im still not sure what was wrong. maybe the valve seat on the intake sits alittle higher so there where no clearence isues with the piston to valve cleaence. but im not sure.

 

[brian11to1]

C-Speedracings Comp. Calc. says the volume of the LS Combustion chamber is 45 cc...

 

[erebunicrx]

right and the p8r is 49 cc's. the diameter of the combustion chamber is 84mm. just like you pistons are 81mm. the cc's are measured by amount of liquid in the combustion chamber in cc's.

 

[brian11to1]

Dayum.... learn something new every day