0PISTONS

I'm building a custom 4 port 13B for my FB with 12A plates, a GSLSE EShaft, and I'm unsure which rotors to go for. I know that S5 rotors are a little ligher and have slightly higher compression, but they are a pain in the *** to find and are more expensive. I can find a pair of S4 rotors fairly easily. My question is that if I have too much trouble finding some S5 rotors and just buy a pair of S4 ones, how much power am I sacrificing? I'd like to pull 200RWHP out of it after tuning. I know this is stretching it and I might not be able to get that number, but I'd like to get close. The motor is going to have a large streetport and is going to be carbed. Will it be practically possible to pull close to 200RWHP with the motor regarless of whether I use S4 or S5 rotors? Also, Since I am using a GSLSE EShaft with S4/5 Rotors, will I need to get the rotating assembly balanced? Thanks.

kahren

get the s5 rotors, if you can, they make a bit more power from the comression but if the engine is ported large you can take advantage of the lighter weight rotors and rev the motor hihger. you have to get the right counterweights for the s4 or s5 rotors. thats what determins the engine balance. you could make the 200whp with either rotors with the right port and tunning

0PISTONS

[quote name='kahren' date='Jul 18 2005, 06:34 PM'] you could make the 200whp with either rotors with the right port and tunning


[/quote]



thats what i was looking for. i know that the s5 rotors will make more power, but im leaning towards s4 because they are much easier to find used. the porting is going to be a large streetport (intake&exhaust). I will make it as large as possible for a streetport while retaining reliability and street driveablity. i know there are many contributing factors, but with this porting (assuming i tune it well) can i pull 200rwhp? if i can meet this goal with s4 rotors, i will just get them for the economy.

kahren

i said this a few times before and will say it again, its not hwo big you port its how you port. but eventually if you go big enouf it will make the power, it might be in the rpm range you are looking for but it coudl do it. if you dont care about havign a higher redline with the s5 rotors and the little added power of the higher compression then go with the s4 rotors. but makign a LARGE street port and having s4 rotors can sometimes contradict since you will want to rev teh engien higher to reach the powerband the port is tuned for.

0PISTONS

well this is going to be a street car, so its not gonna have a crazy high powerband. i haven't done much research on the porting yet since i havent started work on the engine, so i suppose i shouldnt have said that the port was gonna be gigantic. I know its going to be a streetport - i will have to research what designs and timing will work best for what i want. I dont wan't my shift point to be any higher than 8000rpm.

chase78

Yea to get to the 200hp mark s5 rotors will get you there. The problem that I have with the 4 port NA is that much like a



2bbl vs. 4bbl carb



the 2bbl(4ports engine) are large bbl(ports) and the 4bbl(6port engine) bbl(ports) are smaller per port. BUT the 2bbl(4ports engine) will not delivery as much intake volume at WOT as would the 4bbl(6ports engine) b/c the 4bbl(6ports engine) can delivery more volume when all the 4bbl (6ports) are opened. There is ways to get around it like porting the 4port engine to increase volume but you will reduce intake velocity at lower RPMS and a lose torque at the lower rpms.



Its up to you. If you want lots of HP at high RPMS and dont mind a lumppy idle the 4port is good. If you want something more normal that can get 200hp S5 6-port long block with porting+ ecu and harness is good too.



good luck

kahren

if a t2 motor is beign ran NA and a 6 port has the aux sleeves removed, with all else being the same, the 6port will have less low end then the t2 motor due to the aux port timing.

the people that are looking to get the extra power out of the 6port end up removing the sleeves for that extra top end flow. whne both motors are ported properly they both could have very similar top end power. the 6 port gets the power because of the secondary and aux port area being so large, and the 4 port motor because it can flow better then the 6 port.

if you are gonna take the motor appart and can obtain the secondary plates from a 4 port motor you could always port them and have same power as the 6 port but also have more low end IF you are gonna run with the 6 port sleeves removed on the 6port motor.

hope this makes sence to all