dubrado

iTrader: (20)

If i go bigger valves on my 243's (right now i have 241s) I know I have to have the valve seats cut...but do I need to do anythign to my spring seats or anything else on the valvetrain?

different pushrod length? etc....

thanks in advance

2000TransAmWS6

iTrader: (12)

i don't believe so

Xtnct00WS6

iTrader: (8)

different pushrod lengths would be because of the base circle of the cam being smaller, or milling your head...etc.

brad8266

iTrader: (23)

Just valve seats. Keep in mind that bigger valves will reduce PTV clearance too.

dubrado

iTrader: (20)

I was gonna do 2.02 and 1.56 w/a 224 cam

that should be plenty of clearance right?

brad8266

iTrader: (23)

Yeah you should be OK.

Xtnct00WS6

iTrader: (8)

FYI: I'm right within clearance tolerances with a TR 114 224/224 , .045 gasket, milled 243's .010, and 2.02 1.57 valves

Whistler

iTrader: (46)

It doesn't do crap unless the seat is opened up and blended into the bowl of the port.

dubrado

iTrader: (20)

so your'e saying going bigger valves w/o seat and bowl work is not gonna net any gains?

Whistler

iTrader: (46)

Nope. Think about it.

GuitsBoy

iTrader: (4)

Those should actually fit on the stock seats, youll just have to get them cut to the bigger size. Shouldnt have any issues as long as youre using a good valvespring.

DJ_951

I agree they should fit the stock seats too. 1.60 on the exhaust needs to be cut. The other question is their is a ratio between intake and exhaust like 80% and you may want XXX intake want size YYY exhaust do you want. 2.02/1.60 was a classic valve size combo.....but this is a ls1

Not sure the valvespring would matter because of the vavle size? Lift on cam and rpm would matter.

IF??? They fit the stock opening whats to blend?

Studytime

iTrader: (15)

You don't have to change valve seats for a 2.02 valve nor a 1.57" valve. Both of those will fit on the stock seats fine.

Everything. The bowl opening and the runner. That area that you're asking "what's to blend" is only like the second most critical area in the entire port. It's VERY important. The only thing more important would be the short side radii in my opinion.

Aftermarket valves with a thick margin (like the Manley valves) are going to reduce clearance. You'll notice a large reduction from a manley VS. stock even for the stock 2.00" valve. Increasing the diameter of the valve will only further decrease clearance. I guess it was too expensive to have valve reliefs cut in our pistons when they were being cast since we had 15 degree heads. Hmmmm...

Ben T.

DJ_951

Thanks for the answer.

back up question: If you leave the heads stock and just change vavle sizes 2.02/1.57 would it be an improvement or just if you have the heads port and polished-cnc'ed.

Xtnct00WS6

iTrader: (8)

There's a minimal gain and in my opinion, it's not worth the drastic reduction in PTV clearance.

GuitsBoy

iTrader: (4)

I wouldnt say drastic. Theoretically it should only be .003 or .004 less clearance, assuming the valves were hung in the same spot and the valve margin was the same. The trouble is most aftermarket valves have a much thicker valve margin.

I totally agree with the limited gains. With the good results coming in from all the stock valved ls6 heads out there, its hard to justify the cost when budget is a concern.

Proud2bSS

iTrader: (2)

As said above, the port bowls are already a restriction. That's where the FIRST porting should take place. Then increase valve TYPE and sizing to optimize the porting.