On ported ls1's and F13 cam, is there a benifit to oversived valves? Will I get a worthy HP increase? If no, should I buy new vlaves for added reliablility?

 

Talk to your head porter. A valve job was probably the first thing that he did to your heads. Many porters operate in that sequence; valve job then, blend the iron seat into the bowl area. If he didn't put a fresh full-radiused valve job on them, take them and have a valve job for 2.02/1.57 valves cut. Then bring them back to the porter and have him blend the valve job in and deshroud the new valves. That's really what I would recommend if you're not wanting to leave 10hp behind like you were saying in your other thread.

So, in that case a set of aftermarket oversized valves. Bring the valve when you're having your valve job done and tell the machinist what you want (at a performance, not maintenance oriented shop).

Ben T.

 

Like Ben said: It should all be setup together by the porter. If he's a reputable porter, he'll know exactly what size HE will use in his setup and WHY based on HOW he ports the heads.

Just because the valves are bigger doesn't mean the heads will flow more air or make more power.

Mike

 

hmm.. So since I'm porting them myself, what to do... I guess I'll use stock valves, because I cant really just port 1 cylinder, flow bench it, then enlarge the valves, and re-bench, then if I hurt airflow/velocity I'd have screwed my head..

And before you all flame me, I know everyone suggests to not port them myself, but i've talked to alot of people about it and I'm pretty sure I have enough knowledge to get it done nicely.

 

If you're doing a basic clean up around the vavle guide boss, removing the bump, etc., then go with bigger valves. After you have your bowls opened up, then go get a full-radiused valve job. Then you need to blend that in, and add your big valves. Talk to a local machinist, I'm sure he can help you.

I've picked up flow at every lift on the flowbench just by adding larger valves. Larger valves in conjunction with the appropriate sized valve job would show even better gains.

So, port one cylinder and if it works, port the rest of them. Get a valve job, blend that in, and then add your larger than stock sized valves. Bigger valves are your friend! Just remember you will slightly decrease free-drop.

Good luck,
Ben T.

 

Uhh.. free-drop? Sorry i'm a newbie and I don't know what that is.

 

And how should I find out where and what a good size valve job is for my heads/cam? any ideas?

 

Free drop determines PTV clearance if you're running a big (long) intake lobe.

2.02 and 1.57/1.60" valves are plenty big enough.

Ben T.

 

Alright, thats what I figured, I'm not gonna go any bigger than 1.57 though

 

Cost is the same exact thing. 1.60" valves will fit LS1 chambers without issue.

Ben T.

 

I've already got some crazy duration on my cam and I dont want to make a mistake on going too big on exhaust valves, so can I get a second oppinion? I'm going to order new Manley 2.02/1.57's tomorow morning if not. I need to get a move on getting this H/C swap done. I still have one head to port and all my gaskets to buy, plus the actual install. Hopefully by the time my F13 arrives I'll have all my parts.

 

The exhaust valve has PLENTY of room. It's the larger intake valve that you would need to worry about, but you definetly DON'T need to with non-decked heads and an F-13. I was using 2.055 valves on .020" decked heads and an F-15 and still had no PtV clearance problems.

2.02 and 1.60s will work fine.

Mike

 

Alright then, I just ordered them about 5 min ago. 2.02/1.60 on the way.

Thank for everyone's input

Hey Mike hows the new marriage doing!?

 

It's fine. We've been together nearly 5 years, so it basically feels the same

Mike

 

Thats great man! I actually wish I had that lol. I've been juggling different girls for the past couple years... but congrats again