1EVLBRD

what are the porting limitations on stock 241 heads?

RZRSEDGE

iTrader: (21)

Limitations I'm not for sure on; but I was told by the man that did some work for me that it does make a difference if you have an A4 or a 6 speed. So that could be one thing you might want to factor in as well. He said the auto needed to be ported for tq differently than the manual. I don't know for sure but I know that he does alot of local F-bodies. Hope this may help out some. I know it was'nt the original ? but I felt it might be helpful.

1EVLBRD

thanks, car is a m6

Greg Good

As inexpensive as the 243 heads are now there's no way I'd waste my time and money on 241's. All you'll end up with in the end is an expensive set of 241's that don't run as fast as you'd like and have little resale value.

GuitsBoy

iTrader: (4)

IMO it depends on how long you can live with the heads off the car. I dont think youll see more than 5 - 20 HP difference between ported 241s and 243's.

Studytime

iTrader: (15)

Greg, not what I thought I would have seen you post. Is flow quality that much better on the revised Gen III stuff? I know they made the ssr higher, reshaped the roof, the port is wider at the beginning of the bowl area (and larger) etc., BUT once ported I'd have figured a small difference between the two. Right now, I have some ported 241s and some ported 317s in my shop. The look very similar (with the differences I pointed out in the above), but have been opened to the same dimensions. Assuming similar airspeed and flow, I don't see how they could be much different.

Can you please substantiate the claim you made (with any resale arguments pushed aside)?

Ben T.

Studytime

iTrader: (15)

Basically none. You can get the port too large for a 346cid motor and not break through. FWIW, LS1 runners can be enlarged enough to accomodate a 2.100" valve. Be careful around the left of the valve guide, well... you'll figure it all out. Get some scrap heads. They can get BIG before you have to worry about hitting oil or water.

...but that's only if you're porting for a M6.

Ben T.

5ltrBetr

iTrader: (3)

Ported a set of 241's myself I got off eBay. Focused the porting on reshaping the valve stem for good flow passed it onto the back of the valve. Also removed the rocker-arm bolt boss the protrudes into the port. Also port matched the head to the BBK intake. Finally, cut .020 at the machine shop to bring up the compression a bit. Made 412/378 with a TSP T v.2 cam. I am currently swapping this head cam combo onto a 408. I was very happy for my performance per dollar. Heads: $150, self-ported: free, porting kit - $50, 3-angle valve job, cut .020, assembly: $160, total: $360. Gain: probably 40-60 hp (am I being optimistic here???)

Studytime

iTrader: (15)

Yes, you are. Based on your description, that sounds like a great start, but not the full scope of work required to add 60hp.

Ben T.

GuitsBoy

iTrader: (4)

50 or 60 HP gain out of the heads AND the cam maybe. I have a set of home ported heads, milled .040 and this gained me 25 - 30 HP over a cam only Torquer2 car.

Studytime

iTrader: (15)

Keep in mind that guitsboy also has a lot more compression with was some of the gain. His port work is responsible for the rest.

Ben T.

GuitsBoy

iTrader: (4)

I had a lot of good coaching, and a bit of luck with the port design. And even then the actual porting was probably only good for 15 - 20 or so HP, especially since I kept the stock valves. I believe the compression (11:1) and the exhaustive tuning helped me out.

5ltrBetr

iTrader: (3)

Yea, I figured I was dreaming! Anyway, I know the aftermarket heads might flow better and make a little more power, but if I can get 280 cfm at .600 for $360, I'll have a hard time paying $2500 for 300 cfm. That leaves me with $2100 for one hell of a spray!

GuitsBoy

iTrader: (4)

280 CFM is reaching too. I think 260 to 270 is a more realistic outcome for the home porter. Still, that dosnt mean you wont see worthwhile gains. And besides as it was mentioned, porting is only part of the equation. Milling for compression, thinner gasket for a tighter quench, and proper cam choice will help you get more out of your heads.

Studytime

iTrader: (15)

I thought my first LS1 heads were WAY above average (at the time ) and they did an amazing 255 cfm.

Experience (and a lot of it) goes a long way. With none 280 cfm (at .600") is a stretch. I couldn't get in the 280s until a year and half of practice. Looking back, it's not that hard, but beginning to see it is the hard part. If you're home porting, do what Guitsboy did. Do your best and make it as consistant as you can and then mill the crap out of them and flycut.

Ben T.