ported 241 vs 243's
 

I had a leakdown problem on my salavage engine I found when I was changing valve springs (compressed air in the cylinder to hold up the valves) So I bit the bullet and pulled the 241 heads to check them out thinking I had a burnt valve or something. Turns out It was just a bunch of gunk on the seat that wiped off with a rag. Since I'm changing the springs for a bigger cam anyway, I went ahead and pulled all the valves out just to check things over.

So here's my question, I'm pretty good at hand porting heads, should I go ahead and port the 241's and get a valve job and clean them up? That will cost me about $400 and a bunch of time. The last set I did for my son took about 30 hours to do. Or should I buy a pair of 243's from a friend of mine, change the springs and bolt them on? Either case, I have PAC .650 springs to go on.

Just some info on the car, it's a 67 camaro that is destined to be a pro touring/roadrace car. Stock LS1 with a comp 227/235 0.614/0.621 on 113. Typical bolt ons like LS6 intake and headers ect... I'm looking for a fat and wide torque band, not really high top end horsepower.

What do you guys think?

I never had mine on a flow bench or a dyno, but I can tell you the work I did on my 241's really made a hug difference on the ""butt dyno"

I port matched, blended the ports from the mouth all the way to the bowls, then did a lot of work in the bowls around the valve guide till I had a really nice knife edge. After that took them to the machine shop and had them do a valve job and mill the heads.

One thing to watchout for is there is a small dip in the top of the exhaust port to make room for a small water passage under the spring seat that can get thin and break through easily if your not careful

I had about 10 hours in grinding on each head and sore hands, but worth every bit

You will enjoy ported 241s over stock 243s especially since you already have 241s. Your lucky to have some skilll to do it.

port your 241s. do a search and get some pics of what the ported ports look like and have fun.

Here is the dip I was talking about


Attachment 676490

Here is the intake port

Attachment 676491

Thanks for the cross sections that helps a lot, I guess I'll fire up the air compressor and start grinding away! FWIW, here are a few pics of the 243's I did for my sons car.

Attachment 676492

Attachment 676493

Thanks for the advice

Looks like you got the skill, port the hell out those 241s! :thumb: 243s will provide a better gain, however, I'm sure you know. But you can't beat free.

With the right cam, ported 241's have been making awesome numbers lately

Can you get your friends 243's and port them? Would likely make a few more hp than the ported 241s. Either in ported form will likely work better than the stock 243s.

Also, you might find this a good read!
http://www.c5registry.com/documents/ls6/page3.htm

As a cylinder head porter it kills me to see some of the misinformation on these boards. Porting without the use of a flow bench is guess work. However, a guy who isn't foolish can find gains. Here is my experience about 243vs241 heads in ported form. If you are not running a cam well over .600" lift the 241, 853, 806 (any 5.7 head) is the ticket. The 243/799 will flow more up top but does nothing more at low and mid lifts. This being said if you don't have a flowbench none of this "which is better" matters because you will not find the sweet spot on either. So use what you have and you should see a nice gain. And pay someone to cut a nice valve job. Not grind one. If they don't have a machine that can cut the valve job they are not a performance shop.

Thanks for the objective reply. I'm not looking for max flow at 7K RPM's, but I do have a healthy cam at .614 and .621. I understand velocity and air volume and all that stuff (I'm an old Mechanical Engineer) I was just looking for some help to see if it was worth my time to port the 241's mildly or get the bolt on ready 243's. I'm looking for a torquey motor through most of the middle of the RPM band. See my first post for a description of the car and goals, might help. I do have a great performance machine shop that can cut the three angle valve job for me.

Velocity is everything on a street car. With that in mind the 243 has a larger intake runner to begin with vs. the 241. If you do it right by the time you get the 241 ported to the same size as the 243 stock you will have more air flow and velocity.

So if volume stays is the same, velocity is lower on the 243 (stock 241 vs stock 243)?

In stock form the 243 flows about 260 cfm on the intake side. The 241 stock flows 240's.
I could take the 241 head and start porting. By the time I have it the same size as the 243 stock it will flow more. At this point it will have more velocity than the stock 243 and will provide better throttle response and make more power.

I can get a set of 243 ported heads from a buddy reasonably, Here are the flow numbers after they were ported. Is this a better bang for the dollar than the work I have ahead to finish porting the 241's and get the valve job done. Will I be ahead in the long run? Here's the numbers, and from what I've read they seem a little weak on the exhast side, but I can fix that.

Intake 215cc
70
136
199
250
299 Lift
309 .550
312 .600
315 .650

Exhaust 82cc

CFM
57
104
149
194
211
218 .600 Lift

The combustion chamber after porting was around 66cc, I had them shaved 0.020 for a cc of around 61.

Those aren't horrible. Either side. I've seen 460rwhp with no more exhaust flow than that. They would work but don't expect 450rwhp. And your comment about fixing the exhaust port you don't want to do anything. Especially if your thinking about enlarging the port. That is the last thing you do. I had a guy bring a set of 6.0 heads to be tested they had a nice big good looking port only flowed 200 cfm at. 700 lift. The bowl work and valve job were not good enough.

I'll have to check the PTV clearance for my cam since they have been milled. My cam is comp 227/235 0.614/0.621 on 113, so I'll be checking very closely. I'll probally scoop them up and have the valve job checked and bolt them on with my PAC .650 springs. Then finish the port job on the 241's and sell them or save them for my WS6 that has the stock 853's on her. Thanks for the advice.

Decided to Port the 241's myself. Just finished and dropped them off at the Head Shop. They Owner said they looked very good and on par with what he does for his customers. I didn't open them up much at all, just port matched the intake and raised the roof a little on the exhaust side as well as blending in the bowls and cutting down the guide area. I think they turned out pretty damn nice for the cost of the electricity it took me to run my compressor for all those hours! LOL!
Anyone have any idea how much I can mill them with this cam? 227/.614 and 235/.621 on 113 lobes. It's a comp cam. I emailed Comp but no reply at the moment. Gasket thickness?

http://i539.photobucket.com/albums/f.../IMG_02991.jpg
http://i539.photobucket.com/albums/f.../IMG_02981.jpg

You port your heads and you need someone to answer how much you'll mill? You know the answer. MEASURE :)