Hi Guys,

I have just started to have intrest in porting my own race car heads,bought a used sf600 flow bench and some hot to DVDs , started to work on some of old heads that i have. and now i want to work on my own race car heads. the engine is a 402ci ls2 225 AFR heads big cam th400 5500 stall victor Jr intake. (swtiching to super victor soon) the heads are not ported just slight milling. where do i start? do i need to increase the size of the intake ports and match the inatke ports with it. the car never see street or any rpm below 4000. the car is a N/A car last run it made about 10.3@126 60ft 1.44 on a 1969 camaro weight with driver is 2800lb.

Thank you in Advance.

 

Speedtalk has a bunch of good forum posts on it.

 

You probably don't want to hear this, but don't try this yourself. You are very likely going to ruin the heads. Just making the ports bigger may give you more flow on the SF600, but will probably not make your car quicker.

If you must carve up the heads, try to borrow a similar head that has been ported and proved on a dyno and track that it makes more power. Try to copy those ports. Measure, grind a little, measure and repeat a number of times. Keep checking cross sectional areas throughout the port and try to duplicate the exact shape.

Jon

 

If you want something to start with that would be a little safer/less risky, try taking the heads you have, and flow them with the intake on. Then, try porting the intake, and then flow the head again with the intake on and try to get the most out of that you can.

Messing with an afr 225 port is most likly not going to get you any huge gains, porting the intake to get the most flow you can out of the entire intake tract will most DEFINATELY get you a gain, a substantial measurable gain. Probably .2 and a 3 or 4 mph gain from an unported intake.

I'd start with that, plus if you mess the intake up that's a 400 dollar part, the heads, that's about what 6 times that? Better to learn on the cheap part.

 

what i did on my 4 banger when i had it, is to just remove the cast lines on the intake and exhaust ports and then clean it up and polish it. but i am guessing those heads have that done already. porting heads is very difficult, but don't be put of by this, doing things yourself is always more rewarding. it is for me at least. good luck

 

did you ever get to turn on the flow bench ??

 

i agree with old sstroker...being that they are race heads, they are proabably expensive, and the came from the factory where they put alot of R and D into flow characteristics, so if you try to make it better without the right equipment, your proabably gonna make it worse and waste the heads just for a little more flow. if you really need to get them ported, like oldss said, go to a pro. everything has an equal and opposite reaction! good luck though.

 

i agree with most post here
unless you know where to remove material, and how much, you have a chance to ruin them

better off trying , as all ready posted, try the intake , and MATCH port the intake to head...

 

Hand porting is not rocket science. Designing a head to fit a specific engine family for a specific result/purpose might be. And programming a CNC to do these procedures might be close, but... 'detailing', removing flaws/obstructions, blending CNC machining cuts, optimizing contours, and blending throat cuts/seat radi... is not rocket science.
Very true,... a guy with a die grinder can certainly take a good head and 'go backwards' in terms of flow and efficiency. Also, a decent aftermarket head that is intended to be a finished, race ready head (not necessarily RACE ONLY, such as your AFR 225) is probably only going to see very small gains with additional porting, unless you dramatically change their current configuration (valve sizes, combustion chamber diameter, intake manifold type, exhaust header primary size). Stock GM LSx castings are very good about 'telling' us where they 'want' to be ported. However, the high-end aftermarket offerings are much improved, finished ports, that seem to work extremely well "right out of the box", in a wide variety of applications (street, race, n2o, FI, strokers, etc.).
When looking for a good street head, or evolving one into a race head, we are taking into consideration RUNNER VOLUME vs. CFM vs. CUBIC INCHES vs. RPM. The key to a good street head is efficiency-- relatively small runner volumes with decent CFM/flow, for your given/target engine displacement. A race head can generally give up some efficiency in favor of excessive runner CCs (and peak CFM) as long as there are appreciable increases in cubic inches and/or RPMs.
If you have your own flowbench, then you have the luxury of making small, incremental changes in your intake tract (and exhaust). I agree with others in this thread, and start by looking for other places to make improvements. With 'only' 402 cubic inches, your 225cc AFRs are a pretty good match to start with. Having a 4.00" bore, you could probably unshroud the valves some. You might also do a little work around the valve guide, and maybe just inside the throat cut below the final valve angle, and, of course, some intake port matching and blending into the runner. But I can only imagine you getting a couple CFM "here and there" on those AFRs. If you make gradual changes, removing very slight amounts of material, then checking them on your flowbench, you have a pretty good chance of not ruining the heads, and learning valuable technical (and artistic) experience.
If you have time, and want to gain some prior experience, you can buy a cheap set of 853s or 241s (like $100 or less), and have eight ports to experiment with, compare with, and develop your ability to duplicate your work for port-to-port consistancy.
A flowbench really gives you an advantage, and a great learning tool, for doing what many consider a highly regarded talent. Somewhat difficult, and definitely time-consuming, but certainly not something an amatuer can't learn to do, at least for himself.

 

Porting is not easy and If you've never done it chances are you'll lose power through bad port design. there are no good books and the how to videos suck. If you're in Houston get Greg Good on the phone. tell him you want a valve job and a bowl blend. He goes a little crazy and you'll get more than you pay for.
I assure you your car will be faster than before and faster than you could ever make it with your port job.

 

If you are going to take this on yourself, I highly recommend using sanding rolls instead of carbide bits. It's too easy to slip and **** something up with a high-speed metal bit, whereas a sanding rolling makes you work at it. It will slow you down. It slowed me down to the point that I put over 40 hours of work into the last set of SBC heads I ported, but they came out really nice. I haven't found any LSx books on head porting, so I had the advantage of some excellent books with pictures on SBC heads, like those from David Vizard. There are some pictures at the end of this article on LSx head areas to avoid:

http://www.carcraft.com/techarticles...ads/index.html

And here's a company that sells all the porting stuff: ruffstuff.com

Jim