Valve size/porting

finishing the new upgrades.... current setup 9 to1 , comp 260H/.. 212@.050 and .440 lift set at 106.5 ICL , DUI ,large log with mild port 1.75 Intake 1.38 exhaust upgraded valve train 302 short springs 1 piece retainers etc.,, Offy tri power, weber 34 ICHs, Clifford dual outlet header, 3 NX piranha Foggers 75HP. built C/4 with 2,200 stall converter in the works now.... plans are to add 1.48 or 1.50 exhaust with a street/strip port on a flow bench, head studs and 1.6 rockers.... motor made good power to 5,200 before not wanting to turn more than 5,200 to 5,400 but think there is more power with the head upgrades especially with the Nitrous now......any thoughts? I had read before where some went with a 1.47/.48 exhaust valve to minimize shrouding. plus will the 1.6 rockers added lift help take advantage of the larger valve and port work? also will be pumping up the compression to 9.5/9.6 to 1.

I'd love to now more about that nitrous set up !!!
DannyG

Hi, you did not say what gear you hit 5200 in, 1st, 2nd, or ? I think lower rear end gear will give more RPMs. Maybe some race car guys can lend you a rear for a try out. I know my friends would. Good luck

Howdy 64Falcon6:

With what you have I'm surprised you are not able to top out at a higher rpm. Make sure the linkage is allowing all three carbs to be wide open. Have you recurved your distributor to match your carbs and cam? What is your rear gear ratio? I'm confused on what you have now and what is planned. Please clarify.

Q- "I had read before where some went with a 1.47/.48 exhaust valve to minimize shrouding."
A- Shrouding is not a critical concern on the exhaust side. It is on the intakes. Remember, the exhaust valves are smaller than the intakes. AKT The exhaust is leaving under pressure from combustion. For your situation I'd suggest SI 1.5 exhaust valves.

Q- "will the 1.6 rockers added lift help take advantage of the larger valve and port work?"
A- The added .030" over the .440" you already have will not add much except at the very top end. The 1.6:1 ratio will allow the valves to open faster and sooner. With a stock cam the difference is noticeable but with your setup, not so much probably. If you go to the 1.6 be sure to check the geometry and clearances in the entire system.

Q- "will be pumping up the compression to 9.5/9.6 to 1."
A- That's a great idea. How will you do it? Porting should help the top end.

With your NO setup how are you enriching the fuel intake to support the boost?

Keep it coming.

Adios, David

Bronco...I have been to 5,400 in 1st ,2nd, and 4,800 in 3rd with 3.20 gears and 205/70/14s.
It will rev more but seems be leveled off by around 5,200 to 5,400.

CZLN6...will go with the 1.5 valve . May not fool with 1.6 rocker. Running a stock fuel pump with dual regulator. Calculations show enough for 75 HP but I am starting at 30 HP and working up while paying attention to the plugs and AF meter. Right now I am at 52 CC chambers I plan on a clean up cut on the head then a cut on the block when I freshen it up... right now have cast steel rods with ARP bolts I want to add prepped forged rods.

Plates are 5/8" aluminum water jetted with NX piranha nozzles activated by a WOT switch....

Carb and fuel solonoid regs in the background on the DS fender panel.

Hi, it is quite the ride. What kind of top speed have you seen? I would guess over 125 MPH. Good luck

Bronco......I chickened out at around 115 mph .....too fast for where I was at.... it was still pulling good......

When installing larger valves, you'll also need to enlarge the bowls by a specific amount to achieve the desired ratio for valve size to bowl size or just the fact of installing larger valves won't yield much in return. You can't really do that effectively by hand porting and keep the bowl shape from being oval or oblong, so seek a professional machine shop that can do this competently. This is often overlooked when performing this operation and even in head porting in general, and a lot is left on the table so to speak when doing this. Since you mentioned flowbench work would be used in your porting process, you'll also need to make your cam choice based on the amount of flow the ports reach when your finished. Installing a cam that has more lift than what the port flows can has serious negative affects on the engine performance. So try to stay in a reasonable lift on the cam relative to where the ports start to level off on flow.

I disagree on the amount of lift. If you just have the lift at max flow you only have one moment at the max, where if you have higher lift the flow will be at max twice, on the way up & second on the way down.
If you can afford it go with the 1.65 rocker arms. Less friction especially with the Yella-Terra.
At least the new 1.65 rockers have a roller tip.

You can install a cam with slightly higher lift that what a port will flow, but professional head porters and professional engine builders have known and proven for many decades that you will have serious reversion issues if you go beyond a certain amount more than the port will support. It is common knowledge to them, that anything much more than about .050" more than the port flow maximum is the most to realistically use or the higher lifts reduce the benefits more than they gain. For instance, if the port fails to continue increasing flow above .500" lift, then installing a cam of .700" lift will be meaningless and fall into that category.

I agree on that .200" increase is a no no. On the ford six .050"-.075" will not be an issue.

good info,
thanx guys, news 2 me...

According to flow bench Data the ported large log continues to gain flow through .500 where it only gains 1 CFM at .600 on the intake and flows past .600 on the exhaust... the 1.6 will give right at .469 lift. .029 over the 1.5.... also previously asked I am currently running 12 initial and 36 degrees total on timing but will back off 2 when I tune to spray then go from there. goal on the build is 75HP on the nitrous. also although the duration does not change, according to COMP an increase in rocker ratio speeds up the valve acceleration rate getting to .050 sooner there for making the cam feel 1 to 3 degrees larger and even possibly moving the peak torque up by 100 to 300 rpm. will be speaking a little more with the head porter in the near future to see what his recommendations and expectations are.

I would go with the 1.47 or 1.48 which ever one is commonly available ...That will give you some room to refresh with out sinking the seats down. It is harder to put material back on, than it is to remove it. That is still .090 or .100 larger than stock.

spoke with the guy that will be porting the head, seems he is familiar with the 200 head and has ported a few back in the day, 1 with the log cut off with a custom manifold; I told him the setup and was looking for ..... he will add a 1.50 exhaust ,new guides, port and flow...says he can pump up the power from 2,200 to 5,500 which is what I am wanting... will be a while before I pull the head but I will update when I do......