A
Anonymous
Guest
I go to school at Ferris State. For one of my classes i have to do an airflow project. I decided to try and make as much flow as possible out of the stock log on a 200 head. I will look up the casting numbers but its off an 80 200 out of a Mercury Zephyr. I can only do so much per session but im going to post my results after each one HOPEFULLY with pictures of each modification. I say hopefully because i need to find my camera.
OH btw the head will be going on my 79 Mercury Zephyr when its finished in hopes i can run a 15.XX with the stock trans and rear end.
ON TO THE NUMBERS!!
ALL TEST FOLLOW THE SAME CRITERIA WHICH FOLLOWS!!
All tests performed at 25 in of water, on a Superflow 600, using a flowcom for the CFM numbers, no radius on the carb hole or the exhaust port. Temps vary slightly but the room is pretty consistant at 68deg.
The lift points may look different but anyone who knows what their doing flows with L/D ratios and not just at thousanths lift points.
STAGE 1
I simply flowed the head with a stock valve with a good 45deg seat on it.
INTAKE
LIFT....................CFM
.0859....................41.00
.1718..................68.70
.2577..................96.00
.3346..................109.3
.4295..................115.5
.5154..................118.4
EXHAUST
LIFT....................CFM
.0687....................34.1
.1375..................56.6
.2062..................76.1
.2749..................91.0
.3436..................100.8
.4123..................106.7
.4810..................108.5
STAGE 2
This was simply a 30 deg angle back cut onto the valves. I know that there is almost never any gain to doing it on the exhaust but I wanted to see how much it gained/loss.
INTAKE
LIFT....................CFM
.0859....................43.2
.1718..................78.1
.2577..................100.9
.3346..................114.9
.4295..................121.4
.5154..................123.0
EXHAUST
LIFT....................CFM
.0687....................31.5
.1375..................57.6
.2062..................78.5
.2749..................89.7
.3436..................94.3
.4123..................97.3
.4810..................98.8
As one could see a back cut angle on the intake side loses flow nowhere. at some points its up 10cfm. On the exhaust side however it only has gains in semi low lift spots. It loses flow when the valve barely opens and alot of flow when its all the way open.
I havent had time yet but im going to be doing average CFM, peak CFM, CFM gain, and potential flow. I will also start doing velocity when I begin doing port and bowl work.
Stage 3 will be a major unshrouding of the valves and polishing of the combustion chambers with a back cut intake and stock exhaust valve.
Stage 4 will be a 3 angle valve job
Stage 5 will be a 5 angle vlave job
Stage 6 will be bowl work
Stage 7 will be port work/gasket matching
Stage 8 I will make a radius entry for the carb hole and I will also make an outlet for the exhaust.
Stage 9 I plan on enlarging the carb hole and slightly porting that area.
If i get that far Stage 10 will be knocking out the freeze plugs from the log.
As i get updates (AKA work on the project) I will post the numbers up in the format i used above.
WELL what does everyone think so far?
OH btw the head will be going on my 79 Mercury Zephyr when its finished in hopes i can run a 15.XX with the stock trans and rear end.
ON TO THE NUMBERS!!
ALL TEST FOLLOW THE SAME CRITERIA WHICH FOLLOWS!!
All tests performed at 25 in of water, on a Superflow 600, using a flowcom for the CFM numbers, no radius on the carb hole or the exhaust port. Temps vary slightly but the room is pretty consistant at 68deg.
The lift points may look different but anyone who knows what their doing flows with L/D ratios and not just at thousanths lift points.
STAGE 1
I simply flowed the head with a stock valve with a good 45deg seat on it.
INTAKE
LIFT....................CFM
.0859....................41.00
.1718..................68.70
.2577..................96.00
.3346..................109.3
.4295..................115.5
.5154..................118.4
EXHAUST
LIFT....................CFM
.0687....................34.1
.1375..................56.6
.2062..................76.1
.2749..................91.0
.3436..................100.8
.4123..................106.7
.4810..................108.5
STAGE 2
This was simply a 30 deg angle back cut onto the valves. I know that there is almost never any gain to doing it on the exhaust but I wanted to see how much it gained/loss.
INTAKE
LIFT....................CFM
.0859....................43.2
.1718..................78.1
.2577..................100.9
.3346..................114.9
.4295..................121.4
.5154..................123.0
EXHAUST
LIFT....................CFM
.0687....................31.5
.1375..................57.6
.2062..................78.5
.2749..................89.7
.3436..................94.3
.4123..................97.3
.4810..................98.8
As one could see a back cut angle on the intake side loses flow nowhere. at some points its up 10cfm. On the exhaust side however it only has gains in semi low lift spots. It loses flow when the valve barely opens and alot of flow when its all the way open.
I havent had time yet but im going to be doing average CFM, peak CFM, CFM gain, and potential flow. I will also start doing velocity when I begin doing port and bowl work.
Stage 3 will be a major unshrouding of the valves and polishing of the combustion chambers with a back cut intake and stock exhaust valve.
Stage 4 will be a 3 angle valve job
Stage 5 will be a 5 angle vlave job
Stage 6 will be bowl work
Stage 7 will be port work/gasket matching
Stage 8 I will make a radius entry for the carb hole and I will also make an outlet for the exhaust.
Stage 9 I plan on enlarging the carb hole and slightly porting that area.
If i get that far Stage 10 will be knocking out the freeze plugs from the log.
As i get updates (AKA work on the project) I will post the numbers up in the format i used above.
WELL what does everyone think so far?
) The way I achieved them is actually quite simple. What L/D stands for is Valve lift / Valve diameter. You multiply the valve size by .05,.1,.15,.2, etc. etc. I stoped at .518 and .481 because that was the highest L/D ratio i could go to before the springs and such bound up. 
