Bobby455

Does anybody know the flow numbers for olds heads? I found a website where a guy was doing a build and ported out some C heads, they flowed something like 259 cfm at .600, but I'm looking for some baseline numbers, if they're available

GEARMAN69

Stan Weiss has a great resource on flow http://users.erols.com/srweiss/tablehdc.htm#Olds

wr1970

The only thing to remember about that info is this. Mid-Am is bull crap i have been to his shop.No head porting references of anyone using his ported heads. Was not willing to port a set of heads for racers. Reason was he knew i had a stock set of c heads to compare against his. No flow bench. That company is defunct and out of business. He was referred to me by a racer who said he could make a set of heads well know Pontiac guy locally who runs a automotive shop. This Pontiac guy approached me to have a set done by mid-am. After he found out what mid-am said to me he refused to say anything good about Mid-Am. company which went bust less than 6 mo. later. This guy who had the Mid -am company is only twenty miles from where i live.

olds 307 and 403

I have seen numbers on sites from someone reputable, I believe 230/160ish for big valve stock BBO heads. Olds heads vary so much from awful 260 and swirl port 307 heads to decent big valve factory performance heads. I would like to know stock W31 head flow numbers.

Bobby455

That website looks pretty good, it looks like it has DesktopDyno files, which is even better because now i won't have to enter the numbers in by hand. Thanks Gearman

Qwik71442

a few years ago I did some mild porting to a set of 2.07/1.625 C's which consisted of cleaning up the bowl and guide areas. They flowed 256 on the intake & 176 on the exhaust @ .600 when done but unfortunately I didn't flow them in stock form beforehand.

joe_padavano

The problem with any of these published flow numbers is that flow is affected by pressure drop, air temp, port inlet configuration, and even the specific bench. Flow from one stock head to another even varies from one casting to another. Comparing flow numbers from two different benches requires very large error bars on the data. Flow numbers are best when used as before/after comparisons of work done to a particular head and measured on a particular flow bench with the same port inlet/outlet configuration and corrected for atmospheric variability. Anything else is more for bench racing purposes than actual engineering data evaluation.

GEARMAN69

I think this particular stock small valve 7A 1972 head is the representation of the poor stone stock small valve small block head. Yeah I heard the Mid-America stuff was skewed.
My comparison with only big valves and some minimal porting with no polishing or optimizing nor any fancy custom valve job my #6 heads went from 185/140 ish to 240/180 with room to grow

80 Rocket

I just recently did a set of 7a heads. I flowed them stone stock with small valves and this is what I got:

Bench: SF-1020
Test pressure: 28"
Bore size: 4.155"
Flow plate: Olds specific

INTAKE:
.100- 52
.200- 105
.300- 153
.400- 181
.500- 197
.600- 203
.700- 206

EXHAUST (used Olds specific flow pipe):
.100- 54
.200- 99
.300- 126
.400- 142
.500- 151
.600- 156
.700- 159

I went with BBO valve sizes (2.00"/1.625") and worked the short side a bit, reformed the guide boss and blended the bowl into the valve job (used a cutter with angles 30/45/60/75, seat width .039") on the intake side. The exhaust I did very little work, just smoothed the short side a bit and cleaned up any edges. Exhaust seat is .060"

Test parameters same as above:

INTAKE:
.100- 62
.200- 132
.300- 190
.400- 220
.500- 229
.600- 229
.700- 232

EXHAUST (used stub pipe):
.100- 50
.200- 100
.300- 140
.400- 161
.500- 166
.600- 170
.700- 171

Polishing ports does nothing and can actually hurt performance slightly. The best part about these heads is that the cam is only .500 lift and the ports stop gaining flow around .450 so it shows the port is not too big for the cam being used.

GEARMAN69

I wonder if a clean stock W31 head would hit 210 @ .500 then ?

80 Rocket

I would say keep trying until you find the bench that shows it hit 210cfm . What Joe P said above is very true. Port to port is different, casting to casting, there are just so many variables.

I have stacks of flow bench data (Oldsmobile stuff) I have accumulated the past 6 months, but it is all pretty much useless except to me. Flow bench numbers are just a part of the equation, and certainly not the main factor.

Usually, an Olds motor doesn't need more flow, they need parts that work well together with the rest of the combination.

For instance, if you are running a cam of .500 lift with a 2" valve it is unnecessary to chase those high lift flow numbers. Anything after .500 is places your cam will not reach. The biggest mistake would be to hog out the port and try and open the pushrod pinch. 25% of the valve diameter and below........ the valve seat, valve shape, bowl, and shortside radius are all key to improving these numbers. 25% of a 2" valve is .500 lift. Going further with porting just makes the port bigger and hurts velocity.

80 Rocket

Exactly right. That's how I conduct my tests. I also factor in port volume to my testing. When making a port bigger, it should flow more air (if it doesn't, you f'ed up!) but how much more air does it flow. If you do some serious work, and only find marginal gains you have to ask yourself was it worth it? Depends on the application.

GEARMAN69

80 R you posted small valve 7a showing 197 cfm at .500 that's why I simply posted wondering if a clean #5 original 2.00 W31 head might beat it by 10 cfm because I have not seen any flow tests of an original W31 head untouched that's all . My heads were professionally ported by Elliott Portworks but just his budget option $200 job is all mine have done besides a big valves and stock style 455 valve job. Mine did 237 177 at .500 and I am running .500 lift in its first combo. 225 164 @ .400, 201 144 @ .300

GEARMAN69

.
I know all of that stuff and Yes to what Joe posted too. Of course results vary bench to bench and weather and head to head and flow at .700 means nothing to guy running a stock .472 W cam .. The only reason did what I did was that no way would I not do anything to a crap flowing stock small valve head. The parts are cheap more less. Room to grow later with hotter cam swap

80 Rocket

A stock valve job? So its a 0-45-90 valve seat?

GEARMAN69

What ever the guy did at the machine shop I use. I buy the Ferrea or what ever EBay SS valves and they are the stock OEM valve angle and he just does no more than 3 angle like you would on a stock valve job. I learned the basics off it in a Jr.. College class some 25 years ago. but have not done my own. I do my own assembly and spring setup stuff . My porting guy always comments I am giving up some flow in the valve job I am getting so I may let him use his guy next time I have something more all out so to speak. If its a 30 degree seat it would 15 30 45 with a 1 degree interference angle of 29 in the middle if I recall the process and the other would be a 30 45 60 with a 44 degree angle for interference.