Stock 670 heads question
 

Does anyone know what stock 670's flow ? I'm trying to figure what cam to run . One of the ones I was looking at said needed head flow of .500 and I don't know anything about head flow. Thank you

Stock untouched:

Intake Lift------Intake Flow------Exhaust Lift----Exhaust Flow

0.100---------------73----------------0.100------------39
0.200---------------130---------------0.200-----------76
0.300---------------148---------------0.300-----------100
0.400---------------155---------------0.400-----------117
0.500---------------161---------------0.500-----------122
0.600---------------163---------------0.600-----------129

I tried uploading the .flw file for DesktopDyno but the website won't allow it, even as a .zip so screw it, sorry.

So to answer your question, they flow 161cfm@.500 lift on the intake and 122cfm@.500 lift on the exhaust.

Check out gtofreek's engine build, comments, and his stock 670 head flow numbers

http://forums.maxperformanceinc.com/...765803&page=14

..........Intake_______Exhaust__E to I ratio
.100"= 82 __________54________66%
.150"= 118 _________76________64%
.200"= 149 _________98________66%
.250"= 173 _________115_______66%
.300"= 193 _________130_______67%
.350"= 202 _________143_______71%
.400"= 208 _________157_______75%
.450"= 211 _________165_______78%
.500"= 212 _________171_______80%
.550"= 213 _________177_______83%
.600"= 214 _________181_______85%
.650"= 215 _________186_______87%
.700"= 215 _________188_______87%
.750"= 216 _________190_______88%
.800"= 218

That looks more like I have seen over the years.Tom

If anyone wants the file it can be downloaded here:
http://ronspontiacpage.com/reference...flowcharts.htm

Pastry Chef, the numbers you posted have to have been flowed at a lower depression than 28". My numbers are at 28", which is pretty much the industry standard these days. In the earlier years of flow benches, they flowed them at 10", and over the years as flow benches got better, and could flow more air, they started flowing at higher depressions, until now when 28" is now the norm.

For .400" lift, and under, the 670 head is the best flowing head Pontiac made. My number above were done with stock valves, and stock valve job. Also, we recently found out that our flow bench has been reading a little low. We just had it re-calibrated, so that flow I posted is actually a tad low. But a few CFM. 212 @ .500" would actually be 221.4 CFM, intake, and The exhaust was pretty close so it would 172.8 CFM with the new correction factors.

What he said.

Peak Intake flow average @28" from what I have seen over the years by many stock heads is 208 cfm,exh 168, both at .650" lift.

If you need flow numbers @10" and you have numbers at 28" ,multiply those numbers by .598.

If you figure you will be having some 190 cfm of Intake flow the motor should then make you 380 hp if you have like 9.5 comp.

Good info, thanks!

I really feel dumb I don't under stand this technical stuff.

Would the comp xe268h be a good choice ? It shows advertised 268 in 280 ex @.050 224 / 230 with 1.5 rockers .477 / .480 110 degrees. Or is there something better for me ? Build is a 4oo with 670's going to most likely run a Qjet with a tremec 5 speed gm 4616. I have a 3:90 rear but I'm not sure if I'm using it yet or not. Would 1.52 or 1.65 rockers help ?

Car will be mostly a driver with some track time.

Not a good choice for a Hi compression 400.
The xe cams fast ramp lobes will enhance cylinder pressure. The 670's will have more than enough pressure all on there own.
The summit 2802 would be a better pic. JMO.
https://www.summitracing.com/parts/sum-2802

I have an XE274H running with my 670 heads. I have the ROSS -28.56cc pistons from Butler so my compression is below 10:1 and there are still better cams out there even for my combo. I'm not sure if the previous owner of my car chose the cam or the shop that built the engine for him did.

Head port flow is a measure of how many Cubic Feet of Air per Minute (CFM) of air will flow through the port when the valve is open a measured amount AND a calibrated pressure differential is drawing air through.

Typically port flow is measured every .100" of an inch of valve lift, from .100 lift to .550" lift at a vacuum that would raise water 28" in a calibrated cylinder. This gives an idea of how much airflow (and HP) a head will support.

Typically if you take max intake port CFM and multiply by two, that gives an idea of max HP. A stock port flowing 220 CFM at max valve lift will support approx 440-460 HP, without the use of power adders/superchargers, etc.

I've got flowsheets on my 670s, I'll see if I can dig them out.

X2 on cam recommendations. I would use a Sumit or a Crower HFT grind before I used a Comp XE again.

A more realistic peak flow@ 28" to HP conversion for non race built motor is to divide the Intake flow number by 4.
200 cfm stock D ports can make 400 hp.

That must be some of that new math I've been hearing about. :)

No , not new!
Lets do it a couple of different ways.

If you have air flow at 28" h2o you can go direct to hp per cyl by dividing by 4
( 205 cfm /4= 51.25, 51.25 X 8=410 Horse power)

Another popular way is to use flow@10"h2o.
( 205 cfm X .598=122.5 cfm@10". 122.5 X .43=52.6. 52.6 X 8 =421 Horse power

If you have numbers at 10" then
122.5 X 1.67 = 204.5 cfm.

So you can see there all pretty close and will get you well into the Ball Park!

Now I remember why I didn't like math class in school. But I think I can figure this stuff out.

Will the rear gear make and difference on the cam I should choose ? I'll check out the 2802 who makes them for summit ?

I have a crane RAIV cam in my 400 W/670's. I have a video of it in my phone PM me your # and I'll send it to you. The heads are stock, with a Victor & a big Holley.

If I go with the 2802 should I use stock rockers or upgrade to a 1.52 or 1.65 ? Also are the stock valve springs good or should they get an upgrade ?

What is your compression ratio?

Lunati Voodoo 10510703 - depending on the CR.

Advertised Duration (Int/Exh): 268/276
Duration @ .050 (Int/Exh): 227/233
Gross Valve Lift (Int/Exh): .489/.504
LSA/ICL: 110/106

Yes, upgrade the valve springs.