Max Flow From 670 Heads?
 

Saw an ad on marketplace from a guy claiming 670 heads on his 1969 something-or-other Pontiac had been ported to "flow 300 cfm."

My B.S. alarm went off but I started wondering what flow numbers are possible from a 670 head with professional CNC porting?

Max Flow From 670 Heads?
 

I think the highest number I’ve seen is 275. And that highest I heard of is 295. But I don’t know if that’s accurate. And neither was a 670.


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Marty P had a set of 455 HO heads that were severely ported, several holes in the ports,
(many years ago) and they leaked at 290 cfm. A very accurate flow bench was used.

I can believe 275.

Tom V.

Without welding or epoxy work a true 270 to 275 cfm@28” is it with a 2.11” valve and a maxed out throat size.
And that 275 number hinges on if the casting has any appreciable core shift!

The 670 casting just does not have enough short turn height to make for instance the 285 plus cfm that you can get from all out porting work on all the other D port castings from 1968 to 70.

Unrealistically Manipulating the side to side position of a wedge type head like a Pontiac on the bore adapter when doing a flow test can bring in another 5 to 8 intake cfm that will not be had in use when the head is bolted onto the motor with the intake valve up on one side of the bore.

Thanks to all who replied.

Paul C. down in Tucson finished up a set of 7F6's for a 455 I built a while back. They were initially ported by Dan Barton and after Paul was done with them, improving the flow by changing the valve job angles around, they flowed 282 CFM. They didn't appear to be massively ported either, just a very nice job, all done by hand, no CNC program. Paul noted that he flowed several ports and they were all within a couple CFM of each other.

Paul was working on his own set of 670's at the time and experimenting with different things. I don't remember the flow numbers exactly but I remember them being similarly impressive.

Not overly difficult to reach these numbers with iron Pontiac heads but it's not cheap.

He is going to get my HO heads for a freshen up-port work. Might used some custom valves like the 5.7 Hemi valves he used but longer. If he can get 300cfm out of them that would be something.
Thats the plan after I run my High Port a season or two. Going to see how much power I can make with a 9-1 461.

Here’s some info / detail for you folks.

On all of these heads I cover here I am talking about flow numbers that can be and actually still have it be safe to run the heads with water pressure applied to them.

If you want to go to completely unsafe paper thin port walls then you can get greater flow numbers out of these heads if your just looking for what amounts to flow bench bragging rights!

High comp D port heads of less then 80 CC of chamber volume start life on average with 154 CCs of port volume.

If you have a set that has not yet had a valve job that has sunk the intake valve mote then .030”, and if this set of heads has little cord shift then 285 to 290 cfm can be had by very labor intensive porting work.

On heads ported like this your raising the the roof so much that your exposing a lot of the rocker stud hole as seen here in my photo of a number 13 casting.

Next are the round port 455 HO heads that start life at some 172 CCs of port volume or some 12% larger then the high compression D port heads.

All I will say about these heads is that if you are max porting then and you can’t attain the same or greater flow numbers then max ported D port heads then you do not know the proper way and procedures needed to port these 14 degree valve inclination heads properly!

Next up the 69 and 70 RA4 heads that show up out of the factory with between 182 to 184 CCs of port volume, or about 18% greater port area then the D port heads .
These heads will max port out to well over 325 cfm , but not with out raising up the roof so high at the flange that a high port type Intake is a must.

These heads then are better left for most folks being reworked to flow 295 to 300 cfm.

I will not talk about the SD 455 heads and there slightly larger port volume then the RA4 heads because there deeper low compression chambers and resultant lower short turn height means that in fully port form they can hardly beat out the potted flow numbers of the ported D port heads!

With all of these heads I have covered here that flow over 285 cfm where talking about them having been converted over to 45 degree seats, but still only running a 2.11” Intake valve.

In regards to the comment in post number 6 here where it’s stated that it’s not overly difficult to port heads to this level then you need to try hand porting just one D port Intake port into the 280 cfm range, since that’s 3 hours of work to get the port to finish level !!

It's not overly difficult in the sense that one knows what they are doing.

Is that better Steve? Geez I figured that went without saying :rolleyes:

The time involved also goes along the same lines as being pretty expensive, which is what I meant, I thought people could figure that out, LOL In other words I try to give these guys around here a little more credit without the need to spell everything out.

:thumbup: That' sounds cool. I'd love to hear more about it.

Good info Steve25 but that seems like out dated information. Accurate to a point but a lot of those "max" numbers have been surpassed.

Maybe you can ask Paul if these numbers are correct for a head he did sometime ago. 670 head 2.08" 7mm stem intake valve 288 cfm. I only have intake numbers.

Stan

For all you head flow experts, & guys who know how to calculate power related to ET, here's a question.

I assume Randi Lyn Shipp's '67 Bird Stocker runs 670 heads.

The car has run quicker than 10.50, on several occasions.

So, although the NHRA Stock rules call for no porting, how much head flow is required for that car to run 10.50 ?

These old school Stocker combos that can run low 10's & high 9's & are quicker than the same combo was in SS form, back in the '70's, are very interesting to me. I know the unlimited valve spring pressure & cam duration play a big part. But, I don't think that MOST "as cast" factory heads will flow enuff to run the big numbers some are running today. Assume some form of "porting", which would have been illegal back in the old days.

Have read all sorts of methods that have been used to increase flow, such as acid porting, inducing rust, & even hand porting, and then covering it up, in various ways, so that it's hard to detect. Assuming that NHRA finally just gave up & decided to let it go. Have read that "Heads-Up" builds some of the very best flowing Stocker heads. There WAS a section on their site, vaguely describing their Stocker head port enlarging modification. But, that section disappeared, as of the last few times I tried to find it. The Stock section just says "Under Construction".

https://www.headsupcylinderheads.com...der-heads.html

Every last cfm it can flow for as long as the valve can stay open and at a very high rpm.

Equals square lobe cams ;) Keeping the lift per rules but duration is unlimited. Not great for longevity but doesn't matter in class racing where tear downs are part of the game.

Since all any of us can do is guess. I would say around 220 CFM for the intake.

Stan

You rally can’t answer the question as to how much hp is being made to run a 10.5 ET, you have to look at MPH.

In these these types of racing classes the motors are set up to make there best power, but in a very narrow rpm band.
The cars are then geared to run in that narrow band which allows the most average power to be used throughout the run, and also every spec of power is applied to the track!
The last time I messed around with the intake valve job on a stock 670 head I got it to flow 225 to 228 cfm@28”.
If you go by the 225 cfm number then a motor could make 57.8 hp per cylinder at 100 percent VE.
This would come to 463 hp out of 8 cylinders.

In a 3500 lb car this will go 11.3 to near 11 flat in the 1/4 mile at about 120 mph.
And increase of VE by just 5 percent gets you to 485 hp, and now your darn close to running a 10.80 ET.

LOL !

Yeah, it runs good.

But aprox how many cfm do you suppose the heads flow ? :confused:

Will a 400 Stocker engine make that much power @ 240cfm flow ? 250cfm ? 260cfm ? OR ??? :confused:

"... on a stock 670 head I got it to flow 225 to 228 cfm..."

So, you think Randi Lyn's '67 Stocker can run 10.50 or quicker, with no more flow than that ? :confused:

OR, do you think the heads have been "massaged" to flow more ? IF so, how much more ?

I understand about Stocker "tricks" & "set-up" to run quick. BUT, the engine still has to make a certain amount of power to run the big numbers.

SO, since this thread is about 670 head flow, there's no better place to include the 670 heads on an NHRA Stocker.

Aprox how much would heads have to flow in order for a 400 Pontiac engine to turn 8000 rpm ? Is that something you guys can calculate ?

Bryan Phillips also has a 10 sec '67 Bird Stocker. So, I assume his 670 heads also flow more than a non-ported factory stock set.

There is no set answer. The more the heads flow the less cam that is needed. The less the heads flow the more cam that is needed.

I will set the over under on HP @ 530 and take the under to run 10.50 with a DA of zero.

Stan