Flow numbers for 690 heads?

[jim_ss409]

Does anybody know the flow numbers for 690-583 heads? I've read that the intake side flows about 260cfm but I've never seen numbers for the exhaust. :dunno

[MK IISS]

Skip Fix may have the answer to your question.

[IgnitionMan]

Please remember that "flow numbers" really isn't the full guideline in head assesment. In fact, they are somewhat insignificant over other factors like velocity, and especially just where all that volume/velocity is aimed down the bore and onto the piston top/combustion chamber.

Head people that live by flow numbers alone are not well versed in heads if all they are only interested in is "flow numbers".

It is very easy to get Mississippi River flow numbers for some heads, as in Buick, and completely screw the head up by removeing the wickekerbill that aims the mixture to the correct areas in the bore/chamber, on the port side of the valve seat face, by backcutting that wickerbill off the valve.

Not only do you have to flow the right volume "numbers", but get the mix in, with the correct speed (velocity) and put it in the right place for the heads to work. There have been many, many recorded instances where heads/valves were butchered up to give flow numbers that really impress unknowing people, but the heads were failures all the way, because the other key factors were completely ignored in favor of "flow numbers".

Yup, flow numbers are important, but they ain't the whole story, not by a long shot.

[jim_ss409]

IgnitionMan, I hear what you're saying about flow numbers only being one piece of the puzzle.

The reason I'm wondering about flow numbers is because I'm thinking about a new cam and I'm wondering about how well the exhaust flows in relation to the intake. My guess is that it flows okay because I don't see anybody using a lot of extra exhaust duration. The cam I've got right now, 238-248 @.050 seems to work fine and I'll probably go with the same extra 10deg. on the exhaust side of the new cam. But still, it'd be nice to know if the exhaust side is especially weak or strong.

[fatride]

Exhaust flow #s , although not known, can be improved by the typical means, a little die grinder work,polishing the port and by using the correct size/length header tubes. The last one, correct size/length header tube could be the most important for "scavenging". As Ignition man said, velocity is very important. Hogging out the intake and exhaust ports is most often a disaster. (I know that you are miles ahead of that advice Jim.) A good cleanup of the intake Gasket match, leaving a nice pebble finish, narrowing the valve boss, blending under the valve and cleaning up the exhaust with a gasket match and a smooth polish will go a long way in improving the 690s. There is also some thought in having the exhaust port at the header flange a bit smaller opening than the header flange opening to stop reversion of exhaust gasses. Pay paricular attention to header collector length, 18" past the collector flange is the minimum recomended! Because the exhaust gasses are under pressure it has been said that the more attention should be payed to the intake side with the exhaust side recieving a little cleanup! All the things mentioned above can be done in your shop, remember when I did mine Jim??

[jim_ss409]

Ray, I did my heads pretty much the way you described them, nothing radical.
On the subject of port velocity, I'd be interested to see how the 690-583 heads would respond to filling the floor with about 1/4" of epoxy like the head in the picture below. My uninformed guess is that it would improve the velocity without harming the flow. When I did this tunnel ram post... http://www.348-409.com/forum/showthread.php?t=7329&highlight=tunnel I said I might try running a strip of aluminum along the floor of the runners and possibly have it extend right into the port. After reading the latest article by David Vizzard in Popular Hot Rodding, I'm almost certainly going to try that. He says that a tunnel ram flows so well that it's often better to keep the runner size down. I noticed that Ronnie's professionally built intake is made that way. I was happy to see that the article also suggested adding little tabs to the tops of ports that run together. I had done that when I first built the intake (second picture) but I was never sure if it was a good idea or not.

[fatride]

Aside from doing a little cleanup and tuning the headers I would think you would need a flow bench to get into custom work. I have a hunch that some of our very fast members heads have seen some flow bench time and may have some added material somewhere :dunno. I have always taken the consevative approach when working on the W engine with the idea that some things cannot be undone. I do like the idea with the epoxy though. I guess it's time to find a flow bench, eh Jim? :brow

[Ronnie Russell]

These head threads are always interesting. Wished I had more knowledge about the technical side of this. I was surprised when we recieved the Hogan intake and the ports were smaller than the 690 head port. Somebody must have made a mistake!!! Then a friend from New Mexico explained to me that it all has to do with velocity. IgnitionMan was right again. Bigger is not always better. Like so many other things, it requires balance. I have ported tons of small block heads. Got radical on some. So what? Mess one up, throw it down, reach in the pile and get another one. Hence, Rays outlook. Cant do that with W-heads. I too, am very conservative with W-heads. Better to come up short , than go too far. I agree with Ray about it taking a flow bench to get serious with W-heads. But the flow bench is not enough, one must have the knowledge to change sizes and shapes to get benefit without harming overall characteristics. Way over my head. The new heads that will be available to us in the next few months will have good numbers. That will take the guess work out of us home porters. The future looks great. :brow

[jim_ss409]

Yep, the future's so bright,,, We gotta wear shades!:cool: I'm really looking forward to finally seeing some new heads for our engines. I'm pretty quick to take a die grinder to a set of heads too but I'm really conservative when it comes to these 690-583 heads. I think anybody can improve the flow a little by doing some research and just doing the bassic stuff. But I think really effective porting is only accomplished by experts with years of experience.

[dq409]

Nothing a little 6-71 can`t cure !!!! Eh,, Chip !!!!:rofl

[Skip FIx]

I never flowed the exhaust side. Maybe I can get one done sometime. The intake is about right, pretty close to the Pontiac RAIV "good" heads I have. Stil pretty low for a big stroker motor when you consider "good" SB heads flow close to 300 nowadays.

I've read a few articles that mention often porting W heads reduces airflow.Exactly what Ronnie said. I have a flow bench but I don't port heads. Too chicken as most of my projects Pontiac and W you can't grab another off the pile. I do use it to verify what work got done by "experts" and intake mods. Those are easier to fix if you mess up!

Each type motor/head has subtle changes in what really helps flow.

A little off track just had my "pump gas" motor in my Trans Am out to the track last weekend. Best 10.99@ 124.5 3750 lbs mufflers, tailpipes 9" slicks and a Holley 850 on a Torquer II. Been awhile since I filled my "need for speed"!

Here's a picture of the new 500" er going in 79 Camaro we have laying around. I now you hard core W guys wil lbalst me for posting Pontiac. I can lay teh M/T cross ram on it if you like!

[SS425HP]

Skip, is it the RAV heads that have the exhaust ports separated like a BBC? I helped Dean build a set of headers on a GTO in California that had Pontiac cast iron heads with evenly spaced exhaust ports. Big ports, too. Had never seen a Pontiac head that looked like that. Supposed to be very rare as I remember.

As for Pontiacs, Dean was good friends with Jess Tyree. I have met Jess, and he is one fine fellow. Have pitted with him at the NHRR in Bowling Green. There are a lot of Pontiac stories in his head. A lot of fun to be around. Good family, too.

[Ronnie Russell]

Nice looking Pontiac motor Skip. Very serious looking. Is the 79 Camaro a project for Spring 2007? NHRA super gas?? Comp elininator? Whatever, should be one fast car. Good luck.........:)

[Skip FIx]

The very rare RAV had the separated ports like a BBC. Also the intake ports are separate. Actually Pontiac used the Ford Tunnel Port heads for a guide on these. Kind of like Z-11 heads for rareity and cost now adays.The intake pushrod tube goes through the intake port.

The RAIVs, 71-72 HOs, 73-74 Super Duty all have a slightly different "round port" exhaust ports. The center two (#4,6 and 5,7) are slightly separated and all are round. Standard Pontiac exhaust ports are called "D ports" as those center two are siamesed into two mirror image Ds.

Ronnie this project has been full of issues. I had to basically re engineer the Crower rocker shaft spacing and rocker offsets for them. They must not have ever bolted one a plain Edelbrock head no offset drilled pushrod holes even. The aftermarket block had an incorrect machined(too large) main seal groove that we are trying a shims and silicone. Manufacturer said no one else has had that problem. Some rumors one of these blocks Brinnel tested soft at 140. So I'm now calling it "Problem Child"

Goal is 10.0s as dependable as possible. Any faster ful cage, chassis cert, license etc. So maybe click off a 9.90 but detune it. Hopefully spring 07.

[jim_ss409]

"A little off track just had my "pump gas" motor in my Trans Am out to the track last weekend. Best 10.99@ 124.5 3750 lbs mufflers, tailpipes 9" slicks and a Holley 850 on a Torquer II. Been awhile since I filled my "need for speed"!"

This is quite impressive! Breaking into the tens with a heavy car, pump gas and mufflers.:beerbang

[Skip FIx]

Here's the Camaro the new motor will go in and the TA motor.

[models916]

There is a 409 and heads on ebay right now that the seller says are Crane ported 690 heads. I would like to see what Crane did in the past to make improvements. Years back a friend had Crane ported 289 heads that made some HP. Maybe the seller will take some pics for you.

[SS425HP]

Where is the link, Models?

http://cgi.ebay.com/ebaymotors/chevy-409-truck-block_W0QQcmdZViewItemQQcategoryZ33615QQihZ002QQit emZ120045699678QQrdZ1

Here it is!

[Skip FIx]

I remember Crane selling SBC ported heads in their catalog years ago.