[bob prichard]

I have the 670 heads off of my 1967 Firebird 400, four speed with 3.55 posi diff. The motor is bored .30 over, with stock crank and rods, compression is app. 180-190 psi.

I am wondering if there is any benefit to porting the heads while they are off? They will be getting a valve job. I have a set of long branch manifolds that I can add. Any opinions will be appreciated.

I contacted Butler and they are 8-9 months on turn around for porting, less for a valve job. So, any recommendations (preferably in California) for high quality head work. Thank you.

[Dragncar]

Not worth the squeeze unless you do all the other things that go with ported heads.
Cam, forged rods, pistons ect.

[bob prichard]

Originally Posted by Dragncar

Not worth the squeeze unless you do all the other things that go with ported heads.
Cam, forged rods, pistons ect.

Yeah, I hear you. I just don’t want to miss out on this opportunity if it made sense.

[lust4speed]

I disagree. You will obtain a noticeable performance increase with just porting the heads. Engine is basically a big air pump and the more volume the more power. You can increase volume through a larger cam that increases breathing or you can port heads and increase breathing. Plus that part will be done and maybe you have done one or more other improvements.

Originally Posted by Dragncar

...Cam, forged rods, pistons ect.

Forged rods do nothing to increase power nor do pistons. Those items are to increase strength and allow the engine to live longer. A worthwhile investment but not a performance investment. Now cam, intake manifold, and exhaust will be worthwhile parts of the overall performance increase and any one will add a portion of improvement. While the sum is only as good as its individual parts, those individual parts can add their share without having the others present.

[Dragncar]

Originally Posted by lust4speed

I disagree. You will obtain a noticeable performance increase with just porting the heads. Engine is basically a big air pump and the more volume the more power. You can increase volume through a larger cam that increases breathing or you can port heads and increase breathing. Plus that part will be done and maybe you have done one or more other improvements.


Forged rods do nothing to increase power nor do pistons. Those items are to increase strength and allow the engine to live longer. A worthwhile investment but not a performance investment. Now cam, intake manifold, and exhaust will be worthwhile parts of the overall performance increase and any one will add a portion of improvement. While the sum is only as good as its individual parts, those individual parts can add their share without having the others present.

Dude, if you want to advise someone to go through the considerable expense and effort to port a pair of iron heads on a completely stock engine, go ahead.
Now, IMO once you start building a real engine with ported heads you put good pistons and get rid of the JUNK rods.
When you port a pair of heads you get a flow sheet up to at least .700 lift.
His valves might be lifted .412 or so.
Ported heads means more RPM potential and you want him to do it with cast rods.
Elongate the pushrod holes and run some good 1.65 roller rockers and call it a day.
Or just run it as is and have fun with it.
Myself, if I was to rebuild ANY Pontiac 400-455 its getting good rods and pistons.

[Kenth]

The #670 heads flows plenty good for the specs and usage of your car.
Only porting the heads will degrade driveabilty, waste of funds.
Buy new tires, exhaust system, new toys for the kids or a present to the wife instead, thats money well spent.

JMHO

[steve25]

Boy, some of the opinions posted here really make me shake my head in disbelief!

For example if running a Cam of greater lift produces more power due to accessing higher levels of air flow, then why would a minor port job that produces more flow at a lower lift provide that same benefit?

Here's a look at the typical late 60s to mid 70s head that would be on a 350 cid SBC motor.

The bread & butter motors had. 1.94" Intake valve ( 9% smaller then a Pontiac 2.11" valve ) yet would typically flow 215 cfm to a Pontiacs D port average of 205 peak flow.

This is mainly due to the minimum valve bowl diameter in the SBC head being a tad bigger then the Pontiac

The 670 heads have the lowest port angle ( not valve inclination angle) of all the 14 degree heads.

If you rework the Intake valve guide boss and do a light bowl porting job a long with a valve job the uses the full OD of the 2.11" Intake valve you will find that you get handed 25 more cfm @.500" lift then stock , or in other words 230 cfm.

One of the cut in stone rules of Intake port air flow is that if by careful rework you gain a larger percentage of air flow then you have in percentage of minimum port area enlargement then you have not given up any driveablty factors with the motor , but you have in fact picked up better drivability.

[steve25]

Boy, some of the opinions posted here really make me shake my head in disbelief!

For example if running a Cam of greater lift produces more power due to accessing higher levels of air flow, then why would a minor port job that produces more flow at a lower lift provide that same benefit?

Here's a look at the typical late 60s to mid 70s head that would be on a 350 cid SBC motor.

The bread & butter motors had. 1.94" Intake valve ( 9% smaller then a Pontiac 2.11" valve ) yet would typically flow 215 cfm to a Pontiacs D port average of 205 peak flow.

This is mainly due to the minimum valve bowl diameter in the SBC head being a tad bigger then the Pontiac

The 670 heads have the lowest port angle ( not valve inclination angle) of all the 14 degree heads.

If you rework the Intake valve guide boss and do a light bowl porting job a long with a valve job the uses the full OD of the 2.11" Intake valve you will find that you get handed 25 more cfm @.500" lift then stock , or in other words 230 cfm.

One of the cut in stone rules of Intake port air flow is that if by careful rework you gain a larger percentage of air flow then you have in percentage of minimum port area enlargement then you have not given up any driveablty factors with the motor , but you have in fact picked up better drivability.

[Half-Inch Stud]

Grind the valveguide bosses a little, port match to the intake gasket, widen the intake bowl a little, oval the pushrod holes, cut the valveguides for positive seals. New Springs, new 1-piece stainless valves.

Long Branch for sure.

[chiefbigb]

I have ported a fair amount or iron heads. You can get a fair amount of gain with minimal work. As stated blend the bowls. Roll the short turn into the bowl and work the push rod bulge width as well as turn behind it. Like Steve said 230 to 240 is achievable from that and low lift numbers will be good also.

[chiphead]

Having put a ton of money into a set of 670s, I doubt I would do it again. Its much more cost effective to slap on a set of 72CC aftermarket D-port heads for a performance gain.

From my experience, it will cost about 2000-$2500 to take a set of worn-out 670s and make them equal to a set of aftermarket KRE or Edelbrock D-ports. In addition, the aluminum heads will handle pump gas much better than a set of irons, for a given 10:1 compression ratio. I had my 670s ported for 250CFM intake, 210 exhaust, longer valves, hardened seats, roller springs, ti retainers, 10* locks, longer ARP BBC rocker studs, had the crossover filled with aluminum, chambers unshrouded for 80CC. It wasn't cheap and it still barely equals a set of aftermarket heads.

If you want to keep the 670s, have a shop inspect them very closely. If they need valves, seats, guides, springs, retainers, mods for high lift cam, etc etc, it adds up quick. Price it out first and make an informed decision. You can put the 670s on the shelf. The aluminum heads give you a lot of room to grow.

Keep the revs below 5300 and let it eat. My current motor is a box-stock 69 400 with stock 62 heads, 750 QF DP on RPM intake, headers and Summit 2802 cam. The motor is high mileage and worn. With a stall converter and 3.25s, it's no slouch. It'll roast a set of 275 nittos and wind up over 5500 faster than I can shift it. It's eventually coming out for the 670 headed 428. You can make good power with stock D-ports. I only had my 670s reworked because they were going on a serious motor. In retrospect, I should have just gone aftermarket. It's all about future engine roadmap and how much you plan to grow.

The 068 cam is very mild, 417 lift. The stock heads will show flow gains up to .475-.500 lift. Just use a larger cam to open the valves more. Summit 2801 or 2802 and have the valve guides cut down for the additional lift and Viton seals. Ditch the umbrellas and the stock shields and retainers, it'll open up a lot of cam choices at 1.6" Installed Height. But again, that's money into the 670s, so think about how far you want to carry them and how much work they need. The real concern is the 2-piece valves and guides. The 2-piece valves can break if badly worn, and guide work is costly. If it needs guides, it needs valves, because once the guide goes, the valve stem is shot. And the guides locate the valve on the seat, so new guides and worn valves/seats don't make sense. It gets costly. And some shops will soft-pedal what the heads need, to keep costs down. They're used to cheap customers who b@tch at good work. Ask the hard questions about how worn the parts are.

[Sirrotica]

It all depends what you wish to accomplish whether the juice is worth the squeeze. I have a 455 that I built back in 1988 that has a complete stock bottom end, cast pistons, cast rods, and a mild cam. I ported the 5C heads at the time, along with a fresh valve job. Reworked Q Jet, a cast iron EGR intake manifold, along with a set of headers. Considering the investment, the engine was a wonderful performing powerplant. If someone rode in/drove the car, they might think I had way more invested in the engine than I actually did. Attention to details is where you pick up performance, it's not always on how fat your wallet is.

It was in a 76 T/A with 3.23 gears, and a T400. The car delivered many smiles per gallon over the years, and the body finally succumbed to rust belt old age, going to it's final resting place, the recycling facility.

I still have the engine stored away, and will be freshening it back up before I install it in my 84 GP street car. This car will have a 3.50 gear, 9 inch ford axle, and a 4L80E transmission.

Was the head work worth the effort? It was in my case. That all stock bottom end did just fine with the ported 5C heads, Likely it will just get rings and bearings, and go back together with it's born with, cast bottom end. It's a street car, not a race car, I really don't see the need to spend thousands of dollars for forged parts for a proven, well performing, 455 that won't see more than 5500 RPM, here and there, over the years. I have more places to spend my post inflation dollars than on a street engine, that is plenty adequate for what I want to use it for.

I'll also add that every one of my dirt track engines, all but the last one in my 69 GP, had stock bottom ends, cast rods, and pistons, and they all survived for years. I did pay a lot of attention to the clearances when assembling them, but each and every one had cast rods, and only one 428 had forged pistons in it. My race cars beat a lot of brand X race cars with thousands of dollars more spent on the engines. I had a secret weapon though, I started with a Pontiac Stratostreak engine.........

If you know the limitations of the stock parts, and stay within those limitations, the engines can run well, and run a long time, as well as not putting you in the poor house. YMMV...........

I wasn't blessed with a lot of money over my lifetime, and if I wanted to race I had to do it on a shoestring, sometimes that shoestring got pulled pretty tight over the years.............

[bob prichard]

Thank you to all who responded to my questions, it helped to open my mind and think this out. I think I am just going to get a good valve job, with new valves and whatever new parts they may need. I realized that I am not willing to make the changes to a restored stock Firebird that would benefit the ported heads, that would just open a can of worms which I cannot afford at this time. I have my restomodded 65 GTO to play with for now, which is enough.

[Dragncar]

I think you made a good choice.
If someone had the tools, time and ability to do a Jim Hand style port job then I could see it.
But once you start paying someone to do the extra work the numbers do not make much sense.
As post # 11 stated, for the money it would take to do the 670s right you could have a set of new aluminum heads.

[J.C.you]

Just to add my 2cents. There are ported upgraded iron heads out there, people have went aluminum. Usually that would be the most cost effective route.

[Tim Corcoran]

I would say, as others have, just do some bowl work clean up and port match. Since your getting a valve job already it shouldn't be expensive to do the minor bowl work, port match and clean up. Any chevy guy could do that work for you.

[Greg Reid]

Just happened to be re-reading Jim Hand's segment on porting yesterday. A couple of porting questions for you all..
1. Is porting is always done before the machine shop does it's thing? I think yes but just to verify.
2. Valve seat angles.. Do you guys specify with the machinist what you want?
Jim Hand is pretty specific on what he calls out in his book
3. Is it worthwhile for an inexperienced tinkerer to attempt porting with no way to measure flow?

I have a set of heads that have never been run since leaving the machinist. I was thinking about taking them back to replace the press in studs with 7/16" ones and toyed with the idea of trying some porting and blending the intake to head runners and have them re-establish the seats.

[steve25]

Greg, what casting number heads do you have that your thinking of tinkering with?

[Greg Reid]

They're 093s on a '66 WT 389. It'll be in front of a 4spd and 3.55s. All engine components are the born with parts. Did bearings, seals, rings, cylinders were just cleaned up. '65 Tri-power added on. Hooker headers.
Melling 068 cam.
Those press in studs have been occupying rent free space in my mind so I'll probably at least get that done. If I'm going to have the heads off anyway, might give it a shot..
Jim Hand's guidance in the book is well presented and I think I could make improvements using it.

[steve25]

I have never seen Jim’s book.

Does it go into specifics on how to deal with the 093 heads 20 degree valve inclination angle as compared to the later heads?