[crm318]

I need advice on which direction to go with one of these set of heads. I have a set of big valve 1968 #16 on my GTO with a .60 400 (in my sig). They have Crower 68404-16 springs with stock retainers, valve guides machined for positive seals and 2.11/.177 valves with hardened exhaust seats. I ported these heads a couple years back with out the advice of this forum and I honestly dont know how I did. I opened up the bowls and blended the ridge on the short turn of the exhaust. I did a standard intake gasket match, but didnt really touch the push rod bulge or runner. I focused mainly on widening and contouring the bowls. Unfortunatley I didnt measure the bowls or have access to a flow bench, which I know is a huge sin in cylinder head porting. I also gasket matched the exhaust side which I hear is also frowned upon. I had some low readings on a cylinder pressure test and I do remember having a few thin intake seats. It also has a slight inconsistency in the sound while cranking before start up. Although it will shred the tires and chirp hard into second gear, it seems to lack the mid range and top end that these engines are known for. I have a set of completely stock 1968 #15 small valve high compression heads that are worn out and I can get a fully rebuild with hardened seats installed and valves enlarged (transfer springs and guide plates from the 16s) for just under 700 dolllars. So here is the question: since I am planning on buying and installing a set of one-piece Ferrea valves, do I assume that my 16s are alright and give them the new valves with valve job or do I start from scratch and rebuild the 15s with valve enlargement, hardened seats and porting as per the experts on this forum? I just ordered the Pete McCarthy head porting video. Unfortunately, no one owns a flow bench in my area. Here are the only pics of the #16 heads I had before assembling them.

[mgarblik]

If the 16 heads were stock and not ported, there is information on what they flow and what they need. Since they have been worked on some there is honestly no way to know how they are now and if some additional porting can make them better or if they are really hurt. I am sorry to say a flow bench is really needed to evaluate the 16 castings. You have invested considerable time and money in those heads and they are good castings to work with. I would research further some place to have them tested and then decide what to do.

[Half-Inch Stud]

Blend-down the pushrod bulge.

Port match intake& head to gasket.

BLEND valvebowl into valvejob.

BLEND valvejob into Chsmber roof. Unshroud valve curtain into CYL wall.

Clean for re-assy.

[1968GTO421]

You are a braver man than me. Back in 1965 I had a 1964 Olds 394 from a Starfire in my older Olds. Saw a detailed article on porting in HOT ROD and did the job on them. Next trip to the track my ET was .3 slower. Never did another set of heads.

Hopefully one of our members can put you in touch with a person with a flow bench in your area. They do look good, though.

[steve25]

Since it sounds like the 16s have not had the guides done I would tend to say start fresh with the 15s if you have the money to fully rebuild them.

The most critical part of the Intake port is the short turn, and grinding back too much of its runner to chamber C shape will kill your needed port velocity, and then there's only 3 ways to get it back!

Sometimes it's nessary to grind back the C shape , but only once you have the rest of the port flowing more than 245 cfm, which you likely are not doing!

1) re-weld back in the needed meat.
2) spin the motor up higher.
3) place more CID under the Heads by means of Bore or Stroke, or both!

Now that you have Petes video, make a template as he shows even out of cardboard if need be so that you can find out what throat size you have ground your 16s Intake port to and report back if you will.
I can guide you from there .
How much HP are you looking to make from this build?

[Half-Inch Stud]

455 Pontiac could always use a lightly ported head.

[steve25]

That depends on a multitude of factors, but up to 230 cfm@28" gained by a not more than a 6 CC increase in port volume works well if the car is 3800 lbs or less and can shift at 5400, with 3.08 gears or better.

[rohrt]

My .02 would be get the porting video by petemccarthy, and the Jim Hand book to study.
Create a proper shaping valve to check your work.
Open up the pushrod bulge and see if you short turn is wide enough. Call it done and enjoy.

[crm318]

Pete's DVD is in the mail and should be here soon. I didn't really touch the short turn in the intake, I just blended the pronounced ridge in on the exhaust short turn. In using a cam that is over .460 in lift with the possibility of using 1.6 rockers later, do y'all suggest 30° or 45° valves? Seeing as these are smaller chamber heads, would I need the 5.+ length?

[steve25]

Which heads are we talking about, the number 15s?

[crm318]

1968 small chamber

[crm318]

I did notice that the 15s have a large bump beside the exhaust valves guides

[steve25]

The 16s are screw in studs?
Yes ,all of the 1968 castings regardless of casting numbers have the air injection bosses in there Exh ports, but they stopped drilling them thru to the main passage since they had switched over to the open combustion chamber and did not need to use them to meet emissions .

[crm318]

Yep. 16s have screw in BBC 7/16 studs. I actually have another unopened set of them. If my port work is okay on them, all they require to be perfect would be to touch up the valve seats and replace the 2 piece valves. Can those air bosses be ground flat?

[steve25]

Unless you rework ( bullet nose over) the valve guides themselves the air injection bosses are not much of a restriction even though they look like they are!
If you are running a duel pattern Cam and headers and your Intake side is not flowing more then 225 cfm from porting (which they likely are not) then just go thru the Exh ports to smooth things out and your Exh to int ratio will be fine!

And it's best for this level of Exh flow when running headers if you do not port match them , especially on the floor at the flange!

I was asking about your 16s to find out if they where the non screw in stud / small valve version.
Stay with a 30 degree seat Intake valve .

[crm318]

Well, I am taking the heads in to get the studs pulled and I will inquire about valve enlarging. Steve, seeing as you think I should retain the 30° intake seat, how do you perform a 3 angle valve job? Also, do you think using a bowl hog is a bad idea or should it be done manually with a grinder?

[steve25]

You do not want a 3 angle valve job on the Intake, just a 30 seat with a 60 bottom cut.
The OD of the 30 should be taken out to .005" of the Valve OD, then a 60 bottom cut should be applied to take back the ID of the 30 to leave you with a main seat width of .060" to .075" max.
The usage of a Bowl Hog cutter if it goes down deep enough to get the Throat diameter up to 1.66" will add Intake flow for you.

On the Exh side if your steeping up to a 1.77" Valve , then a conventional 3 angle job of a 30/45/60 is all you need, being sure to have the main 45 seat at. .080" wide.

From what I saw from your photo , your Exh seats look pretty beat up so to avoided sinking the 1.66" Valve a ton you should step up to the 1.77" size!

[Half-Inch Stud]

smooth roll before & after the intake valveseat.

[crm318]

Plan on enlarging to the 1.77 with hardened seats. I'll be stopping by the shop today to show them this info and see what kind of equipment they have. What do y'all suggest for the exhaust throat diameter?

[steve25]

A question first needs to be asked as to how much Intake flow are you porting for!

Reworking the Exh Bowl along with stepping up to a 1.77" Valve can net you 170 cfm pretty easy,and 170 cfm makes for good 74% ratio if for example your Intake ports are flowing 230 cfm.

What is average smallest diameter ( left to right) of your Exh ports as it stands now?