I guess my ‘69 heads were kinda thin from rust under the spring seats Yep, I found water Oh well, didn’t like these heads anyway, the shop that did them 25 years ago didn’t know about Buick heads (neither did I) I still don’t know much about porting or airflow other than “The power is in the heads” So my plan with these ‘71 heads I picked up yesterday is to have Michaels Do the install of the TA valves from my old heads, the valves drop right in as the TA intake valve is only .04 bigger at 1.92 verses 1.88 stock, not much bigger but the stainless is better than the stock valve material. Going to have the heads cut .040 for a tad more compression over the .030 my old heads were cut. Do a bit of port clean up, and that’s about it.
Your assessment of that shop 25 years ago not knowing much about Buick heads is a massive understatement! Gez!, I mean there is 100% no need to grind out the roof of these heads anywhere near that deep! Number 1, the runners are already too tall for the height of the as cast short turn! Number 2, you can’t go up any bigger then a 1.92” valve , which also means this. To make good usage of a 1.92” valve you would need to go up to a valve to throat percentage of 88%. This would make for a 1.69” throat which if used would call for a short turn arc of .845”at a minimum. With the low stock short turn that’s in the head you would be giving up a bunch of flow from .150” lift all the way up to .400” lift, which means massively lost port velocity would be taking place. a built up epoxy short turn would need to be put in place and shaped correctly which means having a flow bench to work out the fine details. Here is a drawing of how a port is geometrically designed. In this depiction a throat size of 1.60” is used with a 2.11” valve. This makes for a throat to valve percentage of only 76. To begin to take the best advantage of any given size valve this throat to valve ratio needs to be a minimum of 85%, and could go as high as 91% when your dealing with high flowing race head with a very tall short turn. notice in this drawing that the short turn arc is .800” or half of the 1,60” throat size used. Note that the roof arc is .800” plus the 1.60” throat diameter for a arc of 2.400”. If your following what I am posting here you will see that as you make a throat bigger, then the short turn arc and the roof arc must also get bigger. In the case of the roof arc most factory iron heads have about .060” to ,080” you can grind out before you get into trouble and leave yourself with too weak of a port wall to hold up. In the case of the short turn your can grind on it to lay it back and partially form a more gentle arc like it would be if you made it taller by adding material. This trick however can only be taken so far before your going to not only loose out on low lift flow below .250” lift, but at high lift the excess velocity over the short turn will create sheer and at some lift point above .500” the high lift flow numbers will recede also. As I stated at the start of this post, the Buick small block head does not have the amount of needed as cast short height that it should, and the same thing can be said about the big block non type stage II heads . all of you folks home porting your heads without the aid of a flow bench and many many years of experience must keep in mind this very much carved in stone rule. It states that valve diameter x.20 is the point where up to that lift the valve job is in near full control of how much air is getting into the cylinder. In terms of even a 1.90” intake valve then all the way up to .380” lift the efficiency of the valve job is of supreme importance to the power that will be made! If your running a .550” lift at the valve then a full 69% of the air that the intake port is passing into the cylinder is determined by the valve job that is put in place. I bet some of you are now thinking about the 3 angle valve jobs you have had done by machine shops that not only don’t know about the details of a Buick head, but also do not have a flow bench to find out about them! here’s a quick drawing I made of a side view of a short turn. in this example the shallow side of the combustion chamber is heart shaped and starts close to the valve. This means that the overall height of the short turn can be considered as being from the deck of the head up to the apex/ crown of the short turn in the port runner. So in this example let’s say it’s 3/4” or .750”. This then shows that you can brake up the short turn pretty much into 3 sections to look at. The arc of upper section controls high lift flow numbers above .380” as used in my example, the bottom section arc controls low lift flow up to .380” and the middle section has a effect on the flow of both the upper section of the short turn and the lower. Let me say this, when your enlarging the throat size in a head that is already down on short turn height, then this middle section can be a lifesaver to have to work with when you know what to do with it, as can also be the bottom cut of a multi angle valve job! You home porters going into the valve bowl and just going on intuition and removing metal around the short turn to make a form that to your untrained eye must be the way to go because it now looks more streamlined, are all too many times shooting yourselves in the foot, especially in terms of iron Buick heads that are already lacking in overall short turn height! believe it or not the Nail heads have more short turn height of all the standard production Buick iron heads!
Lololol, I don’t know yet, I COULD have eliminated going .060 by NOT using the spring seats, BUT the machine shop that did the heads waaaaaay back had large diameter Crane springs on the heads, they had cut the guide base to clear the Cranes inner springs. The Crane springs were to large and interfered with the TA rockers, so I removed them and had to use smaller diameter springs. So these heads were doomed from the start so to speak. I’m going to do these heads closer to stock as far as the porting and such, just a quick clean up.
It's a good thing that you went through. It would have been bad to get the engine running and then have them break through.
Mark, with your new cutter the valve guide is the right size to locate so you shouldn't have to go .060 deeper. The ones you went through were ported too much. They should all be the same.
I had thought of that, even tho I couldn’t poke thru with a screwdriver like the seats in the picture, who knows how thin I was on others, and then the spring pressure constantly pushing down
Wow Steve that’s a lot of good info. Sounds like you have a grasp on the head porting science! I’m going to be realistic with this set of heads, I’m NOT going for all out flow, it became obvious to me the 350 head casting does not have enough meat for reconfiguring, nor do I know how to do it properly Soooo, I’m going to keep the ports stock size and keep the velocity up, these heads were designed this way for torque, and from everything I’ve read from you you say hogging stuff out can/will kill velocity and make the engine lazy. So I’m curious with these heads with just the TA valves and a GOOD valve job from Michaels Racing Engines, if my e.t. Or mph will pick up, stay the same, or slower. I MAY go .060 off the head for a bit more compression
Watch taking too much off heads I had trouble putting on that TA SP3 I had to make holes slightly bigger to get the bolts in and the top of the port on the intake is right at the top of the head also.
Mark, TA has 10 degree locks that fit the Buick valves and would let you use +.050 10 degree retainers. Then you wouldn't have to go so deep this time.
Seasonal heat wave, get out there or take them to work and cast iron dust their place up! That's what I did... Plus you get paid to do them and use their compressed air.....
There was enough heat on Sunday I was out cleaning gaskets had heater on never got warm enough takes too long no insulation.
Maybe this weekend I can get out there. If it’s warm enough out I gotta put a new tensioner pulley on the Wifes Tahoe also. After I’m done ruining this set of heads I gotta take ‘em to Micheals to have the seats and guides cut/machined. THEN I can finish assembling and forget to do stuff I wanted to do ‘cause it’s been awhile
