Can’t really say I started porting them ‘cause that’s really not what I did, more so reduced the chunky valve guide boss and contoured or smoothed the transitions in the direction of intake and exhaust flow. I actually sat and looked at the exhaust bowl from the valve side and imagined the exhaust flow out of the head and just smoothed the hard edges around the exhaust guide along with contouring the iron around the guide. I DID NOT go hogging out the ports on the intake or exhaust, as I have no idea what that would do. The first inch of the intake ports were already gasket matched and smoothed years ago. To me, the intake bowl area on the 350 Buick looks HUGE and pretty well contoured, so I left it alone as I have no idea what I’m doing LOLOL. What I did learn from this is die grinder English is UBER important, proper lighting too. I have one more head to do and I’m done, I can’t really see any more areas to smooth, I think the exhaust side is more important than the intake on these heads, I could be wrong. I need to get some sanding cartridges and or flap discs
Not yet Mart, I will as soon as I’m done with at least one cylinder. Yes I have a few before exhaust bowl pics.
Here’s some pics of my butchery LOLOL I’m not shining up any of the iron with sanding rolls, just a quick buzz over to smooth the peaks from the cutters. I used my snap gauges to keep the dimensions very close as far as the size. The intake ports and bowls must have been done when Gellner cut the seats for larger valves, as I don’t see anything I need to do or maybe could improve upon, so I just hit a few spots. I’ll take a pic of my stock ‘71 heads next to these ‘68/‘69 castings that are cleaned up so to speak. This is a lot of work and learning how to control the die grinder and the bits to use is another learning curve.
Removing the sharp edges and the rounding of the valve guide boss makes a big difference in flow at all lifts.
Thanks Jim, that’s what I’m going for the obvious, and to me that seems like the chunky valve guides are a hindrance, that’s what I’m assuming since I’ve never done this before, probably never again LOL! Is it safe to remove the guide boss or will that effect valve stability?
Another question, is there something a home garage guy can use to fill in the exhaust crossover on the center exhaust ports? I know of the molten aluminum trick, but………. I had Pipe plugs installed from the intake side of the head but would like to fill the cavity on the exhaust bowl side, and make it more “flow friendly” I don’t know how much turbulence those two pot holes add to the exiting exhaust gasses
I believe Gellner engineering did what they did years ago when they installed the larger TA valves, I never really noticed till now looking at them very closely. The intake bowls seem to have been done very nicely, that’s why I am concentrating more so on the exhaust bowls
I remember this subject coming up a while back, can't find the thread. I do remember that someone's actual testing showed negligible results when the crossover passages were plugged flush in the bowl area. Simply put, don't worry about it. Devon
Thanks Devon! I was kinda hoping to hear “don’t worry about it” LOL FIlling those myself is beyond my ability, melting aluminum then pouring it, getting 3rd degree burns, starting a fire, burning the garage down, all bad stuff Cool, I’m leaving them be!
Checking to see were and IF I can unshroud the exhaust valve. I see I can trim a bit on the end cylinders, the two center I’m not going to touch, the fire ring is pretty damn close. Max was in the garage helping
Mark, I've always ground out the lug in the chamber, rounded the spark plug hole and CC'd the chamber to make them all the same. The lug is not for swirl but a fixture to hold the heads while machined.
Mark, here are some porting tips for you and some photos. Unfortunately from what I have seen in your photos you have posted up you may have harmed your low lift flow numbers with some of the work you have already put into the heads. Also those who have contributed to your post with there suggestions here done without the aid of a flow bench both concerns me and at the same time there naivety makes me chuckle! in terms of these Buick ( and many other brands) with there shallow depth exh ports you need to be very careful in the reworking of the valve guide and the rear of valve bowl area . Here are two drawings that show why this is. In the first one the squared off 90 degree basic shape of the port promotes low lift flow . when folks dive in to rework work the exh side the first thing they will always try to do is to make general port shape more streamlined, yet since there work is unguided by a flow bench they have no idea where the bulk of the air mass is going for any given valve lift point! In my second drawing the general port shape promotes better high lift flow, but when a novist does such they get added high lift flow at the expense of needed low lift flow. The key to effective porting of shallow depth ports like these SBB heads is to know where to grind. as one of my photos shows the little bit of blending work that I did on the lower part of the valve bowl just above the valve guide on the intake valve side caused a low lift flow loss. Basically in terms of reworking the exh valve guide and not making for a low lift flow drop off you want to resist going in there and Boat tailing the intake valve side of the Exh guide, but on the cylinder wall side you want to do as I did. Boat tailing is ok on this side of the guide because at high lift a lot of the flow is coming into the exh bowl from the center of the cylinder on a angle and heading right to that side of the beginning of the roof. Next up is reworking the short turn. Looking at my next two photos of the form made of the center run of the short turn on up to the crown / high point of the short turn you can clearly see the difference. On my reworked short turn the dotted line shows the stock shape . I started the rework by blending off a good amount of the stock bottom cut. This straighting out must be done carefully because it must be done parallel to the valve inclination angle. if you stick a valve upside down into the bowl it makes for a helpful guide to rework. This cutting back in effect tricks the port into thinking that the short turn is higher ( makes for better high lift flow) when all you have done is slowed down the flow some which when the valve bowl is saturated with air allows more air to make its way over the short turn. The last photo shows the only way to smooth out the short turn around it’s crown after rearcing it on top to .450” radius. After cutting off this long strip it’s torn off length wise to be 1/2” wide and then another length again is torn off to between 3/8” and 1/4” to allow getting into the corner’s of the short turn. Mark, be sure to have your exh valves back cut with a 30 degree so that the 45 seat is left to be .065” to .070” wide. This will help get back some of the low lift flow drop off that I am sure from your photos you have taking place. unshrouding the cylinder wall side of the combustion chamber does not air exh flow at all because no where near as much air is coming up that side of the cylinder wall as you might think! All you have done in the end is given up compression! don’t get me wrong, you do not want the chamber lip hanging off into the bore, but once you have blended that off don’t go any deeper into the chamber.
