This may be a stupid question, but in a 350 head is the area between the exhaust & intake throats of a chamber solid? (i.e. between #1 intake throat & #1 exhaust throat, between #3 intake throat & #3 exhaust throat, etc.)
The answer to your question is a 100% no, the common area between the intake and exh valve bowls is not solid. Here’s the best detail I can offer you since I have never sectioned a small block head, but I will use this cut up Nail head as a example because the factory requirements for minimum iron casting wall thickness are likely very close . In my first photo your looking down from the cut open exh port side of the head and you can just make out where the exh port wall to the right of the spark plug hole meets the chamber roof. in this Nail head the chamber floor thickness seems to average .290” to 330”. The port wall thickness be it intake or exh can be anywhere from .185” to .245”. Most important to you is my last photo where just to better answer your question for you cut into the chamber floor between the intake and exh ports and by the time I got to .370” deep I had already cut into the water jacket between the two valve bowls.
I don't think I could've asked for a better response! Thanks for the detailed info, and thanks for sacrificing that Nailhead head on my behalf.
I'm definitely not planning on going crazy with the port work. I'll clean up all the runners, hit each short turn radius, shape the valve guide bosses some, etc. The heads are already cut for larger valves, and my curiosity was if I'd be able to do much with the awkward "lumps" in the throats that now exist because of the bigger valves.
later today I will post up some info, drawings and photos as to what to do. For starters you can blend in all of those steps left by the cutter into a gentle transition without fear of grinding thru since it should take no more .050" of metal removal to get that blend out done. In the Exh bowl on the Intake valve side that pinch in needs to stay there, I know it looks to be a restriction, but its not. Here's a quick drawing of what I mean , this as if the heads was cut open lenght wise at a point through the valve bowl just before the short turn. Since you have freshly cut seats you want to cut duct tape into narrow strips and cover the valve seats so you do not nick them by accident, in fact cover them with two layers of tape!
Here’s what you can start with in the intake ports. The valve boss intrusion is substantial in these heads and the can be boat tailed/ tapered and also narrowed down a lot, especially on the common wall side of the guide boss which is opposite the exh valve. expand my photo to look close and see how much I removed as compared to what it is stock. If like in my other picture here your short turn has any casting flaws then clean it up well and fill it in with JB weld. Once the JB starts to set up a bit you can wet a finger tip with very soapy water and shape & smooth the fill very easily. let me know when you are done reworking all the intake guides and we can move on to another intake porting step. I find the best type of grinding Burr to use for this guide work is a Ball head short type , not a 6” long type. The ball head types will dig in hard and want to yank your hand around so be ready to fight with it. You can use a foot ball headed Burr for a lot of the rework also, but getting down to blending in the guide to roof transition calls for a ball headed Burr. The very hard part about doing this level of guide rework is to keep / make the beak of the guide point centered on the roof of the port facing the intake flange. The place to start grinding when doing this guide work is at the end of the guide near the seat. Your reduction work there should take the guide down to meet the guide liners that have been installed in your heads.
Thanks Larry. I definitely spent some time (on several occasions) looking over that article. I’m thankful it does exist, but it’s still a shame that it’s basically the only reference for porting these heads.
There's this on 350 head porting - Woukd be curious @Stevem your opinion on it. https://www.teambuick.com/reference/library/350_porting_burek.php
Dano I have seen that article before and what I can say is that the flow bench used was a happy one as compared to my Superflow, and or the lift points used and stated in the low and mid lift points where not dead on at times. here I will post my numbers from a stock head using the stock valves and then the numbers from the article. my numbers will be the first column and the second column will be from the article. I will comment after each flow chart. Exh stock @ 28” .100”/////44.8/////44 .200”/////86.7/////93 .300”/////111.4/////124 .400”/////121.4////128 .500”/////125.7////130 .600”/////127.4 as you can see something is very wrong with the accuracy of the flow numbers from the article between.300” and .400” lift. From the article there is only a 4 cfm change where as from mine there is a 10 cfm change/ gain which is as it should be. That big of a lift point change should produce a nice increase in flow. This discrepancy in the articles numbers leads me to conclude that what was stated by them as .300” lift was way closer to .400” lift, like maybe .380” lift. Int stock @ 28” .100”/////54.8////66 .200”////101.7////119 .300”////149.4////169 .400”////181////198 .500”////193.3////198 .600”////194.8////198 Here once again the big discrepancy in numbers from .100” lift up to .400” lift would now make me have doughs about what is reported in the article in terms of the ported numbers that is provided, maybe not peak flow. But certainly from ..450” lift on down. In terms of work that is done on the exh side, the enlargement of the throat of the valve bowl of .100” would have near wiped out the much needed bottom cut of the valve job which would have cut deeply into the flow numbers up to .350” or more. You asked me for a review and there you have it. There’s more I could comment on, but I will leave it at that.
I was able to spend about an hour this afternoon taking a crack at one of the intake bowls & guide bosses. I feel pretty good about my first go at this, but I'll wait till Stevem (or anyone else more experienced) chimes in before I get proud. haha Before: After:
Finish up the exh, then get ports flow tested. Probably abt $25, if you get good results, port the rest exactly the same.... 3 angle valve job will improve flow #'s.
It’s hard to tell from the angle of that last photo taken of the intake bowl rework, but the boat tail / nose portion of the guide where it meets the roof does not look like it’s centered left to right running down the roof of the port back towards the intake flange . If that is the case then such a condition will block air traveling on the roof. You may just have to round off the junction of the guide and the roof, because once again I can’t tell for sure from your photo. Once your done with all the intake bowls then the upper common wall ( wall area between both intake ports ) needs to get 1/2 hour of rework. Let me know when you get to needing that info. Also there are specific things I can guide you on with the exh ports when you get to them.
I see your not using Duct tape to protect the valve job, is this not the final valve job/ touch up? If this is not the final valve job then in terms of the job done to the intake port you want distinct angles on the way down into the bowl after the main 45 degree. Like 30, 45, 60 and a .020” tall 70 degree if it can be had. The famous full radius valve job on the intake side only serves to worsen problematic wet flow conditions. This then leads to less power being made then what otherwise would take place and produce a increased tendency for ping and detonation.
