Hi all! I have a set of these to port up for a fellow so I figured I would post up details, comments and flow numbers as I go along. All of my flow numbers are at 28”. The first column here is a stock Intake , next is a stock exh and the next is the flow from a light bowl blend of the exh and the next is the change in flow from the bowl blend work. The bowl blend work of the exh was done with a eye for keeping the low lift flow numbers what they are and not loosing any which is common. These test where done with the stock valves that where in good shape and just a light freshen up of the valve job. .050”. 37.8/////19.7////19.2////-.5 .100”. 64.3/////43////42.7////-.3 .150”. 67.4/////64.4////64.6////+.2 .200”. 121.2. 89.5////92////+2.5 .250”. 152.2////115////114.7-.3 .300”. 175.5////134.2////135.2///+1 .350”. 194.5////143.9////144.8///+1.5 .400”. 207////147.6////153.5///+5.9 .450”. 211.6////153.5///160.4///+6.9 .500”. 218.5////156.5///164.4///+7.9 .550”. 222.2////158.5///166.4///+7.9 .600”. 224.5////158.5///167.4///+8,9 I started off with reworking the exh side because from my eye balling of this head the intake side has far more potential then the exh side, and as such the added flow that can be yanked out of the exh will be the limiting factor in the added HP that can be got out of this casting. I think my next move with this head will be to just skip bowl porting work and just cut new seats for a 1.620” exh valve as thats about as big as I dare go and not have the two valves touch. the stock exh to intake ratio up to .500” is a nice 83.7% If you had 9.5 comp and ran a Cam of .550” lift you should have a easy 430 hp on hand with even stock heads.
Hello all! I stayed up late last night and recut the seat and bottom angle to install a 1.620" valve and to make a flow test. This allowed me to open up the throat for greater high lift flow while kepping and improving on the same basic great low and mid lift flow cartactoristics of the stock port. I also blended off much of the 60 degree bottom cut around the short while making it parallel to the valve inclination angle. This had the effect of simulating increasing the height of the short turn ( slowing down the velocity) even though the real height of the crown of the short turn is stock. Photos of stock and the reworked port will be forthcoming. First column is the current flow numbers and the second is flow gain over the stock port from my first post. Stay tuned for more. Flow @28" .050". 28.4/////8.7 .100". 48.8/////5.8 .150". 73.5/////9.1 .200". 103////13.5 .250". 125.2////10.2 .300". 145.2///154 .350". 162////14.4 .400". 166.9//13.4 .450". 171.8//13.3
Nice, thanks for posting. Looking forward to following along. I wish I had flow numbers on the set of ported/big valves (intake & exhaust) I had done 30 years ago. I have a set of exhaust valves for the next set - IIRC they're 1.6. Are you planning on larger intake valves as well?
Hi Dan. Not that I have measured it yet, but with the 1.620" Exh valve that I have in there now I don't think that you could safely go more then .010" larger on the Intake valve and as such if you did I don't think it would buy you much added flow. I will find out likely next week when I move off of reworking the Exh ports and switch to the Intake side. One thing is for sure about the Intake side is that horrible stock casting lip on the short turn of all the Intake ports is cutting into high lift flow that could be had and if nothing else if your staying with a stock Valve size needs to be filled in!
Thanks Steve! It'll be interesting to see if your theory of going with the largest possible exhaust valve at the expense of a larger intake proves to be the better solution. It does seem to be the case that duration is more so the key on these engines and if in my (very) limited expertise in cams I'm understanding your logic correctly, that would make perfect sense keeping open longer. Interesting theory (again if I'm understanding you correctly) that it's possible that the stock or even a ported intake cannot over-supply the stock intake valve size & that the port itself is the limiting factor. Someone will correct me if I'm wrong here but I believe TA slightly moved the valves in the aluminum heads which maybe was to help alleviate the issue you mentioned wrt the intake port and would allow for larger valves. I'm a ways off but looking to build an all out stock "appearing" iron headed 350 so what you're doing is particularly interesting along with having built a 350 prev. w/big valve ported heads. No particular rules package I'm adhering to exc. to keep it somewhat streetable. I already have an intake that Greg Gessler ported. The alum. heads & SP1 intake are tempting as they can be made to look almost stock and I have another 350 GS that maybe I'll go that route on.
Interesting Steve, I’m getting ready to port my iron 350 heads myself, never done it before so I’m going easy. I’m HOPING to not damage the seats, I already have TA’s bigger valves.
Hi dan. I am just going by my 23 years of flow bench work and porting all kinds of heads which like I posted leads me by eye balling these heads to think that the exh side flow will be the limiting factor in regards to reworking these heads . I could be proven wrong as I progress along and if so I will share the results. Mark. so far the the grinding work I have done on this exh side to get the flow numbers I have posted has been easy and consumed 25 minutes of work not including the valve job. It was detail work that made this happen so if you like I can help you with photos and you can pm me to get my phone number, an we can talk. I have found that many times that is the only way to go because even with great photos your still just looking at something rendered down to 2 dimensions from 3 . Many of the most important part of the port to reshape are compound arc’s. Have you already had the seats and top and bottom angles. ( complete valve job) cut for the up sized valves?
Just for the sake of comparison, here’s how this exh port is doing now as compared to a Dart Platinum iron Eagle 215 CC Small block Chevy head with a 1.60” valve and a highly developed exh port and chamber. The first column is the Dart flow numbers, the second is the Buick. total CFM up to .500” lift with the Dart head = 846. Total CFM of reworked Buick head up to .500” lift = 856. .050”. 28/////28.4 .100”. 58/////48.4 .150”. 78/////73.5 .200”. 100////103 .250”. 113/////125.2 .300”. 130/////145.2 .350”. ////////154 .400”. 165/////162 .450”. ////////166.9 .500”. 184/////169 .550”. 192
Just checked and the exhaust valves I have are 1.55" so this'll be interesting. I hope you're onto something here - I'll be happy to sell them if you are!
I am not sure if the owner has that in mind, but it would be interesting to even get the car onto a chassis dyno for 3 or 4 runs to just dial things in.
They moved both. I like this type of educated flow testing project. Very cool. when my closed chamber 350 heads were designed and completed it took hundreds of hours. In that project they welded up the chambers to create a closed chamber head and then tons of time on intake and exhaust. I will post some pics and flow numbers soon however I wouldn’t be surprised if these heads match my 300 CFM intake alum heads.
Sean I don't think these can go that far . They start out with a very good amount of Intake runner area in from the flange for a 350 cid motor, in fact one could argue that velocity wise they have too much in that respect. The valve bowl however would need be taken up to a throat diameter of atleast 1.800" to attain close 300 cfm@28" and I really do not think the port wall thickness is present to make that happen. Also the size of the Intake valve then needed to complement that throat size would be taking up space where the Exh valve lives. This once again as has been mentioned without going thru the big expensive job of moving the valve centers around. I can see these small block iron heads when max ported hitting 270 cfm on the Intake side and still retaining a safe level of port wall thickness for long term usage, but the Exh side could not keep up with a max ported Intake without some expensive welding to buildup the height of the short turn. It's ashame really because in terms of the stock Exh port in these heads , once your passed the short turn , the main runner of the port has plenty of area to flow a good darn amount more! It's sized percentage wise just like the Intake ports in that regard , a tad too big.
