With all the comments here I should not be posting BUT, shouldn't has never stopped me yet. As Jim pointed out a 350 Buick is what it is (3.8") bore. It is not a SBC or SBF, but there are sone things to look at and I think Sean is in the right direction. What other engine has 3.8" bore and after much work and refinement proved to be a strong runner? Yes it's a Buick. We are limited by bore size which in turn limits valve size and then we do not have a killer intake. So in my mind, (I don't care what others think) to build a killer race engine you would need to go turbo or supercharger. Or if you are inclined NOX. I have got invloved with the 350 Buick because I was building a car to teach my wife and step-daughter to drag race. I bought a 67 GS new and have raced Buicks since mid 90s. I mainly run BBBs. I built a 83 Regal to use for my wife. I had a mild 455 in it but soon realized with the torque of the 455 that it would scare the girls until they got some seat time. With the 455 it ran low 11s @ 120mph. Since I was running a stock suspension without an anti-roll bar the left front wheel 2' in the air on launch and a tendency to pull right was not what the girls needed. So, I got the idea to install a 350 buick in the car to make it more driviable for the girls. The project got more involved than I planned but the result was a 12.50 car @ 110mph that was easy to drive. I just did the usual to the engine and was pleased with how it ran. I think it will go in the 11s with some more tuning and a better convertor. Could I have went faster for the same money with a SBC or SBF? Yes, but I was faster with a BBB that did not cost as much to build as the 350. So to use a 350 Buick, it just has to be something you want to do. From a truly et vs dollar comparison, I could have went faster for less, but I wanted to build the Buick. I don't think we have to fight about it, if it's something we want to do, then have at it. Jim N.
I am understanding more about how heads will make more power. You want good flow but up to a certain point, then there will be too much velocity, thus causing turbulence. I wish I knew what the guy who built my engine I purchased from a board member had done to the heads. We do know there are larger than stock valves in it 1.88 intake 1.5x exhaust. Just took quick measurements. I will be very happy if 12.75-12.99 is achieved. 13.00-13.50 will be ok with me as I know some tuning and suspension might get me to my goal. We'll definitely find out when e-town opens.:grin:
Take a look at this link,it should help you understand more clearly why as flow goes up,velocity can only be the same or go down; http://tictac-4g15.blogspot.com/2012/01/head-flow-vs-velocity.html I hope this helps.
As a side note... It would be almost impossible to ''over-port'' a 350 Buick. The cathedral style ports of the 350 SBB help keep velocity high even as the flow gos up:TU: Thats why GM uses cathedral-ports on most LS engines, you can have huge flow numbers and not lose low-end torque:idea2: And Buick figured that out 30 years earlier:laugh:
Exactly,finally some one got it! And just a minor correction, Buick figured it out 45 1/2 years ago, 68s came out the summer of 67 when the 350 was introduced. It only feels like 30 because time flies when your having fun driving a Buick. Nyuck Nyuck Nyuck
Gotcha,that makes more sense,I think they came out around 98,so yeah 30,your right,it was late last night when I posted it.LOL
all these years i had 6 sets of heads ported by different porters and spent thousands of dollars. now i learned i can port them myself, just go in hog them out as much as i can and go fast.:3gears:
Go ahead and try it,but you probably won't like it,unless you're a well digger looking for water.:shock:
Here is some info about porting the Buick 350 head. There is a lot more to porting than just hogging out material, it is an art and overdoing it in the wrong spots can kill performance. http://www.v8buick.com/showthread.php?120529-350-head-project&highlight=heads As stated above, let just say we have a set of very well ported heads and we are using them with a mild low compression engine for a street car with a RPM range from idle to 5000 RPM. The ported heads will perform better in all RPM compared to stock un ported heads. That being said, if a set of heads is heavily ported but not by a pro then there are good chances that there will be a loss in performance. I recommend either paying a pro to do it right, or just smoothing things out yourself and not going too extreme if you do it yourself.
I have The Block Shop do my block work I do my own porting,flow testing(i own A JKM bench) and all my own assy Nick
It's not so relevant to SBBs due to the limitations on how large you can go, but in general a larger diameter cross section in the port and intake runner will reduce the velocity of the air in the runner. That air is stacking up behind the valve when it is closed, and rushing in when it is open so the higher the velocity and the longer the runner, the denser the charge, and this was the theory behind the old cross ram intakes. So it isn't just a matter of port flow, since runner tuning can have a far greater impact on how the engine runs at a given speed, but port size is a part of it and is very important. It is the choke point at the end of the trumpet. So the first task is to decide the desired operating speed range and optimize the intake runners for that range. Then the port work can be done to match the intake. As an extreme example, a very small, long runner dumping into a very large port will dissipate a large part of the momentum gained in the runner, wasting the kinetic energy of the charge in just filling up the port. By contrast a too small port will restrict the charge. But one that is just right *at the selected speed* will pressurize the air behind the valve to the maximum attainable by the momentum and mass of the charge in the runner just in time for the valve to open. Timing is everything of course so as the rpm goes up or down cylinder filling becomes less effective. So yes, you certainly can over port a head, at least in theory and certainly with some engines in practice, although it is far more common that the intake runners are just too large to ever develop any momentum at lower engine speeds. But the SBB is probably not one of them. Jim
On a similar note: The Buick 350 is an induction challenged engine that requires a larger than expected carb due to the fact that it takes some extra air and fuel to reach the potential of the engine flow and power. An engine that has better flowing heads and intake requires less carb CFM to hit a given HP. For example the 455 with well ported iron heads requires about 1300 CFM of carb to perform it's best where as the same engine with better flowing aftermarket heads only needs about 1000 CFM to reach it's peak HP. So my point with all this is that the Buick 350 loves a large carb when using a stock or TA intake... Just removing the restriction of the intake manifold by going with a custom intake set up for the application he can gain leaps and bounds over the potential with the existing intakes.
The 3.8" bore is not the big blame, for underwhelming head flow. Anyone been around a 3.8" bore, Stage II V6 ? Millions of other engines with smaller bores, have very respectable flow rates/velocity. To quote Jim Ruggles, "We've been using ported versions, Stage II heads, on a 3L.(183"), V6, and it pulls like an electric motor". Not just the sqauare inches/cc's, in a port, more importantly the shape. I suggest David Vizards, "How To Port and Flow test". Lots of valuble information. Onward, roverman.:Comp:
Good point Art, but of course those heads have considerably more room for porting. One note about the carbs, the flow rating for 4 bbls is done at a specific pressure drop across the carb of 1.5 inches of vacuum, and curiously enough, 2 bbl carbs are rated at exactly double that figure which kinda explains the seemingly high rating on some 2bbl carbs. But the point is, the more intake restriction the less the flow *of the carb*! So for example if you have a pressure drop of an inch through the intake, ports and valves, that 750 cfm carb may only be capable of flowing 500 cfm wide open. You have to look at it as a system, not just as individual pieces, and the volumetric efficiency, cam profile, intake, and even exhaust tuning has a tremendous influence. Here is another way to look at it. 350 cid engines are often stated as needing 600cfm at WOT and redline. A 600 cfm carb at standard 1.5 in. pressure drop will flow that much. But that means you have a better than 1.5 in. restriction in even the most free flowing system. A 750 cfm carb is going to have a noticeably lower pressure drop at 600 cfm so the overall intake restriction is going to be less and the result will be a denser intake charge and more horsepower. So the only reason we don't put the biggest carbs we can get on the engine is so we can drive it at anything below racing speeds. The 1.5" standard provides a reasonable balancing point, but it is still just an arbitrary number that gained popular support. A guideline in other words, and a means of uniform ratings. But it doesn't mean you can ignore the other intake restrictions in determining what carb will make the engine run best at the desired speed. Jim
Well at least this thread got to degenerate into arguing instead of anyone actually posting helpful first hand experience on what they did to make their SBB run better. :af: The worst thing about it is that it only hurts the Buick community in the long run because anyone who actually thought they might read this and get some useful info will just read it, figure their SBB is a pile of crap and swap in a Chevy motor and thus have no need for Buick performance parts.
Well, personally I have learned a lot about porting and how it affects an engine from this thread even though a couple of members got into it a bit. Essentially I think they basically agreed with each other, just not the terminology:grin::grin:gy
