Fairly new Buick guy. But all in. Having the 462 BBB short block freshened . So looking at the heads while waiting. TA Stage 2 SE. Noticed such a difference on the exhaust end. Kinda crazy. It's oval on one side and flat on the other side. See the pictures. I'm just trying to have some street strip fun. But I believe that there's some exhaust flow there. I spoke to someone who supposedly knows Buicks and he told me to leave it alone. But there's so much meat there! Anyone knows better ? Thanks.
You do not have the needed info in your head to guide your thought process the right way. In short, just leave it the way it is, but just to cover the details, here's why. The reason for this is 3 fold. 1) that straight section of the Exh port within 1 to 1.5" on back into the runner is not the main restriction. The main area of restriction is deep in that runner at the curved area and back down to the throat of the valve bowl. 2) when your header Exh tube is a tad larger the the area at the heads Exh flange the air flow above .300" lift picks up anywhere from 3 to 5%. This can be clearly seen when conducting a flow bench test. 3) that mismatch between your header and the flange area cuts back on Exh reversion. This reduction allows the motor to come on the Cam sooner and make more low speed torque. In short you benefit from a wider power band.
I guess we're going for it. Heard what everyone said. About low end torque and all. Low end torque from what we know is not a BBB issue. We figure a little clean up is really right. I'll let everyone know how it turned out once I get the short block back and put everything together.
Crazy. Never ever seen this. So. Some exhaust ports are round. And some. Not. But factory stage 2. Which everyone knows were rare. In any case thanks for the input. Just curious. Do you think we're correct or not
Personal opinion, for the small amount you're changing for the sake of matching, I don't really see any benefit or deficit. If you were to dive deep into the ports with reshaping, there might be measurable differences, not necessarily for the better since it goes against TA's R&D. The only deficit with what you're doing at this point would be losing the anti-reversion feature you might have had if left alone, but I don't know if even that would be measurable. In my opinion the only major change is going to be loss of personal time. Devon
Certainly no goin back now......but tbh Youre doin them no favors...and yes BBB can have TQ issues...common misconception..you can destroy low speed tq with the wrong components..and push it up to close to 5k b4 peak happens....im with Devon...i dont see any detrimental damage done..but its moot now
Unless youre running forced induction..or N20 theres no real gains to be had on the exhaust side of a performance head in most apps....the piston is pushin it out...same as why a big ass exh valve often times just gets in the way
It’s not just about torque, it’s about about the level of average torque being made in the rpm band the motor is running in. The better the average torque numbers the faster the motor will recover rpm after a shift. In terms of those exh ports on those stage 2 heads I can flat out guarantee you they had a lot of flow development put into them!!! What’s being commented on in this string by people who have zero flow bench time is totally miss founded and proves lack of flow dynamics knowledge. The reason for the D shape on what is the cylinder wall side of each exh port is there to take maximum advantage of the way that exh flow exits the cylinder into the valve bowl and then wants to stay on that outside wall and the roof because it’s the path of least resistance. Velocity probing thru the whole length of a exh port top to bottom in a non Hemi type head like these shows this very clearly! Once a exh valve in a wedged shape chamber like these heads have is open to about .350” lift the greatest mass of exh flow is coming from half the diameter of the exh valve and on over across the intake valve side of the cylinder and chamber. To achieve maximum flow numbers this condition needs to accommodated by the shape of 1) the valve job. 2) the shape of the exh bowl and the direction it’s floor kicks off to. 3) the shape and outer port wall angle of the rest of the exh port out to the flange. Here’s 2 crude drawings I made to show why this is so then maybe some folks will then understand that there notions in there head be it about exh or intake flow are very misguided . One drawing here is as looking down thru the cylinder and viewing the chamber. The other is as looking at a Horizontal cut away of the head. also here’s a picture of a idealized nozzle type exh port. Only with a very straight line exh port like this is a near fully round shape at the flange not going to harm things, in fact even with this nozzle shape the floor at the flange is still very much flat. PS The piston rising up from BDC is far from the start of exh flow. In a non race motor when the exh valve pops open at BDC there’s still about 125 psi left in the cylinder. In a well developed race motor that due to its hopefully higher compression, ( is there for more thermally efficient ) there still maybe some 90 psi left just waiting to jam out the exh valve at low lift. Good low lift exh flow takes full advantage of getting some exh out while the exh port is not saturated with flow as it will be later in the exh cycle. getting a good start of the exh flow out of the motor also means that the piston has less resistance on its way back up the bore and this then means that less torque from the other cylinders that may be firing is used to drive that piston up on the exh stroke. This then leave more torque available to rotate the crank which is the main goal. The gas heat that’s left in the cylinders if very far from making any contribution to power, and the more of it you get out faster helps the whole engine to run cooler.
Doesn't take a flow dynamic professor to know opening that port exit does nothing and that its past the restriction ie the turn...so not sure where anyone said anything to undermine your devine knowledge on the subject
Here’s what todays pro stock heads are like in terms of the extremely tall short turns needed to handle the huge air mass making it’s way thru the port to make over 1200 Hp in NA form with only 500 cid. note worthy is besides the short turn height is how consistent the port area is. In terms of iron factory Buick heads and many other heads that due to the needs of low hood lines in cars, the short turn height is truly minimal when you access the port in a geometric way. This in turn means that with stock heads that small changes in the the shape , width and arc’s used , and the valve job used to form the short turn can make for good changes or bad changes in terms of flow numbers real quick. Most novice’s diving into bowl porting there heads go right to the place where the most harm can be done in terms of the as stock flow numbers. They fire up the grinder and kick right in to reshaping that terrible looking short turn into what to there eye seems like a far more air flow promoting curved radius with harmful effects then taking place that can’t be reversed unless a bigger valve can be used and or a epoxy repair is done, and this is only applicable to intake ports on iron heads.
