Victor Jr port matching
Originally Posted by DeltaT
Also the geometry might change a bit with the heads on the motor and torqued down. I wouldn't port it based on an off-engine mockup. The block is the master - the heads have to key off of it, then the manifold keys off the heads.
Jim
Jim
In addition, it is OK (and even desirable) to have the port opening at the head larger than the manifold exit, but it is not OK to have the opposite, because then there would be a ledge for the incoming air to hit.
I say desirable because a lip opposite the direction of flow will help prevent or minimize reversion. Based on your drawing the 2 lips on each side would be a good thing, if they match up that well when it is assembled and torqued.
Jim
I say desirable because a lip opposite the direction of flow will help prevent or minimize reversion. Based on your drawing the 2 lips on each side would be a good thing, if they match up that well when it is assembled and torqued.
Jim
well all this reading about major porting required to make it work right got me worried, but look at the overlays, they are pretty good. I suppose there is room to gain on the sides but teh wall thickness to the o-ring groove woudl be really thin, not sure if its worth messing with..........
Originally Posted by DeltaT
In addition, it is OK (and even desirable) to have the port opening at the head larger than the manifold exit, but it is not OK to have the opposite, because then there would be a ledge for the incoming air to hit.
I say desirable because a lip opposite the direction of flow will help prevent or minimize reversion. Based on your drawing the 2 lips on each side would be a good thing, if they match up that well when it is assembled and torqued.
Jim
I say desirable because a lip opposite the direction of flow will help prevent or minimize reversion. Based on your drawing the 2 lips on each side would be a good thing, if they match up that well when it is assembled and torqued.
Jim
Bret
Originally Posted by SStrokerAce
Jim, actually the air doesn't even care if there is a lip because the intake is larger than the head port. It's a goofy situation but it works due to the fact that the tuining pulses of the motor like it better.
Bret
Bret
I would like to believe this because on a NA engine the air should be sucked into the heads rather than being pushed in. Is that what you're getting at, Bret?
If there is some mismatch.. say a 1/16 edge exposed on the cylinder head lkeading edge... what do you think the cost might be? Is there any way to quantify that? Not trying to dig too deep into any secrets... just trying to understand your thoughts in this.
Even on a NA motor air is never sucked in - it's pushed in by atmospheric pressure.
I have some aviation engineering books here that talk a lot about air movement past edges, proper forming, optimizing and stuff and a square edge is NEVER the best solution.
I'll stand by my original statement: If the head port inlet is larger than than the intake manifold outlet, that's OK, and may help stop reversion. If it's the other way around, it's bad and should be dealt with.
Jim
I have some aviation engineering books here that talk a lot about air movement past edges, proper forming, optimizing and stuff and a square edge is NEVER the best solution.
I'll stand by my original statement: If the head port inlet is larger than than the intake manifold outlet, that's OK, and may help stop reversion. If it's the other way around, it's bad and should be dealt with.
Jim
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It's called the boundry layer... the air makes it's own cushion. Plus you guys are only looking at one thing here, not the whole game. It's not all about airflow in CFM it's about wave tuning as well.... you can hurt the CFM and help the wave tuning and make more power, i've done it before and it really suprises you on the dyno. (BTW this is the key to really understanding motors, it's the system that makes the power not one detail)
Now you will not see this in most cases but when you run in classes that state your head port must be in this spot x.x inches from the deck, x.x from the valve cover rail, x.x from each other, x.x from the end etc... you get the point they tell you where and how big the port opening can be on the head. Now when you do not have limits on where the intake manifold port placement can be or size there are times when the intake manifold tuning wants a larger cross section for the intake manifold, so you put it there. The conventional thinking was this will not work, but obviously someone found this by mistake and tried it out to see what it will do, and it worked. We are not talking about a street or your standard strip motor here, this is in 2.3+ hp per cube range that this was found and worked.
If you don't think outside of the box you will never find anything new. Read some of of the things McFarland and Sperry say on runner cross section and lengths and how that effects intake manifold tuning. A good place to start would be here... http://www.n2performance.com/
CHarris, 1/16 would not be off the mark at all. Say you did that on every side of a race manifold it could increase your CSA of the intake port by 10%, which would help move the TQ peak of the motor up higher, that is if you were trying to do that sort of thing. ;-) Hope that answered some questions here. It's good that you guys question that statement I made, but there is a reason I said it.
Bret
Now you will not see this in most cases but when you run in classes that state your head port must be in this spot x.x inches from the deck, x.x from the valve cover rail, x.x from each other, x.x from the end etc... you get the point they tell you where and how big the port opening can be on the head. Now when you do not have limits on where the intake manifold port placement can be or size there are times when the intake manifold tuning wants a larger cross section for the intake manifold, so you put it there. The conventional thinking was this will not work, but obviously someone found this by mistake and tried it out to see what it will do, and it worked. We are not talking about a street or your standard strip motor here, this is in 2.3+ hp per cube range that this was found and worked.
If you don't think outside of the box you will never find anything new. Read some of of the things McFarland and Sperry say on runner cross section and lengths and how that effects intake manifold tuning. A good place to start would be here... http://www.n2performance.com/
CHarris, 1/16 would not be off the mark at all. Say you did that on every side of a race manifold it could increase your CSA of the intake port by 10%, which would help move the TQ peak of the motor up higher, that is if you were trying to do that sort of thing. ;-) Hope that answered some questions here. It's good that you guys question that statement I made, but there is a reason I said it.
Bret
Bret, would it be possible to say the head port opening being larger could cause some issues as well? I would think that having a tight intake runner into a loose head port, there may be a stalling, like pressure drop, where as the incoming air might tend to swirl behind the ledge and disrupt airlfow. Just thinking outloud. Glad you explained the opposite though, good knowledge meaning good power too.
Originally Posted by DeltaT
Also the geometry might change a bit with the heads on the motor and torqued down. I wouldn't port it based on an off-engine mockup. The block is the master - the heads have to key off of it, then the manifold keys off the heads.
Jim
Jim
Yeah there could be issues like that due to the area change. The real deal is when you have a well ported head and the cross section of the head casting is larger than the intake, you can have a smaller intake manifold opening that doesn't disrupt the flow but in that instance you might as well fill the floors of the head port as well because if you are reducing the cross sectional area you really don't need that area to make the motor work where you want it to.
Bret
Bret
I love the internet. 