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Expected boost drop w/ported heads?

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saxmanJJ

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Discussion starter · #1 ·
My car makes 10PSI max boost in cold air with a Vortech V3 supercharger.
Right now I'm on the stock 2V heads but I'm in the middle of rebuilding my motor and am thinking of getting some ported heads. How much, if any, boost drop would I expect in the case of replacing my stock heads with stage 2 ported heads?

BTW, I don't mind the boost drop if it means I'll still make more horsepower - I can always add boost.
 
#2 ·
I would guess 2-3 psi. You wont make more hp unless you install a smaller pulley.
 
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#3 ·
ROFL!!! For reals y2k? Adding ported heads to a blower setup won't yield power gains without changing the pulley?

You might see a minor loss in manifold pressure, but you will definitely see gains over stock heads. No question about it. See where you're at after that and then you can decide whether or not to pulley down for some more pressure.
 
Discussion starter · #5 ·
As for a power gain I would expect 30 to 40 peak rwhp at least, no?

Should make more power over 5000 rpms (where our stock heads seem to be a restriction), no?
 
#6 ·
The stock heads are a "restriction" at pretty much all rpms when under pressure. I would expect the best gains to be in the upper rpm range like 5,000 and up because that is when they are being the most restrictive.

It's hard to put a number on it, but I wouldn't be surprised to see a 20-30rwhp gain at your current pressure. You have to remember that your cams are already helping you out quite a bit over a stock longblock 10psi setup.
 
#7 ·
tbirdscwd said:
ROFL!!! For reals y2k? Adding ported heads to a blower setup won't yield power gains without changing the pulley?
Click to expand...
So explain how it makes more without pulley swap seing the blowing will be moving the same amount of air.
 
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#8 ·
I don't know....explain to me how any other mod that removes a restiction to flow in your engine works. Explain to me how blower cams make more power without changing the pulley size......the blower is still "flowing the same amount of air."

Explain to me how headers make more power over a stock cast manifold. For reals man?
 
#9 ·
The topic of this thread was ported heads. Try and stay on track and explain..
 
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#10 ·
I was running 12psi on my stock block and heads but after I had a built motor with stage 2 heads and cams it dropped to 9.8psi and with the same pulley on the novi I made 70 more HP to the wheels without changing any pullies.
 
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#12 ·
y2k02 said:
The topic of this thread was ported heads. Try and stay on track and explain..
Click to expand...
I did explain in a sense. Anytime you have a restriction to flow in an engine, there can be gains by removing it. This is why people add parts which flow more air. Cylinder heads are one of these components. You are forgetting that for a given cfm that a blower is setup to flow the boost pressure is actually a bad thing from an airflow standpoint. If you can flow the same cfm at less pressure you WILL make more power because it will take less power away from the engine to turn the blower. The more boost pressure , the harder the blower has to work and the more load it will be on the engine it is being run by.
 
#13 ·
y2k02 said:
So explain how it makes more without pulley swap seing the blowing will be moving the same amount of air.
Click to expand...
Blowers are more efficient when they have less backpressure.

With that in mind if you lower the PSI a few without changing a pulley you will flow more air through it. It's like trying to blow up a balloon; As it gets bigger and there is more pressure pushing back against you it gets harder to blow up.

Pressure and air flow are not the same thing.
 
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#14 ·
Cams effect dynamic compression. I gained 78rwhp at same boost level with my custom cams.
Thread not about cams..
 
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#15 ·
y2k02 said:
Cams effect dynamic compression. I gained 78rwhp at same boost level with my custom cams.
Thread not about cams..
Click to expand...
I explained how ported heads will improve performance, you want to explain how they won't help performance on a blower car? Maybe something that is not just a blanketed un-backed up statement?
 
#16 ·
ported heads deff help boosted setups. i stated what power i made with mine and im pretty sure stock heads and cams could not match the power my car puts down at the same boost level
 
#17 ·
OK, engine makes 300rwhp n/a. You add a centri with 10psi with stock heads and now it makes 504rwhp.

Same setup now with ported heads makes 340rwhp n/a. You dont change pulley. Now the boost is only 7.1psi because you removed a restriction after the blower. The blower is still moving same amount of air because i spinning at the same rpm. It still makes 504rwhp.
Now install a smaller pulley with the ported heads to make 10psi and it will make 571rwhp.
 
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#18 · (Edited)
As the air in the intake runners pulse, a less restrictive set of heads will allow more air into the combustion chamber allowing more air and fuel to be burned creating more power,haha. Not to mention a denser charge due to less heat.

Trust me, he will gain power with ported heads, in addition to having more potential down the road.

As far as pressure drop goes, you will see a decrease in manifold pressure. Some have reported up to 5psi on a set of profesional worked heads with a blower. I'd GUESS the typical loss to be around 3psi.
 
#19 ·
y2k02 said:
OK, engine makes 300rwhp n/a. You add a centri with 10psi with stock heads and now it makes 504rwhp.

Same setup now with ported heads makes 340rwhp n/a. You dont change pulley. Now the boost is only 7.1psi because you removed a restriction after the blower. The blower is still moving same amount of air because i spinning at the same rpm. It still makes 504rwhp.
Now install a smaller pulley with the ported heads to make 10psi and it will make 571rwhp.
Click to expand...
Your logic is flawed because you think blower rpm is the only thing that affects how much air enters the combustion chambers. Everything in the intake and somewhat the exhaust track will have an affect on how much fresh air can enter the chambers and be mixed with fuel to be ignited and produce combustion.

Intercooler tubing/routing, throttle body, plenum, manifold, heads, cams, headers/manifolds, and to some effect the mid-pipe and catback will affect overall performance from almost any car including a blower car.

Again, if you can move the same amount of air into the chambers at a lower pressure, you will make more power. Blower takes less power away from the engine to spin if it isn't working as hard to flow the same amount of air, and less heat is produced when the pressure is lower.
 
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