View Full Version : Do heads need to flow for a supercharger?

12-13-2004, 05:24 PM
I'm planning on building a 383 with aluminum heads (phase 1). For phase 2 I'd like to add a supercharger. I'm wondering if I need to be concerned that the heads flow the absolute best when at some point I'll be adding a blower.

My manifold is a TPIS mini-ram. I also wondering if I need the larger throttle body if I'm going to add a blower. Thanks!

12-13-2004, 06:34 PM
Turbo and supercharged motors are not as sensitive to porting and camshafts as a N/A motor. There is so much positive pressure on the intake side that a head will flow much more then when flowed. This doesn't mean that working the head some more won't give you some more power!! The first thing you need to do is establish a power goal. Once that is determined you can calculate if the parts you have will get it done. Go from there!

One area to look at if you do port the heads are the mid lift #'s. Also don't stuff a cam with too much duration as it will blow to much of the boost pressure out the exhaust. Lastly keep the lift reasonable. It will provide longer life to the valvetrain!

12-13-2004, 09:13 PM
The heads will definately benefit from work, especially on the exhaust side, since you now have a much greater volume of exhaust to expel. Go for as great of an I/E ratio as you can and concentrate most of the work on the exhaust side, but by all means don't forget the intake ports! Better flowing intake ports mean less backpressure for the supercharger to work against; this is a benefit and will make more power.

Throttle body isn't as much of a concern, since you'll be shoving air through it. Same rules applies as for N/A motors, as you go smaller the response will increase as velocity goes up. Don't go too huge, but don't go too small either. I'm running a 75mm monoblade on my setup and throttle response is phenomenal when the engine is under load. With the TPIS miniram I'd venture to say a 52mm (780 cfm) would be OK for up to 750hp and probably more, but a 58mm (1000 cfm) wouldn't hurt much either. I wouldn't go bigger.

Also, if you want to see the maximum benefits expect to do a SC-specific cam swap for your "stage 2"; a SC-specific cam will build boost sooner as they typically have wider LSA's and less overlap than N/A cams.


12-14-2004, 07:03 AM
Im currently having a new pair of cylinder heads worked for my 490 inch Pontiac that will get a Vortech YSi. This is going to be a street engine, so the max boost will be just over 10 pounds. The intake port volume will be increased quite a bit while the intake valve will only grow in size slightly. The exhaust valve will grow as well, but the exhaust ports will be worked to flow in the mid 80% range of the intakes. In a normally aspirated exhaust flow in the mid to upper 70% range is more the normal ratio. As has been mentioned, keep the cam on the tame side. Wide lobe spacing (114-116) helps keep the boost in the cylinders.

12-14-2004, 08:25 AM
With forced induction applications, heads do not have to necessarily flow all that well. Perfect example... the LC2 motor in the GN's and TTA's. Some of the most absolutely horrid flowing heads on a performance application ever created.... but they can make stupid power with simple upgrades on stock heads, all due to having that little hair dryer on there. Granted yes, with better flow rates, you WILL gain more power, but it's not really critical until you start looking to pull every last ounce of power out of a motor that you can. As far as a cam goes, as was stated above, keep it around a 114-116LSA. But you might want to consider using a reverse split cam (more exhaust duration than intake). These cams seem to do VERY well on any type of forced induction car, and it doesn't take an extreme cam design to make great power either.

12-14-2004, 10:31 AM
Flyboy, having owned a TTA myself I can say that you're right. You can do impressive things with the stock longblock. However, you can make more power at lower boost levels with better heads on the car, simply because the turbo won't have to work as hard to shove air in, and the pistons won't have to work as hard shoving the exhaust out of those restrictive exhaust ports.

Most GN/TTA guys don't bother with the heads because they like the bragging rights associated with "fastest stock longblock" and it's been proven time and time again the stock heads and cam can carry the cars well into the 11s. However it would serve them well to put a better set of heads on the cars (port the stockers, move up to GN1's, etc) then they could make more power at less boost; and less boost means less charge air heating and reduced chances of detonation.

Up to a point, you can simply bump up boost to overcome poor head flow, but it's really only a "crutch" and a cover-up for the real problem of poor flow.

12-14-2004, 05:12 PM
Blown353 hit the head on the nail. While you don't need to have the greatest flowing heads for a FI car, the more air you get through your intake system more effeciently is something to pay attention to.
With better flowing heads you will make the same amount of power(or more) as you did with the old heads, but with less boost. This allows you to run more boost for even more power, but more importantly you get a cooler intake charge.
If you want a really effcient powerful FI engine, getting your heads, intake manifold and inlet piping to flow as effciently as possible will make gobs of torque with a cooler intake charge and less boost.
And to me, anytime you can more more power with less boost....is good.

12-14-2004, 06:44 PM
Thanks for all the responses!

02-17-2005, 06:06 AM
Just remember, BOOST is a measure of RESTRICTION. For a force air engine shoot for a 90% I/E ratio and run a single pattern cam with 112-114 LCA. If you are running a Vortech style supercharge you can run a cam that about 10-15* less duration than you would for an N/A engine and your peak HP/TQ rpms will still be higher than an N/A engine. My little 3.8L ford made peak HP @ 4700rpm TQ @ 3600rpm N/A and with nothing more than a Vortech V1 the Peaks moved to HP @ 5900rpm and TQ @ 4400rpm

DB Z28
02-17-2005, 07:57 AM
Valve size and seat bore size has more affect on SC or turbo engine than a good port job . But if you add a good port job with valve job, blending intake to the head all adds up to get more air to the engine is still the best.

Roadrage David
07-26-2005, 09:31 PM
if you have a properly prepeard block with a outstanding big bore to smal stroke ratio good for lets say 7000 rpm can the vortec ore ati procharger runn with this without problems for longer periods of time ??