[Marty Palbykin]

Originally Posted by 65nss4spdGTO

So what I'm hearing, it doesn't matter what cylinder head is used?

For discussion purposes, I picked 455ci, not planning to use a stock block for the level of power, but more about the ci.

The recipe is: Aftermarket Pontiac block with 3" mains. 4.000" stroke, 4.250" bore, just under 455 ci. Now here are the three head choices, lets assume they all have high quality valves and hardware, the all of the same 10 head bolts, 1 cast iron, 2 casted aluminum. This is a wild street car with a goal of 1250 HP to 1500 HP.

Head 1
Cast Iron, 2.150" x 1.750" valve package, 2.600" CSA at entry, flows 275/220 CFM @.600" lift.

Head 2
HQ casted aluminum, 2.200" x 1.750" valve package, 3.000" CSA at entry, flows 350/265 CFM @.700 lift.

Head 3
HQ casted aluminum, 2.250 x 1.700" valve package, 3.600" CSA at entry, flows 430/285 CFM @.800 lift.

All heads have the same EIIEEIIE layout, uses shaft rockers, they all must use a version of the Edelbrock Victor manifold ported to match each cylinder head with EFI.

What are the pros and cons with each cylinder head, lets hear your thoughts.

Thanks.

Calvin Hill
Hill Performance
708-250-7420

Calvin, A out of the box e head on stan sheldon's 1961 cat made well over 1200 hp at low boost. Unported head and manifold.
My recomendation would be a 3.00 main on a 3.75 stroke long rod of course.
Marty P.

[Travis Q]

Calvin,

For this project I would choose head 1, but in aluminum for the weight difference and for better management of combustion chamber temperatures.

Head 2 is essentially the same head that is currently on the Tempest. CSA is close, valve sizes are close, flow is essentially the same.

In my opinion head 2 and head 3 are overkill for the application, and would be a waste of money for this package. They are simply not needed, and with CSAs that large would probably give up some street manners with a smallish engine like this one.

Turbocharged engines at this power level are just not very sensitive to cylinder head. Spend the money, effort, and brain power where it matters.

[BruceWilkie]

Hot Rods F-Bomb twin turbo 406 sbc by Nelson...

Made 1502 hp at 5600 rpm 28.5 psi

At 6000 rpm 18.3 psi it made 1165.

On 91 octane pump gas at 5800 1025hp 14.6 PSI

Compression is 8.96
Cam Solid XE 276 street roller (4873) lobes 236/236 @.050 115LSA(about .600 net lift)
Air/Air intercooler.

Heads were Brodix 11x

Brodix11 2.08 valve

.200 133
.300 191
.400 235
.500 272
.600 283
.650 284
.700 285

That should give you an idea of csa.

If this is E85/or race gas and a/w intercooled he can likely run to near 30 psi for 1500 hp. with a head similar to that Brodix. Being bigger ci the rpm for peak power would be lower.(If using same sized turbos as nelson example) Probably real close to 13% lower rpm.

Pump gas even with water meth and a/w intercooler, the intake temp needs to be lower than E85 or c16 to minimize preignition risk.
So you increase volume and flow capacity of the heads/intake to lower boost PSI without losing mass flow. The charge temp drops from the lower boost PSI. Keep in mind boost is a measure of restriction to flow.

Turbos are sized to lbs/min air flow required at a given pressure ratio. Hot air at 30 psi can be cooled to lower psi(lower pressure ratio) and still move the same or greater air mass if the turbo can deliver it.

Head 3 is overkill for only 1500 HP IMO

Borg Warners matchbot, though applicable only to BW turbos, is quite good.
here's one to play with...(ignore some of my inputs..I was just playin) http://www.turbodriven.com/performan...6_wrsin=92044&

alter the ve inputs ... the tutorials at the bottom and the ? marks to left of inputs will guide you through. The ve inputs should give you a good idea of your head flow requirements.

[65nss4spdGTO]

Ok,

So it sounds like 1250 HP is a walk in the park.

Calculate the boost requirement for each of the heads listed, also calculate the boost requirement for 1500 HP.

At what RPM is peak HP?

Calvin Hill
Hill Performance
708-250-7420

[Travis Q]

The boost requirement for each cylinder head will be the SAME. If the cylinder head has enough capacity to make 600-650 naturally aspirated horsepower, then any more cylinder head will not do anything at all to make more power, regardless of boost level. Mind you, this statement refers only to ths particular sized engine with a reasonable rpm limit (under 7000 rpm).

I have to giggle to myself any time someone regurgitates that old internet BS..."bigger heads make more power with less boost".

HORSE FEATHERS. Not on a street turbo engine, they don't. Ive seen it done on the dyno and at the track. It's a MYTH.

Race engines are a different story, but only a little bit different! And blower motors are a whole 'nother card game, and cylinder head selection has a HUGE influence on those things.

Peak power rpm is going to be a function of camshaft. Which is a function of backpressure. Which is a function of the turbo used...and since this is a pretty large engine for this power level, it's really safe to assume that relatively small, quick-responding turbos will be used. That means high backpressure, no way around it (but not the death knell that many would have you believe). And high backpressure means you'd better keep the cam small or your intake manifold is going to look like the inside of a coal mine, and engine power will suffer.

Id bet a 450-460 inch engine at 15-20 psi is going to be pretty much all in by 6500 or so with street oriented turbos and cams that follow suit. A race setup would push that up to about 7200 or 7400 but not much more than that on gasoline.

EDIT:
Boost for 1250 hp is going to be around 13-15 psi if the engine is intercooled. 1500 hp will come at 20-22 psi. This is based on 455 inches, 6500 rpm, and 100 degree charge air temps.

[65nss4spdGTO]

Originally Posted by Travis Q

The boost requirement for each cylinder head will be the SAME. If the cylinder head has enough capacity to make 600-650 naturally aspirated horsepower, then any more cylinder head will not do anything at all to make more power, regardless of boost level. Mind you, this statement refers only to ths particular sized engine with a reasonable rpm limit (under 7000 rpm).

I have to giggle to myself any time someone regurgitates that old internet BS..."bigger heads make more power with less boost".

HORSE FEATHERS. Not on a street turbo engine, they don't. Ive seen it done on the dyno and at the track. It's a MYTH.

Race engines are a different story, but only a little bit different! And blower motors are a whole 'nother card game, and cylinder head selection has a HUGE influence on those things.

Peak power rpm is going to be a function of camshaft. Which is a function of backpressure. Which is a function of the turbo used...and since this is a pretty large engine for this power level, it's really safe to assume that relatively small, quick-responding turbos will be used. That means high backpressure, no way around it (but not the death knell that many would have you believe). And high backpressure means you'd better keep the cam small or your intake manifold is going to look like the inside of a coal mine, and engine power will suffer.

Id bet a 450-460 inch engine at 15-20 psi is going to be pretty much all in by 6500 or so with street oriented turbos and cams that follow suit. A race setup would push that up to about 7200 or 7400 but not much more than that on gasoline.

EDIT:
Boost for 1250 hp is going to be around 13-15 psi if the engine is intercooled. 1500 hp will come at 20-22 psi. This is based on 455 inches, 6500 rpm, and 100 degree charge air temps.

Travis,

Thanks for clearing that up. Having limited experience in this area, I appreciate your insight.

Since we have discussed this regarding Turbo's, how is a blower different? I was really expecting to hear comment from Tom V, maybe he can chime in now.

Calvin Hill
Hill Performance
708-250-7420

[Travis Q]

I'm sure Tom will give his input, and it will definitely be worth taking in.

Blowers, specifically centrifugal blowers, differ from turbos in that they do not have a wastegate. That is, you spin the blower by way of the pullies to a specific shaft speed that you want, in order to achieve a certain power level. More engine power requires more air, which means more shaft speed.

If it takes more boost to achieve a certain amount of engine power, there are some very definite negatives that go with that increased boost. First, centrifugals usually have a good bit more clearance between the impeller and housing than turbos do due to their heavier impellers and transmission/shaft system. This means that when you increase boost pressure, you also increase the losses that occur around the impeller wheel. This results in higher air temperatures due to recirculation of previously compressed air. This hurts power. Second, as boost increases, so does the amount of input work/energy required to compress this air. Now, both turbos and blowers require this work input; the difference is that the energy that turbochargers use to compress the air is in excess; if a turbo is wastegated to produce, say, 15 psi, then there is an excess of energy available to spin the turbo. We're throwing usable energy away out the wastegate. A blower is not this way....more boost means more shaft work required, and that shaft work comes right off the front of the crank.

So, it starts to become easier to see that the name of the game with a blower is to let the blower be an air mover, and not an air compressor. This means that we will want to spin the engine higher rpms to move more air; this requires more cylinder head. This way, the engine "uses up" more of the available air supplied by the blower, and the boost is less. Then, pumping losses are less, air temperatures are less, and shaft work required is less.

Turbos just don't have the losses, in terms of air temp, pumping losses, and shaft work requirement (the kind that detrimentally affects engine power). Their engine speed ranges are lower, so cylinder head requirements are lower.

Again, these are generalizations to a certain degree, but hold very, very true for moderate power applications in street oriented setups.

[v869tr6]

Travis, its very nice to have your input on the forum, thanks for sharing! Couple of questions, do you think a 1.75" to 2.5" log manifold will hold back performance with a out of the box E-head? And what would you use for a cam with a 88mm turbo and 4.5" stroke 488 street / strip / dragweek car?
Thanks Ed

[Tom Vaught]

Originally Posted by Travis Q

I'm sure Tom will give his input, and it will definitely be worth taking in.

Thanks for the compliment

Originally Posted by Travis Q

Blowers, specifically centrifugal blowers, differ from turbos in that they do not have a wastegate. That is, you spin the blower by way of the pullies to a specific shaft speed that you want, in order to achieve a certain power level. More engine power requires more air, which means more shaft speed.

Roots (old school 6-71, 8-71, etc) and Screw Type Superchargers (Whipple and Lysholm) are definitely blower rpm limited. Maybe 6000-8000 rpm on the old Roots stuff and maybe 14000 blower rpm on the Old Eaton GM/Ford production type units. The Lysholm & Whipple units can run in the 18000 blower rpm range. So if the engine runs 6000 rpm you can basically speed the units up to 3 times the engine rpm or in the Whipple supercharger case 18000 supercharger rpm. Any more than that, the cases/gears get too hot and they have mechanical issues. Centrifugal superchargers can live forever in the 40,000 rpm range and can have good durability up to about 55,000 rpm. 62,000 rpm you better have a couple of spares in the trailer.

Originally Posted by Travis Q

If it takes more boost to achieve a certain amount of engine power, there are some very definite negatives that go with that increased boost. First, centrifugals usually have a good bit more clearance between the impeller and housing than turbos do due to their heavier impellers and transmission/shaft system. This means that when you increase boost pressure, you also increase the losses that occur around the impeller wheel. This results in higher air temperatures due to recirculation of previously compressed air. This hurts power. Second, as boost increases, so does the amount of input work/energy required to compress this air.

A good friend of Travis and I, (Dave Austin), gave me a spreadsheet one time that allows you to figure out how much horsepower it takes (either off the crank or from the exhaust energy to move move 1 lb of air mass thru the engine. The spreadsheet says it take .9 horsepower (input work/energy) to move 1 lb of air mass thru the engine. Air mass allows you to make a given horsepower from the engine. 1 lb of air mass thru the engine will make between 9.5 and 10.5 horsepower. So in simple terms if you want to make 400 horsepower, you need 40 lbs of air mass going thru the engine. That same spreadsheet tells me that if I want to make 1000 horsepower I need 100 lbs of air mass. Simple enough on turbos and superchargers so far.

But now lets talk about using a centrifugal supercharger driven by a belt specifically.
Ok the turbo makes 1000 hp at the flywheel with 100 lbs of air mass. To move the air thru the engine (with the turbo) we used available exhaust energy. The centrifugal supercharger driven by a belt unfortunately does not have that available exhaust energy driving the supercharger. It needed to make more than 1000 horsepower from the engine, it had to make 1095 horsepower because it took 95 horsepower (input work/energy) to drive the supercharger to compress the air and still get that 1000 hp at the flywheel.

So again another rule of thumb: to move 100 lbs of air mass thru the engine, it take about 100 horsepower. In the turbo's case we are using energy normally going out the exhaust pipe so little change in the crank hp and with the supercharger we are robbing the engine of 100 horsepower at the crankshaft to move the air. Changing ONE NUMBER in the spreadsheet (the boost pressure) to 25 psi says that the engine now needs 40% more (input work/energy) to drive the supercharger whereas the Turbo still has an excess of exhaust (input work/energy) available. So to cut to the chase, You bolt on a supercharger you basically give up 100 horsepower at 15 psi to move 100 lbs of air mass thru the engine. and will actually make 900 hp at the crank. You step up the boost pressure to 25 lbs of boost pressure and you now give up 140+ horsepower from the engine to move 100 lbs of air mass at the higher pressure thru the engine. So in reality you have to actually are making around 850 horsepower at the crank.

Why the higher boost pressure? The difference being maybe in one case you have nice big ports (which allow more rpm as Travis said), so you are not having to compress the air charge as much and can move the air mass at only 15 psi gage pressure. In the second case, with less efficient ports, you might see 25 psi on the gage for the same air mass thru the engine at the lower rpm.

Originally Posted by Travis Q

Now, both turbos and blowers require this work input; the difference is that the energy that turbochargers use to compress the air is in excess; if a turbo is wastegated to produce, say, 15 psi, then there is an excess of energy available to spin the turbo. We're throwing usable energy away out the wastegate. A blower is not this way....more boost means more shaft work required, and that shaft work comes right off the front of the crank.

Agree!

Originally Posted by Travis Q

So, it starts to become easier to see that the name of the game with a blower is to let the blower be an air mover, and not an air compressor. This means that we will want to spin the engine higher rpms to move more air; this requires more cylinder head. This way, the engine "uses up" more of the available air supplied by the blower, and the boost is less. Then, pumping losses are less, air temperatures are less, and shaft work required is less.

So basically you can move more lbs of air mass per minute thru the engine by increasing the engine rpm but maintaining the lower supercharger rpm and be more efficient vs keeping the rpm low and spinning the supercharger much faster to get the same air mass Lbs/min thru the engine. Jimmy Keen used to spin his 347 Ford engine to 9000 rpm while keeping the supercharger rpm at 62,000 rpm and only 21 psi of boost pressure. Other guys were running 28 psi of boost pressure on the same sized engine at lower rpm of the engine, AND GOING SLOWER DOWN THE TRACK!

Originally Posted by Travis Q

Turbos just don't have the losses, in terms of air temp, pumping losses, and shaft work requirement (the kind that detrimentally affects engine power). Their engine speed ranges are lower, so cylinder head requirements are lower.

Again, these are generalizations to a certain degree, but hold very, very true for moderate power applications in street oriented setups.

So lets say you pick a version of the Head 2 Cast Aluminum, but with a 2.19"x 1.71" valve package that had the same 3.000" CSA at entry and flows 335/255 cfm) vs the Head 1 cast iron head, that flowed 275/220 cfm). Right off the bat you now have a new head that flows 22% more cfm vs the cast iron head. More cfm & less resistance to that air flow with a bigger bore, bigger valve, and larger CSA.

You put this head on a new 454 Pontiac engine (4.25 bore/ 4.0" stroke) vs the old 4.181" bore/ 4.21" stroke and you raise the rpm of the engine to 7000 rpm.

You keep the same supercharger but change the pulley ratio to allow the same 55,000 rpm but at 7000 engine rpm, (but now the boost will be lower because as Travis has said you have more "Putts" per minute and I think that you will have the answer to your question, Calvin.

Tom Vaught



the same supercharger that was used on the 455 engine (4.21 stroke) was installed on a 454 cid Pontiac engine (4.25 bore/ 4.0" stroke) and you raised the rpm of the engine by

[Travis Q]

Originally Posted by v869tr6

Travis, its very nice to have your input on the forum, thanks for sharing! Couple of questions, do you think a 1.75" to 2.5" log manifold will hold back performance with a out of the box E-head? And what would you use for a cam with a 88mm turbo and 4.5" stroke 488 street / strip / dragweek car?
Thanks Ed

Ed -

I think that on that particular engine that you will see very little if any degradation in performance with a nice log manifold. Notice that I said a NICE log manifold, lol....you still want things to merge as smoothly as possible, and have a good design to it. Use your head, and you'll be just fine. I've seen some really nice engines make in excess of 1700 hp with such manifolds.

Wow, I've never run such a large engine with that size tubo. That's a bunch of stroke! It's not going to want much camshaft, because it's going to have a lot of backpressure. It'll probably be done at 5800 or 6000 rpm (not necessarily a bad thing!) so I would keep it small....like high 240's/low 250's on the intake valve, low 240s on the exhaust valve, around .600 lift or so, put it on a 144 to 116 LSA.

[Travis Q]

Originally Posted by Tom Vaught

So basically you can move more lbs of air mass per minute thru the engine by increasing the engine rpm but maintaining the lower supercharger rpm and be more efficient vs keeping the rpm low and spinning the supercharger much faster to get the same air mass Lbs/min thru the engine.

This is it, in a nutshell. All of the guys that run fast with centrifugals live and die by this one principle. Read it, reread it, and revolve the whole combination around it, because this is the whole enchilada regarding what it takes to go fast with a Vortech or ProCharger.

[65nss4spdGTO]

Originally Posted by Travis Q

The boost requirement for each cylinder head will be the SAME. If the cylinder head has enough capacity to make 600-650 naturally aspirated horsepower, then any more cylinder head will not do anything at all to make more power, regardless of boost level. Mind you, this statement refers only to ths particular sized engine with a reasonable rpm limit (under 7000 rpm).

I have to giggle to myself any time someone regurgitates that old internet BS..."bigger heads make more power with less boost".

HORSE FEATHERS. Not on a street turbo engine, they don't. Ive seen it done on the dyno and at the track. It's a MYTH.

Race engines are a different story, but only a little bit different! And blower motors are a whole 'nother card game, and cylinder head selection has a HUGE influence on those things.

Peak power rpm is going to be a function of camshaft. Which is a function of backpressure. Which is a function of the turbo used...and since this is a pretty large engine for this power level, it's really safe to assume that relatively small, quick-responding turbos will be used. That means high backpressure, no way around it (but not the death knell that many would have you believe). And high backpressure means you'd better keep the cam small or your intake manifold is going to look like the inside of a coal mine, and engine power will suffer.

Id bet a 450-460 inch engine at 15-20 psi is going to be pretty much all in by 6500 or so with street oriented turbos and cams that follow suit. A race setup would push that up to about 7200 or 7400 but not much more than that on gasoline.

EDIT:
Boost for 1250 hp is going to be around 13-15 psi if the engine is intercooled. 1500 hp will come at 20-22 psi. This is based on 455 inches, 6500 rpm, and 100 degree charge air temps.

I'm still struggling with this. I've thought about it quite a bit today, my conclusion turns to engine size, RPM and boost pressure. So lets push this head number one to the extreme. I know that NA, that style of cylinder head will make around 1.25 HP to Ci. So we are looking at an engine making around 550-575 HP. Add 13-15 lbs of boost, the engine should make around 1200 HP?

Now take an engine that makes 1.75 HP to Ci with the same cubic inch, we are looking at around 800 HP NA.

Why wouldn't a smaller boost amount make the same power as our target?

Calvin Hill
Hill Performance
708-250-7420

[Travis Q]

Calvin,

I'll answer your question with another question (don't you hate that? LOL)....this isn't a trick question, and it will reveal the answer to you. This concept literally took me YEARS to wrap my feeble brain around, but once I understood it, it changed how I look at NA vs boosted engines. I'm still learning from this concept. I think that you will understand it quicker than I did....

So here it is:

Lets say you have a given engine at a given engine speed, and you change the heads. Lets say that with this change, you pick up power without an increase in engine speed.

What changed to result in the power increase?

[65nss4spdGTO]

Originally Posted by Travis Q

Calvin,

I'll answer your question with another question (don't you hate that? LOL)....this isn't a trick question, and it will reveal the answer to you. This concept literally took me YEARS to wrap my feeble brain around, but once I understood it, it changed how I look at NA vs boosted engines. I'm still learning from this concept. I think that you will understand it quicker than I did....

So here it is:

Lets say you have a given engine at a given engine speed, and you change the heads. Lets say that with this change, you pick up power without an increase in engine speed.

What changed to result in the power increase?

Increase in torque.

Calvin Hill
Hill Performance
708-250-7420

[Travis Q]

Volumetric efficiency goes up.

What this reveals is that the small head really didn't have enough capacity at the engine speed range that we were trying to operate the engine in.

I've seen dyno sheets from engines that didn't gain anything from a head change when everything else was held constant. In this case, the original heads could deliver what the engine needed in that specific engine speed range.

The interesting thing about turbo engines is that if the naturally aspirated VE is a little short for the combo, the turbo increases the VE somewhat. That's why the smaller heads perform like they do! The turbocharger changes the VE of the engine by changing the pressure differential that it's operating at. But remember....once the cylinder is full, it's full, and a bigger head isn't going to fill it up any more.

Also remember that these statements are for street type engines. race engines accelerate a lot differently, and a high acceleration rate turbocharged engine's cylinder head requirement is a bit different than what we're discussing here. I've got some data from our 482 that shows this very plainly. Our engine is not a high acceleration rate engine, and you have to change the combination around to suit it.

[65nss4spdGTO]

Have you seen as you increase boost, power gains begin degrading?

Calvin Hill
Hill Performance
708-250-7420

[Travis Q]

I have not. Power will continue to increase without degradation so long as you don't increase air temperature (which on a gas engine comes down to intercooler effectiveness), run out of compressor wheel capacity, or run into some issue such as insufficient valvespring pressure.

Usually we run out of compressor wheel first, especially in a street oriented application. This is a situation where you only want to be as big as you have to be to achieve your goals; any larger and you will suffer from response issues and possibly compressor surge. So I usually see that as long as I don't run off the side of the compressor map, power goes up as I increase boost.

[v869tr6]

Here is a picture of my manifolds before they were complete.

[65nss4spdGTO]

Tom V,

Thanks for your input.

Over the past few years, Mark and I have had many discussions on boost/power. I think it's only a matter of time before I put something together for myself.

Calvin Hill
Hill Performance
708-250-7420

[65nss4spdGTO]

Originally Posted by Travis Q

Volumetric efficiency goes up.

The interesting thing about turbo engines is that if the naturally aspirated VE is a little short for the combo, the turbo increases the VE somewhat. That's why the smaller heads perform like they do! The turbocharger changes the VE of the engine by changing the pressure differential that it's operating at. But remember....once the cylinder is full, it's full, and a bigger head isn't going to fill it up any more.

The easiest way to increase VE in an NA motor is raise torque RPM.

If two motors each make 600 lb-ft., but one engine makes that same torque 500 RPM higher, that engine will make much more HP power.

So we put on bigger heads, longer duration cams and more valve lift.

How does valve lift effect boost power?

Calvin Hill
Hill Performance
708-250-7420