Tom Welch
Enthusiast
CNC = consistancy.
Tom
Tom
CNC vs. Hand Ported Cylinder Head Upgrades?
- Thread starter Tom Welch
- Start date
Jay Herbert
Enthusiast
As Tom says, "CNC=consistancy". Many use CNC because, once they got it, it is the same every time. I work at a place that uses CNC high machines to machine to microns....
Scroll Technologies
The computer controlled numerical control machine (CNC) merely repeats the program and cuts the head the same every time. Now, this makes a few assumptions
1) The setup is the same
(machined part is in the smae place relative to the cutting tool)
2) The cutting tool is set the same.
CNC eliminates (replicates) a lot of the hand work done in a standard porting job, there will still be a little.
Hand porting can/is part art, part science. A good hand port person will use a flow bench to tweak his porting job to balance and optimize flow. This is going to sound strange..... but CFM is not CFM as the character of the flow matters to HP/Torque... Tom can likely fill you in more on that.
I remember reading an article about the guy that does a majority of NASCAR intakes, why one guy? well he knows the little tweaks that give the power "where" it is needed.
Scroll Technologies
The computer controlled numerical control machine (CNC) merely repeats the program and cuts the head the same every time. Now, this makes a few assumptions
1) The setup is the same
(machined part is in the smae place relative to the cutting tool)
2) The cutting tool is set the same.
CNC eliminates (replicates) a lot of the hand work done in a standard porting job, there will still be a little.
Hand porting can/is part art, part science. A good hand port person will use a flow bench to tweak his porting job to balance and optimize flow. This is going to sound strange..... but CFM is not CFM as the character of the flow matters to HP/Torque... Tom can likely fill you in more on that.
I remember reading an article about the guy that does a majority of NASCAR intakes, why one guy? well he knows the little tweaks that give the power "where" it is needed.
Torquemonster
Enthusiast
Some would like us to believe that heads are a black art... a bit like magic.
Actually its a bit more scientific than that - but the variables in shape etc are almost infinite - so therein lies the art in finding the best shape for a given application. ONCE you have that shape - then CNC is the way to get more of them - exactly the same.
MORE is not always better, sometimes it is just more... lest that's what my wife tells me. Makes me feel better anyway, but I digress...
Remember the old Boss 429 Mustang with Hemi heads?
They flowed about 770hp stock but were dogs on the street.... like the 4V Cleveland was to the smallblock. But there was huge potential in there. Huge flow numbers but no velocity = poor low speed operation, poor fuel distribution... pig to drive.
Along came a very clever chap whose name just escaped me, and they reworked those heads - filling in the ports and reshaping them, until they obtained supersconic air speeds on the bench. The result was the SHOGUN 429. That head on the 429 set track records across the USA and those records stood for about 15 years. It was so successful Bob Glidden went and bought every single inventory item up so no one else could run them - that's why no one could beat him for so many years.... not very fair - but that's life
It is not just the peak flow figures that matter, but the flow turbulence and airspeed as well. Have you ever wondered why a mildly ported 318 Mopar can outgun a fuelie head 350 Chev with same cam and carb in most street applications? The 318 ports are so small you have to fold a cockroach in half to fit it in there - they do not flow big numbers, but boy can they generate some air speed when shaped right - supersconic speeds! Up to 400hp they'll provide violent power in a light car across a broad rpm range.
Back to the Viper. The best head comes down to who can:
1- create a head that is not too thin it has a limited life - nothing like a shot of water through a stress crack to put your fire out!
2- design a shape that maximises air speed and air swirl and improve low speed flow
3 - at the same time, create a port that flows the big numbers on the top end - but not necessarily the biggest numbers.
Here's something to remember - the valve spends how long at maximum lift?
Not long right?
It spends a lot more time opening and closing - so flow at low to medium lifts is the key to any engine that must make power over a broad range... as that is where the air is getting in.
There are ways to increase airspeed in an existing port - such as a faster cam ramp - and Mopar cams will take a LOT more ramp than a Chev can with its 0.904" lifters.... there's some real power in there for the few who know.... look at a Hughes max velocity cam and you'll get the picture.... a cam like that would not run on a Chev. They need roller cams just to run what a Mopar can take on a good old hydraulic max velocity grind. But the big cam guys typically don't do it, as the money is in Chev so they make Viper grinds off Chevy ramps... Another way is to increase compression... cylinder pressure not static compression is the key... another is a good seal - the old honing plate round and taper tolerance of 0.0002" trick (50hp here on a typical big V8)... another is to run a tight quench.. there I go again, but there's another 30-40hp minimum in just that alone on a stock engine, plus much less detonation!
by the way - if running a fast action cam I recommend Oil Extreme - its the only oil that can take over 265,000psi and increase the TBN. It's a secret few racers know about and is a lot more slipery and stronger than Royal Purple or Redline.... remember you heard it from me first... Ask Nemcheck or David Vizard about it, they'll tell you. You could run it as an additive or the complete oil - but its safe to run thin oil with it - that adds more power. Do not run thin oil without it though on a fast action cam - a good cam will last about 1500miles on ordinary oil... and that won't impress anyone except at the track - Oil Extreme is your friend here - it'll live.
Everything should work together.
Back to heads - once someone has found a winning head port combo with excellent velocity, CNC is the way to duplicate it. Guys who claim they can duplicate heads perfectly by hand are a dime a dozen, guys who can actually do it are rare as rocking chair poop and are legends.. but even they still could not be as accurate as CNC - just as Tony said.
Actually its a bit more scientific than that - but the variables in shape etc are almost infinite - so therein lies the art in finding the best shape for a given application. ONCE you have that shape - then CNC is the way to get more of them - exactly the same.
MORE is not always better, sometimes it is just more... lest that's what my wife tells me. Makes me feel better anyway, but I digress...
Remember the old Boss 429 Mustang with Hemi heads?
They flowed about 770hp stock but were dogs on the street.... like the 4V Cleveland was to the smallblock. But there was huge potential in there. Huge flow numbers but no velocity = poor low speed operation, poor fuel distribution... pig to drive.
Along came a very clever chap whose name just escaped me, and they reworked those heads - filling in the ports and reshaping them, until they obtained supersconic air speeds on the bench. The result was the SHOGUN 429. That head on the 429 set track records across the USA and those records stood for about 15 years. It was so successful Bob Glidden went and bought every single inventory item up so no one else could run them - that's why no one could beat him for so many years.... not very fair - but that's life
It is not just the peak flow figures that matter, but the flow turbulence and airspeed as well. Have you ever wondered why a mildly ported 318 Mopar can outgun a fuelie head 350 Chev with same cam and carb in most street applications? The 318 ports are so small you have to fold a cockroach in half to fit it in there - they do not flow big numbers, but boy can they generate some air speed when shaped right - supersconic speeds! Up to 400hp they'll provide violent power in a light car across a broad rpm range.
Back to the Viper. The best head comes down to who can:
1- create a head that is not too thin it has a limited life - nothing like a shot of water through a stress crack to put your fire out!
2- design a shape that maximises air speed and air swirl and improve low speed flow
3 - at the same time, create a port that flows the big numbers on the top end - but not necessarily the biggest numbers.
Here's something to remember - the valve spends how long at maximum lift?
Not long right?
It spends a lot more time opening and closing - so flow at low to medium lifts is the key to any engine that must make power over a broad range... as that is where the air is getting in.
There are ways to increase airspeed in an existing port - such as a faster cam ramp - and Mopar cams will take a LOT more ramp than a Chev can with its 0.904" lifters.... there's some real power in there for the few who know.... look at a Hughes max velocity cam and you'll get the picture.... a cam like that would not run on a Chev. They need roller cams just to run what a Mopar can take on a good old hydraulic max velocity grind. But the big cam guys typically don't do it, as the money is in Chev so they make Viper grinds off Chevy ramps... Another way is to increase compression... cylinder pressure not static compression is the key... another is a good seal - the old honing plate round and taper tolerance of 0.0002" trick (50hp here on a typical big V8)... another is to run a tight quench.. there I go again, but there's another 30-40hp minimum in just that alone on a stock engine, plus much less detonation!
by the way - if running a fast action cam I recommend Oil Extreme - its the only oil that can take over 265,000psi and increase the TBN. It's a secret few racers know about and is a lot more slipery and stronger than Royal Purple or Redline.... remember you heard it from me first...
Ask Nemcheck or David Vizard about it, they'll tell you. You could run it as an additive or the complete oil - but its safe to run thin oil with it - that adds more power. Do not run thin oil without it though on a fast action cam - a good cam will last about 1500miles on ordinary oil... and that won't impress anyone except at the track - Oil Extreme is your friend here - it'll live.Everything should work together.
Back to heads - once someone has found a winning head port combo with excellent velocity, CNC is the way to duplicate it. Guys who claim they can duplicate heads perfectly by hand are a dime a dozen, guys who can actually do it are rare as rocking chair poop and are legends.. but even they still could not be as accurate as CNC - just as Tony said.
rcdice
Enthusiast
Any opinions on the Mopar GTS-R CNC ported heads?
I've been kicking around the idea of adding a set to my GEN II with a cam upgrade at the same time. Using a Mopar "factory" tested port job appeals to me. Any comments?
I've been kicking around the idea of adding a set to my GEN II with a cam upgrade at the same time. Using a Mopar "factory" tested port job appeals to me. Any comments?
rcdice
Enthusiast
STU,
If I go with a custom port job, Greg Good would be my first call. However, I constantly go back and forth with how far away from stock I want to take this car. In my mind, using a Mopar provided set of heads is kind of stock. Kind of "dealer added option" stock. A stretch I know, but it makes sense to me. Getting any hp numbers on either the Mopar Street Performance heads or the GTS-R heads has been very difficult. I can find the specs on the Mopar site but no hp/tq info. Kind of frustrating actually.
Anyone have any details?
If I go with a custom port job, Greg Good would be my first call. However, I constantly go back and forth with how far away from stock I want to take this car. In my mind, using a Mopar provided set of heads is kind of stock. Kind of "dealer added option" stock. A stretch I know, but it makes sense to me. Getting any hp numbers on either the Mopar Street Performance heads or the GTS-R heads has been very difficult. I can find the specs on the Mopar site but no hp/tq info. Kind of frustrating actually.
Anyone have any details?
Go Fast For Life
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I have a set of the CNC GTS-R heads on my car now. Here is a comparison of the flow characteristics vs. a stock head.
Keep in mind that these heads hold about a quart more coolant than the stock heads. So flow characteristics are only one of the benifits of these heads.
I am going to pull the heads off this summer and have them hand ported to improve the low lift flow.
Keep in mind that these heads hold about a quart more coolant than the stock heads. So flow characteristics are only one of the benifits of these heads.
I am going to pull the heads off this summer and have them hand ported to improve the low lift flow.
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rcdice
Enthusiast
Great info! Thank you.
Any idea what the compression is raised to with these heads? Also, do you have any idea of average hp/tq gains of the GTS-R heads vs. the Street Performance heads vs. stock? I'm curious as to any numbers that are head specific before any kind of cam swap. I haven't been able to get even a basic guideline anywhere, any info would be appreciated.
BTW, like those custom stripes on your avatar pic.
Any idea what the compression is raised to with these heads? Also, do you have any idea of average hp/tq gains of the GTS-R heads vs. the Street Performance heads vs. stock? I'm curious as to any numbers that are head specific before any kind of cam swap. I haven't been able to get even a basic guideline anywhere, any info would be appreciated.
BTW, like those custom stripes on your avatar pic.
Go Fast For Life
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The GTS-R heads have a smaller chamber than than the stock heads. My motor is a 542 and we used dished pistons to keep the CR at 9.8:1. So I have no idea what the CR would be with just the heads.
Unfortunately, the stock cam doesn't offer enough lift to really take advantage of the heads. The cam I am using only has .560 lift which is the reason I want to increase the low lift flow of the heads.
If you are looking to simply swap the GTS-R with the stock heads and pick up a lot of power, I'm afraid you will not be happy.
Don't want to discourage you, just trying to save you some time and money. If these heads are re-worked, I think they can give you 75+ extra HP. I'm not sure that a set of reworked stock heads can't give you the same gain though.
Hope this helps.
Thanks for the compliments on my car.
Ron
Unfortunately, the stock cam doesn't offer enough lift to really take advantage of the heads. The cam I am using only has .560 lift which is the reason I want to increase the low lift flow of the heads.
If you are looking to simply swap the GTS-R with the stock heads and pick up a lot of power, I'm afraid you will not be happy.
Don't want to discourage you, just trying to save you some time and money. If these heads are re-worked, I think they can give you 75+ extra HP. I'm not sure that a set of reworked stock heads can't give you the same gain though.
Hope this helps.
Thanks for the compliments on my car.
Ron
cgmaster
Viper Owner
I have a set of GTS-r heads that I just got. They are not stock from the factory however. I have found that they have larger valves and I think they have had some additional port work and Larger valve seats installed. They should make a difference on a race engine but I am not sure how much of a benefit they would be on a stock engine. I bought a whole GTS-r engine to rework for racing and limited street use using race fuel.
Go Fast For Life
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Have you flow tested the heads? It would be interesting to see what they flow?
Greg Good Cylinder Heads
Enthusiast
The few sets of those I've done really shined at high lift. Along the low and mid-range they were comparable to a well done set of stock castings.
Ron, one thing that will fire up your low and mid-lift flow is to lay the chambers back some and unshroud the valves more. It really wakes them up. Of course that's going to make you need a flat top piston to get the compression back up again.
Greg
P.S. Ron, you probably have more lift than you think going down the track. The valves are more than likely "lofting" over the nose of the cam to some extent. Every engine is going to be different, depending on the stiffness of the valvetrain, cam acceleration, and spring characteristics, but it's a common thing. It takes a Spintron machine to measure it. Lofting is just a precursor to valve float. It's a controlled valve float. It makes more power because it adds area under the curve to the valve event. A typical Nextel Cup engine will loft the valves .030"-.040". An NHRA Pro Stocker, .050"-.060", some more, but the valvetrains don't stay together. I'm waiting for some information on hydraulic roller setups, but I'm told that they are not exempt from lofting. I would hazard a guess that you're actually up around .600" with loft.
Go Fast For Life
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Greg,
You are the man. Thanks for the thoughts. I had the same thoughts about laying the chamber back. Remeber the closed-chamber BBC heads compared with the open chamber ones. Laying the chamber back on the closed chamber castings really helped them flow a lot better.
Thanks again for the thoughts.
Ron
You are the man. Thanks for the thoughts. I had the same thoughts about laying the chamber back. Remeber the closed-chamber BBC heads compared with the open chamber ones. Laying the chamber back on the closed chamber castings really helped them flow a lot better.
Thanks again for the thoughts.
Ron
joe117
Enthusiast
Greg,
Do you think that the Viper V10 is going to loft the valves much at Viper V10 rpm?
Do you think that the Viper V10 is going to loft the valves much at Viper V10 rpm?
Greg Good Cylinder Heads
Enthusiast
Yes, but depending on the cam. I've had several hydraulic roller cams Cam Doctored over the last few years and the scary thing is that often the tappet acceleration is higher on the hydraulic roller than for a baseline drag race or circle track solid roller cam. The rub is that we can't run solid roller springs on them. That in itself makes most hydrualic roller setups prone to valve float.
As a rule, everything onthe valve side of the rocker needs to be light, everything on the pushrod side, stiff. That means lightweight valves and retainers, and big diameter thick wall heat treated pushrods. Next to lightening the valves and retainers, having a stiff pushrod is the best way to tame an overexcited valvetrain.
As a rule, everything onthe valve side of the rocker needs to be light, everything on the pushrod side, stiff. That means lightweight valves and retainers, and big diameter thick wall heat treated pushrods. Next to lightening the valves and retainers, having a stiff pushrod is the best way to tame an overexcited valvetrain.
joe117
Enthusiast
Greg,
Doesn't the higher ratio rocker,
that you might run with a hotter cam,
give a little mechanical advantage to the valve spring when it comes to keeping the push rods and lifters down where they belong?
Doesn't the higher ratio rocker,
that you might run with a hotter cam,
give a little mechanical advantage to the valve spring when it comes to keeping the push rods and lifters down where they belong?
Greg Good Cylinder Heads
Enthusiast
It's not the lifter you're worried about, but the valve. The higher you go on the rocker ratio, the higher the acceleration the valve sees. Don't picture the engine sitting on an engine stand and you're rolling it over with a wrench. Consider what's going on at 6200 rpm. The valve has a lot of velocity, or inertia, on opening and closing. The higher ratio rocker increases the velocity of the valve and make it harder to control.
Also, a weak pushrod will make the valvetrain harder to control because it will flex on valve opening, then "unload" at the top of the lobe, giving the valve extra motion. When this is happening you can put more spring pressure on it with the hopes of reducing it, but this usually won't fix it, and it may even make things worse, because the pushrod responds by flexing more, and consequently "unloading" more at the top of the lobe.
There's a lot I need to learn about all this valvetrain stuff. I've learned a good bit from friends that run Spintron machines. One thing I've learned about is spring surge. That's when the iniertia of the spring is so high on valve closing that the bottom of the spring actually raises up off the spring seat of the head. A good valvetrain guy can look at the bottom of a valvespring and tell if it has been doing that or not. If the bottom of the spring is pretty shiny and worn, it's probably been surging.
A customer that has a small block Chevy brought me his heads after last season to freshen up. He had somehow let a 1/4" valve cover stud get into the valley of the head. When I took the heads apart IT WAS UNDER ONE OF THE SPRING CUPS and had chewed the spring pad all up on the head. Evidently the springs on those heads were surging enough for that stud to get under a spring seat. I never would have believed if I hadn't seen it. I told one of my Spintron buddies about it and he wasn't surprised.
Anyway, sorry for highjacking this thread.
Also, a weak pushrod will make the valvetrain harder to control because it will flex on valve opening, then "unload" at the top of the lobe, giving the valve extra motion. When this is happening you can put more spring pressure on it with the hopes of reducing it, but this usually won't fix it, and it may even make things worse, because the pushrod responds by flexing more, and consequently "unloading" more at the top of the lobe.
There's a lot I need to learn about all this valvetrain stuff. I've learned a good bit from friends that run Spintron machines. One thing I've learned about is spring surge. That's when the iniertia of the spring is so high on valve closing that the bottom of the spring actually raises up off the spring seat of the head. A good valvetrain guy can look at the bottom of a valvespring and tell if it has been doing that or not. If the bottom of the spring is pretty shiny and worn, it's probably been surging.
A customer that has a small block Chevy brought me his heads after last season to freshen up. He had somehow let a 1/4" valve cover stud get into the valley of the head. When I took the heads apart IT WAS UNDER ONE OF THE SPRING CUPS and had chewed the spring pad all up on the head. Evidently the springs on those heads were surging enough for that stud to get under a spring seat. I never would have believed if I hadn't seen it. I told one of my Spintron buddies about it and he wasn't surprised.
Anyway, sorry for highjacking this thread.
joe117
Enthusiast
So how do the V8s run 8k rpm if the similar Viper valvetrain has problems at a little over 6k rpm?
Greg Good Cylinder Heads
Enthusiast
Joe, I'm not aware of a V8 street engine similar to the Viper and running a hydraulic roller cam that can turn 8000 rpm, except in neutral.
Most all of the small block Chevy and Ford stuff I've been involved with valve floats before 7000 typically. The LS1 stuff is real popular right now, and with the Comp Cam X-ER lobes they valve float before 7000 rpm too, unless you put a LOT of spring on and have titanium retainers. Then they'll go a little over 7. Titanium valves will typically add about 1000 rpm to the valvetrain, but they're not reliable on the exhaust side for street use. The plus side to the LS1 is that a company called Morel makes a close tolerance lifter for it and open spring pressures as high as 485 pounds (they may take more, that's all I've run so far) can be run without experiencing bleed down and lifter noise. Too bad Morel doesn't make Viper lifters. Plus the LS1 valves are shorter, and therefore lighter than the Viper.
Stugots, thanks for the kind words, but I'm probably pretty far from being the man. I just try as hard as I can to do good work for people. Call me at 713-290-1103. If those Ford heads are cast iron, call my other number, 1-800-NO-WAY.
Most all of the small block Chevy and Ford stuff I've been involved with valve floats before 7000 typically. The LS1 stuff is real popular right now, and with the Comp Cam X-ER lobes they valve float before 7000 rpm too, unless you put a LOT of spring on and have titanium retainers. Then they'll go a little over 7. Titanium valves will typically add about 1000 rpm to the valvetrain, but they're not reliable on the exhaust side for street use. The plus side to the LS1 is that a company called Morel makes a close tolerance lifter for it and open spring pressures as high as 485 pounds (they may take more, that's all I've run so far) can be run without experiencing bleed down and lifter noise. Too bad Morel doesn't make Viper lifters. Plus the LS1 valves are shorter, and therefore lighter than the Viper.
Stugots, thanks for the kind words, but I'm probably pretty far from being the man. I just try as hard as I can to do good work for people. Call me at 713-290-1103. If those Ford heads are cast iron, call my other number, 1-800-NO-WAY.
rcdice
Enthusiast
Greg,
Lets say that a guy was "hypothetically" considering doing a heads and cam package to his 2001 Viper. Lets also assume that this individual wanted to keep his stock heads and would therefore be looking to purchase a second set to modify. That being the case, would you recommend starting with a set of stock heads, Mopar Street Performance heads or Mopar GTS-R heads?
While money is always an issue, lets say that there is some flexibility if there are clear advantages in going with the higher priced after market Mopar heads as a starting point.
The GTS-R heads seem like the "high end" way to go with Beryllium copper valve seats and Magnesium bronze guides. Also, extra cooling capabilities as mentioned by Ron above.
Opinions? Thanks.
Lets say that a guy was "hypothetically"
considering doing a heads and cam package to his 2001 Viper. Lets also assume that this individual wanted to keep his stock heads and would therefore be looking to purchase a second set to modify. That being the case, would you recommend starting with a set of stock heads, Mopar Street Performance heads or Mopar GTS-R heads?While money is always an issue, lets say that there is some flexibility if there are clear advantages in going with the higher priced after market Mopar heads as a starting point.
The GTS-R heads seem like the "high end" way to go with Beryllium copper valve seats and Magnesium bronze guides. Also, extra cooling capabilities as mentioned by Ron above.
Opinions? Thanks.
Stugots, thanks for the kind words, but I'm probably pretty far from being the man. I just try as hard as I can to do good work for people. Call me at 713-290-1103. If those Ford heads are cast iron, call my other number, 1-800-NO-WAY.
LMAO
I'll have to find out if they are LMAO and if so I'll call 1800-NO-WAY lol
Greg Good Cylinder Heads
Enthusiast
Bob, the extra water jacket volume is definitely a plus. Also the performance castings have thicker port walls and a head porter doesn't have to dodge the water jacket to get good flow. If money's not an issue, get the better casting.
joe117
Enthusiast
I wasn't talking about stock LS1s. But I guess that the answer is that they have the same problems.
Greg Good Cylinder Heads
Enthusiast
I figured you were talking about heavily modded engines.
Yeah, you're right, they all have the same problems.
I've had several sets of LS1 heads come in with intake seats that were pounded down into the seat pocket from valve float. It'll push out a pretty good size lip in the aluminum on the short side radius where the seat and the port meet. Only thing I can do then is replace them with a larger diameter seat, and put more spring on it and a stiffer pushrod.
Yeah, you're right, they all have the same problems.
I've had several sets of LS1 heads come in with intake seats that were pounded down into the seat pocket from valve float. It'll push out a pretty good size lip in the aluminum on the short side radius where the seat and the port meet. Only thing I can do then is replace them with a larger diameter seat, and put more spring on it and a stiffer pushrod.
Chuck 98 RT/10
Enthusiast
Good tech here. Thank Greg. Have you done any heads for road racers?
