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Aftermarket cams

Anyone have an aftermaket cam, such as the Webcam. Im getting ready to do a engine rebuild. I'm putting a new cam in, but was debating upgrading a bit.
Just lookin for some feedback.

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Old 10-07-2004, 11:53 AM
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www.jmengines.com

dont waste your time with the web cam.
Old 10-07-2004, 04:45 PM
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I agree the JM cams are the best out there but are a little expensive, I know some one is running a WEB cam but I dont remember his name, anyways if your looking into doing performance stuff then do it right the first time and go with JM
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Old 10-07-2004, 07:02 PM
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The JM's are a little too pricey for the amount of HP gain.
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Old 10-08-2004, 04:43 AM
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I use web cams in 3 of my cars that I work on here. All of them have a nice lopey idle to them and can really make a car move.. a set of cams for my car cost me about $600, so being 650 for a 2V cam isnt all that bad. In that area of the industry, dont be cheap because it will bite you in the ass in the end. A cheap cam also has a tendancy to break down because of poor hardening or being a regrind. It will eat up the mating surfaces of the cam and the bucket shim below it. Meaning now both will have to be replaced.
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Old 10-08-2004, 10:47 AM
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Been building racing engines for over 20 yrs, most of which is marine racing stuff,so trust me I know what some stuff can cost. I just think that the $/Hp ratio for that part is'nt all that great. These cars are not cheap to modify by no means . But I cant see spending $$ on something that will not give you much of a hp gain. If the price was for the whole cam kit( cam, lifters..) than mabye I could justify the price.
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Old 10-08-2004, 11:35 AM
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Why just look at peak HP numbers? In the Real World, that doesn't really mean anything. It's great bragging rights, but since we don't drive Fast and Furious style Civics, there's not much point. Instead, how does the cam change the HP/TQ curve? Where are the peak HP and TQ numbers located now? Where does the cam "come alive"? Where does it "die"? I'd take a cam that increased low and midrange torque with a sweet curve over a cam that gave me 25 more HP at 5800RPM. But, all that being said, I guess it really depends on your preference for your engine, but my point is it's not so black and white as to say how much HP does it gain.
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Old 10-08-2004, 04:59 PM
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slowtoady couldnt have said it any better...everyone in the magazines and in the import industry has it stuck in their head that making the most hp gets bragging rights. Sure I could make a crazy amount of horsepower, but a lot of cars that make record setting hp only see it in the last 1000 rpm of the engine. Ive seen guys with Supras trade 25 or more +hp in the midrange or low end to have 3 more hp at redline. You will never use that horsepower.

IMO I would buy the first cam..the one that makes hp from 3600 to 6500....perfect for me because I dont plan on going farther than that.
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Old 10-08-2004, 10:16 PM
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I agree with BlueBullet, the 3600-6500 rpm is perfect, Its the RPM range your in the most and its already the sweet spot for these engines
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Old 10-09-2004, 06:30 AM
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I agree with slow toady, peak hp means nothing, especially in a street car. The majority of advertised HP claims are a joke because most engines will never see the rpm range that these #'s are based in. As I stated in a previous post, I look at the cost to power ratio when I put a motor together. Mabye I should have said, "cost to performance ratio" in this case. My bad.
Like I said, the majority of my work is Offshore racing motors, which are designed and built to run flat out for long periods. All the power is in the mid to upper range. I guess out of habit I look for the most hp attainable.
I just wanted to know if anyone was using these cams and if they were happy with them , as I really dont have much experience, with my 944 motor, as far as major performace upgrades. although I am building a set of intake manifolds using Weber carbs and another for a Holley carb.
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Old 10-10-2004, 07:46 PM
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perfect example...DSport mag is dyno testing all these parts for the EVO. As I studied the article, they mention all this 45hp increase from all the parts that they did, but if you do the math it doesnt add up...why? Because they were using an HKS F-Con standalone engine management for one...and this is their 'stage one' package with no mention of a full standalone unit. They have complete fuel and timing control whereas the stock computer doesnt. That and they tuned it on the ragged edge for a few passes to eek out that few hp in order to make that 45 hp gain. They clearly state in the bottom of the article in a well worded sentence that they pulled out some timing due to knock and EGTs were too hot...but they didnt say how much hp they made after that. Im pretty sure people dont go driving around with crazy high EGTs or the knock sensor going full alert...

I hate such BS articles..
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Old 10-10-2004, 08:54 PM
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I know , it's a joke. I have customers come to me waving a magazine or telling me something they saw on such and such tv show. "Hey do this to my engine"! 9 times out of 10 I wind up explaining to them how that stuff isnt the same in the real world. Especially with dyno testing, once you drop that motor in a car or boat, variables change.
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Old 10-11-2004, 05:43 AM
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BlueBullet, I read the same articale, I thought it was soooo funny when I saw that they had timming and egt problems but hey we made 45 more HP. HAHAHAHAHA 45 unusable HP
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Old 10-11-2004, 02:08 PM
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On a 944NA engine, I wouldn't even bother with a cam. It just moves low-end torque up the powerband to give you higher peak-HP. But the car won't actually be that much faster, you'll have a narrower powerband that requires lots of shifting to use the increased power between 5000-7000rpm.

Best bang-for-the-buck upgrade is probably nitrous for the NA. Otherwise, best upgrades would be starting from the inside out, with getting the high-comp. Euro pistons. Then head mods like full D-porting with narrow-stem flat-head valves. Piston & heads would end up giving you about +20hp. Add a cam for perhaps another +5hp in the 4000rpm+ range, -5hp below that.

Last edited by DannoXYZ; 10-14-2004 at 12:20 AM..
Old 10-14-2004, 12:16 AM
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um the JM cam is good for 3500- 6500 rpm in the sweet spot the HP increase is 12-18HP with stock exhaust. I would go for a Cam before Nitrous, The cam will really open up the mid rang power and with a Performance exhaust I bet it will do better.

Dannon I think you are thinking about Adjustable Cam gears they only move the power band around and a cam can give you more power.
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Old 10-14-2004, 02:41 PM
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Uh... I have profiled all three of the JM cams and can tell you that one of them is identical to the the Web cam profile #274. I've also got dyno-charts of several of them as well.

"um the JM cam is good for 3500- 6500 rpm in the sweet spot the HP increase is 12-18HP with stock exhaust."

If you read AutoThority's claim on their chip-upgrade for 944NAs, they claim 15hp. What results do you get on the dyno? If anyone wants to do a dyno-comparison before & after of a cam-swap, I'll gladly pay for your dyno fees. You will see a zero-sum gain where what you gain in the upper-RPMs will be exactly what you lose in the low-end..

If you poll the high-end engine-builders, like Gomes, Norwood, Hennessey, Lingenfelter, Milledge, etc... you'll get the same answer. That is the cam is the last step and it should be custom-ground to tie together all your previous mods like pistons, valves, heads, headers, intakes & exhaust. That's because any upgrade will have a rippling effect on all the other components. The cam is one area that's adustable in multiple ways in regards to lift, duration and timing. All three of these should be optimized with all your other upgrades and usage-goals in mind. If you get a cam early on, any upgrade you get after that will require regrinding a new cam-profile to get optimum results.

I also offer a 944NA and 951 cam for $390-490 and they are all custom-ground to fit your mods. There's no way you can pull an off-the-shelf profile and have it be fully optimised for your car and intended goals.

BTW, adjustable cam-sprockets are a simple way to generate different cam-profiles without needing a regrind, but they are a compromized solution compared to grinding a new cam. That's because on our cars, it will adjust both intake & exhaust lobes in the same direction. Often times, the adjustments you want to make is in opposite directions, such as advancing the exhaust and retarding the intake timing for high-RPM power. It's possible to do this with DOHC 4-valve configuration, but on our cars, you need a new cam ground with the new specs.

Last edited by DannoXYZ; 10-14-2004 at 03:07 PM..
Old 10-14-2004, 02:57 PM
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Beaver... from Milledge about my car and his cam...

Me... What HP gains would you expect on average?

Him...This totally depends upon other equipment but if the turbo can maintain boost pressure to 6500 rpm (which the stock turbo cannot) I would expect 25 to 40 bhp on a near stock engine running stock boost. If
the turbo can maintain 16 psi without exhaust back pressure exceeding 22 psi, I would expect much more, maybe 60 to 75 more than a stock turbo cam.
Old 10-14-2004, 03:06 PM
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I do agree that A cam should be fitted to your upgrades, But Cams dont just move the power band around, The way to move the power band is to change the postition of the lobes, wich a new cam will do, what your forgetting is the Lift and length of different cams lobes, this will change how much air is sucked in and for how long and what speed, it will change all the breathing of the engine, more air more fuel more power for whatever given RPM the cam was made for, Yes you will give and take some HP but to gain HP from 3500-6500, and loose it anywhere else is fine with me.

Yes the 8V setup does have its limits but thats just something you need to work with. Also on building a engine you could do it eather way one being get the cam and build the engine around that cam or two being build the engine and then get a cam that you will hope best fits the upgrades.

Another problem is that custom grinds are expensive and you would need tons of dyno time to get the perfect cam for your setup and on top of that Im not a big fan of REGRINDING.

As for performance chips you cant compare them with cams, First off a chips HP rating all depends on how far you can tweet the AIR/FUEL ratio and TIMMING. You cant really play with eather one to much on a NA. A turbo car with a chip is a all out different story, the limits on a Turbo chip all depend on the engine components since boost and fuel can be increased to the max the engine can handle.

Ohh and Cam gears do not make different cam profiles, they simple change the timming of the cam retard or advance, it does not effect lift or deration of the stock cam.
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Old 10-14-2004, 06:32 PM
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"As for performance chips you cant compare them with cams, "

Sorry, I wasn't comparing chips with cams. I was illustrating the difference between vendor's claims and actual real-world customer experience. Without dyno-proven before & after charts, I usually take their claims and divide it in half to come up with probable real-world results.

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Old 10-15-2004, 02:21 AM
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Ok also, I should have said "cam-specs" rather than "cam-profile". Cam gears to the same thing as grinding a new cam with the same specs... more about this later. Let's do a quick tutorial on cams...

First, review my CamProfiles.pdf diagrams so that I can illustrate the various cam-specs and how they affect an engine's breathing at various RPMs and the resultant VE, torque & power curves. The various specs of interest are:

- cam-duration
- intake/exhaust valve open/close
- lobe-centers
- lobe-center separation
- valve-lift
- overlap
- ramp-up, plateau-width, and ramp-down rates

Now, imagine you're in the action area, inside the combustion chambers. From that perspective, you don't even know about a cam, all that matters is the valve's action and how that interacts with the pistons' movements and the resultant air-flow pattern that generates. Another thing that's very apparent is that the flow of air through the engine is not straight, like a turbine, but rather, gets pushed back and forth by the pistons. The valves then open & close at the right times to divert air in & out the proper ports. This reciprocating action causes pressure-pulses to travel back & forth through the engine all the way from the AFM to the muffler and back. The frequencies and overlaps of these pulses create harmonics which affect the filling of the combustion chambers.

The events that affect these pulses the most are, in order of important, intake-valve closing, intake-valve opening, exhaust- closing and exhaust-opening.

Exhaust-opening is the least important because it occurs at the end of the power-stroke. Most of the energy has already been extracted from the expanding combustion gases, so opening the exhaust-valves at the very bottom of the stroke to maximize the expansion push on the piston isn't that advantageous. While you can do this at low-RPM, at higher-RPMs, you want to open the exhaust-valve earlier and earlier (like 20-40 before BDC) in order to have enough time to purge all the exhaust gases from the cylinders.

Exhaust-closing is the other end of the exhaust-stroke and it determines how much exhaust you can extract. Early exhaust closing is good at low-RPms because it prevents excessive dilution of the incoming fresh air-fuel mixture with remaining exhaust. It also prevents a backwash of exhaust from fighting the incoming charge. However, at high-RPMs, an early exhaust close cuts off the flow too early before all of it can get out. Also a late closing like 20-30 ATDC has the trail end of the exhaust gases actually pull in the intake-charge and helps fill the cylinders.

Intake-opening is the next important factor. This affects emissions the most. Opening the intake late prevents mixing of the exhaust & intake-charge and gives clean emissions and good low-end power. However, at high-RPM, you want the intake to open earlier (10-30 BTDC) in order to have more overlap to take advantage of exhaust-scavening.

Intake-closing is by far the most important valve-event in controlling cylinder-filling. Like the others, optimum timing changes with RPM. At low-RPM, you want an early closing, like around BDC in order to not have the compression-stroke push your intake-charge back out the intake-port. This gives the most compression-time as well. But at high-RPM, the air is stretched out by the higher velocity and you need extra time in order to fill the cylinders. In which case, a later intake-closing 40-60 after BDC results in better cylinder-filling.

Combine these four valve-events together and we can calculate a duration for the intake & exhaust valves. Right in between the opening & closing events is the lobe-center. It's easiest to talk in terms of duration & lobe-centers than actual valve-opening & closing times.

The other factor aside from valve opening & closing times is valve-lift. More is not always better as some people think. That's because the air actually flows at 90-degrees to the port when the valve starts to open. The flow-area is like a cylinderr or drum that's described by the circumference of the valve. Once you have more than 20-25% of the valve-diameter, more lift doesn't give much more flow because now you're limited by the cross-sectional area (diameter) of the port. For example, if you've got a 1" diameter port, it doesn't matter if you open the valve 1" or 0.5" because at that amount of lift, the surface-area of the flow-circumference is larger than the diameter of the port.

And at high-RPM, duration is more important than lift because of the plateau period (average time valve is at a certain lift). A lower lift lets you have a wider-plateau and keep the valve open longer at maximum lift. On Norwood's 700bhp 951, he actually reduces valve-lift compared to stock in order to rev the engine faster.

Relating to the plateau time is the ramp-up and ramp-down rates. The lighter the total valvetrain weight you have (this includes the lifters and oil within on our cars), the faster you can open and close the valves. Increasing valve-spring tension also allows you to open & close the valves faster, but there's a point of diminishing returns where the extra friction counteracts any gains you get. Or course, the best solution here is a solid-lifter conversion that reduces weight tremendously and allows for very agressive ramp-up & down rates (thus widening plateau time for same cam-duration).

As you can see, there are numerous factors that needs to be juggled just in spec'ing a cam. And it has to be done in conjuction with all the other engine specs. For example, when designing an engine, you have to ask yourself:

- what kind of driving are you doing?
- what kind of gas do you have available?
- what's the final torque/HP goals?

These will dictate, first, the compression-ratio you can use. If you have high-octane gas availble, you'll want to maximize compression. A 12.0:1 engine will require at least a 280-degree cam, which would be a complete waste on a 9.5:1 engine (a 250-degree cam is better here). A high-revving race engine would need a cam with 120-degree lobe centers or so and a 65-degree intake-closing. One designed for stop-light drag-racing could use the opposite, something with less duration and 110-degree centers, but higher-lift for low-end torque.

So the process is fixed once you've determined your compression and installed the pistons. At that point, you can juggle other things that'll bolt-on such as intake-manifold and exhaust-header lengths, throttle-body size, etc. Once those are defined, there's a certain cam-spec that's optimum for that configuration.

Even then, the optimum cam-spec is dependent upon RPM. Best low-end torque is made with a cam with early intake-closing, close lobe-centers and short duration. However, as engine-revs increase, to keep torque-high to generate high-RPM HP, you want a later intake-closing with wider lobe-centers and more duration. Thus, the evolution of variable cam mechanisms on the newer cars. VTEC and VarioCam are early types of this with distinct low & rpm cam-specs. VTEC switches between two different cam-lobes while VarioCam rotates the cam-timing. More recent innovations allows continuously variable cam-timing along with duration and valve-timing as well, such as BMW's SuperVANOS, Toyota's VVTi, Porsche's VarioCamPlus, etc.

So the effect of changing cam-timing is the same as changing the cam-lobes themselves. For example, let's take the stock '86+ 944/924S cam part# 944,.105.155.09 with 228-duration and 115-degree intake lobe center and 113 exhaust lobe-center. This gives a nice torque-peak around 4000rpm with a good powerband 1000rpm before and after (3000-5000rpm).

A simple mod is to retard the entire cam by about 10-degrees with an adjustable cam-gear. This results in cam-specs of 228-duration, 125-degree intake LC, 103-degree exhaust LC. This moves your torque-peak about 1000rpms up and the powerband is now 4000-6000rpm. The higher-RPM torque ends up yielding about +10 peak-HP. You could've gotten the same result by grinding a new cam with the same specs of 228-duration, 125-degree intake LC, 103-degree exhaust LC and using the stock fixed cam-gear.

But this mod is a compromise because it doesn't increase valve-duration or overlap and actually moves the exhaust-lobes in the opposite direction that we want. To widen the powerband more and get more peak-HP, we want to move the cam-lobes in opposite directions: advance the exhaust and retard the intake. So a even better cam-spec would be 250-duration with 120 lobe-centers for both intake & exhaust. This opens the exhaust-valve earlier for better high-RPM scavening. The lower 120 LC keeps the torque-peak lower than the cam-gear mod for a wider powerband. Which is created by getting even more high-RPm flow due to the longer overlap (8-degrees more) and 16-degree later intake-closing. So this cam-spec would end up giving +15hp rather than +10hp and has a wider powerband from 3500-6500rpm.

But if you wanted to have a dual-purpose autocross and open-track car, you'd use this 2nd cam with an adjustable cam-gear to fine-tune the power-band. You'd advance it about 5-degrees to get more low-end torque for the autocross with a 3000-6000rpm powerband. Then on the big tracks, you'd retard the cam 5-dgrees to get a 4000-7000rpm with more high-RPM peak-HP.

As you can see, the cam is the last step in the process and allows for customizing the powerband to best suit your needs. I've never swapped out pistons, intake-manifolds or exhaust-headers between different tracks, but I've definitely tried three different cams and made multiple timing-changes to each one in a single day... heh, heh...


Last edited by DannoXYZ; 10-15-2004 at 02:41 AM..
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