Well...Not really. Higher lift relates to more airflow. It can create torque or HP or both, depending on overlap. Over lap kills torque and increases HP.

Whats a mild cam upgrade for the 1g nt? Without upgrading valvetrain. Would i need a bigger pump, possibly an AFC? I want something more than stock turbo cams thank you

Originally posted by Mike1992
Whats a mild cam upgrade for the 1g nt? Without upgrading valvetrain. Would i need a bigger pump, possibly an AFC? I want something more than stock turbo cams thank you

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You could probably do an entire turbo conversion for the same price as cams

Well...Not really. Higher lift relates to more airflow. It can create torque or HP or both, depending on overlap. Over lap kills torque and increases HP.

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Yes more lift relates to more airflow but overlap does not always hurt torque. If all else is equal, a cam with a tighter lobe separation, more overlap, will have more peak torque. Of course this only applies if the exhaust back pressure relative to the intake pressure is not too high. This occurs because of the late exhaust opening point. However, the torque is "peaky" because at higher rpms the cylinder needs an earlier opening to allow time for the exhaust gases to be effectively removed from the cylinder. The peak horsepower will be less because HP is time, rpm, based. So as the torque falls quicker with a tight lobe separation the peak hp will also drop.
If you want to see it, try playing with some HP and Torque graphs in Excel. Make a column for RPM, HP, and Torque. Use the formula for HP=(TorquexRPM)/5252 to obtain the HP from the entered Torque values. Depending on your RPM range it is possible to get more area under the HP/Torque curve by having a "peaky" torque band verses a "wide" torque band. You can also see that having a wide Torque band can give you more high rpm HP but less total useful area.

Chris

Originally posted by anoldsman
Yes more lift relates to more airflow but overlap does not always hurt torque. If all else is equal, a cam with a tighter lobe separation, more overlap, will have more peak torque. Of course this only applies if the exhaust back pressure relative to the intake pressure is not too high. This occurs because of the late exhaust opening point. However, the torque is "peaky" because at higher rpms the cylinder needs an earlier opening to allow time for the exhaust gases to be effectively removed from the cylinder. The peak horsepower will be less because HP is time, rpm, based. So as the torque falls quicker with a tight lobe separation the peak hp will also drop.
If you want to see it, try playing with some HP and Torque graphs in Excel. Make a column for RPM, HP, and Torque. Use the formula for HP=(TorquexRPM)/5252 to obtain the HP from the entered Torque values. Depending on your RPM range it is possible to get more area under the HP/Torque curve by having a "peaky" torque band verses a "wide" torque band. You can also see that having a wide Torque band can give you more high rpm HP but less total useful area.

Chris

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Good explanation, but in my small experiance, when I see cams move peak torque to a higher rpm, its never as high...320 at 5k instead of 330 at 4k, but much more hp, for the reasons you listed. Is that just poor cam design? I though more overlap reduced volumetric effciency as a rule, so you lost some torque potential?

Good explanation, but in my small experiance, when I see cams move peak torque to a higher rpm, its never as high...320 at 5k instead of 330 at 4k, but much more hp, for the reasons you listed. Is that just poor cam design? I though more overlap reduced volumetric effciency as a rule, so you lost some torque potential?

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The reason for this has to do with the time available to expel the exhaust gases. It is much easier for a cylinder to remove the exhaust gases at 4k than it is at 5k. Try to think of it as the injector available time to inject. As the rpms increase there is simply less time to do the task. If you want to obtain the highest torque numbers but at a higher rpm, you need to increase the duration as well as close the exhaust later.
As far as volumetric efficiency is concerned, let’s assume that the intake closing is at the same point with two setups. Setup A we have an exhaust opening of 42 degrees before bottom dead center (BBDC). In Setup B we change the lobe separation 5 degrees. The exhaust opening is now at 37 degrees BBDC. We just allowed the exhaust gases to "push" on the piston for another 5 degrees. This will increase the VE. However the torque will fall off quicker as the rpms increase so the peak hp will be less. This is because of the lack of available time to expel the exhaust gases. Now this assumes that the intake closing is not changed. If it is, a whole new range of possibilities can occur.

Chris

Originally posted by anoldsman
The reason for this has to do with the time available to expel the exhaust gases. It is much easier for a cylinder to remove the exhaust gases at 4k than it is at 5k. Try to think of it as the injector available time to inject. As the rpms increase there is simply less time to do the task. If you want to obtain the highest torque numbers but at a higher rpm, you need to increase the duration as well as close the exhaust later.
As far as volumetric efficiency is concerned, let’s assume that the intake closing is at the same point with two setups. Setup A we have an exhaust opening of 42 degrees before bottom dead center (BBDC). In Setup B we change the lobe separation 5 degrees. The exhaust opening is now at 37 degrees BBDC. We just allowed the exhaust gases to "push" on the piston for another 5 degrees. This will increase the VE. However the torque will fall off quicker as the rpms increase so the peak hp will be less. This is because of the lack of available time to expel the exhaust gases. Now this assumes that the intake closing is not changed. If it is, a whole new range of possibilities can occur.

Chris

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This is why I do not design camshafts.

Thanks for the info. Just to ask: Changing things like intake manifold, exhaust manifold, camshafts and head porting all change the VE of an engine? I would assume yes, but assuming makes an ass out of you and me. Thanks again.

-Groomz

Thanks for the info. Just to ask: Changing things like intake manifold, exhaust manifold, camshafts and head porting all change the VE of an engine? I would assume yes, but assuming makes an ass out of you and me. Thanks again.

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Yes, it is a package deal. A change to any one of these will affect the VE of the motor.

Chris

hopefully your still watching this thread, but with the higher lift of the comp cams, do you recommend upgraded springs and retainers so u dont go floating valves? i got the more aggressive ones, but im weary to install till i get some crower/springs retainers i think with the high lift.

hopefully your still watching this thread, but with the higher lift of the comp cams, do you recommend upgraded springs and retainers so u dont go floating valves? i got the more aggressive ones, but im weary to install till i get some crower/springs retainers i think with the high lift.

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You will not need aftermarket springs or retainers with our catalog cams. However, if you are trying to turn 9000+ rpm with our largest 101200 cams and old factory springs, I would use the Crower pieces.
Even thought they are competitors of ours, I would highly recommend the Crower pieces. This is for two reasons. One is that we do not currently sell anything that will bolt in; we might if the volume of cam sales becomes high enough. The second reason is that I have a set in my car. The custom grinds that I am using are very aggressive and went into valve float at 6500 rpm. After I put the Crower pieces in, the valve float went away. The savings in weight is tremendous verses the stock stuff. The small pressure increase is just an added bonus.

Chris

you say you dont NEED them, but ive seen HKS 272s float valves, and these have quite a bit more lift to them, is theyre a decent chance theyre gonna cause valve float? im only currently revving to 7k but the 272 incident happened revving to 6500rpms.

>you say you dont NEED them, but ive seen HKS 272s float valves, and these have
>quite a bit more lift to them, is theyre a decent chance theyre gonna cause valve float?
>im only currently revving to 7k but the 272 incident happened revving to 6500rpms.

Something else must be wrong with your set-up, 6500rpms is way too low to experience valve float with 272 cams. How did you determine that you were floating valves? Valve marks on the pistons?

Could you be running too much oil pressure and “pump-up” your lifters?

Leon
RR

My springs have 232k on them and see 8k regularly on 272's. I was trying 9k shifts last tiem I went to the track....no float.

i seen hks cams w/ 272 Duration and w/ 9.8mm lift. and then i see the same cams(hks 272) w/ the same duration, but w/ the 10.3 lift. whats the difference? im rebuilding my head and i want to know which lift is better w/ a stock block.

thanks,
john

Originally posted by clipise
i seen hks cams w/ 272 Duration and w/ 9.8mm lift. and then i see the same cams(hks 272) w/ the same duration, but w/ the 10.3 lift. whats the difference? im rebuilding my head and i want to know which lift is better w/ a stock block.

thanks,
john

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The 10.3mm is for the HKS272 intake. The 9.8mm is for the HKS 272 exhaust. Lift is dependent on head flow. If the heads flow well past the 10.3mm/9.8mm, then more lift will yield more power.

Chris

Originally posted by GRNDSM
>you say you dont NEED them, but ive seen HKS 272s float valves, and these have
>quite a bit more lift to them, is theyre a decent chance theyre gonna cause valve float?
>im only currently revving to 7k but the 272 incident happened revving to 6500rpms.

Something else must be wrong with your set-up, 6500rpms is way too low to experience valve float with 272 cams. How did you determine that you were floating valves? Valve marks on the pistons?

Could you be running too much oil pressure and “pump-up” your lifters?

Leon
RR

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I agree 100% with Leon. Something else is wrong. The springs could be severely worn or you are having lifter problems.

Chris

was my buddies car, he had some nice valve marks on the pistons, springs/retainers were stock but brand new. oil pressure was normal, balance shafts still in. I dont know, everyone that does sell the comp cams has told me i should throw in crowers before running these cams. Im gonna do it, just really dont feel like swappin em, im sick of workin on the car after all the recent stuff ive done =[ Mike huml told me without a doubt go with crowers before isntalling them, hes runnin the comp cams in his 'race car'.

Originally posted by anoldsman
The custom grinds that I am using are very aggressive and went into valve float at 6500 rpm.
Chris

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Those grinds would'nt be available would they?

Originally posted by anoldsman
The custom grinds that I am using are very aggressive and went into valve float at 6500 rpm.
Chris

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Originally posted by MNGSX
Those grinds would'nt be available would they?

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Yes, you can purchase this grind. However, just be sure that you have a good set of springs and retainers. It would be a custom cam order. Just ask your dealer to order 8722/8725 107 +9. It is a dual pattern cam with 203/0.415" intake 211/0.390" exhaust. We can make it a single pattern style if you need it. It all depends on your modifications. PM me if you want to discuss it further.

Chris

Who sells the comp cams?

Slowboy racing has them for $469. I'd like to know if there are any other places as well.

jazzyjay Who sells the comp cams?

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Originally posted by jazzyjay
Who sells the comp cams?

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I just ordered a set from Summitracing.com, go under Manufacture select Comp Cams INC, then put the part number 101100 for the street or the 101200 for race ones the list them for 459.95 plus 8.95 handling fee so its 468.90 shipped a bit cheaper than SBR and includes shipping

ill post pics when they come in

Eric C
97 GS-T
50-Trim

Originally posted by jazzyjay
Who sells the comp cams?

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I am not sure of all of our vendors that sell the cams but, we have worked with both Forced Performance and Turbo Trix in the past. They are both great shops that are able to help you with anything DSM related.

Chris

Thanks for the quick replies

sorta old thread but curious if you guys have gotten any numbers from tests or from others who are using comp cams?