Dual Pattern Cams?
Thread Starter
Safety Car
Joined: Aug 2000
Posts: 3,909
Likes: 26
From: Clymer PA
Dual Pattern Cams?
I pretty much have my mind set on getting the Comp Cams 294S Magnum Solid Lifter Cam. I noticed that Jeg's has two cams to select from:
Comp Cams 294S, Lift .595/.595", RPM Range 2500-6500
Comp Cams 294S, Lift .579/.605", RPM Range 3500-6500
Why would someone want to go with a dual pattern cam if the effective RPM range is only from 3500-6500RPMs when you could go with the same cam that has identical grinds on the intake and exhaust that is effective from 2500-6500RPMs. Could someone please explain this? Does that cam make more power?
I was initially going to go with the .595/.595" lift cam, but am now curious as to the benefits of a dual pattern cam. Thanks.
Comp Cams 294S, Lift .595/.595", RPM Range 2500-6500
Comp Cams 294S, Lift .579/.605", RPM Range 3500-6500
Why would someone want to go with a dual pattern cam if the effective RPM range is only from 3500-6500RPMs when you could go with the same cam that has identical grinds on the intake and exhaust that is effective from 2500-6500RPMs. Could someone please explain this? Does that cam make more power?
I was initially going to go with the .595/.595" lift cam, but am now curious as to the benefits of a dual pattern cam. Thanks.
Racer
Joined: Jan 2000
Posts: 277
Likes: 0
From: Cookeville, TN
Cruise-In III Veteran
Re: Dual Pattern Cams? (bence13_33)
You do realize that you will need a car for a daily driver after you do all of these mods. Your vette will go fast but it will be a PITA to use it as a daily driver. Also you might also think about some frame mods so you dont rip your motor out of its mounts.
I think that you would like your BB better if you did less mods. My slightly moded BB will out perform my LT1. ( In a strait line). You are also going to have to also beef up your front end, rear end and maybe upgrade to a Muncie trans to handle the extra power. just my opinion :D
[Modified by Jeff73454, 10:27 AM 10/29/2001]
[Modified by Jeff73454, 10:29 AM 10/29/2001]
I think that you would like your BB better if you did less mods. My slightly moded BB will out perform my LT1. ( In a strait line). You are also going to have to also beef up your front end, rear end and maybe upgrade to a Muncie trans to handle the extra power. just my opinion :D
[Modified by Jeff73454, 10:27 AM 10/29/2001]
[Modified by Jeff73454, 10:29 AM 10/29/2001]
Le Mans Master
Joined: Feb 1999
Posts: 5,877
Likes: 1
From: Park Ridge IL
Re: Dual Pattern Cams? (bence13_33)
Dual pattern cams are generally used to compensate for poor flowing exhaust ports or exhaust systems. They are also used in forced induction and NO2 applications to aid the exhaust system, since you are mechanically or chemically intriducing more air/fuel than normally possible.
You'll notice that the dual pattern cam has more lift and probably more duration on the exhaust lobe. The intent is hold the exhaust valve open farther and longer to aid in scavenging the spent exhaust gases out of the cylinder. You only really need to use a dual pattern cam if your exhaust ports are weak. If you know your cylinder head flow, you can determine this by figuring out your intake to exhaust efficiency. For a given valve lift, divide the exhaust flow (cfms) byt the intake flow (cfms). If the result is less than 70% (.70) or so, you would probably benefit from a dual pattern camshaft. The higher your intake to exhaust efficiency, the better. Also, if you are running a restrictive exhaust system, a dual pattern will help out somewhat.
You'll notice that the dual pattern cam has more lift and probably more duration on the exhaust lobe. The intent is hold the exhaust valve open farther and longer to aid in scavenging the spent exhaust gases out of the cylinder. You only really need to use a dual pattern cam if your exhaust ports are weak. If you know your cylinder head flow, you can determine this by figuring out your intake to exhaust efficiency. For a given valve lift, divide the exhaust flow (cfms) byt the intake flow (cfms). If the result is less than 70% (.70) or so, you would probably benefit from a dual pattern camshaft. The higher your intake to exhaust efficiency, the better. Also, if you are running a restrictive exhaust system, a dual pattern will help out somewhat.
Thread Starter
Safety Car
Joined: Aug 2000
Posts: 3,909
Likes: 26
From: Clymer PA
Re: Dual Pattern Cams? (Jeff73454)
Jeff:
I don't really see why it will be so hard to still use as a daily driver (during the nice days). It may be hard on gas and noisy but it's not like it's going to be lacking bottom end power. The wide ratio 4 speed and the 3.70 rear end will help out very nicely. As for breaking stuff, that will occur any time you beat on any car. I don't plan on doing clutch dumps, running slicks or power shifting so I can't see why my tranny (or driveline for that matter) won't hold up.
Monty:
Thanks for the information. I don't think I need a dual pattern cam.
I don't really see why it will be so hard to still use as a daily driver (during the nice days). It may be hard on gas and noisy but it's not like it's going to be lacking bottom end power. The wide ratio 4 speed and the 3.70 rear end will help out very nicely. As for breaking stuff, that will occur any time you beat on any car. I don't plan on doing clutch dumps, running slicks or power shifting so I can't see why my tranny (or driveline for that matter) won't hold up.
Monty:
Thanks for the information. I don't think I need a dual pattern cam.
Safety Car
Joined: Aug 1999
Posts: 4,862
Likes: 118
From: Texas
Re: Dual Pattern Cams? (bence13_33)
Bence, that 294S is going to be a very rough idling cam w/ **** poor vacuum. Also a solid lifter cam will require constant lash adjustments which are a PITA. I would suggest you run a Sealed Power hydraulic roller cam for a few more bucks. They have one in the .550" 280 duration range that will out perform the more radical solid lifter cam. It will also run smoother and have much better low end as well as excellent top end power. the best part is you won't have to pull off your valve covers and get freeking oil everywhere setting your valve lash every 3 months.
Drifting
Joined: May 2001
Posts: 1,651
Likes: 13
From: Holly MI
Re: Dual Pattern Cams? (Cam Potter)
Setting valve lash is extremely important. I work for an OEM supplier of valvetrain components and more than 90% of the failures we see are from excessive lash. Excess lash allows the valvetrain to bounce/float on the cam lobes. When this happens, the valve seating velocity skyrockets, and that sends vibrations through the valvespring itself. These vibrations make the system worse, and in many cases the system reaches its critical frequency and the spring breaks. This is worse case, but before that happens, you will lose power at high RPM.
Even though the solid lifter is capable of making more horsepower, the hydraulic lifters are more user friendly and will make more power more of the time unless you are constantly checking lash. I think this is one of the things to consider when you think of a daily driver. If you're willing to pull the valve covers and adjust the lash every time you change the oil, this may not apply to you.
Even though the solid lifter is capable of making more horsepower, the hydraulic lifters are more user friendly and will make more power more of the time unless you are constantly checking lash. I think this is one of the things to consider when you think of a daily driver. If you're willing to pull the valve covers and adjust the lash every time you change the oil, this may not apply to you.
