cam emissions opinions
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From: lowry crossing, texas
Car: 1984 Z/28 Camaro
Engine: 350ci
Transmission: T-56
Axle/Gears: 9" 3.73 spool
cam emissions opinions
have a 350 short block almost ready to assemble, want to ask about cams, as concerned with emissions. a friend stated i shouldnt run more than 224 duration @.50 if i wanted to pass emissions.
i was considering the CC XE268h or the CC XE274h
Hydraulic flat tappet
RPM Range 1,600-5,80
Dur at 050 inch Lift 224 int./230 exh.
AdvDur 268 int./280 exh.
Valve Lift with Factory Rocker Arm Ratio 0.477 int./0.480 exh. lift
Lobe Separation (degrees) 110
RPM Range 1,800-6,000 RPM
Dur at 050 inch Lift 230 int./236 exh.
Adv Dur 274 int./286 exh.
Valve Lift with Factory Rocker Arm Ratio 0.487 int./0.490 exh. lift
Lobe Separation (degrees) 110
set up as i have planned at the moment, not set in stone as i dont have the parts yet, (waiting gonna take it slow)
350, .060" over, flat top seal power pistons "hyper", moly rings, stock .20".20" crank, stock rods arp bolts, 4 bolt mains arp bolts, clevite 77 main rod and cam berings, vortec heads(upgrade springs and heads for more lift, maybe screw in studs?should i)roller tipped comp rocker arms 1.5, rpm manifold, 600cfm edlebrock, accel ditrib, msd 6al, external coil. as far as ehaust goes i will have shorty style hookers, after that its in the air, want to try 3 inch cats after the headers and a mufflex 3.5" or 4" system cause i think itd sound the way i want it to.
what do yall think, what have you tryed? is the 268 too much even to pass the sniffer? can i get away with more? i think ill stay at these two for my daily driver needs.
P.S. if i did have screw in studs do the stock self aligning style rocker arms still work?
i was considering the CC XE268h or the CC XE274h
Hydraulic flat tappet
RPM Range 1,600-5,80
Dur at 050 inch Lift 224 int./230 exh.
AdvDur 268 int./280 exh.
Valve Lift with Factory Rocker Arm Ratio 0.477 int./0.480 exh. lift
Lobe Separation (degrees) 110
RPM Range 1,800-6,000 RPM
Dur at 050 inch Lift 230 int./236 exh.
Adv Dur 274 int./286 exh.
Valve Lift with Factory Rocker Arm Ratio 0.487 int./0.490 exh. lift
Lobe Separation (degrees) 110
set up as i have planned at the moment, not set in stone as i dont have the parts yet, (waiting gonna take it slow)
350, .060" over, flat top seal power pistons "hyper", moly rings, stock .20".20" crank, stock rods arp bolts, 4 bolt mains arp bolts, clevite 77 main rod and cam berings, vortec heads(upgrade springs and heads for more lift, maybe screw in studs?should i)roller tipped comp rocker arms 1.5, rpm manifold, 600cfm edlebrock, accel ditrib, msd 6al, external coil. as far as ehaust goes i will have shorty style hookers, after that its in the air, want to try 3 inch cats after the headers and a mufflex 3.5" or 4" system cause i think itd sound the way i want it to.
what do yall think, what have you tryed? is the 268 too much even to pass the sniffer? can i get away with more? i think ill stay at these two for my daily driver needs.
P.S. if i did have screw in studs do the stock self aligning style rocker arms still work?
Last edited by blackgold84; Feb 5, 2005 at 12:36 AM.
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From: Toledo, OH
Car: 1992 Firebird
Engine: forged 357
Transmission: 700r4, 2200-2400 stall, vette servo
Axle/Gears: stock pegleg 2.73 drum (temp)
OVERLAP:
This is the killer for street engines. Overlap is the amount of degrees that the intake and exhaust valves are open at the same time. Unburned air/fuel mixture will be pushed through the cylinder when both valves are open and straight out the exhaust. This decreases mileage, increases emissions, and make the engine run rough at low rpms. It also decreases low-rpm torque, and hurts throttle response.
All cams have some amount of overlap. Stock cams all try to keep the overlap low for the above reasons.
More duration with no other changes will increase overlap. One way of lowering overlap after it's been increased by more duration is to increase lobe separation. This is because moving the lobes away from each other decreases the time they are open simultaneously.
This is the killer for street engines. Overlap is the amount of degrees that the intake and exhaust valves are open at the same time. Unburned air/fuel mixture will be pushed through the cylinder when both valves are open and straight out the exhaust. This decreases mileage, increases emissions, and make the engine run rough at low rpms. It also decreases low-rpm torque, and hurts throttle response.
All cams have some amount of overlap. Stock cams all try to keep the overlap low for the above reasons.
More duration with no other changes will increase overlap. One way of lowering overlap after it's been increased by more duration is to increase lobe separation. This is because moving the lobes away from each other decreases the time they are open simultaneously.
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From: lowry crossing, texas
Car: 1984 Z/28 Camaro
Engine: 350ci
Transmission: T-56
Axle/Gears: 9" 3.73 spool
how do i find what the overlap would be?
judging by the site i should stick at or under 224 degree intake duration...
also i have heard that making the lobe seperation bigger costs power? does this have any truth
judging by the site i should stick at or under 224 degree intake duration...
also i have heard that making the lobe seperation bigger costs power? does this have any truth
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Joined: May 2003
Posts: 1,995
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From: Toledo, OH
Car: 1992 Firebird
Engine: forged 357
Transmission: 700r4, 2200-2400 stall, vette servo
Axle/Gears: stock pegleg 2.73 drum (temp)
Originally posted by blackgold84
how do i find what the overlap would be?
judging by the site i should stick at or under 224 degree intake duration...
also i have heard that making the lobe seperation bigger costs power? does this have any truth
how do i find what the overlap would be?
judging by the site i should stick at or under 224 degree intake duration...
also i have heard that making the lobe seperation bigger costs power? does this have any truth
LOBE SEPARATION
Lobe separation is the number of degrees the intake and exhaust lobes are separated. More separation decreases overlap (see overlap below). However, tighter lobe separation makes more high-end hp.
Lobe separation is the number of degrees the intake and exhaust lobes are separated. More separation decreases overlap (see overlap below). However, tighter lobe separation makes more high-end hp.
Joined: Mar 2000
Posts: 43,187
Likes: 42
From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
Overlap is a combination of duration and LSA.
The best way to make sure it will pass is to get a cam the manufacturer recommends for an emissions-legal application of your type.
The best way to make sure it will pass is to get a cam the manufacturer recommends for an emissions-legal application of your type.
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Joined: May 2003
Posts: 1,995
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From: Toledo, OH
Car: 1992 Firebird
Engine: forged 357
Transmission: 700r4, 2200-2400 stall, vette servo
Axle/Gears: stock pegleg 2.73 drum (temp)
Originally posted by five7kid
Overlap is a combination of duration and LSA.
The best way to make sure it will pass is to get a cam the manufacturer recommends for an emissions-legal application of your type.
Overlap is a combination of duration and LSA.
The best way to make sure it will pass is to get a cam the manufacturer recommends for an emissions-legal application of your type.
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Joined: Jan 2002
Posts: 3,852
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From: Valley of the Sun
Car: 82 Z28
Engine: Al LT1 headed LG4 305
Transmission: TH350
Axle/Gears: 3.73 posi with spacer
For emissions you want a cam with atleast a LSA of 112, more like 114 or 116 though if a wilder cam.
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From: lowry crossing, texas
Car: 1984 Z/28 Camaro
Engine: 350ci
Transmission: T-56
Axle/Gears: 9" 3.73 spool
does any one have cam sugestions, i basicly want my power to be in the 1800 to 5800 range...
and friend suggested a cam similar to the hot cam, does anyonemake this for a hyd flat tappet motor?
found this one, is this close to what i should try
Computer Controlled Hydraulic Flat Tappet Camshaft
Lift: .464''/.464''
Duration @ .050'': 222°/226°
RPM Range: 1800-5800
says its rec. for tpi 350ci
and friend suggested a cam similar to the hot cam, does anyonemake this for a hyd flat tappet motor?
found this one, is this close to what i should try
Computer Controlled Hydraulic Flat Tappet Camshaft
Lift: .464''/.464''
Duration @ .050'': 222°/226°
RPM Range: 1800-5800
says its rec. for tpi 350ci
Last edited by blackgold84; Feb 6, 2005 at 10:39 PM.
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Joined: Aug 2001
Posts: 814
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From: San Jose, CA, USA
Car: 88 IROC-Z - original owner!
Engine: LB9 with K&Ns, MSD, Foil, Taylor
Transmission: WC T-5
Axle/Gears: BW 9-bolt, 3.45 posi
What's the LSA on that cam?
What's the LSA on a GM Hot Cam?
My LB9 stock cam has a 117 LSA which is widern'hell.
What's the LSA on a GM Hot Cam?
My LB9 stock cam has a 117 LSA which is widern'hell.
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From: lowry crossing, texas
Car: 1984 Z/28 Camaro
Engine: 350ci
Transmission: T-56
Axle/Gears: 9" 3.73 spool
one i just posted - 112°
hot cam -
Hydraulic roller tappet
RPM Range Idle-6,000 RPM
Dur @ 050 inch Lift 219 int./228 exh.
Valve Lift 0.525 int./0.525 exh. lift
Lobe Separation (degrees) 112
hot cam -
Hydraulic roller tappet
RPM Range Idle-6,000 RPM
Dur @ 050 inch Lift 219 int./228 exh.
Valve Lift 0.525 int./0.525 exh. lift
Lobe Separation (degrees) 112
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Originally posted by blackgold84
one i just posted - 112°
hot cam -
Hydraulic roller tappet
RPM Range Idle-6,000 RPM
Dur @ 050 inch Lift 219 int./228 exh.
Valve Lift 0.525 int./0.525 exh. lift
Lobe Separation (degrees) 112
one i just posted - 112°
hot cam -
Hydraulic roller tappet
RPM Range Idle-6,000 RPM
Dur @ 050 inch Lift 219 int./228 exh.
Valve Lift 0.525 int./0.525 exh. lift
Lobe Separation (degrees) 112
Last edited by anondude13; Feb 9, 2005 at 01:18 AM.
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Joined: May 2003
Posts: 1,995
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From: Toledo, OH
Car: 1992 Firebird
Engine: forged 357
Transmission: 700r4, 2200-2400 stall, vette servo
Axle/Gears: stock pegleg 2.73 drum (temp)
Originally posted by r3pp3r
I'm not sure. I think hotcam got tied to 1.6's because of the "hotcam kit" that included cam, rockers, and springs.
I'm not sure. I think hotcam got tied to 1.6's because of the "hotcam kit" that included cam, rockers, and springs.
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Joined: Jul 1999
Posts: 18,457
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From: Loveland, OH, US
Car: 4
Engine: 6
Transmission: 5
Every single cam that people have been recommending, is a roller cam, optimized for fuel injection. The "305" grind, the LT4 HOT cam, etc.
You don't have fuel injection; and maybe not a roller motor either.
You don't want a cam set up for TPI. TPI imposes specific restrictions and requirements on cam design, which aren't an issue for you. There's no point in partially crippling your motor.
Vortec heads NEED a cam with a bigger exhaust lobe, than their intake. They have all this great intake flow that comes from re-locating the intake ports to somewhere else, which is of course what "Vortec" means. But they have the same sucky exhaust ports that stock heads have always had.
An excellent choice, which will almost certainly pass emissions, is the Comp XE262. It's made for carbed cars, and doesn't penalize you by being set up for FI instead.
You don't have fuel injection; and maybe not a roller motor either.
You don't want a cam set up for TPI. TPI imposes specific restrictions and requirements on cam design, which aren't an issue for you. There's no point in partially crippling your motor.
Vortec heads NEED a cam with a bigger exhaust lobe, than their intake. They have all this great intake flow that comes from re-locating the intake ports to somewhere else, which is of course what "Vortec" means. But they have the same sucky exhaust ports that stock heads have always had.
An excellent choice, which will almost certainly pass emissions, is the Comp XE262. It's made for carbed cars, and doesn't penalize you by being set up for FI instead.
Joined: Mar 2000
Posts: 43,187
Likes: 42
From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
FWIW, I absolutely breezed through the dyno sniffer here with the Crane 2050, World S/R 305 heads, functioning EGR, Hooker 2055's & 3" cat, on an LG4 based 305 with over 150k miles on it.
You, on the other hand, are eliminating a big chunk of what makes it easier to pass emissions - computer feedback control. Personally, I wouldn't downgrade like that, but it's your funeral.
Good luck.
You, on the other hand, are eliminating a big chunk of what makes it easier to pass emissions - computer feedback control. Personally, I wouldn't downgrade like that, but it's your funeral.
Good luck.
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