Thread: smallblock cam selection

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OK i have a 350 chevy with 11:1 compression forged pistons, kmj rods, forged crank, ported and polished 202 fuelie heads, ported edelbrock super vic intake and 1 7/8" hooker super competition headers,3:90 gears,and a 4-speed in a 3100lb 74' Nova and i was wondering if this cam would work heres the specs its from kmj performance. Would it be too big?


New Small Block Chevy solid tappet Camshaft and matching lifter kit. Excellent High Torque Modified Engine. If you have tight corners and need something to come on fast this is the cam. 1/4 to 3/8 mile tracks. Optimum Power band of 3200-7200 RPM. All you street bracket racers know that circle track camshafts make the most horsepower and provide for the best acceleration in your small block chevy.

Intake lift: 562 Exhaust Lift: 584

Lobe Seperation 106

Advance Duration 290 intake 300 exhaust or at .050" 259 and 269 respectively.
Valve Lash is .018/.020

Too much cam for 11.0:1 SCR. That cam needs 11.5 to 12.5:1. 11.0:1 needs 244/252 on 106 LSA with intake close at 45 degrees ABDC. You're gonna run out of head before you run out of cam.

Hey Tech. Can you tell what RPM's a cam should be able to turn buy the Duration and center lobe? Kurt

Ya Tech What Camshaft would you Run in this 350? And would you Make other Changes other then the Fuelly Heads ?

Originally Posted by vara4

Hey Tech. Can you tell what RPM's a cam should be able to turn buy the Duration and center lobe? Kurt

You can get an idea from the duration, but the lobe center can be all over the place, 104-114. The rpm numbers I've shown here are indicative of the power range of the camshaft, not necessarily the min and max r's of the grind.

This is from a chart I have on flat tappet hydraulic cams for a SBC....the number following the LC is the intake closing point @ 0.050". For those of you playing along at home, Lobe Center, Lobe Separation Angle and Lobe Displacement Angle all mean the same thing. These are not to be confused with Intake Centerline, the point of maximum lift of the intake lobe.... or Exhaust Centerline, the point of maximum lift of the exhaust lobe. If the intake centerline is 106 degrees AFTER top dead center and the exhaust centerline is 114 degrees BEFORE top dead center, then adding 106 and 114 together and dividing by 2 will reveal a Lobe Center of 110 degrees. A lobe center of 114 will give a dead smooth idle and high manifold vacuum. A lobe center of 104 will give a choppy, machine gun idle and low manifold vacuum. The last figures are the ideal static compression ratio to run with that particular cam timing. I didn't have all of them, but it shouldn't be difficult to fill in the blanks.
184/194...104/16.....500/4000
184/194...112/19...1000/3200
192/204...112/23... 800/4600...7.75-8.75
194/204...104/21.....800/4400
204/204...110/27...1000/4600...8.0-9.5
204/214...110/32...1200/4800
206/218...112/30...1200/5200...8.0-9.5
210/210...110/30...1400/5000...8.5-10.0
210/216...114/34...1600/5400
212/218...114/35...1600/5400...8.5-10.0
214/224...112/34...2000/4800
216/216...110/33...1600/5400...8.75-10.0
216/228...112/35...1800-5600
218/218...106/31...1800/5400...8.75-10.0
218/230...112/36...1800/5800...8.75-10.75
222/222...110/36...2000/5800...9.5-10.75
224/230...110/37...2200/6400...9.5-10.75
226/226...106/34...2400/6200...9.5-11.0
228/228...106/36...2800/6400...9.5-11.5
228/228...112/41...2800/6200...9.5-11.0
228/232...107/37...2800/6000...9.0-10.5
228/234...106/36...2800/6400...10.0-11.5
230/230...106/37...3000/6400...10.0-11.5
232/232...107/39...3000/6000...9.0-10.5
232/236...106/38...3000/6400...10.0-11.0
236/236...107/41...3200/6200...10.0-11.0
236/242...112/40...3200/6600...10.0-11.0
236/244...110/43...3000/6800...10.25-12.0
238/238...106/41...3200/6400...10.5-12.0
238/244...106/41...3200/6800...10.5-12.0
244/252...106/44...3400/7000...10.5-12.0
246/246...106/45...3400/7000...10.5-12.0

As the intake valve closing point numbers get larger, the intake valve is closing farther away from bottom dead center while the piston is headed up in the bore on the compression stroke. Compression cannot begin until the intake valve closes and as the intake valve closes later and later with a bigger and bigger cam, more and more of the fuel/air mixture that has just been drawn in through the intake valve, gets pushed back out the still-open intake valve by the piston and up the intake tract to disrupt the signal at the venturi. Result: rump-rump. As the cam gets wilder, it takes a higher and higher rpm point for the motor to "get up on the cam" and smooth out to begin making power.

This also explains why you have to coordinate the static compression ratio of the motor with your cam choice. The amount of mixture left in the cylinder after the intake valve closes has to coincide with the squeeze you're gonna put on the mixture. Close the valve too late (long cam) with a low static compression ratio (the most common rookie mistake) and you have a lizard due to insufficient cylinder pressure. Close the valve too early (short cam) with a high static compression ratio and you have a motor that will detonate on pump gas due to excessive cylinder pressure.

I had a buddy call and tell me he's got a 351M for me if I want it.
And I have some extra stuff laying here that I picked up and some I
got when I bought my cleveland motor. Most stuff will interchange
except the rods crank and intake. I've got a Erson cam Laying on
the shelf that will fit it. It's a TQ 50 series Erson But is probably to big
for everyday driving.
ADV.296 in./306 ex.
@50. 228 in./235ex.
gross lift. 545/545
center lobe. 110
springs 95 pounds closed and 315 pounds open.
Thinking of getting a crank kit for a 400 and putting in the block
since the 351M and the 400m blocks are identical. Kurt

Pay attention to the 0.050" timing and forget the advertised duration. Unless you have the timing card, you don't know if they calculated the advertised at 0.000" or 0.004" or 0.006" or ?????? Looks like a streetable cam to me.

So if i extensively port the heads and polish piston tops and chambers and raise my compression to say 12:1 would the cam be big enough to ward off detonation on say 98 octane gas or if i ran water injection.

i don't know much about dynamic compression but i heard if you have alot of static compression and you have a big enough cam you could run it on pump gas.
Is that right?

P.S. i will eventually get a good set of aftermarket aluminum heads.

also the cam spec sheet said high torque, is that high torque for a street car or do they mean high torque for a circle track car?

Originally Posted by zwuvlu

So if i extensively port the heads and polish piston tops and chambers and raise my compression to say 12:1 would the cam be big enough to ward off detonation on say 98 octane gas or if i ran water injection.

i don't know much about dynamic compression but i heard if you have alot of static compression and you have a big enough cam you could run it on pump gas.
Is that right?

P.S. i will eventually get a good set of aftermarket aluminum heads.

also the cam spec sheet said high torque, is that high torque for a street car or do they mean high torque for a circle track car?

Please post EVERYTHING that is on the cam card.

Thanks Tech. Kurt

i didn't mean cam card i meant what was on the website i haven't bought the cam yet. i was just looking for a decent priced cam with enough lift to make use of my .600" lift valve springs, i know i shouldn't base my cam selection on that but it was only $100 for a cam and solid lifters. any other suggestions would be appreciated. Thanks Tech.

Originally Posted by zwuvlu

i didn't mean cam card i meant what was on the website i haven't bought the cam yet. i was just looking for a decent priced cam with enough lift to make use of my .600" lift valve springs, i know i shouldn't base my cam selection on that but it was only $100 for a cam and solid lifters. any other suggestions would be appreciated. Thanks Tech.

Yeah, you're correct in thinking that's no way to choose a cam. What exactly have you bought? Do you have pistons and rods yet? How about the crank and headers and intake? And by the way, those headers are too big for a 350. 1 3/4" would be a God's plenty.

First, you determine the rpm range you want to operate in, then set the static compression ratio to coordinate with the cam, then choose the cam, then choose the springs to work with the cam according to the cam manufacturer's recommendations. Then you choose headers, intake and carb to work with all the rest of it. Then you choose a converter and gears based on the power range of the cam.

Originally Posted by zwuvlu

OK i have a 350 chevy with 11:1 compression forged pistons, kmj rods, forged crank, ported and polished 202 fuelie heads, ported edelbrock super vic intake and 1 7/8" hooker super competition headers,3:90 gears,and a 4-speed in a 3100lb 74' Nova and i was wondering if this cam would work heres the specs its from kmj performance. Would it be too big?


New Small Block Chevy solid tappet Camshaft and matching lifter kit. Excellent High Torque Modified Engine. If you have tight corners and need something to come on fast this is the cam. 1/4 to 3/8 mile tracks. Optimum Power band of 3200-7200 RPM. All you street bracket racers know that circle track camshafts make the most horsepower and provide for the best acceleration in your small block chevy.

Intake lift: 562 Exhaust Lift: 584

Lobe Seperation 106

Advance Duration 290 intake 300 exhaust or at .050" 259 and 269 respectively.
Valve Lash is .018/.020

Tech what Camshaft would You use in this Build ?

i already have the heads, crank,pistons and headers and that is all the other parts i mentioned i was going to buy so if you have better ideas on what i should buy i would definetly consider them because you have way more knowledge about this stuff than i do.

also i will eventually transfer all these parts except pistons and i might get better heads and longer rods into a my 400 block for a 377 stroker so a little bit big on things probably wouldn't hurt since this engine is very temporary.