Camshaft help

[Whooppass]

Looking for a recommendation, I'm building up a 383 SBC for my 67 Camaro. Im ordering up parts and I've been talking to a few different cam companies, right now that the only part I'm undecided about. Quick list of other parts for the build are,

AFR 195 with 64cc chambers
COMP Cams Ultra Pro Magnum Rockers 1.6
5.7 Scat I beam rods
Icon flat top pistons
RPM Performer intake
Hooker headers
Tremec 600 5sp
12 bolt w/ 4:11 gear

Compression should be around 10:7:1

OK so that's set, here are the cams,

110345-10
.565/.580 Valve lift
247/253 @ .050
300/306 advertised duration
110 lobe separation
106 intake centerline

Or this



Part #150-3103
Advertised Duration 292/294
.050" 233/235
.100 202/204
.200 152/150
.300 94/79
Lift .548/.510
Centerline 104/112
Lobe Sep. 108


I've narrowed it down to these 2 cams, please don't suggest anyothers. If you've been through the process of building a motor you know the frustration of going round and round with cam choice.

[1BADBET]

youll be much happier with the smaller cam. The big one is going to kill some bottom end power and you don't have the head and intake to support higher rpm, it will lose everywhere. The smaller one is a much better match for your combo, it will sound nice and make gobs of bottom end, with a 6 speed and 3.73s it should be a blast!

[HellPhish89]

I agree on the smaller cam. The issue with cams is: NO ONE actually tells you what you actually need it to be doing. They wont explain the physics at all or any of it.

You need it to fill the cylinder as quickly and as fully as possible. You need it to evacuate the cylinder as quickly and completely as possible on the other side. The valve events determine dynamic (actual) compression. They also manipulate scavenging and greatly effect the mass flow compression (air that smashes up against the back side of the intake valve.)

With that as this is the advanced section: Fastest valve events your valve train can support are best (highest ramp rate you can safely use). You also want lift that is higher than that of the max flow of your cylinder heads. This allows your average lift to be closer to the heads sweet spot/peak for a longer time. Essentially, get to max lift as fast as you can to use the head more closely to its potential. This maximizes that pressure and therefore density of the air on the back of the valve (will ultimately help raise VE). Closing the valve can go either way really. You can close it slower to keep velocity up or slam it shut to build up that MFC (mass flow compression) for the next cycle.

The next part I think is duration.
You want the valve to be open long enough to fill the cylinder as completely as possible but not so long that air velocity drops. The velocity drop is what kills low RPM performance.

Exhaust side is slightly different. You will be served well to use the exhaust events to help pull in a/f during some of the intake cycle. You also want to use the camshaft and the headers to create a high exhaust flow but also a high exhaust velocity. The quality of the exhaust port GREATLY affects the exhaust lobe of the cam. The LS3 heads have mediocre exhaust ports but REALLY good intake ports so.. a 20* duration split is not unheard of to help crutch the exhaust side. I think rule of thumb is the e-port flow should be 65-70% of the intake port flow. The stock LS7 cam (210/230 .591/.591 120 lsa) makes a great stock replacement camshaft for the LS3 (lift is reduced, obviously, due to the lower rocker ratio).
With that.. my ideal for that 383 with those heads would be something like this:

.600 lift intake/ .610 exhaust (you can manipulate not just lift but also ramp rate with rockers but for this thought experiment... 1.6 rockers)

.050 duration would be 230 on the intake side and 235 or so on the exhaust side.

advertised (.200 i think) would be 280 intake/ 283 (max 285) on the exhaust

LSA would be 110 to 113. depending on what I need for overlap.

Those specs would be pretty hard on a valve train but todays tech means you can get away with it without fear or daily tinkering.

Hopefully I didnt screw any of that up too bad, you learned something, and you feel less confused about the camshaft voodoo.

[Whooppass]

Thank you, I had to reread your post a few times to make sense of it all. I keep over thinking this build to where I want to change everything. But for now I think I'm about 80% content. People say the duration is small, but I don't want to be revving to the moon, I'm not building a race motor. I'll have power way down low (1800)and can take it to 6200ish. That's perfect for me messing around town and for future auto cross/road race.

No its not going to be a balls out 7000rpm single plane monster 383, but that was never my goal. The cam matches my intake and was ground for the heads and the power band I wanted. Thanks again.

BTW this is the cam I had made

[Ben@SpeedTech]

What are you doing with the car? The first cam is a nice street and all around cam, the second would be pretty nasty in drag racing and autocross, but as has been said the intake should be bumped up to an air gap dual plane or even better a single plane like a Victor Jr., (I wouldn't waste time with something like a Torquer II) to take full advantage of that cam's power range. I have run cams somewhat similar to both of those in street driven cars. Both cars had 406" SBCs. below is a comparison of what they were like to drive. If you don't like to read long posts skip to the last paragraph.

The one with the smaller cam had less lift than your smaller one, roughly about .510/.520 with 1.6 rockers, duration was similar. I used factory ported 400 heads, focusing a little more on the exhaust ports and all bowls and valve areas were nicely blended, and with dished pistons was about 8.5:1. With an air gap dual plane and 600 carb it pushed my 3700 lb (with me) G body wagon to sea level 13.60s @ 99 in the 1/4 with a stock converter in the TH350 and 3.42 gears. Power really came on around 2500 and it was dead at 4500. I think with better heads and maybe a 700 carb it may have pulled to 5000, maybe 5500. This motor did ok in autoX, it made gobs of flat line torque. I don't think it would have made a good road course motor without overdrive. It was great for a daily driver, had a bit of a lope at 600 rpm idle, would smooth out at 800+. BUT at autoXs I got a little sick of getting walked by the beefed up LS engines, my car just didn't pull like them on the straights and that widens the lap time gap. Comparing to other engines with similar builds I'm guessing it made about 325 hp and 400 ft lbs at the flywheel.

My other car is a 3100 lb Nova backed by a 4500 stall and 4.56 gears. It has a flat top piston 406 with fully ported and polished World Products Sportsman II heads, 1.6/2.02 valves, a Vic Jr. single plane intake and a 750 carb. The cam is a custom ground .562/.562 lift and 260/262 duration at .050 solid flat tappet with a 110 center. This cam idles rough at 1200 rpm, and will load up and stall at 800 rpms. Vacuum is awful so power brakes are a challenge. Power down low is nothing to be super excited about, but this thing really comes alive at 3200-3500 and it will easily rev to 7400 (I'm too scared to go any higher than that), although I normally shift at 6500 because of the stock cast crank. It makes crazy torque and will easily fry 275-60-15 street tires, from a cruise at 30 mph and down shifting to 1st gear it blows the tires away and fries them through all of 1st, 2nd, and into 3rd. At the track on drag slicks it's ran mid 11's in the 1/4, with a 1.63 best 60' time and pulls the tires about 3" high off the line. This used to be my daily driver. Desktop dyno said this motor should be 562 hp @ 6500 and 511 ft lbs. @ 5000. Take that with a grain of salt...

The cam in the Nova is supposedly good to 7500 but I felt power start to drop off somewhere after 6500 or so. Cam "power ranges" include everything from a poorly built motor to a race motor. If your cam says it has a power range of idle to 6500, don't plan on that being realistic. My "small" cammed 406's cam says 1800 to 6000 but it comes on hard at 2500 and dies off after 4500. If your cam says 2000-6500 I'd plan on good strong power from maybe 2500 or 2800 to maybe 5500, maybe less peak with your intake.

Generally speaking, for a good pro touring car that you plan to race (and want to be competitive) you should realistically be around 500-550+ hp in an average 3200+ lb muscle car. Looking back, having run both types of cam's/engines as daily drivers/racers, well, I like to do well at races so when the wagon's engine let go a few months ago instead of rebuilding it I decided to pull the drag motor out of the Nova and it's in progress of getting transplanted in the wagon.

The lower power motor was super nice for a cruiser, around town and driving to races. It idled well, people who knew cars could hear a little rumpety rumpety and it had decent vacuum for power brakes. It made plenty of torque for pulling out in traffic and passing on the freeway. Going to the wilder motor I am giving up some low rpm "streetability" in favor of having obnoxious power, but yet it's not so much power it's not useful. (I think boosted high hp LS motors are mostly a joke in autocross) On the freeway it runs about 3000-3200 in 3rd gear so it's right near the new 3000 converter's ready to boogie when I drop the pedal mark. Around town it will likely be a little lazy taking off at normal speeds from traffic lights, but who cares, at low rpms it'll still have more power to weight ratio than most of the cars on the road around me. As I said before I drove my Nova daily and I never felt frustrated because it lacked power at low rpm cruising. At the track I'm almost never below 3000 rpms during a run so for the most part it'll be grooving right in it's power range. With the higher rpm potential I can keep it in 1st longer, which will help with my 3.42 gears. The lower gear range will further serve the power I need to pull out of corners, so long as the sticky autoX tires will hold their grip.

Sometimes it's not a bad idea to plan for the future. A good case in point is a regular customer of ours with a 70 Chevelle opted for a "more streetable" 430 hp LS3 crate motor, rather than the 525 hp crate motor we usually use. After getting bit by the autocross bug he's now upgrading cams to the 525 hp specs. Just my opinion from my experience- If you want a nice cruiser only, use the smaller cam and drop to 3.50 or 3.73 gears and be done. If you want to race on occasion and be somewhat competitive, don't waste time building something that later on you will likely want more, get the proper intake and go with a bigger cam. By nature the larger cubes will tone it down slightly, as will an air gap dual plane which will only give up roughly 10-15 hp compared to a single plane. In a 500+ hp motor that's not that big a deal and it will start and run better in low rpms and when it's cold out. With a stick shift and 4.11 gears your car would react well to the bigger cam. I really don't think you'd be too disappointed with low end power and you'll have plenty of mid and higher end power which is where you'll be in performance driving situations anyway. Unless you're just not into going fast, or are dead set on 14" of vacuum, I think most performance swayed folks wouldn't regret the bigger cam. Thanks for listening.

[Whooppass]

Thanks for the long read, i actually stopped for a beer on the way home to read it lol.
The custom cam is already finished, I'm just waiting on the lifters to come in. I've gone back and forth to many times to count, I want a great cruiser, I'll be street driving 90% or more of the time. Currently I have a 302 with double hump heads and a duntov 30/30 and I'm happy with it. This build will be way more power than the 302 and from what I've read this cam should work out very well. Will it be the fastest, of course not. But I think I'll be happy.
One day I'll build a 434, that will be a nasty engine.

Hellphish came up with a cam pretty damn close to what Comp Cam came up with. So I'm going g down the right path.

Thanks for the help, we'll so how it goes, should still put down good power.

[HellPhish89]

Thank you, I had to reread your post a few times to make sense of it all. I keep over thinking this build to where I want to change everything. But for now I think I'm about 80% content. People say the duration is small, but I don't want to be revving to the moon, I'm not building a race motor. I'll have power way down low (1800)and can take it to 6200ish. That's perfect for me messing around town and for future auto cross/road race. No its not going to be a balls out 7000rpm single plane monster 383, but that was never my goal. The cam matches my intake and was ground for the heads and the power band I wanted. Thanks again. BTW this is the cam I had made

The more displacement you have, the more duration you can run before it becomes a less than desirable street engine. This is mostly due to the larger engine not just flowing more air but keeping that air's velocity up. In the LSx world, incredibly 'small' high ramp rate camshafts have been making the power of the big lopey dopey monster cams. Comp's LSR and LSL lobes are pretty insane.. .600+ lift w/ 215/220ish duration @.050. They are perfectly streetable too with todays valvetrain tech and materials. Just remember that flow is only part of the equation, you also need an equally high velocity. Velocity is your low end and mid-range torque. If you would like, I could send you my mass flow compression sheet to play with.