Nitrous cam question ??

[ERV JR]

I had a cam speced for the engine I am buliding which will see between 350 and 400 hp tune up in the plate, from comp a 2 different engine builders out here in Ca. and all said the same thing about the LSA, they rec a 114 LSA. the other day on another site there was a question about nitrous cams and LSA and there were guys that were saying that they spray as much and that the 114 makes less power and that it should be on a 108 or 110 . What do you guys say and if you dont mind saying what are you guys running ? Help me before I order a cam thats crap !

[mytmouz]

On a sbc, I haven't made more power on less that 112. If it were me, I'd pick a builder, go with what he says, then blame him when it's wrong.

[John_Heard]

How much compression?

[pdq]

Hello,
I’m new here but I’ll take a stab at it with a meaningless opinion.

My guess as to the differences in opinions concerning LSA would be old school ideas from early nitrous development that advancing the exhaust and retarding the intake (wide LSA) was the best and safest way to get rid of heat. Today’s cyl head guru’s, have now learned to work their magic on nitrous assisted engines by producing head work and design that increases velocity and efficiency over out dated cyl heads being used at the beginning of the nitrous era. New head/camshaft design and development, i.e. (shorter intake & exhaust lobes) and (improved port management)
have allowed the delay of the intake opening without penalty and the delay of the exhaust opening without changing the exhaust closing point, thus tighter LSA.

Patrick Budd from ProCar explains it this way: (if using a PG)
“The solution may lie in providing the engine with more ability to accelerate via shorter timing events, helping it pull up and away from the shift on its own. A slightly tighter LSA (removing the duration from the exhaust opening pulls the centers slightly closer- we have no beef with the exhaust closing point) will also set up a hard accelerating engine through the upper- midrange. The last thing a nitrous fed engine wants to do is sit at a steady state, and anything we can do to help it accelerate up from the rpm drop on the 1-2 will pay off in et and reliability.
By trimming timing events to the minimum, we’ve arrived with a combination that runs harder, more predictable, and with greater reliability.”

I believe we all could learn something from Patrick Budd’s theory on camshaft & timing events. Very interesting.
Also, maybe this will help? ... Go figure… Good luck…It’s getting late… Good Night…

Engine Size - Use to pick durations.
RPM Range - Use to pick durations.
Rocker Ratio - Use to pick lobe family and durations.
Valve Train Weight - Use to pick lobe family.
Valve Springs - Use to pick lobe family.
Exhaust Flow - Use to finalize exhaust duration
Lobe Family - This is a group of lobes that have similar open/close ramps, but different durations.
Intake Duration - Get intake duration and lobe family correct and you're 90% there.

[John_Heard]

You can take what Patrick's saying to the bank...

My first cam I put in my 505 was one spec'd out and ground by LSM, way too much duration and a wide LSA, cranking compression showed I was bleeding way too much out the exhaust. I also saw indications of reversion into the intake manifold. I had Patrick Budd spec me a cam out and it picked the car up a bunch on motor only, cranking compression came up quite a bit also which made sense. I can't say all the gains were in the camshaft as I also had a lot of work done to the heads that winter, but I'm pretty sure it had a major effect.

You are right to ask questions about this stuff, choosing the right cam makes a HUGE difference. The guys that's talking the tighter LSA and shorter durations are more than likely the ones you should be listening too. Sometime's it's hard to find the right one, it's not uncommon for some more serious players to go through many different variations when dyno testing trying to find the sweet spot.

If you want one that is going to be pretty darn close I would not hesistate calling Patrick Budd up, have him spec you one out. It'll be ground by Crane to his specs and the price is very reasonable. http://www.procarperformance.com/ The only problem you may run into will be catching him as he's real busy.

The other person I would think seriously about talking to in your neck of the woods would be Joe Sherman http://www.joeshermanracing.com/ Joe has had some experience building engines in your class with Nitrous and he's very sharp.

[ERV JR]

Thanks John , i palned on calling Joe sherman this week its hard to reach him I have tried before and he doesent answer often. As far as the comp ratio it is 14.5 to 1, and i had one cam speced on a 111 LSA from comp but four others on a 114. I have a really good deal @ comp and would like to buy direct to save some cash but am thinking i would be better to go thru someone and get the right cam and just order the rest of the valvetrain from comp

[sunsation540]

i'm just a local racer here in okla and not to bright at that ,i have all my cams custom ground and i use 2 co ,to do the work. and i can tell you from the dyno and track work that duration and lobe centers are 60% overlap and lift 40% i won't bore you with it much 555 bbc single 4, 800 780 276 282 306 320 108int 112 exh makes 927 800 780 276 282 306 320 112 int 112exh makes 956 800 780 276 282 112 int 116 exh makes 974 N/A and on a 300 kit the first one makes 1140 second 1168 third makes 1226.. the first 2 are for sale as are about 10 others that don't work the duration matches CUI and RPM of the intended use lift 10% more than the max port flow widen lobe centers the bigger it gets...test and test and at 1inch lift it takes 118 to remove over lap

[John_Heard]

Thanks for sharing that info John - interesting stuff, boy I'd sure love to have an engine dyno at home to just play with that stuff to see what works. I think there's a real lack of that going on in the industry.

[hsutton]

I had a cam speced for the engine I am buliding which will see between 350 and 400 hp tune up in the plate, from comp a 2 different engine builders out here in Ca. and all said the same thing about the LSA, they rec a 114 LSA. the other day on another site there was a question about nitrous cams and LSA and there were guys that were saying that they spray as much and that the 114 makes less power and that it should be on a 108 or 110 . What do you guys say and if you dont mind saying what are you guys running ? Help me before I order a cam thats crap !

Hi Erv, How big is your motor, what is the car's weight, which transmission and what are the rear gears? All these factors influence the overall combination. Wide lobe center angles and big exhaust lobes help keep the motor from eating itself up when you turn the juice on. Do you have an oversized cam core or the standard Chevy size? Comp Cams #11-735-9 would probably work pretty well with most 550" sized motors with good flowing heads.

[ERV JR]

Oh sorry its a 408 sbc with 23 deg heads, with 14.5 comp, the cam rec was a 800 base circle

[ERV JR]

Car weight will be aprx 3200 with driver, trans is a th350 , a 28 11.5 et street, and will be testing with a 4.11 gear to start.
I called Joe Sherman and talked with him for a while and he said the cam I had in mind would be would be what he would rec. Any other input would be good