I have always read that the wider LSA's will help with nitrous ? I bought one of those " special nitrous cams" that's supposed to make good power on motor and great power when spraying. I feel on motor my car is low on HP ( but has 15" of vac and daily drives very nice) and then on the botle it's just picking up as set HP levels per the nitrous. My actual car times are misleading to HP because my car is light. But here's what i get from my calculations.
motor 361 HP
100 shot I'm getting 94 through the mufflers
150 shot i got 160 HP open headers.

to me this doean't seem all that great ?

here's my combo.
1985 carbed corvette 3130 race weight
355 9.8-1
Canfield 195's
comp nitrous cam 268-284 218-230 465 lift 113 LSA 108 ICL
was RPM intake, now vic jr ( because i want to spray 250 this year and NOS says not on a dual plane)
1.75 headers 2.5" duals
turbo 350, 2800 stall ( 10" converter)
D-36 3.07 gears 26" tall tire.

my times
motor 12.63@109
100 shot 11.38@118
150 shot 10.98@124

Anyway i was wondering what your opinion is of these "special cams". Also how much power is usually picked up by going to a solid cam over a hyd ?

thanks
Mike

Everything I've tested says that more power on the motor means more power on the bottle. "Nitrous" cams tend to have wider LDAs and less overlap, and that tends to narrow the torque range. I haven't seen a case, for example, where a wide LDA made less power on motor but more power on nitrous than a cam with narrower LDA. If the 110 or 108 cam makes a better curve on motor, then it also makes more power on nitrous.

But that's just my opinion.

DF

thank you , that's what i was looking for. I think i'm giving up too much on motor, before i start spraying the car.

"wider LDAs and less overlap, and that tends to narrow the torque range"

Doesn't a wider LDA's and less overlap typically broaden the torque range???

Wider LDA/LSA allows you to run greater exhaust timing while maintaining decent driveability through controller overlap. I just installed a Comp NX279HR and on paper it has the same overlap of the good old Comp 280H.

NX279HR 279/294, 230/242 on 113LSA 60.5* o/l at seat, 10* o/l at .050

Comp 280H 280/280, 230/230 on 110LSA 60* o/l at seat, 10* l/o at .050

So far, my motor has showed signs of running lean, a good sign actually.

grn69chv,

I have thought about stepping up to that cam, can you share with me the rest of the motor combo and if you have any HP or times as of yet ?

My cam has neg.2 deg over lap @ .050 according to Jay Allen. I don't know how to configure that #.

I also thought the wider LDA would make the TQ curve flatter and longer, but a narrower LDA would peak higher ?

thanks guys for the info.

Mike

Wider LSA gives a wider flatter torque curve. Tighter LSA, a narrower peakier curve. Overlap is calculated using seat to seat duration not .050" duration. Here is how to calclulate overlap (http://members.uia.net/pkelley2/Overlap.html). Mike, you have pretty low compression. Going to a larger cam might not make more power.

First, no hard data on performance. I did drive the car last weekend and immediately noticed 2 issues to resolve, not necessarily in order.
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Edited : Added combo info
'69 Chevelle, complete car including A/C. You can guess the wt if inclined - add 250# for the driver.
Combo is 408 BBC, 9.5-9.6/1 CR, 290 oval ports with 2.19/1.72 valves. T400/3000 converter w/ 3.73 gears. 1-3/4" headers in to 2-1/2" mandrel exhaust.

On street tires, coming out of the hole sideways with 2.20 60' times, on/off the throttle the car ran 14.20/99 mph and 14.06/97 mph. With real tires it should have been in the low - mid 13's. I would suspect with the change in cam, some suspension mods that I have made [mainly much softer springs in the front end and a change in ride height - overall lower] along with some drag radials and a proper tune the car should run 12.80 - 12.90's.
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The motor tended to have a cough at part throttle a condition I did not have before - mind you it was 35 - 40 degrees out and I have blocked the manifold exhaust crossover completely this time. Also, the ,motor was breaking up by mid 5000 rpms. Again I believe partially contributed to by valve float and aggravated by a lean condition. Again, assumptions on both, but I have taken steps to address both.

I do suspect that once I get the tune correct, and find the happy medium for the valve lash and maybe play with the spring pressure to get the rpm stable, the performance will be improved. I use the ill state of tune as a good measure. Whenever you create a lean condition, it means you are moving more air, that is a positive. I can see increasing the primaries by 2 jet sizes and the secondaries by possibly 6 - 8. That is a huge difference for nothing more than a cam change. Unforetunately, it is doubtful the car will see any track time until March or April to validate things.

Regarding overlap. I often don't comprehend how this all comes into play, but I was advised to not only look at seat O/L but to also look at O/L at .050 with a target for 10* O/L at .050 for what could be considered the limit of a good idle - whatever that means. Am inclined to think that information is accurate.

Darn that's a long post - hope the boss doesn't get pissed at me - oh wait, I AM THE BOSS. Well so much for setting a good example!

Pat i called JAy Allen and Camshaft Innovations and both told be not to bother with O/L @ adv. they both said i needed to know overlap @ .050 ?? That's all i know about that ? I have considered a cam change, but i'm leaving alone for now. I'm asking this because i"M starting to think this buy a nitrous cam to make big gains on the nitrous may only be true in a pro mod car. I have picked up well, and my car runs great #'s, but the motor HP is low to me with the heads i have and the nitrous gain is as advertised, not like i'm getting 150 out of a 100 shot. On another note i do have 15" of idle vac @ 750 RPM. So maybe there's an adv. there to wide LDA and not a nitrous gain ?

mike1985, did jay say he could make more power over what you have? did he sound like he was as smart as udharold? i have been thinking about calling jay allen for a while now. just looking to se if he would be worth a shot. thanks

94guy,

He was very smart. You need a 4 page info sheet to begin with and his cams aren't cheap.But he guarantees a HP gain. He goes into detail about area under the curve on lift and duration. He also told me that in order to really pick up 50 motor HP i would have to switch to a solid, which I'm not opposed to. I was reading a thread on here where UDHarold stated he has some street rollers going 5K miles with no troubles, I was hoping he would respond to this thread so i could also question that aspect, but he never replied. I have e-mailed him personally and then posted on here publically and have had no luck with UD Harold. I don't know that one guy is smarter or better than the other, but i do know Jay Allen personally called me back and talked to me on the phone for 45 min.

Mike

Mike,

I have to apologize, I admit I'm very bad about answering E-Mails. My time on the computer here at the house is somewhat limited. I rarely get home from work before 7:30, sometimes I have to cook supper, and I have a 27-year old daughter who uses the computer a lot too.
However, I know better than to say the overlap at .050 is more important than the advertized duration overlap.
Take for instance 3 cams, all with 250° duration at .050". They are all ground on 110° LSA and they are straight-up, for the ease of understanding the concept. Their timing at .050" is IVO 15° BTDC IVC 55° ABDC EVO 55° BBDC EVC 15° ATDC, for 30° overlap at .050.
Cam A is Old-School, 320° at the seat, timing 50-90-90-50.
Cam B is Not-So-Old-School, 300° at the seat, timing 40-80-80-40.
Cam C is New-School, 280° at the seat, timing 30-70-70-30.
Overlaps at the seat are 100°, 80°, and 60°, respectively.
Which measure of overlap do you think would influence the engine more, at .050", or at the seat?
At 15° BTDC the piston is still moving upward and pushing exhaust gases out of the cylinder. Clean air and gas doesn't start into the cylinder until some time after TDC, depending upon how much reversion entered the cylinder during overlap, ie--WHERE did the intake valve come off the seat.
Now as far as Nitrous-cams, I have never seen the need for them for 100-150 HP shots of Nitrous. You give up too much with the wider LSAs vs the gain, which is mainly in controllability when the spray is on. I mainly use wide LSA cams for 400 HP and up Nitrous engines.
An hydraulic with a 10° split and a 110-112 LSA makes a perfect street-driven NO2 cam, for those 100-150 HP engines.....

UDHarold

You give up too much with the wider LSAs vs the gain, which is mainly in controllability when the spray is on. I mainly use wide LSA cams for 400 HP and up Nitrous engines.
I am curious as to why many of the smaller cams in the voodoo line (i.e. Voodoo 262/268) are ground on 112 LSA, since it is widely acknowledged that the typical SBC gives up torque with wide LSA cams when compared to cams ground on tighter LSAs. Care to educate me? smile.gif

We gain 1" of vacuum for a 3 or 4 HP loss.
The gain in vacuum makes the cams more EFI-friendly, meaning we don't have to have 2 different cams, and besides, we have a lot of extra hp to spare!
We dyno-tested several of the cams on 108, 110, and 112 LSAs. My pre-test predictions are what we are making.

UDHarold

UDHAROLD,

Thanks for taking the time to explain the OV issues to me. I couldn't understand why some of those guys were telling me that the .050 was a point of interest and not ADV.

The voodoo cams are on a 112 LSA and i'm asssuming a 108-106 LSA and my nitrous cam is 113 LSA and 108 ICL, by numbers alone this doesn't seem like that much, but is it ?

thanks again

Mike

Not meaning to create a stir or heated debate here, but you still have to be aware of the O/L @ .050 as well as seat O/L. If this were not the case, then in a typical example of a short duration solid cam, where you know there exists very little seat O/L, the motor will sit there and rap away at idle. As example, look at a solid with 276/284 on 110. At seat, you only have 60* O/L, which in most cases (big block anyway) would produce a mild ilde quality. But at .050, this cam is going to be in the range of say 238/244 to 244/250. .050 O/L will be 21* - 27*. This cam will a real nice lope to it. I was advised a couple of years ago (by someone from Lunati) to also take a hard look .050 O/L as well as seat O/L. It has to play in somewhere. Any time the motor sees O/L and low RPM, there is a cause and effect.

It is actually the area-under-the-curve during overlap, and it extends from intake valve open until exhaust valve close, and it is both valve's area-under-the-curve.
This is why you can have 3 cams of the same seat duration, but different .050s, and have different idles/vacuums.
look at my old UD 288/296s:
288/296H8 41-67-81-35 13-38-43-16
288/296F8 41-67-81-35 25-50-65-18
288/296R8 39-69-79-37 24-51-64-19
All 3 of these cams are on the same 108 LSA, all are with the intake on 102 INT CL, all 3 have 76° of overlap at the seat. The 2 racy cams have the same amount of overlap at .050, occuring slightly different in time, as does their seat timings.
All 3 of them will idle slightly below 1000 rpm with a well-adjusted carb. Maybe I am arguing about 'how many Angels can dance on the head of a pin', but I know that the .050" opening point IS NOT SEEN by the engine---It is on the wrong side of the intake cycle, with the piston pushing gases out of the cylinder, not drawing them in. The intake valve opening point does govern how much reversion enters the intake port, and therefore when airflow starts into the cylinder.
At low RPM. the exhaust closing has as much effect as anything, as it allows exhaust gases to be drawn back into the cylinder, as well as just having too many milliseconds of exhaust gas exposure over overlap.
All this typing has exhausted me.......

UDHarold

Nothing like a good tutorial. Thanks Harold. In laymans terms, it would appear to me from your explanation that the .050 measurements play into the "area under the curve", if I may be so liberal as to create an analogy. So in effect, while not being the sole determining factor, both seat AND area under the curve will effect the low rpm driveability, idle & vaccum?

Good stuff, Harold. Thanks!

This is cool stuff. I always hate it when I have to read it several times to understand it. But of course, if it has Harold's name on it, it's worth the trouble!!!

Troy.

Originally posted by UDHarold:
My time on the computer here at the house is somewhat limited. I rarely get home from work before 7:30, sometimes I have to cook supper, and I have a 27-year old daughter who uses the computer a lot too.

UDHarold If you have a 27 year old daughter still at home, that means the suppers you are cooking are too damn good! ;) You have to change that around Harold. The 27 year old daughter needs to do some of the cooking and Dad needs to get on the computer sometimes! :D

UDHarold,

You have more than addressed my question conserning LSA and nitrous, you've even went further than i expected with and excellent explanation of O/L @ .050 and ADV.

The seconds question i had in the origional post. was all things being equal in the engine and just switching cams from hyd to solid to roller what would the power difference be with each type of cam ? Lets say keeping the power band from 2500-6000 in a SBC. Also you have said before in a post that you have Sr cams lasting 5K miles with no problems ? What parts selection is needed to accomplish this?

Thanks

Mike