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Solid Roller cam recommendation 496 BBC

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#22 ·
gnicholson said:
How Do You Know What LCA Is Needed?
Now we come to what would normally be a real stumbling block. Exactly what LCA does an engine need for optimal results? The bottom line is that it's all related to how big a cylinder the intake valve has to feed. The bigger the cylinder in relation to the valve, the tighter the LCA needs to be, and vice versa. That is the main factor. Additionally, but to a lesser extent, we also find that as the compression ratio goes up, the optimal LCA gets wider. This is good because it means smaller valve cutouts in the pistons. For an engine in the 9 to 11:1 CR range, the LCA selection chart will, 99 times out of 100, deliver accurate results. For each ratio above 11:1, it pays to spread the LCA about 1 degree for every two ratios of compression increase..........This was taken from one of David Vizards cam articles. This basic premise has always worked for me. For a 496 up to about 6500 rpm 106-108 LCA would work the best. Ofcourse the duration and therefore overlap has to be right too. All I'm saying is take that 112 cam ,close the int. sooner and open the exh. later . That will tighten the lobe center and leave the overlap the same. Doing that is going to make more torque .The 112 cam will only over take it above 6-6500 rpm maybe. The cams from Rehrer Morrison etc. are all high rpm drag cam shafts thats why the lca is spread. Here is a company I have used for cam recommendations.They have a specially designed computer program {520}792 1156
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First, the cams from Reher Morrison etc are not all for hi compression engines
They also build street performance engines as does GM
If 106 worked they would all be using it
It doesn't, they don't.

So,,,, here's the deal,
While I am always open to something I believe will help in my opinion,, this ain't it :D

As I stated a few posts ago, this ain't a small block & I have in the real world, on the street, down the drag strip & on the dyno been here 30 years ago
So I guess we will just have to agree to disagree on this. ;)

I do not really care what the compression is within reason & I do not pick a cam based on compression in itself.
A large engine likes cam,,, sorry to all the DCR buffs out there :p

If you are going to feed it to a reasonable RPM the valve needs to be open XX amount of time.
Overlap & intake/exhaust tuning are only applicable over a very limited RPM range.
Any place else overlap is without question a bad thing.
It at any point except this certain tuned range where the gasses are headed the correct direction it is going to cause problems but it is a "necessary evil".

All of the quoted theories aside this is what you recommended for this combo:
"250/260 on a 106 "
I feel this is bad information based on everything I know & have seen.

I feel it would be a pig to drive on the street & there is just no reason I can think of to do this.
These engines make in access of 600lb ft of torque on a bad day & 540 is closing on 700 without much work at all complete with 112 centers & even more in some cases all at 10.0-11.0 compression.

Now if we are going back to your 280° advertised cam you mentioned for your tow truck things change somewhat :D
But if you can get a 496 to RPM decently with a 280 degree cam you are doing something no one else I know is.

Anyway, if it works for you that is great, it don't for me ;)
 
#23 ·
gnicholson said:
All I'm saying is take that 112 cam ,close the int. sooner and open the exh. later . That will tighten the lobe center and leave the overlap the same.
Click to expand...

Huh? You lost me there....how are you going to close intake sooner/open ex later...and keep the overlap the same? That by definition will change the LSA.
So unless you shorten the duration on the lobes, if you change them as you say..the overlap will increase. That's exactly what you are doing when you tighten LSA.


Now you said Lobe Center.....are you talking about installed centerline somehow in here?


I've read Vizards stuff...and while he's interesting sometimes...I ain't buying his cam theory all the way. If you run the numbers he'd have us all with 95*-99* LSA angles on some big motors. Now that's going to take a heck of a short lobe to keep overlap in check. His idea of little short lobes, real tight LSA to get desired overlap is great stuff for a little roundy rounder screamer....but it ain't gonna make a 540 scream with big power!

I even challenged Hunkins to use all his cam theory on his 496 buildup. Even he didn't go for it on his stuff for the magazine. Vizard didn't even follow all those goofy charts when he picked the cams for HIS buildups.

Maybe I'm way off base here..but I'd love to see them prove some of this stuff. And then when it's all done I want to see it cruise around on pump gas with decent manners like a nice little 112 LSA will do in a 540. AND make 800+ HP on 93 octane (on a dyno NOT at Westech!)


JIM
 
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#24 ·
PDQ67,

Here I am.......

Nothing gets me out like a Big Block with a 4-speed....

Driving a 496 on the street with a 4-speed calls for a wide LSA, or ownership in a tire store.
All engines react the same to LSAs, tighter LSAs give more mid-range torque and a rapidly rising and falling power band, and wider LSAs give a wider, flatter power band. Wider LSAs are a lot more forgiving in traffic.
I cam make cams on whatever lifts and durations you want. Bob West's cam is one of my favorites, and is heavily oriented to race use. I have it every 4* from 247* to 291* at .050. I also make an excellent series with .725" gross lift, .700" net lift, in the same duration numbers. I have made a few with 257/265 at .050 for 496s and 540s. The ramps on this one are designed for 24 hour racing if necessary.
All my cams are unsymmetrical, and that's why they are in odd duration numbers, so you know it's unsymmetrical. The .020s at 28 to 31 degrees bigger than the .050s.
All my roller/hydraulic roller cams are steel billets, with or without the EverWear Gear option. The billets are made by Crane, CamMotion, or Camshaft Machine Company. I have used Crane and Camshaft Machine Company(CMC) both for over 30 years, and they make good cores. I have used CamMotion for about 7 or 8 years, and they are the one of choice for special cores.
My phone is 662-301-1245, you can call me anytime, but Wednesday around 11 to 1 I have to go to Memphis to inspect our new cam boxes---Call me later.

To everyone, It's GOOD to be back!!!

UDHarold
 
#25 ·
UDHarold said:
PDQ67,

Here I am.......

Nothing gets me out like a Big Block with a 4-speed....

Driving a 496 on the street with a 4-speed calls for a wide LSA, or ownership in a tire store.
All engines react the same to LSAs, tighter LSAs give more mid-range torque and a rapidly rising and falling power band, and wider LSAs give a wider, flatter power band. Wider LSAs are a lot more forgiving in traffic.
I cam make cams on whatever lifts and durations you want. Bob West's cam is one of my favorites, and is heavily oriented to race use. I have it every 4* from 247* to 291* at .050. I also make an excellent series with .725" gross lift, .700" net lift, in the same duration numbers. I have made a few with 257/265 at .050 for 496s and 540s. The ramps on this one are designed for 24 hour racing if necessary.
All my cams are unsymmetrical, and that's why they are in odd duration numbers, so you know it's unsymmetrical. The .020s at 28 to 31 degrees bigger than the .050s.
All my roller/hydraulic roller cams are steel billets, with or without the EverWear Gear option. The billets are made by Crane, CamMotion, or Camshaft Machine Company. I have used Crane and Camshaft Machine Company(CMC) both for over 30 years, and they make good cores. I have used CamMotion for about 7 or 8 years, and they are the one of choice for special cores.
My phone is 662-301-1245, you can call me anytime, but Wednesday around 11 to 1 I have to go to Memphis to inspect our new cam boxes---Call me later.

To everyone, It's GOOD to be back!!!

UDHarold
Click to expand...
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It's about damn time :hurray:

Welcome back Harold,, I missed you at the PRI show, came by about 10 times but they said you didn't make it
Maybe next year,, I still owe you a hot dog ;)
 
#26 ·
I cant disagree with anything UD HAROLD wrote. In my 1st reply to this post I said the cam Bob West had that was ground on 108 looked like a good one.In my last post I was trying to give an example. A lot of cam recommendations are too big duration wise and are ground on a wider lca to avoid too much overlap.If you took a cam like thatand left the int. opening and exh. closing the same but ground the cam with the int. closing sooner andthe exh. opening later you would have the same overlap with less duration and thus a tighter LCA [LOBE CENTERLINE ANGLE]. Make no mistake ,speccing a cam with a tight lobe center is less forgiving if you have too much duration;like was said earlier driving a car on the street with too much overlap sucks. Also unless your chassis can handle the extra torque you might be better off with a little more duration and a wider lobe center. That is enough from me on this. Mike I think your very kmowledgable on this and I enjoyed reading yours and everyone elses response.
 
#27 ·
gnicholson said:
If you took a cam like thatand left the int. opening and exh. closing the same but ground the cam with the int. closing sooner andthe exh. opening later you would have the same overlap with less duration and thus a tighter LCA [LOBE CENTERLINE ANGLE].
Click to expand...

OK...I can go along with your thinking on that statement I suppose..or at least I understand what you're saying. You make a smaller lobe and tightenthe LSA..you get the same overlap.

But I'm with Mike....duration is needed to do certain things. A lot depends on cam etc...and exactly what range you want to play in. Look at the Engine Masters...you see lots of short (but insane rates of lift) with tight LSA's and advanced I/C. But again...who cares what the average Hot Rod makes at 2500 rpm? You'll hopefully never be there except when cruising around.

You like little durations and tight LSA's. They work fine in the right applications. I have a Crower circle track cam that I like in a couple of different friends motors. It's a *fast* little lobe...with 238/244@.050 but only 268/274 adv on a 107 LSA. We stick it in around 102-104* and it flies! We currently have it in a nasty little 327 and also in a torquey 383. Thumps pretty good in the 327...nice little lope in the 383. Pulls 7500 in the 327.....makes unreal RWTQ on the chassis dyno in the 383.

Tight LSA's wake up little motors. Big motors don't need that..they are on the other end of the spectrum. We recently dyno'd a pump gas 632 with a 277/282@.050 cam on a 114 LSA. The sucker was still pulling past 7000 even with relatively small heads and intake ( as well as cam) for a 632.

I know for a fact that my 540 is absolutely much better off with the current 112 LSA cam than any of the previous choices. Getting a big motor to not sign off past 6500 rpm takes a little re-thinking. I'd rather have a 540 that can pull hard past 7000 rpm than one that will blow the tires away even more and run out of steam at 5500.


JIM
 
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#30 ·
Silver 79,

One word: Harold


more words: Harold is Harold Brookshire, among other things he designed the original CC Hi-Energy line of cams and owned UltraDyne for many years. Also recently did the Lunati VooDoo series. This is similar to (or better than) having Harvey Crane or Ed Iskendarian stop by to help you out. Recommendation: pay close attention to what he says.
 
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