DAPSUPRSLO

iTrader: (14)

I have looked at a few books before (by Vizard) and heard this same comment other places as well.

"For a given motor combination there is only one lobe separation angle (lsa)that produces maxiumum horsepower..... Big bore short stroke combinations fall within the realm of 105 lsa to 110lsa with longer strokes as tight as 95lsa". This was a rough paraphrase, not exact quote.

I don't understand this. I guess if you are only talking about peak power and not power under the curve then maybe this would hold true. But then again you can get overlap by not only fooling with lsa but also changing duration as well which will do other things to the power band just like changing lsa.

Obviously other things are considered in lsa choices, mainly tuning and driveability. Is this why people aren't choosing lsas in this range? As we all know the ls1 has a longer stroke and smaller bore then a 350, wouldn't this dictate lsa's in the neighboorhood of 100 to 105 or so?

I understand that it is all in the combination. Obviously cams with these kind of lsa's need very efficient exhaust systems. Also, you will need gears that suit your tire size as well.

Obviously when you choose cams with tighter lsa's you run into p/v issues more as well, especially with our 15 degree heads and pistons that run out of the bore, verses a 23 degree sbc. Is this part of the abundance of 112-114 lsa cams also?

Does Mr. Vizard just not know what he is talking about? Does the efficiency of the lsx heads negate the need for this amount of overlap?

This is only for n/a applications, no power adders. This is meant for open discussion, any suggestions are welcomed.

DAPSUPRSLO

iTrader: (14)

Do you think it maybe the intake limiting our intake charge that makes us choose higher lsa's? Fireball suggested this over on Eastern Fbody.

PREDATOR-Z

This was also addressed in a previous thread, but after pages of discussion we pretty much came to the conclusion that:
1- Yes Intake is restrictive but only after a certain point (We found this when people swapped FAST 90/90TB and got no improvement on stock headed motors <or mildly ported>), sometimes the opposite.
2- Also found that from a tuning angle, going too tight on the LSA was a nightmare, untill we saw the light in SD tuning.
I try to educacte myself by following some of the LS1 news and methods used in Aussie Land, and I found commonly used intakes such as "individual TB intake". Yes one TB for every cyl.
Now you should hear this Monaro/GTO with this Huuuge cam on a 106 lsa, idle and purr as gently as a 224 on our MAF systems.

DAPSUPRSLO

iTrader: (14)

Cool, thanks for the reply. I am getting ready to shove in a 239/246 106 lsa cam in a stock shortblock. I was told that it could be tune in closed loop. I guess I will have to find out as I get it backed together.

RX-Ben

iTrader: (7)

OT-

Where are you finding info about the Aussie LS1 scene? I am usually pretty handy with google but I couldn't find anything good.

Thanks
Ben

DAPSUPRSLO

iTrader: (14)

You haven't found anything that I haven't. That is not where those cam specs came up with. Some of those guys chime in every now and then though, especially when cam specs like the ones I have presented are brought up as this is there speciality apparently.

LS1_PNYTAMR

iTrader: (1)

wow guys ive read most of all these threads and ya'll really know your ****! keep em coming, 4, 5, 6, 7, 10,... newer ppl like me can only learn! thanks!

Bo White

iTrader: (59)

Most of David Vizards info(which is spot on and great) is based off of carbed applications. Most fuel injection systems are vacuum sensative so less overlap is required. I have most of Davids books and a big fan of his stuff.

J-Rod

Big Aussie cam

http://users3.ev1.net/~black_ops/video/242-106.mpg

I like Vizard's stuff. He actually designs cams based on data (like head flow), and application.

RX-Ben

iTrader: (7)

Wowsers. That cam sounds so tame. Think the ITBs played a role in getting the idle so smooth?

Ben

DrkPhx

iTrader: (15)

Not neccessarily true. He wrote an article for GMHTP about camshaft selection that was Gen III specific and some of the points (including the one about the LSA) were mentioned in the article. It was an excellent article and I'm constantly referring to it a good reference point.

J-Rod

https://ls1tech.com/forums/showpost....&postcount=150

Ben R

Remember to take this with a grain of salt. Most Pro-Stock cams are on big LSA's. Typically betwen 116 - 120.

madpwr1

iTrader: (3)

great read, thanks for postin it

Richiec77

iTrader: (3)

J-ROD you are always on point with the GOOD cam info. Thanks for the article. I had to print that one out.

LSonederfull

/This is true, but Pro Stocks do this to get max rpm power band and also with ultra high compression(as much as physically possible)these LSA's give more piston to valve clearance than tighter ones allow. .850"+ lift really makes things tight.

Ben R

Actually, they do it because it takes a lot of density to get a 500" engine turning 10,000 RPM to get to the edge of detonation.

"A typical Pro Stock camshaft is a 570 lobe 284 duration on the intake 560 lobe 304 duration on a 117LSA. The rockers are 1.85 intake and 1.8 exhaust. Its no real super secret."

That's from Darin Morgan.

HumpinSS

iTrader: (1)

What issue was that

LSonederfull

Thats why i said they use that LSA to get max rpm power band. Any one willing to give up there cam specs for a competitive pro stock is probably just copying others anyway. Not a leader IMO.

Ben R

You're right, Reher Morrison sucks.