Street SBC cam - ideal LSA opinions??? - Chevelle Tech
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post #1 of 27 (permalink) Old May 25th, 09, 12:55 PM Thread Starter
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Jake
 
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Street SBC cam - ideal LSA opinions???

I have read piles of threads and other info on this and still can't make sense of it. I got too ticked to read any further when a thread mentioned that cam companies started changing LSAs just to be able to market/sell more high-lift/big duration street cams. LSAs from 106 to 114 are readily available.

I am trying to match a cam (either single or dual pattern) to my street only 355.

Thanks!!

1972 Malibu Sport Coupe - Victory Red on Black - 350/TH350

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post #2 of 27 (permalink) Old May 25th, 09, 12:57 PM
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Re: Street SBC cam - ideal LSA opinions???

Uh ho, not again......

no offense, but you might be opening up a can of worms with this topic.

70 Chevelle SS clone (632 CI powered).
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post #3 of 27 (permalink) Old May 25th, 09, 1:02 PM
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Re: Street SBC cam - ideal LSA opinions???

I like a 108 myself.Great LSA for street,imo.Comes on faster than 110,but still wide enough before running out of steam.Then again,you gotta factor rear gears,compression,heads,carb,auto or manual trans,etc. into the equation.As stated from above,do a search on this.This topic has been beaten and ressurected to death.

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post #4 of 27 (permalink) Old May 25th, 09, 1:25 PM
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Re: Street SBC cam - ideal LSA opinions???

Yeah, I liked the 108 LSA cam that I had on a small block engine. I had a manual trans in that car, so that might matter. I dunno.

70 Chevelle SS clone (632 CI powered).
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post #5 of 27 (permalink) Old May 25th, 09, 5:56 PM Thread Starter
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Re: Street SBC cam - ideal LSA opinions???

I've searched and read. I hate gray areas, and that's all I seem to read. If nobody wants to play along, thats cool.

Here's more info...

TH350
rear - 2.73 currently, if I ever switch it will be no more than 3.55
heads - 601s (prolly close to 9.7:1)
pistons - 4 valve relief rebuilders
bottom end - stock, cast, 20k miles tops
intake - edelbrock 2101
carb - holley 600 VS/EC
HEI
1-5/8" primaries to 2-1/2" pipes/glasspacks/turndowns

1972 Malibu Sport Coupe - Victory Red on Black - 350/TH350

I do all my own stunts.
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post #6 of 27 (permalink) Old May 25th, 09, 6:21 PM
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Re: Street SBC cam - ideal LSA opinions???

There is no "one" best" LSA for any application.

There are advantages and disadvantages to EVERY facet of cam design, LSA included.

In general - and keep in mind, this is GENERAL, and not specific to any particular grind or manufacturer or combo - if you take the same cam with the same lobes, and grind several copies that are otherwise identical except with a variety of LSAs: ones with narrow LSAs will tend to idle rougher, have more low-RPM torque, reach their torque peak at a lower RPM, have higher peak torque, and power will fall off faster once that peak is passed (i.e., peak torque RPM and peak HP RPM relatively close together). Ones with a wider LSA will idle smoother, have higher idle and cruise vacuum, lower peak torque, and torque will not fall off near as fast once the peak torque RPM is exceeded (wider, flatter torque curve with lower peak values, spread out toward the top). A narrow LSA will make the car go faster IF the gear and converter keep the engine operating within that narrow band around the peaks AT ALL TIMES... i.e., a single-purpose strip car. A wide LSA will make the car go faster if the engine has to operate over a wide variety of conditions, especially RPMs; and will generally get better gas mileage on the street, especially when operated well below its peak torque RPM like 2.73 gears and a stock converter will enforce.

One is not "better" than the other; rather, it's a matter of suitability for purpose.

Gievn your combo, I would suggest a cam with low to mid 2-teens of intake duration; more exhaust than intake (with the crappy stock exh ports, you'll benefit from the lobe split), and LSA toward the higher side (110 minimum, 112 - 114 preferred). The Comp XE cams and the Voodoo cams are good examples of modern cams geared toward motors like yours, with no gear. Consider using a solid. Avoid cheap generic cams like the Edelbrock product line or the Summit cams or other clones of those same ancient designs, if you want to be competitive.
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post #7 of 27 (permalink) Old May 25th, 09, 7:06 PM
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Re: Street SBC cam - ideal LSA opinions???

What RB69SS396Conv says: X2

kirkwoodken
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post #8 of 27 (permalink) Old May 25th, 09, 7:27 PM
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Re: Street SBC cam - ideal LSA opinions???

Exactly!

Just a street car.
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post #9 of 27 (permalink) Old May 25th, 09, 7:43 PM
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Re: Street SBC cam - ideal LSA opinions???

Quote:
Originally Posted by kirkwoodken View Post
What RB69SS396Conv says: X2
Quote:
Originally Posted by eric13617 View Post
Exactly!
Right !

However many drag race cars that are properly set up for drag racing can go faster with a tighter lsa.

Street cars it really depends on the engine, car and most important the DRIVER

I would go no wider than 110 and no tighter than 108 on a 218-220 @.050 in this application. A 218/218 108 would work good
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post #10 of 27 (permalink) Old May 25th, 09, 7:58 PM
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Re: Street SBC cam - ideal LSA opinions???

Quote:
Originally Posted by Highway Star View Post
I've searched and read. I hate gray areas,
I think there will always be "gray" areas because answers that you would receive in this topic will be greatly based on opinion, preferences and perhaps to a lesser extent, even theory too. There are so many facets to cam design. So I don't believe that it can be a cut and dried case. I do have my own preference that I had made mention of in my last post, but other than that, perhaps the best thing that you can do is take a poll. the poll will be based on peoples' likes/dislikes, and their opinion. But that mostly what you should expect from a topic like this anyway. Good luck.

70 Chevelle SS clone (632 CI powered).
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post #11 of 27 (permalink) Old May 25th, 09, 8:23 PM
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Re: Street SBC cam - ideal LSA opinions???

Interestingly, what Butch is recommending is what numerous cam grinders have offered for the SBC through the years: A cam closely related to the original Duntov. And for a hydraulic, cams close to the 327 and 350 high performance hydraulics. These are sensible street grinds, not something that NEEDS gearing in the 4's or above. A flat tappet cam with numbers like those will be peppy and not break your wallet. Also sound nice while idling.

kirkwoodken
406 SB, Original Bill Thomas '63 Rochester FI
AFR 210, Lunati 501C2LUN, 255/263@.050", .628"
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post #12 of 27 (permalink) Old May 25th, 09, 8:27 PM Thread Starter
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Re: Street SBC cam - ideal LSA opinions???

Thanks!!

Right now I am sporting a "blue racer" crane grind, 284/284 advertised, 218/218 & .450"/.450" @ .050 on 110 lsa. We suspect a wiped lobe on the friggin thing, and I might be picking up a cam/lifter set. I have been told by some pretty trustworthy folks around here that this cam is WAY too big for my setup. The consensus has been towards a Comp 268 or an Isky 274. If I recall, the Isky is on a 106 lsa, and the comp is 110 or 112. That is sort of what prompted the question about lsa. The lopey idle is neat, but I'd rather have the car able to get out of its own way rather than sound tough.

The car has a 2000-2200 stall B&M converter in it, by the way.


Right now there's a set of 624 smogger heads on it, which will be switched out prolly when the cam is stuck in. I've got access to a set of 601s (mentioned above) that will bump SCR up to around 9.7:1. My cam profile will play a big role in what the DCR winds up being, and I want to make sure this is right. I know I won't really know exactly what I am working with until the heads are off and some measurements are taken. I don't know EXACTLY how far the slugs are down in the hole, and I know that I need that figure before I can get finalized on cam grind, gasket thickness, etc.

I want a torquey street engine. Revving over 5000 or 5200 is not important to me. I am shooting for 350+ torque and 300+ horses, which I think are not unreasonable numbers.

Everyone always (myself included) thinks what RB says is pure wisdom. He suggests a wider lsa, 110 or 112, but not from summit.

I have to confess, my wallet really likes the looks of the summit 1103. It is a dual pattern, 214*/224* & .442"/.465" @ .050" on 112 lsa. That fits the bill pretty well. What is wrong with it? It is pretty close in profile to the voodoo 60101. Are we getting into lobe shape and valvetrain-friendliness now? I really don't know.

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post #13 of 27 (permalink) Old May 25th, 09, 9:00 PM
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Re: Street SBC cam - ideal LSA opinions???

My rule for lsa is simple(too simple?) the better the head for a given c.i.d the wider the lsa-350 somthin with stock type heads maybe a 108-killer heads maybe 110 or slightly more.
Your primary goal seems not too be allout ooommmpphh so drivability is next-a 110 or 112 would work great-wide powerband and flat torque with good idle
I would stay away from generic cams-a CC 268HE is great in mild 3fiddy's
The more modern cams do work better though the tried and tru 268 just flat out works for applications like this
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post #14 of 27 (permalink) Old May 26th, 09, 8:40 AM
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Re: Street SBC cam - ideal LSA opinions???

Considering the gears, I would run a cam with no more than about 6* split, on a 108 to 110 lsa. You need as much low and midrange as you can get because of the gears and relatively low stall convertor. The comp cams 260AH-8 will absolutely run rings around the summit K1103 in this application...I've used both and there is no comparison under 5K rpms in an under 9.0-1 compression 350. The 1103 will pull harder on the top end, and thats about it. Either cam will ping in your setup with the small chamber 305 heads/9.7-1 compression unless you are conservative with the timing curve, but then you are giving up power/torque.
The 1103 will pull to 6K rpms with fresh stock valvesprings in a 350...the lobes are pretty gentle.
The comp 268HE will work pretty nicely with this setup too, as would the crane 272 energizer, or the Isky 264 Mega cam.

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post #15 of 27 (permalink) Old May 26th, 09, 9:40 AM
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Re: Street SBC cam - ideal LSA opinions???

You tend to learn a lot more about lsa after you go too far with the overlap and have to ditch power brakes. On my old 350 that was 10:1 with Dart 200 IEs, that point was somewhere between the Isky 264 and 270 (both are on 108 lsa). My brother had a similar setup (but with the WP heads) and switched from the XE268 to the 274 and still could use his stock booster. The CC XEs are on a 110 lsa with a 106 icl (if you line up the dots).

I crutched the Isky 270 with Rhoads lifters for a while to keep the power brakes and they seemed to work. I was concerned about them not letting the cam get to full lift, so I changed them out and added a vacuum cannister for the brakes. It would work great for 1 stop, but at a light you would start to creep forward after a while. Something had to go and it was the booster. The vacuum cannister is now my coolant overflow tank.

Once you get away from needing the vacuum for the brakes, you can get more aggressive with the cam and lsa. If you want to keep your stock brake setup, be real careful with your cam pick.
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