I'm really into LS motors (now), but for 30 years was a smallblock enthusiast. So, why are the LS cams so "smallish" in duration and overlap, but so largish in lift compared to the old motors? Is it the heads? The emissions specs? The engine management system?

Just curious...

Russ

 

I looked into what you and I am wondering if you are confusing gen 1 350 cam specs. The cams in the late 60's early 70's show an advertised duration. Once you look at the duration at .050 you will see they compare to the cams we use now. However the cams now have about .200 more lift and I think they actually have more duration then cams of the past.

 

If you look at the flow charts for a "double hump" head vs a LS1 head, the flow numbers past .450" lift are what make LS1s like to have higher lift cams.

 

Well, for starters the roller cam really allows for amazing ramp rates, and the incredible heads allow for you to take advantage of some astronomical lift numbers. You really can get a lot of air and fuel into and out of the LS architecture.

 

I'm not "confusing" the Gen I, I'm trying for a comparison. I had smallblocks back in the late 60's with much larger cams than the LS motors currently run and I'm simply wondering why the LS cams are soooo much smaller in duration (all considering the 0.050" lift duration).

Rollers would play a major part. I (well, my son) has a 383" Gen I with Dart Iron Eagle heads and he's running a retro-roller with 242°/248° and 0.570" lift. That motor is relatively tame. Since our LS heads flow so much better, why wouldn't you run a cam with 250° or better duration on a base (347") motor?

Russ

 

Because you don't need to. Not unheard of to get 400rwhp with a cam in the 22X range. Not getting there with an SBC on the same specs.

 

I grew up with gen 1 small blocks also. You can get cams with just as much duration for LS motors as you can for Gen 1 motors, and into the 250 degree range as you say. From what I remember though, cams in this range were not very streetable with gen 1 small blocks, but it's been a while. Some guys run cams this big in LS motors, but they are not street friendly so you don't see alot of talk about them. And for a street or combo street/strip car the reason they are not very common is because you can make great power without all that duration. But like Gen 1 small blocks, the more cubes you have the bigger cam you need and can tolerate on the street.

 

I'm running (well, about to run) a carb'ed otherwise stock 347" LS-1 with a TSP Torquer V.2 cam in my non-daily driver swap vehicle ('72 Maverick). I'm thinking I could have gone a bunch bigger, especially with the carb setup and a 3600 stall 9" converter. Time will tell...

Russ

 

could you have? yes... do you need to? depends on what your wanting..

the torq. V.2 is a very nice cam..

do you want good track times? good dyno numbers? whats the rest of your mods/future mods.. gears/intake/heads/exhaust/tire size/etc....

and a stock ls1 is 346...

 

Hmm, 346. Yes, that's what happens when you have big fingers!

I'm not going to the track, just looking for fun! NOT a daily driver. The car will prolly weigh around 2800#, has a 9" detroit locker 3.50 gear, 200R4 trans, PI Vig 3600 stall, minitubs and 325DR's. Motor has a stock longblock with the torquer v.2, Vic, JR intake, Holley 750 dualfeed/double pumper/mech secondary/carb, BBK 1 3/4" longtubes, will have a 2 1/2" X-pipe with Dynomax raceflows dumped. I'm thinking I could have gone with something in the 240° - 245° range with no problem.

Russ

 

if you go bigger your going to have a turd out of the whole.. the cam you have now will make torque lower.. giving it a little more out of the hole.. going bigger will take that away... will you still make the same tq numbers? yes, probably better.. but with your setup, its going to take you too long to reach that to benefit, its going to hurt you.. especially for a street only car..

your on a huge tire (much more than you will need)..
a relatively small stall (especially for the weight of your car, the liter the car the tighter the stall gets)
3.50 gears (more like a 3.10 or around a bout with those tires..

you absolutely dont need to go bigger on the cam right now... not until you change some other things... your half way matched on your mods right now... if you go to an ms4/trex/polluter/ any other donkey dick cam.. your car is not going to be very well matched.. to run a cam with a high 230/low 240 you need at minimum...
4k+stall... (NA you can go up to a 4400-4600, if your gonna spray stay at a 4k)
410s
and you should be able to hook with a 26 inch tire.... put a LITTLE money in suspension.. and you will be fine.. if you absolutely have to (to make yourself feel better)... you can run a 28 inch tire.. but its just going to hurt you out of the hole.. i would try your hardest to stay with a 26 inch..

with the 4k+ stall 410s and a 26 inch tire and sub 3k lb weight.. it will be a force to be reckoned with out of the hole..


main thing i can suggest right now... stop paying so much attention to you cam selection.. it is one of the less important things in the grand scheme of things.. concentrate on intake/heads/stall/gears/tire size.. that will affect more all together than going from a Torq. V2 to a 240 cam... i promise..

SIDE NOTE----- i forget you wont take it to the track.. you may need a 28" even with suspension for street only... i concentrate on what my car is going to do at the track... and then hope it does nearly as good on the street..

hope that helped some..

 

Forgot to mention the Caltrac bars (absolutely the best way to hook a leaf sprung car). My GN powered S-truck with Caltracs dropped 1.8 seconds (on my G-Tech) in the 1/4 just by switching from a 3k restalled 12" converter to the 3200 VIG. Now I get 1.6 60ft times and 12.00 1/4 times on street pavement with a 275 Nitto. If you've never had Caltracs or a "real" converter, you just can't know! Both of these pieces will give me a big boost.

I'm not obsessing over the cam (I feel I have a good one)I'm just trying to get a handle on why the "new" smallblocks have such different "requirements" over the old GEN I motors. BTW, thanks for your time!

Russ

 

i know minimal to nothing about GEN 1s.. so im not even going to touch on the subject...

no problem!