Charlie207
Full Access Member
Well, I quoted you, so.... start there.
6.2 ls3 GM performance crate engine
- Thread starter Reddenali
- Start date
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so what I believe is happening there, something to do with lobe angle. so gm made an interesting cam for the ls7. this is a 7L that needs to idle dead smooth and here's the kicker. run to 7k redline with no veritable anything and pass emissions. a buddy had one for a while, got to drive it and it runs cleanly all the way to 7k and idles like any stock ls.
if I'm remembering right they did this with a super wide LSA. you get no chop, but also give up mid range tq but able to have enough duration to make it rev to 7k. that's what vvt is trying to work around, wide lsa. so once you go cam that's OK with some chop and doesn't need to pass oem emissions. tighten up the lsa, get a cleaner air supply in the piston and you end up with more mid/low end tq.
my buddy with the ls7 before he got rid of it put a stage 2 cam in it and it picked up a good amount of tq under 3k, didn't really do as much as he had expected up top, and since you have more tq then you need in a manual tranny 7L 3200lb car. the cam honestly was more annoying then anything, especially because he went thru 3 different tuners and it never really idled right form open exhaust to closed exhaust. living in a hoa he really needed it to run well closed up. in the end the cam was the down fall of the car and he got a c7 z06 instead and is enjoying boosted life.
but yeah, long story to say I'm not surprised at all that a aftermarket cam that doesn't have to follow the same emissions standards as the oem does still makes more low end than a stock wide lsa does. even with the crutch of vvt.
now vvt on a dual over head cam engine with aftermarket cams being a whole new can of worms. that can be solid gains because you can get one set of valves out of the way of the pistons and take advantage of it. if you add turbo to that combo. it becomes magical in the hands of a good tuners.
I believe the camaro guys have to fly cut pistons to get much use out of vvt cars. where vvt cam in the automatic cars but not the manual.
Great perspective. Thank you for sharing!
Yes, DOHC with dual cam phasers (4 total), is whole different animal altogether.
Yessir, I think we're on the same page.
Marky Dissod
Full Access Member
GM has been coerced by CAFE MpG test scores to undergear every V8 vehicle since the early 70s.
Mid 90s Cadillac Fleetwoods V4P (7000lb tow pack) came with 3.42 axle -
and evaded the Gas Guzzler Tax by 0.1 gallons per mile.
It sorta explains why the most common axle gears for LT1 B- & D-cars was either 2.93, or 2.56.
When I swapped out my Caprice wagon's 2.56 axle for 3.42, I did not lose a single MpG, I only gained passing ability.
Edit: forgot to mention
my wagon's top speed went from 131MpH with 2.56, because I became afraid for my engine, as the 'acceleration' was glacial
to 141MpH with 3.42 because I became afraid for my lack of courage and am happy to have given up prematurely
mikez71, you need 3.42 or 3.73. If you tow very heavy very often, 4.10 would not be out of the question.
That'll give you additional power from as low as 600RpM.
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Then how about actually saying something useful in response? I’m speaking from experience and you’re just pulling stuff from you know where.
Most aftermarket cams don’t make real power until 3k RPM. Explain how that’s wrong? It isn’t. If you’re ok with WOT everywhere or at least running the engine up to 4-5k every time you take off to get the power and kill your gas mileage, that’s fine, but that doesn’t make what I said even remotely wrong, or however you so eloquently put it.
