Conv389drv

I notice that the stock LS1 cams have a very short duration (by hot-rodder standards anyway), yet they still produce a high output per cubic inch, and at a relatively high rpm too.

If I remember right, the cam specs at .050 are something like 206 degrees duration! That's pretty conservative; I don't get how the engine can perform so well at higher rpms (and make good power) with a cam that small.

Can somebody shed some light on this for me?

ME Leigh

Great head design, far superior to anything before it!

kevinc

...and you ought to see what they do w/ a more radical cam. 400+ rwhp with 230/237 .59x" lift is almost the baseline.

MrDude_1

the heads are a really great design. the intake manifold is designed to be part of the heads intake tract... its so well designed in fact, that early versions of the head had the air going in too fast.... it was only "pouring in" thru the back of the valve... they added a little "hump" to the plenum floor to slow it down... letting the air use the entire valve to fill...

its a very nice setup. with nothing more then a 224* cam (with fast lobes), and careful tuning, you can see 400rwhp.

1989GTATransAm

iTrader: (3)

Just backs up the saying that the heads are the most important item. I would rather have a good set of heads with a small cam than the best cam and a poor set of heads. Of course you have to add the intake and exhaust track into the equation. Allen

ME Leigh

So you are saying they added a plenum hump, so they could get better flow past the valve. Poppet valves flow the best when air flow is equal on all sides, creating a "cone of flow"

MrDude_1

no, not in the plenum, not even in the intake.. its in the head.

you'll see what i mean if you ever look at a cross section pic of the intake tract.

basicly, it just slows the air a bit and lets it use the whole "cone" as you call it.... instead of just the back of the valve.


its a really nice head. add in the better valve angle (15* i believe... compared to SBCs 23*) and emphsis on efficency and you have a powerful motor that accepts alot of mods.



basicly its the equivent of putting a performance head on a SBC with a mild cam.. it makes great power, and is streetable.. add a cam and you'll see a larger then normal increase... mod the head and you see even more.

ME Leigh

The cone is formed on the front side of the valve, in the chamber.

I'm not sure what you mean by dumping on the backside of the valve. Thats how its supposed to be. Maybe the hump is to induce swirl.

ME Leigh

Here is a LS6/LS2 head

ME Leigh

lets see if i can get this to the top this time

MrDude_1

can you find one of a LS1 head?

Damon

The LS-1 is more than just a great set of heads (although they are very good heads). There are little tricks all over the place from oil pan to intake manifold.

Like the cam..... it uses a very big base circle. This allows them to create some VICIOUS opening/closing rates on the lobes. Stuff you can't do reliably on an earlier engine. Plus the overall design of the valve train allows them to use some very high rocker ratios, allowing very high lifts and get all the goodness that the cam has to offer.

There's a zillion little things that add up to one really good engine. It's more than just the heads, but they are obviously part of the equation.

MrDude_1

lol yup, its more then that...
for example, they had that big cam...... but a big solid chunk of metal is heavy... so they rifle drilled it..... basicly, theres a hole running down the whole cam... making it lighter..

great motor..

Conv389drv

Yeah, I suspected that the cam might have a really fast opening and closing rate, so that even with the short duration it still acts like a bigger cam. It didn't occur to me that that was the reason behind the large base circle design of the cam. So that's another mystery solved! (thanks!)


See, I've been looking at the specs of the LS1 to determine what theories and ideas on that engine might be applied to the gen 1 small block (if any).

Speaking of the heads, I noticed that the intake port volume is 200cc (correct?). I would've thought this was large for a street motor, but maybe the high flow rate allows a larger port without low end torque loss. Any thoughts on the theory there?

daverr

iTrader: (1)

as stated earlier a major portion of the advantage of ls1 engine is it valvetrain.they have a higher rockarm ratio compared to the older engines.

on a side note why dont i see alot of ls1 engines with bigger cams? the most big cams i see are in the 230-240 .50 range.And generally they dont spin in the 7000-8000 rpm range.




the older small block chevys have way better cylinder head selection than the ls1.

MrDude_1

take the only comparable heads. they would be all alum, fully ported heads or they would have a diffrent valve angle.. like 18* heads for example.


now look at the price. you could buy a used LS1 longblock for that price.


now remember that you're comparing it to STOCK and ported stock LS1 heads.


right now, the only true aftermarket LS1 head is AFRs head.... wait a few years and im sure there will be more head options.

but the potential for this motor (in a street/strip enviroment) is so huge that it cant be ignored.
name me one N/A small block chevy that runs mid 11s, gets 27MPG on the hwy and runs for 130,000 miles without issue in a daily driver that idles in traffic like a stocker.
you would be hardpressed to find it. and when (if) you do, its some tweeker guy who knows what the hell hes doing.
look at all the 4thgen idiots with cams who are doing the same thing.





so yea. SBCs have a larger head selection. LS1s have a better head design.

daverr

iTrader: (1)

sbc 18 degree heads totally outflow any ported ls1 heads, performance costs money.


same can be said with sbc

i cant name one howabout u name one.the part about 130000 miles with an aggressive cam to run mid 11`s without any problems is bs.how many ls1 u hear that break valve springs .
the ones i seen that ran mid to low 11`s had a 427 and didnt idle like a "stocker"


ive sbc run 9`s and 8`s NA. ls1 heads dont even come close to whats available for sbc in the aftermarket.Did u ever see that 4 v head available for the sbc?????theres a guy on this forum with a 800 NA sbc ,look up member seejgo.

remember the sbc have a long history .

MrDude_1

ok. now go look at the stock internals list for LS1s. without going into the motor, they're in the 11s.

my friend jay has his daily driver street car. with minimal weight reduction (he takes the seats and muffler out at the track, then puts them in for the drive home), headers, lid and stall, hes running mid 11s.

drives, idles, ect like stock.


theres 100s like that out there.
my point is, you dont NEED a agressive cam to run mid11s. you can do it with the stock cam.

once you get into the LS1 world, you realize that while the max guys in SBC world are faster, more of the "normal" people are faster in the LS1 world.. with less compromise.

its just newer technology in a proven design.

now name a 11sec 3500lbish SBC car that gets mid 20mpg and is totally reliable with nothing but fuel and a oil change for thousands of miles?
they're out there, but you cant just list them off the top of your head, huh.... see my point.

great! if i had access to the parts, i could build one too.
but single digit NA cars are not the kind of car you can jump in and drive across the US to vegas in. you probly dont want to take it to quicki mart on a regular basis. its a race motor. it costs money. and you end up with a nice race car. thats NOT what the gen III+ motors are about.

yea. have you ever seen one in real life?'
niether have i. the 4 valve heads are cool, but look at the big picture. you end up with custom engine components that need to be checked on a regular basis. if somthign breaks, you cant skip down to autozone for a part.. sure you could run that with a mild cam and have a really comparable motor. but look at the cost. you have the heads, the EFI, headers, everything... cost wise, for a street car, its just not worth doing.. so if you get it, you're building a ***** to the wall, all out motor... and thats NOT what this is about.. its about performance without compromise

theres are guys on alot of forums with alot of fast cars. that doesnt mean i had anything to do with that.. or that it has anything to do with what im talking about.

im not ignorant, i grew up on SBCs.. but im also not to closed minded to learn about other motors and learn more.
for a goal of 11s to high 10s in a reguarly driven civil street car, the LS1 is the motor of choice.
you want to go faster? id suggest either a diffrent motor or a much much lighter car.

MrDude_1

just so you know, im not just saying all this because im putting one in my car.

i was actually putting in a pretty well build solid roller 400 in my car.
once i had it running, i started to think about it.
ever since i was in high school, ive wanted a huge aftermarket everything 400... but times change.

what i really want now is a car i can jump into and drive. quick and somthing i can tweek on, sure.. but for the most part, i want to be able to jump in it and drive across the country if i so choose.


i thought hard about this for months. for 2 months i didnt even touch the car.

then i brought out everything SBC ive gathered over the years..i sold it all. i mean everything...
with that cash in hand, plus $600, i bought my LS1 drivetrain.

ive looked into it. for a car like mine, this is the best option availble to the general public.