3timeracin

iTrader: (15)

I currently have a new comp 244/252 111lobe sep installed on a 108icl

Car runs good now after a nightmare of tuning problems and ran 10.40's with carb setup and ran 10.70's today with the injection after an all nighter to switch over last night. I read alot that the big cams dont work ? what about a setup like m ine does anyone this i have power to be gain or better ET's going to a smaller cam or a different cam I have changed cams a couple times but all have been pretty large 24x/25x stuff all over .600 lift went 9.36 with old cam and 300 shot. If anyone has a setup like this please let me know what you are running for a cam ? I would like to see what the cam gurus like Rick at synergy and Patrick G think as I always see them suggesting L92 cams for DD cars, but this is a different story I am not looking to go 12's My ultimate goal is high 9's NA if at all possible and maybe a cam would help get me closer ? OH yeah I forgot it has 2 stage nitrous I have not used yet 250hp fogger and another 125hp wet nozzle.

My car is 80%race and 20% street driving 3200lbs
408 callies crank rods and wiseco pistons (compression is 10.85)
Has carb intake and eldebrock big 105cc elbow
90mm TB and 85mm MAF
TH350 trans brake new 4000RPM coan stall
4.22 9" and 28x13.5 et street's

Put down 468RWHP with only 24 degrees timing

mike c.

iTrader: (1)

I just posted up a post called LG Motorsports g6x3 l92 cam is in. I switched from a 248/254 cam to LG's g6x3 234/244 cam and gained. go Take a look.

3timeracin

iTrader: (15)

Thanks I checked it out looks good, I just tried a 238/252 112ls today and picked up alot under the curve and 16 peak hp its amazing smaller is better sometimes....heres the biggest kicker I have been having the higher KPA reading typical of the carb intake and elbow setup 93 to be exact I just switched to an accufab 4150 style throttle body and eliminated my maf. The KPA was aorund 100+ and made an amazing 43hp more this is on an engine dyno keep in mind...

Patrick G

iTrader: (14)

If he were running an L76 intake like you, that would make a lot of sense, but for a single plane intake, you can afford to go a little bigger because the motor is going to make power at a higher rpm. The key is not to go excessive on the overlap though, even with a single plane. The ideal cam depends on how important the nitrous performance is. If this is a 100% nitrous application, then you're going to be looking at a big split to the exhaust with a much earlier exhaust valve opening point. If NA performance is equally important, then the cam needs to split the difference between ideal NA valve events and ideal nitrous valve events.

3timeracin

iTrader: (15)

I have been testing with an engine dyno not chassis dyno like most people on here. What I have found is the l92 setups dont built any runner air pressure between cycles on the intake valve and this is caused by the large intake volume of all the setups people have ? I have switched to an Accufab 4150 Throttle body and the airpeed is tremendously better the engine gained torque and the high KPA's everyone sees on these was virtually gone.

I feel the cam situation is just a crutch for a poor intake situation that has an easy fix. Reduce volume and loose the elbows this will create airspeed and build runner pressure between cycles. for example almost all the top performing 9 second NA cars have a carb or some sort of 4150 throttle body look at Collin's car it has a big cam and works even with his relatively low stall and footbrake launchs.

I switched to the Accufab 4150 TB and went back from a 234@.050 cam to a large 24X/26x cam and made the same torque numbers and 22 more hp.

I even cc'd one of those old 2x4 tunnel ram intakes with a dart 215cc head and the combined volume of that was still less thatn mu L92 setup with elbow ? hard to believe but true and you know as well as I do this kills airspeed and will mess with tunes and power numbers. look at the lS7 heads they have less cross section for a reason.

Maybe im crazy but I think people are a followers and when someone knowledgable says its a cam problem you need a special cam everyone follows instead of doing research to be sure its just a cam problem. no offence to you but people could get the same results with porting the exhaust and a different throttle body setup ?

WKMCD

iTrader: (2)

I agree with what you're saying but some of us a limited but what fits under the hood for our pusposes.

3timeracin

iTrader: (15)

The accufab throttle body on the carb intake is the same height as the factory L76 intake its only 2" thick check it out on there website.

WKMCD

iTrader: (2)

Interesting...Don't even get me started - again..

3timeracin

iTrader: (15)

Another thing to keep in mind is these heads have enough intake flow for 640hp with adequate compression but not enough exhaust flow. They really only need to be balanced the as cast intake to exhaust flow is ratio only 68% average. these people that are running ported heads are not gaining from the intake porting as they think they are gaining on the exhaust flow increase. Take a look at any CNC L92 head the intake only has porting on 1/3 and the cross section the most important part is virtually unchanged ? now look at the exhaust ports on a CNC'd head you will see a drastically different port from the as cast version.

Also another thing to consider is the intake port is the same cross section as an old big block at 3.19 square inches and we now how they can run ? But they have a balanced intake to exhaust port flow and they dont require any special cams just to prove a point.

94 guy

iTrader: (125)

how much power did you put down with the accufab 4150? also this is a th400 car?

HTMtrSprt

Actually the intake ports move more air than necessary for 640 HP, but they won't do it at the air speed required to make more power (unless you make radical changes). The exhaust ports are adequate JUST AS THEY ARE. If they weren't, someone will have to explain to me how I have a motor making 706 HP with them. Over 100 pulls on my engine dyno w/ 3 different engines, 4 different L92 head configurations (including 2 different intake valve sizes, 3 different exhaust valve sizes, different valve seat angles, etc.), 6 different cams and 3 different intake manifolds has told me the limitations on L92 head combos is the INTAKE port, not the exhaust.

3fingas

iTrader: (16)

A little more to it then that, first if its streetable with oem hood you have to turn air flow 90* with either a carb hat or carb cover, then filter it. Some also shim the k-member. You definately create a restriction with the hats but very very little loss in power. The plus is you can throw the MAF back on. Then the inevitable is modding the cowl and hood (SS).

This is what I was faced with when I built my forged LS3. I got excellent power with the SP/4150 accufab combo with a 220/244 110+, 590/498 @7200 on the e~dyno. For me, the combo works cause the car isnt a DD. IMO

TBSS-RAGE

iTrader: (1)

just for reference my setup is:

LPE CNCed L92 heads with stock sized light weight intake valves
L92 truck intake with mild porting (smoothing the internals ridges)
LME 441 LS7 Shortblock

4L70E tranny with 3400 stall

4.56 gears and 20" wheels - both of these will drain on a chasis dyno

the cam was speced as a LPE experimental my builder got, the specs are what i understand which are vague but will translate to the discussion...

the duration split is right at 10 and the lift split is like 15 and i have no idea what lobe was used.....

as i understand the specs: 240/250 @ .050 .655/.670 114 LSA 110 ICL which we installed 4 degrees advanced....

this is a pick of the dyno done on HPP's dyno in lewisville, tx....

this is motor with TR6's and 25 deg. of timing on pump gas and 21 deg. of timing on pump gas with a 100 shot on Nitrous Outlet Plate

3timeracin

iTrader: (15)

Well as far as I know its all math and if you take my flowbench numbers and use the normal idiot equation of cfm intake flow X 2.0=HP I had 322 cfm x 2.0 thats 644hp the only variable is compression so you must have 13.1 or higher to make 706hp normally aspirated ? air speed is determined by piston speed and cubic inches. The larger the cylinder the more vacuum it creates drawing in more air increasing air speed in the port but you can also increase air speed by decreasing cross section. The less corss section you have in the runner the less time it takes when the intake valve closes for the air in motion to stack up or create pressure on the back of the valve. So its not just the head that dictates air speed its cubic inches actually thats why if you take 2 indentical heads and put one a 350 and the other on a 434 they will actually make the same power but you will need to spin that 350 8500rpm to move the same air to make the same power the 434 does at 7000rpm. I find it hard to believe still because every L92 setup Ive done has made more power with bigger headers not a bigger intake ? and everyone I see on here making the most rear wheel horsepower is using huge split cams with 10 or more degrees on the exhaust including myself now and it works thats funny for it being the intake. Same goes for GM they have a L92 specific camshaft that has almost 20 degrees more exhaust duration must be there wrong too ?

3timeracin

iTrader: (15)

Exactly thats some very stout numbers considering your power losing drivetrain and exactly what I have been using is cams like that because they work.

3timeracin

iTrader: (15)

Yes but compare your power to others with more of everything and still not making that much thats alot for that little cam.

LSwonderfull

The exhaust duration on my cam is only 8* bigger than intake, and i run 1 and3/4"headers and my motor made 650 flywheel hp with as much as 550 ft llbs.
I ported intake and exhaust ports on my L92's and the exhaust did not pick up tremendously in flow, pipe diameter has more to do with peak power rpm, it doesnt limit power as much as many believe. I see some speak of turning 7500 rpm hydraulic roller, i have done alot to get past 6900 and it is not working past 6900. I also found that L-92 heads are so adequate in flow on my 402" that the carb pulled low cfm #'s thru the air flow meter for the amount of power the engine was making. Only around 700 cfm at 6900 rpm.

HTMtrSprt

My heads flow 340 cfm and the engine in question is a pump gas 454 w/ 11.1:1 compression and a hydraulic roller with an LS7 intake.
Port speed is determined by HP and port cross section regardless of displacemnt. Ever notice that everybody's big L92 head engines seem to make about the same max HP?
The engine seems to be sensitive to exhaust valve timing with regards to carrying the HP curve i.e.- the valve needs to open at a certain time in order to a certain HP, but port flow seems to have virtually no effect on HP.
The intake, with it's big cross section has relatively low port speed (in the runner) so hanging the valve open too long WILL cause intake reversion. Close the valve a little earlier to trap the cylinder and let the large port carry the HP.
The problem with the intake is that when you start making, say.....630 fwhp, the port speed at the bowl is so high the air stream will not stay attatched to the floor as it turns toward the valve. This causes the air stream to tumble and spill entirely out the far side of the valve seat area instead of some air going out the far side and some going out the near side. The valve is a crucial component of directing the air through the seat area and when you open it too far, it's no longer in a good position to guide the air stream through at higher speeds so the stream goes turbulent and VIOLA!..... no more air flow.... no more HP!

3timeracin

iTrader: (15)

your car is carbeurated that has a big influence less reversion and so on. My red car made the same carbed and runs consistant 10 teen's on motor with only 9.5 compression.

3timeracin

iTrader: (15)

The only reason HP can dictate air speed is the more HP you make of course the airspeed will be higher it takes more air to make more power. and they all do make about the same but at different rpms depending on cubic inches. I know a 408 and a 454 both making say 700hp will both have the same airspeed to make the same HP but the 408 will make it a higher rpm because it creates less internal vacuum per revolution hence ci dictating hp and air speed at a given rpm ? the only variable in cubic vs hp charts is compression.

If you say HP dictates air speed 100% the air speed would always be a constant all engines would make peak hp with stock L92 at the same rpm reguardless of size ? Right

No thats wrong thats why your 454 will make more power at any given rpm than a 408 will with the same head. The larger cubic inch moves more air at a lower rpm correct ? yes, so that means the cubic inch is increasing the air speed making more power, hp is not increasing air speed cubic inch is. The only spot they can be equal is at the peak hp reading wich will be at different rpm's. because why ? cubic inch difference, right.