screaminz847

For a bit of history - car is a 2001 Coupe I purchased off of corvetteforum back in April. It dynoed 360 RWHP /335 RWTQ with the following mods:

LS6 longblock
LT headers, Corsa catback
Vararam


I installed an England Green Whiplash II cam recently, and I'm very pleased with the results. I will say I have questions, as I'm curious to say the least.

Car made 420 RWHP / 350 RWTQ with the cam.




I was pleased that there was no loss of power even down to 3000 RPMs. Perhaps even more surprising to those that say you give up a lot on the low end for more at the top, I didn't lose anything all the way down to 2500 rpms:



Note that this was an unfinished tune run, but I asked the dyno operator to start it at 2K, and he did it at 2500...


On to my questions.

First - why does it peak SO high? I know it's a big cam, but most of the other dynos I've seen of this peak around 6200 - mine is peaking at 6600, and the torque is only just starting to taper. I'd think it would be good to shift at 7K+ for best E.Ts, no?

Second - Why is torque so low? It's not terrible, but I feel that it's about 30 - 40 RWTQ down from most other combos, across the board. Even stock, it seemed that it made less torque than most combos. I'm at a loss - any thoughts?

My thoughts were possibly the bottom end was a 5.3 and not a 5.7. The heads are indeed 243s, and had yellow springs. I checked the casting number on the back of the block and it's indeed an LS6. That throws out my idea that it coudl have been an L33 block.

My only regret was that I didn't degree the cam (though it would have been with nothing to compare to, as EG wouldn't even give me the valve events). Also, with a cam this big, if the cam or timing set were off a few degrees and it was too far retarded, I'd think I'd have valve clearance issues, no?

My tuner (Mike Bruce with B&B Corvette in Columbia, SC) said it took more timing than he normally sees. That also led me to thinking it might have been a smaller displacement motor.

I'm going to put a bore scope on a cylinder this weekend to see if the pistons are indeed the flat top LS1s. Since the block number is right, I don't see what else it could be.

I'm open to suggestions and criticism.

I will say - this cam drives great for something this big. I used to have a GM847 cam in an LT1 and never had an issue with it. Big cams are the way to go I think...

screaminz847

120 views and no replies - no one has any thoughts on why torque would be low?

1989GTA

Not knowing the specifications of the camshaft it could be posible you traded horsepower for torque.

Also, "That also led me to thinking it might have been a smaller displacement motor."

Sounds like you are not sure what combination you have.

screaminz847

Sorry, I should have clarified - the Whiplash is from England Green - 24x/25x .630 lift.

As for the combination - unless you purchase brand new, you never KNOW what you have.

However, I was told when I purchased the car that it had a 2002 LS6 longblock in it.

I'm trying to determine where the torque may be, as even my baseline numbers seemed a bit low on torque. I don't think I traded "torque for horespower" if that's what you meant, because as you can see from the graph, I only gained both - there wasn't any loss of low or mid range torque to gain high rpm power.

I was using deductive reasoning for the "thinking it may have been a smaller motor." Wouldn't a smaller displacement motor peak later? Mine peaks at 6600, while most cars with this cam peak around 6200.

However, I've confirmed the following items:

Block casting number is LS6
Intake manifold is LS6
Cylinder heads are 243s, and had yellow springs

The only other thing I can possibly think of is perhaps it has thicker head gaskets to lower the CR. Would that not lead to lower overall torque? I would think that would lower HP too though, and power is good, or at least I think so. The motor also took more timing that what my tuner normally sees - another thought of perhaps lower CR.

Any thoughts?

outkast6991

iTrader: (34)

The tq is down due to the duration of the cam itself. The peak is so high due to the cam as well

30th t/a

iTrader: (51)

I disagree. Big cams can make big torque, just higher in the rpm range. This guy should have way more torque that 350ftlbs. As where this setup is making peak power at, I think it look just right for a 24x/25x cam in a 346cid.


I wonder if you installed the cam off a tooth on the timing gear? possibly retarding it.

screaminz847

That's my current thought - but if so, I would think with a cam this big I would have thought there would be piston to valve clearance issues.

Here's the kicker - other than making sure its not a full tooth off, I'm pretty stuck as far as degreeing it. Without known values to compare it to right? I guess I could have it put on a cam doctor to get the valve events, but I was hoping to not have the car apart for more than a day.

Slowhawk

iTrader: (12)

It's the cam design. Made to have a peak hp number.

eb02z06

iTrader: (18)

IMHO-that cam doesn't belong in a stock 346.

I woudln't be happy with that sacrifice in torque.

screaminz847

Did you look at the graph or read the first post?

If you look at it, I did NOT lose any torque, and only gained. The car only made 335 ft. lbs or torque before the cam. Power and torque are identical until 4000 rpms, when the bigger cam overtakes it. Most Z06 dynos I've seen with similar mods make around 360 RWTQ.

After doing further investigation, I wonder if my exhaust is a restriction - it would explain why torque was low even on the stock cam.

I was told it was LG longtubes, and it is indeed longtube headers, and resembles LG's, but the OD on the primaries is only 1.745". I called LG and they said they never made a 1 5/8 ID longtube, but with .047" wall thickness, that would be what these are.

The interesting part is they have merge collectors. I can't find any C5 corvette 1 5/8 longtubes that have merge collectors. The car also had cats- unbeknownst to me. I thought they were resonators (doh!). I'm hoping removal of them helps in the power and torque area, as one may have been clogged.

One of the headers also has a dent/crush in one of the primaries. I thought that would limit peak power, and not reduce power everywhere. I'd replace these with 1 3/4 long tubes before fixing that primary though.

I'll get some pics up to see if anyone may be able to Identify the headers.

Anyone else think 1 5/8 headers would reduce overall power and torque?

screaminz847

Here's some pics of the exhaust - can anyone identify it?

Headers and x-pipe



Merge collectors:



Primary size:



Collector choke:



Collector exit:



Passenger top view:



Any clue who may have made these?

eb02z06

iTrader: (18)

Headers are measured by the OD, just like the rest of the exhaust. When you buy a 2.5" catback-it's 2.5" OD, not ID. Same goes for the header primaries.

My stock Z06 made 375/366-throught the factory manifolds.

IMHO-you don't need a 242 intake lobe in a 347 unless this is a track only car with a set of 4.10's

You can make more usable power throughout the curve with a cam at least 10 degrees smaller.

1989GTA

No clue on who made them but everything looks right. Tubing is measured by the outside diameter. Those are 1 3/4" headers. Looks about right on the merge collector. The X-pipe is a style used by some including LG Motorsports. From the outside I don't see a problem.

screaminz847

That's my point - your car with manifolds made 30 FT. lbs of torque more than mine did with longtubes. I know all dynos are different, but I wouldn't think there would be that much disparity, especially since its low across the board.

I guess you could classify this as a track only car as I only drive it on nice days, it's not a daily driver by any means. I do have a z06 transmission and 3.90s - is that not enough? I thought 3.90s in a MN12 were like 4.56s in a C5.

Also, it appears that the torque is much flatter than most other cams in that size range - Most seem to start in the 350 range, creep up to 380 - 400, then taper. Mine is relatively flat.

zacht

iTrader: (18)

that cam seems huge! did you measure ptv clearance with it? plenty of people on here running smaller cams have ptv clearance issuses.

ive never heard of that cam, im in for more specs on it. no way its 'tailored' for a stock LS1 car...

Blk98Vert

iTrader: (2)

England green designs their cams to be thrown in a stock LS6, so yes it is

screaminz847

Exactly, it is designed for a stock LS6. I probably wouldn't run it in a 3800 lb trans-am, but in a 3100 lb vette it's fine.

I've since had it confirmed (here and elsewhere) that LG measures OD for their primaries. (There seems to be some discrepancy as to who measures how, tho industry standard is OD for tubing.) It does appear that the Cats were put on after the X, which I think is opposite how LG normally does it, It's all slip fit, and in a straight line, so I'm going to see if moving the x pipe further away from the collectors does anything. I believe there is some debate on the forum regarding that, so I'll see if it makes a difference.

One of the primaries is dented pretty bad right before the collector - I didn't think that would lower average power, but limit peak. I may have that fixed as well, since it will only help.

Slowhawk

iTrader: (12)

Dented headers can hurt mid range power.

EG cams are big, they are pointed towards high rpm power, not torque. I agree with Arun that a good speced cam in the low 230's range would make more power across the curve which will make the car faster.

A.R. Shale Targa

iTrader: (2)

Torque comes from cylinder pressure or DCR. This is why more cam timing
needs an increase in static (numerical) compression ratio to bring back the
missing cylinder pressure. The IN valve is opened longer(to allow more air in) and it is also closed less which builds cranking compression. In order for a 242
size intake lobe to fit a non-notched factory flat top it probably has a later
opening and closing point which just can't trap the pressure that produces
lower and midrange torque. Torque is what you want, it's what moves weight,
and it's what a dyno measures. Horsepower is merely a mathematical figure
derived from where in the RPM range the engine developes torque.
The ZO6 guy's stock engine had a 204 degree intake lobe with 10.45 comp.
producing around 200 psi of cranking compression whereas having a 242 lobe
in a 10.45 comp. more than likely down in the 120-130 psi range and will
not be making good power until the air-pump is spinning 4000-7300 rpms.
The MN12 tranny and 3.90 gears will help a bunch although I'd still suggest
4.10s since the gear spread (numerical drop) is larger than an M6.
If later funds allow send your factory heads to Advanced Inductions for their
CNC and combustion chamber work. If you were to jump your comp.
ratio up to almost 11 to one plus the added flow youl'd pickup at least 40
peak horsepower and probably 50-60 ft./lbs. of midrange torque.
http://www.advancedinduction.com/LSX...cGMLS2Head.php

screaminz847

OK, I dont disagree - why would my LS6 engine with LTs and full exhaust make 30 ft. lbs LESS than his stock then? Please don't say lack of backpressure - It's proven time and again that LTs and exhaust will increase power pretty much everywhere.

I have no issue with driveability if that's why you recommend 4.10s - I thought the MN12 was geared a good bit shorter everywhere than the M6.


THat's exactly where I plan to send them.