Darth_V8r

iTrader: (4)

Even if you change the cam, the fast102 will still make more power. I wouldn't consider this an either/or situation. Personally I would go just s touch bigger than 227/231. More like 231/235-114+2. That'll allow it to breathe more and delay that IVC for better top end.

brobinson216

iTrader: (11)

What's the compression on this motor?

Have you purchased a Fast yet?

blk00ss

iTrader: (66)

Rise of the Phoenix

iTrader: (27)

Compression is 11:1. I have not purchased the FAST setup yet.

Martin Smallwood

iTrader: (2)

Think about all of the stock cube LS1's out there that run 14-18 degrees of overlap with 1 x 7/8" headers that do not have these issues. Some have 1.55" diameter exhaust valves, some have 1.575" and some even have 1.600". Different exhaust port volumes as well. With all different kinds of camshaft specs thrown in the mix.

The fastest cam only LS1 cars on the planet all have 16+ degrees of overlap@.050 and 1x7/8" headers.

My personal 2002 Camaro with a stock bottom end LS1 with nothing done to it but ARH 1 x7/8" headers, ported Fast 92/96 combo and a 239/247 110LSA camshaft made 425rwhp/390rwtq through a TH400 with a 5000rpm stall converter, a 12 bolt, spool, and on 275/60's with 19psi of air in them. That car went 6.38@104mph at 2980 lbs. raceweight. Had it been a 6 speed like the OP's with a stock 10 bolt and 275/40/17's it would of made 460+rwhp if not more and well over 400rwtq.

I highly doubt it's the camshaft, but I will be glad to sell the OP a brand new camshaft with less overlap for my cost and free shipping if he would like to test a different camshaft.

Martin Smallwood

iTrader: (2)

The highest powered stock cube LS1 I've ever been involved with made 500+rwhp and 435+rwtq with AFR 205 heads, Fast intake and 1x7/8" headers through a 4L60E and an aftermarket rear end. Anthony Samsel's car.

That car ran low low 10's on motor at almost 130mph at 3100-3150lbs. The AFR heads have great exhaust flow and a large 1.600" exhaust valve like the RHS heads(albeit they have a 1.575" diameter exhaust valve). The cam I did for that car has 22.5* degrees of overlap @.050". The cam was a nearly direct copy of the camshaft that I had in my car: 239/246 .624/.595 110lsa. 12 degrees more than the OP's with nearly identical exhaust port volumes and exhaust valve diameter(actually larger exhaust valve diameter) along with nearly identical exhaust port flow.

The cam that was previously in Anthony Samsel's car was a 231/235 113+2 cam with 7 degrees of overlap. IIRC it made right around 455rwhp/400rwtq. We changed the cam, and put a .040" head gasket on the engine and made 502rwhp/437rwtq.

Here is the dyno graph showing the two camshafts power outputs.



I realize that the OP doesn't have AFR heads, but Brian mentioned the AFR heads in his statement that he felt it was over scavenging.

Rise of the Phoenix

iTrader: (27)

Martin, I appreciate you taking the time to post in here. I also appreciate the PM's on FB. I know you wanted me to measure the primary length, which I'll do tonight and report back. Do you think that has something to do with why we lost power past 6,000 rpm's? I've seen a lot of other dyno results of guys running the Speed Engineering 1 7/8" headers and they have no issues at all making power clear to 7,000 rpm's. That's what has us so baffled. The car never had an issue making power to 6,500 RPM's (this was done on two dyno's) and carried that power past that point. It wasn't until after the bigger headers that the power nosed off hard right around 6,000 rpm's and the higher you spun it past 6,000 rpm's, the more power it lost.

In your professional opinion, if I were to add a FAST 102/102 setup and obviously have the tune touched up for said FAST 102/102, how much do you think I would gain, and how far do you think it would carry power? Basically, would it solve the high RPM power loss?

SoFla01SSLookinstok

I'm also glad Martin chimed in. The main things I was thinking of were header primary pipe length, primary collector length, not the extension, & the tune of the pipes if any.

Great results, as usual, on that cam swap Martin. With the power starting to fall just after about 6600 it looks like that motor wanted more somewhere.

Darth_V8r

iTrader: (4)

Martin, that torque curve is nice! 426 pounds of torque from roughly 4600 to 6200 on a 346!

Bet it sounds crazy at idle. Or trying to idle

slow trap

iTrader: (22)

i agree but look how bad that monster cam falls on it's face past peak power compared to the smaller cam on the wider lsa. imagine that cam with 12-15* less duration.my dilemma with my loss of top end on my 408 with a tight lsa cam after switching to larger headers is the same,even though i switched to a ported 102 setup as well.i am just a shade tree novice but i am really thinking of either switching cams to something similar in dyration or slightly bigger but like on a 113 lsa with 3 or 4* advance to keep my dcr up there or while i am at it just switching over to an llsr setup. may just leave it like it is and say f$$^ it haha.

ddnspider

iTrader: (26)

Martin,
I don't think anyone is directly blaming the cam, I think its more about the package, i.e. this cam, these heads, these headers. Maybe I missed it, but do you have any observations or theories about why the OP's specific setup did what it did when he swapped headers only? You posted plenty of info about other setups, and no complaints there. Just curious if you agree on THIS SPECIFIC setup that its about over scavenging or is something else at play?

nmass399

Have you checked fuel pressure, what fuel pump are you running?

Rise of the Phoenix

iTrader: (27)

Fuel pressure was good throughout the runs with both headers.

nmass399

Ok just curious, I guess the only way to know for sure if something is wrong is to do another dyno with it. Or maybe something else to look at?

Darth_V8r

iTrader: (4)

I'll throw this up for discussion. On the graph Martin posted, you're correct, slowtrap. The higher overlap cam does fall off faster. BUT it has way farther to fall before it even equals the other cam, and it's holding 426+ pounds of torque from ~4500-6200 RPM, which is crazy good for a 346. If I'm racing I'd rather have that larger cam, but if probably go with shorter intake runners also. Something like the MSD Air Force. Mamofied for max flow.

Second, some friendly advice. DCR is a good indicator of low RPM throttle response but that's about it. I look at valve events to get the motor to run the way I want, ignoring DCR for the cam. If I want peak power above 6500 rpm, I want IVC around 46 degrees. Maybe higher if I want to keep making power into the 7000's. EVO gets earlier as well. Close to 55-60. The later IVC reduces DCR. Ignore it for cam selection. After you get your cam selected, you can say you want a certain DCR so just mill the heads to get the number you want.

In the OP's case he does have a relatively early IVC, sort of like mine. His cam and mine are pretty similar animals. But with the right heads and plenty of airflow it'll still rev. That exhaust scavenging makes way for fresh air and fuel. That's why overlap makes power. Only real difference between his and mine - assuming slight differences in head design, is the LS6 intake and throttle with 3" mouth vs fast 102/102 throttle with 4" mouth and much larger plenum.

A 232/236-115+2 would carry further, etc, but would not get the peak power available from a 232/236-112. And both would STILL be held back by the induction IMO.

Rise of the Phoenix

iTrader: (27)

He made several pulls, and all showed the same trend with the power loss up top. Even messing with the tune didn't help.

SoFla01SSLookinstok

Slow trap & phoenix seem to have had the same problem arise, on different size motors/combos, after swapping headers. Ask yourself, when did the problem start? What if you switched to a different header? Do you think the problem would still be there? I'm a guy who was just a mechanic for a pretty long time. No lsx guru here either. As was stated by me, & others, a fast will make more power every time. No matter the combo.

The more input the better. This is why we do dyno runs before & after anyway. To see what really happened.

On the dyno chart Martin posted, between the two cams, this is what I am thinking. As you can see the smaller cam actually carried power better in the rpm. The new cam is making much more tq & about 50hp more at 6500. Thats a lot more air/fuel being used than it was. I would guess something else may be restricting the potential at high rpm. Rule out the cam. Could be fuel, spark, air, or exhaust. As i'm sure it could be other things as well.

Rise of the Phoenix

iTrader: (27)

So basically you're saying that a better induction system will do wonders, and the cam and cam's valve events are actually not bad for how well the exhaust ports/exhaust setup flows?

98_WS6_M6

iTrader: (18)

It seems a few people have suggested this and I'd have to agree as well. Probably the cheaper choice to go with over a cam swap for now with everything else that would have to be changed with changing the cam (timing set, gasket set, head bolts, custom push rods. And either way you're going to want a better intake/tb eventually for how well the rest of your setup flows.

BREWS02WS6

iTrader: (6)

+1. I was thinking about this earlier. At this point, it seems you've lost the need/ability to do a header comparison. Whether you keep the cam or change it, you've been wanting intake. If it were me, I'd scrap this header mess and move on to intake. See if that gets what you're after, maybe on a different dyno. Then you can decide if a different cam will suit the whole thing better, and do a comparison at that point.