Fellas,

On the Thunder Racing website (http://thunderracing.com/catalog/?ac...d=3&pcid=289 ), they have a head/cam package for LS1 cars that includes a set of the 205CC AFR Heads and custom TR cam w/ 214 int 230 exh duration and .601 int and .578 exh lift. On a 2000 Trans Am, the package made 394 SAE RWHP w/ 375 RWTQ. Claim to have stock-like idle, stock manifolds, exhuast, and no computer reprogramming. Made me think of two things:

1. How much power can a stock block N/A LT1 car make while still having a stock like idle and low end torque? (Look at the dyno graph the new cam made more torque EVERYWHERE from 2K up). I know there are several good head guys on the board who can make close to that power w/an LT1, but I'd be suprised if the cars still idles like STOCK. I realize those AFR Heads have great flow number b/c they're a clean sheet design, and we're more limited by the LT1 factory design. Yeah I know I could just go to a 383 but I don't want to touch the bottom end. The idea of stock drivability w/ 400 RWHP appeals to me w/o having to go forced induction.

2. That's a crazy amount of lift. I've never seen that much lift for an LT1 cam (especially for a comparatively short duration cam). I'm assuming there's a reason like the ramp rate is too fast or someone would have done it by now? Any thoughts to keeping the duration somewhat short (around 210-216 int and 220-230 ext) with a larger LSA of say 115-117 and making something close to .600 lift? Is this possible w/ 1.6 roller rockers?

Has anyone ever tried to port a set of heads to say 200cc and run a cam like that? Lloyd Elliott, I was specifically thinking of your LE2 heads with a cam similiar to the Thunder Racing one. Any cam sage advice is appreciated as to why this is not possible/practical.

 

Answer to the first question is Lingenfelters 383 LT1's. Baby cam monsters.

-Dustin-

 

I've always wondered how that cam would run on an LT1 with LT's.

 

I find it very hard to believe they made almost 400 rwhp through stock manifolds, stock exhaust and no computer reprogramming. I got to spend a little time with a 99 or 00 C5 six speed that had a Vette Dr's heads/cam package with the bolt ons, it made 384 whp (on a dynojet) and the idle was definitely not "stock like". It had full aftermarket exhaust, air bridge and a tune. I really do not know the cam specs, as that was the first Vette Dr's package I've seen, but the owner said it was a "230/230" cam- although he definitely could have been wrong as well.

It doesn't have as much to do with the stock block as it has to do with head flow. The better your heads flow, you can run a smaller camshaft and still hit your goals. Smaller camshaft=smoother, more stock like idle. What I'm getting at here is if you want a car that idles smoothly and makes big numbers, you're going to have to really pay attention on your headwork. Professional ported LT4, AFR or Trick Flow and a worked intake to go along with it.

Look at the cam I'm using for my LT1- .608/.578 lift. You can have a cam ground almost any way you want it.

I think some of the ported LT1 castings end up being 200-205 cc after the material is taken out of the runner.

I didn't look at your link above, but if you could get a flow sheet of those heads they are using that would help out in doing the comparison here.

 

Dustin - you're missing my point. I'm looking for a H/C package I can bolt on my stock 350 motor and make that kind of power. I realize a 383 would make that easy but rebuilding the bottom end would add at least $3k to the project. I'll do it when the stock bottom end finally gives up but right now I've only got 78K miles on the motor. If the LS1 guys can have a kit, that gives nearly 400 RWHP and have a stock idle/drivabilty, we should be able to get close to that with ported heads and a similiar cam and maybe some LTs.

Also I'm unfamiliar with LS1 cams. Are they interchangeable with LT1 engines? I would assume no just off the water pump drive and sensor locations...

 

no, they are totally different. LS1 engines have different valve placement in the heads, so there's one huge reason it won't interchange

 

Fast Z, first here's the link for the AFR LS1 heads: http://airflowresearch.com/pages/205cc_mongoose.htm
Flow number (intake) .200 : 140, .300 : 200, .400 : 251, .500 : 281, .550 : 292, .600 : 298 (CFM). 205 CC head with 2.02/1.6 valves. Very impressive numbers and coming from AFR I don't doubt them.

Based on the intake flow numbers reaching 280 - 300 cfm from .500 to .600 lift, I could believe the numbers they got. Also LS1 and esp LS6 manifolds are famous for making almost as much power as most shorty headers for LSX cars. Think about it a stock Z06 dynos between 350 and 360 RWHP w/ 210 cc heads that typically flow around 260 CFM and a cam that 204/218 with .550/.550 lift. This package is noticably bigger than a Z06 setup so I could see them picking up 30 to 40 RWHP over a Z06 setup.

You also bring up my second point again. Ok so there are LT1 cams that make .600 lift. Your duration is in the 230 to 240 range. I would assume your idle is no where near stock like. Why hasn't anyone made a shorter duration cam with those same lift numbers? Shouldn't that help maintin idle and vacuum while still flowing more air (assuming your head flows more at .600 vs .500 lift).

I'm well aware the head and cam determine your HP, but I also know increasing displacement means either you can make a given HP with better drivability or for a given drivability (vacuum, idle, whatever metric you want to use) a larger motor will make more power - assuming you haven't reached a bottleneck somewhere in the system. Bottomline, for a given size motor, in this case 350 CI, the more HP you want the less drivabilty you will have with natural aspiration. I know making 400 RWHP is not hard to do on a 350, but I'm betting it's not easy if you want to car to have near stock drivability just based on the cam involved to get you there.

 

This is a good thread lets see if I can help you guys out some.

The first key is the heads. We don't have a cylinder head that bolts on that makes crazy flow numbers with really excellent flow. If edelbrock was smart they could have done something with that LT head they have, but then we would be looking at the cost of things like the LS1 AFR's.

That's a biggie cost. The AFR heads are more than a LE2 package total. Anything can be done if money is no object.

Now on the other hand, Lloyds new LE2 ports are probably a good place to start if you want to make a lot of power with a small cam. A sleeper cam wouldn't be too hard to make either. I did one for a motor a few years ago that was a lot like the TR Cheater cam and with heads that flowed better than those AFR LS1 castings it made 570hp on the engine dyno. Which would be more than enough to get you 400rwhp with a stock sounding idle. Problem is it wasn't cheap and the same motor with a LE2 cam will make 620hp.

I'd like to see the LE2 heads and LE1 cam make 400rwhp, but it's not going to even have a stock sounding idle then.

We could make it sound less lopey and improve the idle vacuum even more but I'm afraid that the 10hp loss is not really worth that.

The last part of the problem on making all that power with a stock idle is the intake manifold. A big plenum and long runners will take the chop out of a cam AND make a ton more power, the LS1 intake pretty much helps that all out. The Accel SuperRam would be a good way to go, but you would have to adapt the base plate to fit LT1 heads.

Bret

 

I don't doubt those numbers either- AFR makes a great product.

I still find it hard to believe, but whatever. Doesn't really matter if a Z06 puts down 355 rwhp, since your average six speed LS1 trans am might do 290 rwhp. You're basically talking about adding 100+ rwhp by just bolting on a set of heads and stuffing a cam in and not touching anything else on the car. I tend to be skeptical, so if you want to believe their claims then that's cool.

You're making this more complicated than it has to be. I remember a while ago looking in Brent94Z's signature, he had a six speed LT1 with a HOTcam in it that made something like 399 rwhp. Having had one, I know the HOTcam is a perfectly streetable cam, that will make power to 6200 where I set my shift points, and also still had enough low end to lug my car up hills at 1500 rpm. It was a little choppy at idle, but I did have the idle set kind of low because I personally liked how it sounded. Do some more idle tuning, quieter exhaust, raise the idle some and you could cut a good bit of the lope out.

 

I wanted to add about the cam....

The lift in the LS1 cars is with 1.7:1 rockers, the LT1 stuff has the stud mounted rockers so you would need a really stiff 1.7:1 rocker and a good cam core to pull that off on a LT1.

You can do a good cam with 1.6:1 rockers and have it idle like a champ and still make good power. If you all want it we could make a LE SSleeper cam lol, I have one that I know works for that around here, now it just has a name.

Bret

 

Fast Z, first they didn't get +100HP; they got +60HP. The car already had 335 RWHP prior to the H/C swap. Agree that's a very healthy RWHP for a 00 Trans Am with minor bolt ons. Still it's an intriguing idea. Understand your skepticism though.

Brett, was hoping you would comment. Making .600 lift with 1.6 RR shouldn't be that hard right? Since 1.6 RR are what LT1 typically run, you would just make about 10% more lift (vs 1.7 LS1 RR) on the cam itself (.375" lift on the cam w/1.6 RR would make .600 lift vs .352" for 1.7s)? Any concerns about ramp rates or valve float with a high-lift, low-duration cam? Seem to remember Chevy had problems w/the 02 Z06 cam and springs (which is high lift low duration cam) - that's why they waited a year to bring them out - recollection is issues with ramp rates/valve floating. So if an LE2 setup typically get around 400-420 RWHP with an LE2 cam, what HP would those same heads get with an cam like the CheaTR cam? 360-380?

Another questions for Brett/Lloyd - LT1 heads seems to top out around 275-280 cfm short of going really big intake vol (which kill low rpm torque). Would the LT4s or an aftermarket set (AFR, TFS, etc) be significantly better? Would 300 CFM be possible while keeping intake volume to <210cc? How much power is 20 CFM really worth anyway? (ie what's the correlation factor between CFM and HP)? If it's 20 HP, not sure that's worth the extra $1000 for the aftermarket heads for me.

For me, if I could trade 10HP up top to get a stock like idle and drivability, I'd make that trade. That's just me though. I like the way my basically stock LT1 will happily climb a hill at 60MPH at 1500RPM. I like that I don't have to shift to pass in practically any gear. That torque curve "as broad as the Mississippi" (if any of you remember to orginal GM brochures) is why I love my LT1 over rev happy import cars. Yeah 'll trade some power up top for the 95% of my daily driving - it puts a smile on my face, and the other 5% I'm fully aware you'll never beat everyone anyway.

 

The .600 lift isin't hard with 1.6's but it is at 214 @ .050. That's where you are getting lots of deflection, lots of side loading on the lifters, and you have to pay attention to everything to get it right.

As I said, since i've been farting around this morning (family conversation leaves a lot to be desired, I could care less about talking about money) I pulled out a cam i designed 3 years ago just to see how it would fit in the LE packages since it basically works identically to the CheaTR cam but for a SBC/LT1. That cam with the right setup could make 390rwhp with Lloyds new LE2 heads. Pull killer vacuum at idle and drive like stock. I think the LE SSleeper name fits for it.

I have a set of 207cc AFR's that move 300cfm in the shop now, it's just that they are about a $3500 set of heads!

The LT castings can get you where you want to go for the money. Over 280cfm is possible and I think Lloyd is getting them there consitantly now, I want to throw a set on my bench and see.

On the engine dyno it's more of a 30-35hp trade from the LE2 to the SSleeper cam. You will get all the advantages that you are talking about in terms of drivability though. If you daily drive the car then it's a different set of circumstances from the guys who want a all out fun car.

Bret