Tommy Tucker

So now if we go from there.....
increasing the lift will increase power all across but will limit any further increase in duration (no fly-cutting remember!) and dropping the LSA will increase duration slightly on it's own but will improve breathing after 2500rpm.
Am I getting warm? Increasing the duration will limit the lift but increase the fill at the top end.
What about spring issues with the XE-R lobes? They're pretty fast ramps aren't they?
What am I better to sacrifice.....more lift or more duration?
Tom.

TTtop

iTrader: (6)

The XE-R lobes are very fast and much harder on springs, you'll probably want to go with some good double springs.

Also, 1.8 Roller Rockers are not recommended for XE-R lobes, so you would have to ditch those for some 1.7s.

To avoid flycutting you don't want more lift, but if you lowered the lsa, you get some duration increase. I think I would lower the lsa to 110 and go with that.

Most of the bigger cams (>>224) are just making more peak hp, not a lot of extra torque down low but with some good mid-range torque, and killer upper-range torque.

A guy who went by "DailyAlumminumBlock" tried a 224/224 .581/.581 110 a couple of years ago and made some obnoxious torque on stock LS1 heads. His dyno torque curve looked like mine except with 10-15 ft.lbs. higher all across the range from 2k-5.5k rpms. Above 5.5k, the stock heads ran out of flow and leveled off at 405rwhp.

His peak #'s I believe were 405rwhp/410rwtq. If he had had some Stage II racing heads, then his peak hp would have certainly hit 440rwhp.

Hope that helps some!....Randy

GrannySShifting

iTrader: (10)

a 224/224 cam is way to small for a 383 motor in my opinion unless it has a serious set of heads on it. Theres no reason to go that small either for driveability, unless youwant "Pure Stock" Idle. 232/236 making 50 ft lbs more and 70 hp more would be well worth the slight tradeoff in driveability with a 383 inch motor

Compression helps "tame" cam to a bit, and I think helps low speed driveability. All due to lessening reversion. If your not looking to turn alot of rpm, Id run an aggressive intake lobe, relatively tight LSA. Something like a 224-228 XER/230-234 XE on a 110-111 LSA

As light as that thing is though, woudlnt you want to try and trade off some power under 3500 rpm to keep the front end pointed straight, or do you do alot of accelratign from that low an rpm? Are you goign for max torque 2500-5000 or 3500-5500?

Tommy Tucker

Yep, bang on. Keeping her straight is an issue with a stock LS1 even. You can spin up in any gear. You just have to be progressive with the right foot!!
FYI mine is a stock 346 bottom end.
I do like the idea of limiting the lift to about .58 and increasing the duration on a 110-112. (Revving out on a higher lift cam is asking for trouble.) That would help reliability on a long hard session at the track and I do like to drive it 'on cam' (used to like my Jap bikes). I was just a bit wary of a gutless bottom end.
So what would be the typical characteristics of the 230-234 XE on a 110-111 LSA in a really well breathing 346?
I'm really finding this helpful in focusing on making sure that everything is fit for it's purpose. Thanks guys.
Tom.

FASTONE

Hey Tommy, glad to see so many responses to your question.It may be me but I noticed you seem to get duration related to lift??Duration is the degrees the valve is open and has nothing to do with actual lift.Also lda or lobe separation does NOT increase or decrease duration,it WILL CHANGE VALVE OVERLAP.All 3 are completely different from each other.Sounds like some are agreeing with my recommendations,A tight lda is what you want for neck-snapping midrange.Hope I helped some?????

FASTONE

Tommy,like Grannyshifting said if you have a lot of static compression then you should run more duration.Say you have 11.5 you could run a 236 duration with no problem.If you had say 10 to 1 you could run say 228 or even less,Shorter duration will raise cylinder pressure,but maybe too high with a high static CR.You will get knocking or pinging!!Not good!!

FASTONE

Who told you a tight LDA WOULD HURT TOP END?wE"RE TALKING 109 or 110 not 106!I have a 109 in my 408 sb Chevy and it pulls like a bitch to 6500,REALLY!!!!

Tommy Tucker

Thanks Fastone. Nice to get some positive posts with good info. Not just flames and ****.
I have predicted a realistic CR between 10.9 and 11.1/1 with the 5.3 heads and the thinner gaskets. So I have a bit extra static comp. If I'm not going for monster lift I might be able to take 30 thou off the heads to raise the static further (We have 95 & 97 octane here) in the future.
With my straight through exhausts (2 foot of 1 3/4 primary pipe and 3 foot of 3" diameter secondary with no cats) I won't have much back pressure so could probably cope with some extra duration with less reversion affect.

I meant (if I didn't make it clear ) that I thought a short LSA would leave the motor dead BELOW 3000, but I guess that if I can avoid reversion with the increase in static CR and the reduction in back pressure it won't be so bad.
What about tuning with a 230/230 110 in a 346? Any issues there (apart from idleing at 1500rpm!)
I would like to see a dyno sheet for the above if any one has one.
Tom.

PREDATOR-Z

Also exhaust tuning is a factor to increase low torq, such as 1 5/8 stepped to 1 3/4.
and let us not forget the heads. Small runners with high velocity and good quench.
There is more to meeting your requirements than a cam IMO, look for the whole package without neglegting drivetrain of course.

Tommy Tucker

Already have the most freely flowing tuned exhaust you are likely to see this side of a single seater.
I had kind of thought that the cam would be the last piece of the jigsaw.
I have the flow in and the flow out, that's where the inherent power is derived, now I need the correct cam to distribute it. Or am I missing something here ?
I'm not buying any new heads so I'll be making the best of what I have. I think they'll be fine for a 346.
I think I'll have to be a bit more specific about where I want the big numbers to kick in. I don't need Tq off idle because of the light weight and the type of driving I'll be doing (3000-6000 rpm sustained on the track). But because it will be sustained highish RPM I don't need the very high lift if I can get the mid and upper by dropping the LSA. I dont mind an 1100 idle.
I'd like to know if the RPM ranges that the cam grinders are accurate.

PREDATOR-Z

Try to contact some people from the LS1 community in Australia. IMO your setup will be mafless, and you could surely benefit from lower lsa's while still using a good amount of duration.
They (Aussies) have a lot of experience with independent throttle body intakes and are running cams as low as 106 lsa (On the street), and putting out insane ammounts of trq lower in the band.

Tommy Tucker

Now that is some new information!
That's one hell of a low LSA but it could be for me if it delivers. I'll be swapping the stock cam in for emissions testing .
Never driven anything with a cam on such a low angle. What's that going to behave like???

Anyone have a link to an Oz site while I'm searching?

Tommy Tucker

Just found one here !!!!

PREDATOR-Z

Here is something to tickle your fancy

Here is a video of a 242/242 106LSA with a 8 individual TB setup and speed density tuning.

http://users3.ev1.net/~black_ops/video/242-106.mpg

marc_w

I'm thinking you would be interested in the TSP (Texas Speed and Performanace) torquer cam. It's something like 231/231, high 500's on a 112.

I'm sure it'll lope, but you'll get that with any "no F'n around" performance cam.

Edit, it's a 233/233. Here's a link.

GrannySShifting

iTrader: (10)

A 230/230 cam is not really that hard to tune for with or without the MAF. Ive done 240/248 on a 110 LSA cams in auto cars, with lockup converter in 346 inch motors, and it really drives pretty damned good, gets 20+ mpg on trips to the Ocean with 4.10s

Lighter car, and more gear makes things more driveable then the reverse...

Even a 228-234 XE-R intake lobe I dont think would be asking a TON from your valvetrain as long as its good parts and setup correctly with the right spring pressures. Ive spun Comp 918s to 7000 rpm with 240 dur lobes and .600-.610 lift
224XE-R/228XE lobe on a 110 LSA maybe, or a 228/232 on a 110+2.

I dunno they are still going to make alot of torque. For ex. stock head car I tuned, with a 240/248 cam 110 LSA. Makes what normal cam onyl cars make for torque 365-370 at 3500, then it flatlines to 4500, then picks up another 25 ft lbs. it doesnt really have a weak bottom end (its more like on par with average 224 cam, then its about 20 ft lbs up, then its on par again, then peaks again 20 ft lbs up, like steps) just that when it comes on its peak at 4700 rpm it does so hard, like a turbo spoooling up. Kinda interesting feeling.

Depending on what kinda traction, tight lobe stuff seems like it gives up torque sub 2500. Mayeb if you want to keep it steady state, maybe a wide LSA may even be your answer. From what Ive seen, offers more torque at low rpm, carries it further out from the torque peak, but softer midrange then a tight LSA. Maybe not having it come on the cam so hard may be a good thing?

FASTONE

Good info GrannySShifting,on that 110 lda cam you mentioned a loss of power below 2500 but it may have been the 240 duration as that would cause a lot more overlap then say a 230 on 110.You don"t think the tight LDA would give Tommy the snappy low end he wants?

JimMueller

iTrader: (9)

I've got a copy of the graph. Don't have a place to host it but if you PM me I can send it via e-mail. The cam was a 224/224 565/565 106icl/110lsa XE grind.

marc_w

That's what I was trying to explain with my little cam - it just picks up at 2K.

Since throwing more timing at the lower RPM's, the step isn't as pronounced.

Grant B

Remember a road course car is going to stay at WOT a LOT longer than a drag car, so valvetrain maintence may become more of an issue.

BTW, awesome car. What transaxle are you using? I know the Porsche G50 930 4-speed will handle the power, but I think some of the Ultima guys have gotten away with using the weaker G50 5-speeds.