stockA4

It's a 235/239, 111+2
Is this the biggest cam I can fit in my 4.8 without flycuting or replacing the timing set? I want to daily it on the street with the stock converter and no tuning.

seriously though, what kind of low rpm manners could be expected with good tuning out of a stock 706 headed LR4 with such aggressive cam timing?

How much bottom end is the loss of cranking compression going to lose it?

What kind of exhaust and gearing would it need to get to work somewhat properly?

thunderstruck507

iTrader: (18)

1 3/4"- 1 7/8" long tube headers and 3" duals or 4" single

with a 4l60e and a 4000 min converter I would say 3.73 gears or deeper

expected shifts in the 7,000-7,400 rpm range and expect it to be a turd below 4,500


Those would be my expectations...might not be as bad as I think, but that's what I would count on so I didn't feel like burning the car if it was a POS after the cam.

Quite frankly I think it's a terrible idea if that wasn't obvious lol.

98CayenneT/A

I'm in the process of running the polutter v2 239/244 .635/.610 and threw all my research I decided to do what is needed to run it the right way. If I was not willing to go this route there is zero chance I would of went with it.

Here is my setup.

- Polutter v2 239/244 .635/.610
- PRC 243's milled .030
- Head gaskets .040
- CR will be around 11.3 after I cut valve reliefs
- I already have 3.73's
- Pulling my yank ss3600 out to have it re-stalled to a
PT4400
- willing to spin it to 6700-6800 rpms.
- also rebuild my own transmission so that's not a concern.

Any other way I would not of considered it.
This is in a Ls1

JakeFusion

iTrader: (7)

Since the stroke in the 4.8 is less... you need an earlier IVC just to get the same RPM range that you see in a 5.7. I would aim for an IVC around 41-42 and I would aim for an EVO of around 55.

So three cams come to mind:

230/242 110+4 = same overlap as the cam you're looking at now. Will peak at 6300 and carry to 7000. Will make a lot more midrange power. And work with a 4000 stall, 373 gears, and 10:1 CR. 16 degrees of overlap. Will drive like ****.

226/240 112+2 = 9 degrees of overlap so will drive better and has similar valve events. Would still use a 4000/373 combo.

222/234 113+3 = 2 degrees of overlap so will drive well and will still lope in a 4.8. Could use a 3600/342 combo here. But again, a 4000/373 would be ideal.

All would do better with more compression. There's just no way around it. Last two should clear without flycutting.

But all would peak in that 6300 RPM range and carry out to 7000. They would drive differently. The second two is what I'd decide between. There might be a 10HP difference between them due to the overlap. But the graphs will look similar. Both would drive okay... the 226/240 would sound better. But the 222/234 would drive better and idle better.

stockA4

Thank you Guys very much for all the replies and input.

I saw that cam on tick's website the other day and I thought it would make for a good bench race. I'd really like to see what an all out 4.8 is capable of but the reality is my plans are for a much tamer daily setup.

I'm sorry I baited you guys with a donkey dick but it seems like its the only way to get your attention lately haha.

I have a 2002 Z28 A4 with 2.73's
The car is completely stock other than poly motor mounts and various suspension bushings, an old whisper lid with FRA, a cutout ahead of a stock Camaro SS catback, and 2002 LR4 swapped in place of the trashed LS1 I bought it with. I put a stock 02' ls1 cam and LS6 springs in the lr4 before I put it in. The car has a great wideband tune and runs really well. It seems like it pulls hard all the way to 7k, even on 87 octane. I plan to get some data and real world #'s before I change anything else.

so I basically have a stock 02' Z28 with a little less displacement and compression, but the same cam timing as the bigger engine. I just have to spin it higher to make the same power.

My wife drives this car to work in shitty St. Louis traffic every day and she absolutely loves it. We are planning to autocross the car for fun this summer with a local solo club. The long gearing and the lack of low end torque compared to the original LS1 make the car very forgiving and easy to drive fast. It's like having a 4th gen version of a TPI 305 IROC-Z A4 that's capable of a lot more RPM's !!!


Jake,

I want a little more cam but not too much! That last cam you suggested would be great if I was willing to put long tubes and a loose converter in this car but that's not going to work. It's keeping the stock intake and exhaust manifolds and it really needs a stock type converter to serve its intended purpose and remain 100% street. I'm not worried about 60' times. I would maybe consider a Gm trailblazer type 278mm converter in place of the 300mm that's in it right now but that's about as radical as I'm willing to get with the transmission in this car, given what I intend to do with it.

You suggested an IVC event of 41-42 degrees for the cams you came up with. Could we keep that same event albeit with a little less duration and overlap and open the exhaust a bit later so as not to overly dilute the incoming charge at lower speeds and retain most of the engines low speed power while still pulling well past 6500?

That was kinda my original plan and I have a cam sitting here on my shelf with that exact IVC. I bought it a while back but I'm hesitant to put it in the car now as I'm a little afraid I'll over-cam it for its intended purpose.

The cam I have that I was planning on running is a Comp Xr265Hr "high-lift"
its a 212/218 .558/.563 115+0

IVO -9
IVC 41
EVO 44
EVC -6

How far off am I? I'm not looking to set the world on fire here, just have a little fun

JakeFusion

iTrader: (7)

I'd reduce the IVC down to 38 and the EVO to 45. It would peak in the 6100 range and fall off after that but you could set to 6500 and let it rip. But that's with longtubes. If you keep stock manifolds you need an earlier EVO.

I would still go with more lift and more curtain area since it acts as crutch even with stock heads.

So something like a 216/222 .612/.595 112+2... with headers.

Or 216/232 .612/.587 112+2 with stock manifolds.

stockA4

that's a bit different from where I was at!? a 216/232 112+2 vs. 212/218 115+0 ?

that cam has 0 overlap @0.050 whereas the cam I was planning to run has -15 @ 0.050! wouldn't all that added overlap and longer exhaust duration affect low end grunt and response more than just closing the intake 3 degrees later and hanging on to the exhaust for 6 more degrees?

I was under the impression that the longer rod of the 4.8 increases the pistons "dwell" time at TDC, allowing the engine to more affectively utilize a somewhat shorter overlap period? I realize everything with cam timing is a trade off and I just want to understand what I'm getting for what I give up if I decide to go custom over what I've already got.

thanks again, and bear with me please, just trying to understand

stockA4

Bueller?

A.R. Shale Targa

iTrader: (2)

Cam Motion has a cute little 205/210 drop in that would work nice with that TB converter or another one that would like your LS6 springs and help with the lack of headers is the LPE GT2-3......207/220@.050"118ls

Jakewet28

Curious to see how this is going to work out. I've got a LS2 with the V2 and similar heads to what you're going with minus the milled portion and smaller gasket. I was thinking about doing both of those over the winter to bring up the midrange a bit with the higher compression. When I talked to Tick they suggested against the smaller gasket because "the pistons are bad for touching the head" (which I thought was odd since I've seen quite a few people running thinner gaskets).

stockA4

The 207/220@.050" 118.5 actually looks really good for what kind of animal I'm looking for, maybe with a few degrees of advance put in it.

I think I'm set on putting the Comp 212/218 115+0 I have right now in it though, classic shelf grind and its pretty close, even milder than some of the others that have been suggested.