AdsoYo

iTrader: (1)

No idea what my quench is, sorry. With the overlap, doesn't that cause bucking by effectively pushing some of the exhaust gas into the intake every time the intake valve starts to open (exhaust is pressurized and intake has a vacuum so the path of least resistance is the intake once the intake valve starts to open). With such high compression, you're effectively pushing more exhaust into the intake than you would with lower compression. At high load high rpm this doesn't really matter much but at low load low rpm where the cylinder charge is small and the vacuum in the intake is high, it might be enough to dilute the cylinder charge to the point where it doesn't always fire properly.

I still don't think it's ignition/detonation because the behavior didn't change at all going from stock to 24x, and adjusting spark with hptuners doesn't make any difference to the way it feels either (until I start going below about 30 degrees then it gradually feels worse).

Up in Washington there are two tuners I've been able to find with good reputations. One is Thomas Wong in Vancouver who put it on his mustang dyno. The other is Ellis Groo who's on this board (his name is toofast4luv or something like that) and he did a ride along with me. He wasn't able to change it with hptuners either and thought I had bad rings. After I got home I did compression and leak down tests and found out they were fine, 88/90 psi on the leak down for all 8 and 185-205 psi for the compression.

I agree, good sounding cam but I want to take advantage of whatever progress has happened since.

KW Baraka

iTrader: (7)

That looks like a copy/paste paragraph, there.

I'm not gonna dispute the general theme of that paragraph, but having had nine different cams in LT1/4 engines from 350ci to 398ci, I'm just telling you what I've experienced. And in my experience, a 3* overlap cam like the CC-503 shouldn't come close to making a jumpy engine; even with just an OK mail-order tune......let alone an 'on the road-tune'.

Like I said, if it ain't the tune (and I'd bet a dollar that it ain't) then it's something more 'mechanical' in nature.....something within the engine, itself.

OK....but something in your power-train isn't acting as it should.....and I'm highly doubtful that you'll fix it with a different cam or another tune.

KW

BALLSS

does your bucking occur regardless of what gear you are in as long as you re at the 1800-2000ish RPM range?

Or just in 6th cruising at hwy speeds (65mph)?

if the later than stay in 5th....or get 4:10's

lt1-xjs

Exactly, you're in the lugging range. 4:10 will give you 200 more rpm at that speed and 4:33 another 300 rpm.

AdsoYo

iTrader: (1)

Any ideas? I asked Ellis if it could be in the valve train and he said no it didn't feel right. The timing gears and chain looked ok when I did 24x. The rings are good.

It happens at slower speeds in the lower gears. At around 65mph it finally starts to clear up and is gone by 70mph unless I'm going downhill at 2% throttle. 70mph is 1800rpm and 65 is about 1600rpm.

I don't want to have to cruise around above 2000 though. I tried that for a while and didn't like the mpg hit and extra noise (it was cool at first).

BALLSS

FWIW with my 4:10's and a 27" tire at 80 MPH I am 19xx RPM at 80 MPH. I don't even shift into 6th unless I am going over 65 MPH

I think if you are in 6th with the 3:73's say around 65 mph you would be "lugging" the motor some. IDK what tire size you have. But lugging the motor with a cam might contribute or cause your bucking issue as if I understand correctly the issue is at any speed when RPMs are around 1500-1800???

That was why I was asking gear ratio

lt1-xjs

Per your requirements I'd just go with the LPE 211/219.

AdsoYo

iTrader: (1)

Gotcha. Yeah 65mph in 6th could easily be considered lugging the way it behaves. I typically stay in 5th until around 65+ too. At 1800 though the torque feels pretty good and I don't think I'd consider it lugging especially at the lower speeds.

Yes the bucking happens in any gear below 2000 (except 6th at 70mph) and even above 2000 at exceptionally light loads.

My tires are 275/40R17 I believe.

I think you're right and people on the forums absolutely loved it. I'm turned off a little because 1. it's over 20 years old and 2. it's expensive. The LPE cam is $350 while the Comp 466 is $280.

lt1-xjs

Just for reference, at 65 mph you are at 2000 rpm with the 3:73. At 71 mph you are 2200. This is the actual rpm, not what your tach says.
4:10's at 65 would run 2200 rpm.

AdsoYo

iTrader: (1)

Using this calculator, I get 1,567 rpm at 65 mph and 1,711 rpm at 71 which is also what my tach and hptuners show.

http://www.wallaceracing.com/calc-rpm.php

lt1-xjs

Ok the .5 OD. You are just loping down the highway.

KW Baraka

iTrader: (7)

No matter how many OTHER people like this cam, you're running way too much compression for it to work on your set-up.

You need at least 224* intake duration for your set-up.

KW

AdsoYo

iTrader: (1)

In any case I'd rather adjust my cam to my driving style instead of adjust my driving style to the cam.

Why's that? What happens when you run low duration with high compression?

Catmaigne

iTrader: (6)

You are just sacrificing power and choking a 383 by doing that. I wouldn't be afraid to spin it higher. It's the nature of the beast.

Going to a smaller cam would increase the DCR... Going beyond 9:1 will make it more likely to ping. The baby cc304 (close to LPE 211/219) in my Buick with stock shortblock and 11:1 SCR has a DCR 9.

ACE1252

Is it possible that the plug heat range could be causing some kind of issue?

I think I'm running the stock heat range in my machine. I know I have a bump in compression ratio compared to stock as both my heads have had a service deck. I just to don't know by how much.

I've looked over his tune several months ago and didn't see anything really crazy going on....but I'm certainly no professional tuner.

I've got tip in bucking off idle at very, very, light throttle, but no issues anywhere else with the CC503. Crusing speed mirrors the stock cam in driveability.

With the 24x, your EGR is tuned out right? Is the EGR on the manifold blocked off or does it have an actual EGR valve still on it?

AdsoYo

iTrader: (1)

I've tried a couple different heat ranges that didn't make a difference. Yes the EGR is tuned out and blocked off.

SS RRR

iTrader: (2)

There are restrictions at higher RPM compared, but the cam was designed for those in mind who wanted instant torque, which in a 383, could peak in the 400rwtq and still get high 20mpg fuel efficiency as well as pass emissions. It just depends on what an individual wants.

Catmaigne

iTrader: (6)

I meant spin higher as in cruising RPM range. I usually keep mine between 2k-2.5k when driving around and am turning 2.4k in 5th at 65 mph. I avoid 6th really isn't very useful without breaking the speed limit. I have no problem getting low 20's mpg on the highway on an AFR headed 383 with LE 226/239 and my current tune is somewhat half-assed.

AdsoYo

iTrader: (1)

Yeah I drove around like that for a summer and didn't like it. At this point I've spoken with Phil @ AI, Chad Golen, and Lloyd.

Like I said earlier, Phil thinks I should take it to a shop and have my sensor outputs checked (even though I told him I ruled out all the sensors already) otherwise get a hot cam if I want a smaller cam. I felt dismissed honestly.

Chad and I spent some time on the phone and strongly suspects the tune. He thinks I should find a local pro who's willing to spend hours with the car getting everything just right. I disagree, I think that I've tried every possible combination of variables over the course of these last 2 years and there's nothing left to try in the tune. Plus no one like that exists in Oregon. He said if I want less cam then the Comp 466 is a good choice.

Lloyd basically said he understands where I'm coming from and suggested a 219/227 .549/.565 114 LSA cam. More low end, less top end, no overlap, 9:1 dynamic compression (although after searching that term, it sounds like it's relevance is questionable). Seems like a great guy so I'll continue to email him and see where we end up.

KW Baraka

iTrader: (7)

Yeah. The 'word' is that Phil can be a bit short if you call and he feels that you don't know exactly what (product-wise) you want from him.....

It's only questionable until you blow-up your under-performing engine.

But it DOES become less relevant the closer you get to optimizing your quench......

KW