just curious, if you are replacing the headers and mid pipe with 3" stuff and you make the hp to warrant why would you not do a 3" catback to complete the system? clearly $$$ is one reason but i wouldnt want to neck down the system
Custom Cam Install this Fall (Pics, Vids, Dyno, Todd Warren)
- Thread starter Intervention302
- Start date
- Joined
- Feb 28, 2007
- Messages
- 19,524
Skip 1-3/4" primary and go straight to 1-7/8" if you're replacing them..
Todd said 1-3/4 when I asked him. The 3/4 apparently fit a bit better as well. Although, with the motor out, probably wont make much difference
Valid point, but in my mind the most important bit is beginning of the exhaust, not the end.
I can upgrade to full 3" down the road possibly
What did yours make? Mine is identical but it's not together yet.
Sent from my Pixel using the svtperformance.com mobile app
Update... So motor work looks like it's going to be over the winter.
My mechanic just had back to back surgeries and is taking a while to get to 100%
In the meantime....
I had the opportunity to essentially "trade in" my gen 2 Whipple 2.9 for the gen 3.
I can't wait to see what she can do!
Only downside here is that I won't get an apples to apples Dyno chart of the cams before and after.
I'm hoping for 700whp+ on pump 93
Sent from my XT1650 using Tapatalk
My mechanic just had back to back surgeries and is taking a while to get to 100%
In the meantime....
I had the opportunity to essentially "trade in" my gen 2 Whipple 2.9 for the gen 3.
I can't wait to see what she can do!
Only downside here is that I won't get an apples to apples Dyno chart of the cams before and after.
I'm hoping for 700whp+ on pump 93
Sent from my XT1650 using Tapatalk
What is this "trade in" you speak of? Decent resale and got a new one during the black Friday discounts??
Pretty much yeah. $3655 shipped for the gen 3 is hard to beat!
Keep in touch man
Sent from my XT1650 using Tapatalk
I'll tell you right now that's not the fault of the Comp stage 3 cams. I had and installed those cams and had the exact same problem. Low RPM bucking and stuttering, difficulty pulling off and even engine stalling. PITA.
I also spoke to Todd and he sold me some custom cams. They did the EXACT same thing. There was no difference.
I started digging in and trying to figure it out. Swapping cams and re-degreeing them myself to my own specs a few times over trying out different theories.
Here's what I found. It's all in the vacuum produced by the cams and the boost bypass valve actuator. In short the bucking and stuttering and shuddering of the motor at those low RPMs is because the motor doesn't have enough vacuum to hold the boost bypass valve open so the valve flaps back and forth and as it does that the motor stutters and bucks accordingly.
At first I tried switching to a low vacuum boost bypass valve that only takes around 3" of vacuum to hold it open and it helps a lot but it has its own set of problems. When the motor is at only 3" of vacuum that's not hardly much of any vacuum so the rotors of the blower are filled with air. As the valve closes the blower surges air into the motor. As a driver you'll feel the motor surge as the valve closes and you'll see a lean spike on your logs. It gets very annoying and even at highway cruising as you're lightly on and off the pedal going up inclines for example on the interstate you'll feel the car surge a little as that valve moves since it only needs 3" of vacuum to switch states.
The ultimate fix is to put the stock bypass valve back which takes around 10 ~ 11" of vacuum to hold it open and put a few degrees of negative overlap in the cams (as opposed to positive overlap). I believe I'm around 8 degrees of negative overlap. Now your car will see around 14" of vacuum at idle and you can pull off like a stock car. Low RPM loads no longer buck or stutter and the car drives much like it did on the stock cams. What a world of difference. You also don't have that nasty surge and lean spike as the valve closes since 11" of vacuum doesn't have much of any air in the rotors and it doesn't surge into the motor.
Regardless if you go for Comp cams off the shelf or Todd's cams be sure and pay attention to the overlap and vacuum at idle / low load conditions for that boost bypass valve or your drivability will suck and you'll hate the car.
I spoke with Todd over my concerns about driveability and whether of not to install a low pressure bypass.
We decided to keep OEM bypass, but he told me he would want my cams degreed a bit wider.
Less lope, more top end power, but more importantly, better driving characteristics.
He didn't mention exactly what the wider setup would be. But that he would communicate with my mechanic about it
Sent from my XT1650 using Tapatalk
Wider LSA (lobe seperation angle). Yes the lopey sound or choppy idle will not be as noticeable if at all but it'll drive great and make power. Some guys prefer the nasty choppy idle sound and can live with the poor drivability that comes with it. Not me, I pick drivability over sound any day.
You don't set cams by LSA. You figure out what ICL and ECL you need and of course pay attention to overlap. The LSA is a result of that. Degreeing your cams by LSA is kinda backwards.
Yes very happy, as mentioned in my first message my car drives and pulls off like stock.
I guess that's what I meant. What are your centerlines?
LSA = ICL + ECL / 2 right?
I'm still trying to wrap my head around all this
We can talk via PM, or maybe give me a call one day!
Last edited:
Hell no. I enjoy Malcolm 101. Post up in here.
Basically when I started out with my Comp Cams 106460 (what everyone calls stage 3 cams), I had them degreed like this initially.
Notice the 8 degrees of overlap. Of course at the time neither I or Todd had any idea about the boost bypass actuator issue.
I then went with slightly smaller cams thinking that was my issue. The degreeing of the cams was also a little more conservative with only 0.5 degrees overlap. Still suffered the same horrible drivability issues.
You soon learn to become proficient at re-degreeing and swapping cams in the engine bay. Pretty quickly your nights turn into this.
This is not my final setup but really close (don't have pic of final setup handy).
Notice the -4.5 degrees overlap. It's not much but it makes a huge difference. I mean like night and day for drivability. For your reference our stock cams have -35.5 degrees overlap.
I could talk forever on the choices of why the ICL and ECL are where they are but I'm not a cam expert. I've done my share of tinkering and figuring stuff out for my exact setup. There is of course of many other variables and engine setups.
If truly interested you can do some reading on when to open and close the valves on a forced induction motor (supercharged with a PD blower specifically) and it'll make more sense to you.
BTW after figuring out the boost bypass actuator / valve issue with our cars and the need for vacuum down low I sent Todd a nice long message explanation since I'd worked with him on degreeing cams and even purchased a set from him trying to fix this. He's aware now and I'm sure will get you drivability if that's your goal.
Edit: I should give a huge amount of credit to Ed over at modfords. We chatted a lot and he gave me tremendous insight and guidance as I was going through this process and figuring out the cams and what to do with them. With his help I certainly figured out the problems and got to a solution much quicker.
Anyhow, back to your custom install....
Users who are viewing this thread
