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 $$$ is one reason but i wouldnt want to neck down the system
Skip 1-3/4" primary and go straight to 1-7/8" if you're replacing them..
just curious, if you are replacing the headers and mid pipe with 3" stuff and you make the hp to warrant why would you not do a 3" catback to complete the system? clearly $$$ is one reason but i wouldnt want to neck down the system
What did yours make? Mine is identical but it's not together yet.Interested in your results... My new engine is being built now with Todd's cams. I have a 2.9 crusher setup with 10.5:1 CR on E85
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Pretty much yeah. $3655 shipped for the gen 3 is hard to beat!What is this "trade in" you speak of? Decent resale and got a new one during the black Friday discounts??
Keep in touch manI am in the process of doing Cams .
Subb'n to see the progress
My buddy has a set of comp stage 3 and they sound amazing. However, they don't drive all that great. If the rpms fall below 1200-1500 on take off the car coughs and bucks pretty poorly.
I spoke with Todd over my concerns about driveability and whether of not to install a low pressure bypass.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.
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.
So the question is... how wide are yours now?
And I assume you're happy with them?
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!
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!
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
Really appreciate your insightBasically when I started out with my Comp Cams 106460 (what everyone calls stage 3 cams), I had them degreed like this initially.
View attachment 1446194
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.
View attachment 1446195
You soon learn to become proficient at re-degreeing and swapping cams in the engine bay. Pretty quickly your nights turn into this.
View attachment 1446196
View attachment 1446197
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.
View attachment 1446198
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....