So I called a vendor yesterday and inquired about changing my cam. I told the guy what I wanted and discussed some points on it. I was told what I was looking for didn’t exist or was a unicorn cam. Lol. I just let the guy go, it was about 15 minutes before closing and he seemed a little agitated anyways.

but basically this is what I told him. I have a 5.7 right now with a single turbo and the cam is a summit ghost cam. He says “ghost cam”...what is that? (Sarcastically, at least that’s how it sounded. Whatever). So I tell him it’s a 222/233 on a 115 lobe sep. and I have a 3200 stall. I let him know it pulls to 7200-7300 as it is on12lbs boost. Then I tell him that motor is coming out and a 5.3 is going in, bigger (but tight stall) and I’ll be adding more cylinder head flow while I’m at it. Boost will be around 20psi. Ok. So then I tell him I’d like to step down a little on cam, carry still to 7000ish and maybe pick up a little fuel mileage and less fuel usage at idle. Maybe it might pick up a little lower end tq too being a smaller cam vs the bigger cam I have now. He tells me the cam I’m looking for does not exist. So I’m like huh? I then explain my train of thoughts...and it didn’t matter. So I let him go. But my thoughts are.....

smaller engine can take a smaller cam and still turn the same rpm as the bigger engine. But you have to find the right duration for the step down in cubic inches. And more boost should allow me to turn 7000. I was thinking like a 218/226 on a 115-116 lobe sep.

less cam and less engine will use less fuel
bigger stall MIGHT counter act that but I had a 3600 and went to a 3200 with no mileage change. So I figured go back to that. Plus the 3600 is tighter because it was a power adder series vs a regular SS series like I have now.

I lock up the convertor at low speeds as it is right now so convertor slip doesn’t factor in as much.

He then said maybe if I could do some “magical” tuning to it I might could pick up a little fuel mileage but he doubted it. I honestly and disappointed in how he reacted and the things he said because this company I have run their cams in the past and really like them. I recommend them to people all the time. My buddy just bought one from them on my recommendation.

am I asking too much? What you guys think?

 

If you are building a 5.3L why would you want to limit its RPM to less then that of your stock 5.7L? I don't follow the logic.

Not sure why anyone would spend hundreds of dollars on another cam to save 1-2MPG either. Sounds like the people that buy a new car in the name of getting 5mpg better mileage.. they didn't think that one through did they? 5.3L should get better mileage then the 5.7L did right off the bat so you may be satisfied without doing anything different.

 

You need a cam that gets the dynamic compression up and an AFR/timing/turbo size combo that has you cruising in low vacuum. This will increase your efficiency at cruise and get the mpg up. But that stuff will also fight your max rpm. Always a trade off.

 

I was thinking that too...

it’ll cost me what, $100-$180 if I sell the cam I have? What’s wrong with not wanting a lumpy cam and having noisy make up for it? You don’t “need” a big *** cam for my anemic power goal. So why run a big cam if I don’t have to?
maybe you think I’m being silly, but given the choice, what would you rather....750hp and get 20mpg or 750hp and get 15-16mpg? Maybe look at it in that perspective instead of the “o you want to build a hot rod but you are worried about fuel mileage, you big dummy” point of view. That, I don’t get. We have the technology to not have to settle for shitty gas mileage and a turbo makes it that much easier. So why would anyone even argue that?

Exactly. I thought I’d want to cruise in high vacuum tho? Seems like my mileage on my dash goes up when my vacuum is up?
and yea, I need a cam that makes better power at my cruise rpm.

 

The more vacuum the harder the engine is sucking on the TB inlet. When the low vacuum comes from turbo airflow less vacuum helps.

 

so maybe I need to not have the wastegate open at cruise? I think that’s how it is because using my controller, at low rpm and throttle angles I have set it to bleed off boost. Well I guess that wouldn’t matter if it’s not in boost anyways but I wonder if it’s keeping the wastegate open in ANTICIPATION of boost? I might email cortex and see how that works. Now you got me thinking.

 

I've never heard of a wastegate open at idle/cruise lol. The vacuum/lack of boost keeps it closed. You're just letting the turbo free wheel I guess. I was 3800lbs in my 9:1 383 turbo TA and routinely would pull 30 mpgs on the highway.

 

The same cam generally gives more performance in a smaller engine. A cam that's mild in a 5.7 will seem a bit more aggressive in a 5.3 and even more aggressive in a 4.8. It may not be a noticeable difference to most people if you're only downsizing by a few ci like you're thinking about doing.

If you want to decrease ci and decrease the cam spec to keep the same manners then find the dyno chart for your current setup and then just look for a cam that gives a similar chart in a 5.3

 

I agree mostly, but I still rather rev it out further on a built engine since I rev my SBE junk higher then that already. I like driving my car so MPG is good, its easy to have power and mpg like you said. I make more then 750hp and get 20MPG on E85, on pump gas I was 25+. Summit stage 2 cam which really isn't all that different from cam you have 226/230 113 I think it is.

Wut?? You sure you know how a wastegate works? Sounds like your spool really sucks if you actually managed to configure it like that lol Not sure why anyone would... but whatever.

 

nah not at idle. Your probably right. Now that I think about it, there’s no boost being built to move the diaphragm in the wastegate. Lol. What was I thinking? You have to excuse me, I hadn’t ate lunch yet. I was hangry.

 

aight. You starting to convince me to just run the same cam. Guess if I dont like it, I can change it later.


yea I know how a wastegate works. I wasn’t thinking clearly when I wrote that. I was thinking about lunch. And also agitated about something else (nothing forum related, and oddly not your fault. Lol)

 

I was like well technically if you had a weak WG spring and you hooked up vacuum to the top port you could possibly manage to have the WG open at idle lol Kinda like a BOV with too weak a spring. I've seen so many incorrect vacuum routings that anything is possible these days.

 

nah. I wasn’t thinking. Brain fart. No food yet.

 

I thought the summit ghost cam aka the sleeper cam was designed to be a non aggressive, stock sounding cam? Just curious as I dont know much about cam specs. Reading the info off summit I would think it would be the opposite of a big lumpy cam.

 

As if the Summit Ghost cam is a lumpy cam. If you want a small cam get a Lingenfelter GT2.

 

it’s not. In my 5.7. But it does lope, yes. But when I go to a 5.3 the cam will act even bigger. I had a 212/218 in a 5.3 that loped a little so imagine 10 degrees more duration would lope even more.

I like the ghost cam. And I really don’t want to get rid of it. But I’d prefer better fuel mileage and make up for what I lost with more boost.

im probably just gonna keep the ghost cam tho. I wouldn’t mind turning that bitch 7500rpm.


this isn’t exactly a non looney cam either....this is the ghost cam idling

 

You'll never be happy.

Sell the GTO and buy a C6ZR1.

Kthxbai.

 

ok. I’ll sell it to you. $15k. Then I’ll go buy one. Ok. Bye.

 

hmmmmmmmmmmmn.

Nah, for real tho... you have a good build the way it is.

 

Better gas mileage? Do a 3.8 swap.