10 to 1 compression ratio...true dual exhaust no cats...stock tb at the moment...exhaust should be fine. Could use a bigger tb...I'm not looking for a race engine just some good power out of it.

 

Understand you're not wanting a race vehicle, so maybe the Air Gap is the bee's knees...But the Gibson Headers and TB are really hurting you, especially the TB.

At least get a 55x52, you can't over TB these things like a carbed motor, and Magnum 360's love to breathe, you have a 408.

 

I know it needs a bigger tb not in the budget til spring, but I really don't think the headers are hurting that much, I don't think these are what are causing my issue thou...

 

With 10:1 compression? You are choking it more than you may think.

 

You have headers that aren't much better than stock, you have to breathe out before you can breathe in.

It doesn't matter that you have dual exhaust with the shorties.

 

Iv been working with several respectable race engine builders on figuring out this issue...I called and asked about the headers, they said for the cam duration and compression and displacement of my engine having short tube headers will not cause the problems I am experiencing, they said it sounds like a sensor issue but they don't know where to point me because there expertise is on carbed motors...so lets work on new ideas. I changed out the plugs when I did the compression test and they all showed lean. I have a vacuum guage and wideband air/fuel guage and a snap on scanner with access to data on every sensor and also what that sensors voltage is, so what do you want to know?

 

this is a question - given the bolted in equipment that he's got, how do you determine what is wrong?

Does an expensive scanner tell you anything?
Is a dyno required to evaluate performance?
Is a tuning programmer required to change timing and/or fuel?

how do you prove that the cam is, or is not, suitable?
how do you prove that the throttle body is, or is not, big enough?
how do you prove that the exhaust is, or is not, big enough?

Is there a 408 textbook that tells you what combinations are proven to work?
Can any shop with a dyno do all these things?
how much would it cost?

 

He has a 408 that's low on power, I'm saying the stock TB and shorties are killing his power. If I had a bigger TB I'd send it out so he could try it but I have a 950HP sitting on my engine now.

Other things to consider: Was the cam degreed in or just installed dot to dot?
Was the valve train geometry checked? Valve springs should be ok, stock Eddy springs are good to .585 lift.

 

It all seems kinda odd to me.

I have a 408 with stock TB and now back to stock exhaust manifolds, I do have 3" exhaust from the cat back.

My cam may not be as big as yours but mine runs great so far. Still have a basic tune but with a new born at home I don't have alot of time to get the truck out and play with it to help Sean fine tune it.

 

Yes valve train geometry is good and has been double checked...was told the cam was degreed in..I didn't install it thou...engine came as a long block...