Quote:
|
Was wondering what changes you are thinking about that differ from Pete's grind specs. I run a Pete spec ground cam - it sounds nice which was one of mine goals and seems to do good at highway cruzin' speed. My truck clocks at 60 mph about 2600 rpm. I think this is about where the power band comes in due to the cam grind. My truck sees mostly highway speeds and most generally pulls a car trailer lightly loaded. You can relate my truck's usage to that of 379 Peterbilt pulling a chrome reefer - gets the job done with a little flair. Sure there's better builds and combos but hey - it's a little different that any run-of-the truck - and it gets more looks that any 2023 decked out $100,000 truck when you pull up to gas pump.
I guess it's all in what you want - but the truth is anything you do to a 60 yr. old GMC V6 motor will never be equal to what a truck engine of today's manufactured engineered marvels can do in performance. BUT when we raise our hoods we CAN see a motor and are ABLE to work on it. This is just my thoughts - give me and other GMC V6 caretakers your inputs - for now I think I go out and crank-up the 1960's Diamond T "Cat" powered road tractor and blow some smoke while dreaming about a V12 powered "Crackerbox". Have a good day!
|
The reason for the changes is a comprimise between the stock cam and Pete's cam. A powerband of 2600 is a bit high for a 3200 rpm engine in my opinion. I like the low end torque and want to retain this. So a powerband around 1600-2000 or so. I hope to achieve this with the modified design.
Figured I added some info where I explain my reasons:
Most people agree that there are two key events in a camshaft: intake valve closing point and valve overlap. The others are important too, but not as much.
Generally speaking, intake valve closing determines the place where in the rpm range the torque is generated. Valve overlap has about the same effect. The intake can be timed later for higher rpm power. Valve overlap can be extended for higher rpm power.
Intake valve closing point:
The stock cam: 61-70 degrees ABDC, depending on the year.
Pete's cam: 46 degrees ABDC (After Bottom Dead Center)
Modifed design: 50 degrees ABDC - I agree with closing the valve earlier to up dynamic compression as much as possible.
Valve overlap:
Stock: 63 degrees, might vary with the year.
Pete: 33 degrees
Modified: 45 degrees - Searched the middle ground, as a compromise between the two.
I am thinking Pete's cam has a sweet spot at about 2600 rpm where the pulses act to charge the cylinders better. According to the 'books,' it should behave as a lower RPM cam.
Not trying to build a race monster, but hope to improve the usable power as much as possible.