Originally Posted by Racer
High end HP and a good bottom end are mutually exclusive. They don't co-exist.
Then again, it depends on what you consider "good bottom end" and "good top end". Your definition is probably different to mine. How much you are willing to compromise? It's all about compromise - a balancing act.
The more top end power, the less bottom end. Assuming you are only trying to boost your bottom end, make everything as small and efficient as possible. Raising the comp as you mentioned will a big help.
Also incorrectly porting your manifold and heads can make the situation worse. You must be careful. Best gains for your application are found in the bowl, not the ports, so start there.
Maybe you can clarify exactly what you are trying to acheive in terms of power delivery?
Thanks Racer, I will try to clarify what I want / expect from the porting and exhaust. I have read that my heads and manifold "run out of air" at about 5000 RMP. My engine is an infrequent visitor to that speed but now and then I like to rev her out an most of the time that is done in 1st / 2nd gear for overtaking or on the strip. Certainly the car feels very
"sluggish" as it passes 4,000 / 4,500 RPM. My 1/4 times are really good for 60' etc but everything catches me up high and I feel as I just coast over the line maintaining my speed towards the end. This is the symptom I’d like to remove or make better. As far as compromise is concerned, I don’t want to have to take my engine past 2,500 every time I want to make any power – or in other words I don’t want to start to feel sluggish when off the line… that’s not what a V8 is about in my mind.
With respect to the porting, I was going to mildly port the whole thing. Short side radius, the throat, pushrod bulge, valve boss etc.
Raising the compression ratio will provide gains over which portion of the rev range?
Have I cleared some of my ramblings up a bit? I guess for daily driving the engine operates primarily between idle and 4,000 – occasionally 4,500 and 5,000 even less frequently. This is my definition of “top end” and I’m looking for better breathing and pull from maybe 2,000 to these top end engine speeds. Are my plans in line with this objective?