Ok 1st the shop that built my engine doesn't do many pontiacs, and the ones they do do are typically standard rebuild. That being said we went for dyno tune today going to set the Rev limiter and figure out redline. The theory we were going by was we would start at 5500 go up by 200 rpm and till we saw a power drop. At 7300 she was still pulling. I told them to stop. 4.5 stroke on factory block I started sweating it a bit. Gotta take it back next week to finish but still. Should I be happy she wants to keep on pulling or do pontiacs typically pull tell they die? Just curious, I know I'll be pushing it at the track but I was planning on about a 6k shift point now from the test I am looking at substantially higher. Just nervousness I guess.
Glad you told them to stop - I hope no damage has been done. With that said, there are many factors that determine the RPM limits of an engine. Waiting for the power to drop is the most absurd thing I have ever heard UNLESS
they have already calculated a few formulas that determine max RPM's of an engine assembly and were observing power drop off based on head flow or carb flow(?). If you put a 2 Bbl carb on your engine and the power dropped off at 4,000 RPM's, would your machine shop guys figure that was it and set the redline for your engine at 4,000? On the other hand, if you had 2 Holley Dominators on the engine and it would allow the engine to rev to 10,000 RPM's, would your machine shop guys buy you a new engine when it blew up at 8,000 RPM's as they were looking for the "drop" on the dyno? Sounds scary to me, BUT, I am not an expert on this subject
by any means. The 409CI I had would never quit pulling and kept on making power past 6,500 RPM's. I learned that the limiting factor was the factory outer spring which would break at 6,500 RPM's or so. The inner spring kept the valve from dropping and damaging the engine. Finally figured this out after the 3rd broken spring - 6,400 RPM was max in an all out drag blast. So what factors determine an engines redline?
There are many factors that come into play in determining your max RPM for any given engine. Most widely used is the piston speed in feet per minute based on the piston material/pin and its total weight. Other considerations are head flow CFM's, fuel flow, carb size, cam, valve springs, crank journal size, bearing speeds, oil pressure, side loads, the rod to cylinder bore angle, and other info that needs to be calculated via known formulas that will determine your engine's RPM limit - not trial and error. Perhaps your engine builder already calculated these numbers for you and knew these before doing what he was doing to determine engine RPM's in 200 RPM increments? I know my 455CI build will be limited by the factory iron heads and not any of the engine internals.
Here is a neat read that gives you some idea about the piston speeds. There is a section on "Calculating RPM Limits." Understanding Piston Speed in High-Performance Engines
Although this is about Ford engines, it gives you a good explanation and some comparisons within the Ford engine family plus recommended piston fpm speeds and a simple formula at the bottom to determine an engines max RPM.
Hope this helps with your question.