Compression

rumblefish360 said
OK. IDK a whole lot about these machines. A lot of times and even in here once in a blue moon, someone asks the question, and I don’t see much of a reason to be concerned with power output at 1,00-1,500 when your cam is something like 250/260+@050. No one is putting a cam like that in there car with 2/76 gears riding on 28” tires looking for street manors in the city. Unless you’re crazy? Maybe driving your top end machine built for something like a 1/2 mile oval track? But why would anyone want to build that for driving in rush hour in the city?

Yea, I know it happens….

Loading the dyno that low to know how much power it has at 1,000-1,500 with large street cams, small or big race cams seems silly to me.

Is there a reason?
Have you done this?
Why? For what purpose is that t needed to be loaded and tested @ such a low rpm with cams of 250@050 and greater?
What customer needs to know this and for what?

As I said, I only have been told what I said. I’m not arguing with them or you over it. I’d just like to know.

Have you loaded the dyno @ WOT with a 250*@050 cam down to 1,000 rpm?

I’ve been told it’s also related to the cam size and function of the build. If I have an engine with a sizable cam where any meaningful power comes in at 3500/4500, what’s the point of knowing what’s at 1K/1500/2000 rpm.

I’ll just live with what it makes and use the right converter coupled with the gearing and tire size to out out along. After all, the engine means business not at the low rpm’s but where it picks up.

This is what I noted on the shows and what I’d be after.

I have loaded down a [email protected] cam. I’ll be doing my own junker in a few months and I’ll load it down that low. That’s how I figure out how much timing the engine wants, and where it wants it.

I know some guys get weird when you load an engine like that, but it can be what happens in the car, even though I’m very careful to not be rolling along in 3rd or 4th gear at say 20 MPH and then stomping on the throttle.

I’m not sure even with an ignition with individual cylinder timing could produce a curve that would keep the engine out of detonation in that particular case.

One of the things I’ve had to learn (and it wasn’t easy because I’m pretty stuck in my ways until I can prove something I’m doing is wrong) is that these engines are hyper sensitive to timing, especially around peak torque.

It gets even worse when you run a ton of cam and no compression (or not enough compression for the cam timing) in that the engine wants a big load of initial at idle but by peak torque the engine wants less timing than it does at peak power.

So somehow you have to slow the curve down enough to not get more timing than it wants at peak torque and still have enough curve left that at peak power you can get full timing.

The only way I know to actually sort that out is to load the engine down that low and watch power and manifold vacuum and then take notes so you can go to the distributor machine and figure out a way to do it.

I also now have a blow by meter hooked up, and you can bet that will show even trace detonation because that kills ring seal.