Using the Dyno to Help Solve Problems

[DaveMcLain]

Many times people tend to think of a dyno strictly in terms of making horsepower and torque improvements and doing engine development but they can also be used for non development activities.

A good example is shown in this video where I'm trying to solve an oiling problem on a customer's Big Block Chevy that's used in a jet boat. He's had problems with his engine losing oil pressure if he runs the engine at or above 4700rpm, exactly.

We have been able to duplicate the problem with the engine mounted on the dyno which has been a giant help. We've also found a pan/pickup combo(stock 366 truck engine) that does not cause the problem even when running sustained rpm much past 4700, 5500-6000rpm continuous. The problem with the truck pan is that it will not fit in the boat situation, it's too deep.

We still have not found an aftermarket pan that'll both fit the boat and keep good oil pressure above about 4700rpm but I'm confident that we will, soon...



This video shows the engine running and the problem happening. Having a very large oil line on your pressure gauge and a large analog tach is essential on any dyno.

[gofaster]

To get away from the deep pan and go back to a pan that will fit the boat, you could consider this:

Add a compartment to the side of the original sump, add a baffle (and maybe a trap door) for windage separation and extend the pickup tube to place the pickup in the new compartment. That would help keep the pickup out of the cranks windage and keep it in oil. This worked well on circle track engines I ran years ago.

[DaveMcLain]

What I want to try next is to use a stock car pan and then do exactly as you're talking about to get a little more capacity.

[1960flh]

Dave;

I fought this same issue in the mid 80's on SB motors using Morso box pickups and melling HV Oil pumps. The issue was pickup to pan clearence <1/2" with the 60 weight Valvoline the pump would cavitate causing a pressure drop (you could see the bottom of the pan flex). I also found this when usig stock pickups with HV pumps the screen was to fine same issue. Boy did i buy alot of bearings .

Since this is marine and they normally run cold, viscosity could be adding to the issue. Just as a test on the Dyno try a really thin oil 5w-30.

Also what is the tempriture of the oil at the last bearing in the circuit?

Just some thoughts.

[DaveMcLain]

In the testing we've been running the engine under a moderately heavy load for 10-15 minutes to really warm the oil. In the boat the coolant temp tends to be at around 160 degrees but the oil temp gets quite warm due to the load on the engine. Shooting the sump of the pan with a heat gun reveals a temp of about 180-200 degrees which seems to be about where it stablilizes after some run time.

Running at under 4700rpm the engine has about 65lbs oil pressure and at idle that drops to about 40lbs or so. We have not messed with different viscosity oils on the dyno but he tried some 10W-30 in the boat with the same results, we're running 20W-50 in our testing just like he's been using.

With the oil temp up like it is I don't really think viscosity will make a whole lot of difference because when we've drained the oil pan hot it comes out like water...

The current pickup configuration is about .400 off of the bottom of the oil pan, right where the guy at Hamburger's recommended it to be..

[DaveMcLain]

Yesterday evening I did some more work on the big Chevy. This time I installed another stock oil pan and this one will fit in the boat, I think it's a Chevelle pan. Anyway, this pan easily out performs both of the aftermarket pieces in this application with no oil pressure fluctuation at 5000rpm continuous operation at more than a 200 horsepower load, problem solved. Now I'm going to make a kickout on the side of this pan to add some more capacity for just in case situations and call it good.

Personally I think the problem with the aftermarket stuff is the size of the pickup....