The last time we had this 470-inch Mopar big block on the dyno, it made 751 hp with Trick Flow heads and a dry sump oiling system. The dry sump setup that we used for those tests worked great, but it was complex and expensive, so we started looking around for something different. Fortunately, Peterson Fluid Systems recently introduced a new belt-drive oil pump and vacuum pump combination that looked like it would fit our needs. The Peterson oil pump uses the same mounting bracket as our dry sump setup, and the auxiliary vacuum pump would give us more pan vacuum than we had before.

To complete the conversion, we needed to replace our dry sump pan with a wet sump pan, but that just took a phone call to Summit for a Moroso aluminum pan. The Moroso pan has a full-length dragster style sump and an AN-20 rear pickup. A -20 line is used between the pan and the pump, while -12 lines are used on the pressure side between the pump and the filter and then back to the block.

Adding the Star vacuum pump system to the engine required a little fabrication to mount the Star intake/exhaust tank. The Star tank acts as an air/oil separator on the intake side and a puke tank for the exhaust air. Once the Star pump and tank were mounted up, we plumbed the system with -12 Aeroquip Startlite hose. With everything mounted and plumbed, we headed back to the dyno.

Our first dyno run was a baseline test with the engine configured the same as it was in the previous dry sump test. There was a decrease in peak power from the previous test dropping from 751 to 741 hp. The power didn't hold on as long with the wet sump, which told us that windage, was robbing power at the higher engine speeds.

With our baseline confirmed, we added the vacuum pump and re-ran the tests. The Star vacuum pump created 15 inches of vacuum in the crankcase and the power increased from 741 to 760 hp. The power increase was only seen at engine speeds over 6,000 rpm so you would need to shift the engine up around 7,000 rpm for the car to be faster.

Once the baseline for the pan vacuum system was established, we decided to try a quick intake swap to see if we could find any more power. As you might recall, during previous testing of this engine we had found that our Wilson-modified small port intake made better power than our "out of the box" large port intake. Since the large port intake didn't perform very well, we sent it to Wilson Manifolds between dyno sessions for their competition porting work. Once bolted on. we found that the Wilson porting work paid off nicely with an increase of another 15 hp. This final improvement moved our max peak power number up to healthy 775 hp. At this point we are knocking on the door of 800 hp, which is probably pushing our luck with a stock block!

Teardown note:

After pulling the engine off the dyno we noticed that there were several ounces of oil in the vacuum system puke tank. This was a lot of oil for such a short run time so we figured that we had a gasket leak. A quick look around the engine found a loose valve cover bolt, which we think, was causing a small air leak. Without the air leak our pan vacuum might have increased and perhaps the power numbers would've been slightly higher. Since this was a new combination we didn't realize that we had a leak but now we know to keep an eye on the puke tank during the test.

Engine Details

This is a Chrysler 400 engine block with Molnar 3.91-inch crankshaft and 6.700-inch connecting rods and JE pistons. We're using Trick Flow 270cc heads with K-Motion K-950 springs, a Comp Cams 264/268 solid roller with HXL and HXX lobes, and a Jesel belt drive and distributor. Fuel comes from a Holley 950 Dominator. The machine work, engine assembly, and dyno testing was performed by Gray's Automotive in McMinnville, Oregon.

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See all 22 photos Peterson Fluid Systems designed an adapter that connects the Star vacuum pump to the rear of their oil pump.

See all 22 photos The vacuum pump is attached to the adapter with eight small bolts. The pump can be rotated to simplify hose routing.

See all 22 photos Peterson sells mounting brackets for Chevy and Ford engines, but since we have a Mopar we had to build our own bracket.

See all 22 photos The Moroso oil pan has a full-length dragster type sump with a single -20 pickup located at the rear of the pan.

See all 22 photos One advantage of using an external oil pump is that the oil pan can be fitted with a full-length windage tray, which is more effective than a tray that only covers part of the pan.

See all 22 photos Oil is routed from the pressure side of the pump to a remote filter, then back into the engine at the block plate. The oil pressure lines are all -12 size.

See all 22 photos The breathers are removed and blocked off when installing the vacuum pump. Sealing the engine tight allows the pump to pull a vacuum in the crankcase.

See all 22 photos Star Machine makes this slick intake/exhaust tank. The tank acts as an air/oil separator on the intake side and a puke tank on the exhaust side. Having both functions combined into one small tank saves space on engine.

See all 22 photos The oil and vacuum lines need to be kept away from the headers. Proper hose routing is much easier to accomplish on the dyno than in a car!

See all 22 photos Once the oil pump and vacuum pump testing was finished we ran a quick comparison test between two fully ported intake manifolds. The Indy intake on the left has Max Wedge size ports that match our cylinder heads, while the Mopar intake on the right uses standard size ports.

See all 22 photos Wilson reshaped the plenum, smoothed out the transitions, extended the runners, and fully polished the full interior.

See all 22 photos The runners on the Indy intake were ported and matched to the intake gasket.

See all 22 photos The intake on a Mopar big block is dry, so it only takes a few minutes to change. Remove four bolts on each side and the intake is off.

See all 22 photos We used a two-inch merge type spacer for all tests.

See all 22 photos The crankcase was filled with eight quarts of 5W-30 Mobil 1 for all tests.

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See all 22 photos The final dyno pulls were made with 18- and 35-tooth pulleys for a 51% drive ratio. The pulley ratio is important since the vacuum pump loses efficiency if it is spun too fast.

See all 22 photos Here is the previous dry sump system that we are using as the baseline comparison. This was a 5-stage pump with 4 scavenge sections pulling from a billet pan. A full write up of this engine test was published on the Hot Rod website back in May of 2017.

See all 22 photos The wet sump was down a small amount of power from the previous dry sump configuration. The peak-to-peak difference was not large, but the wet sump was down 20 hp at 6,800 rpm.

See all 22 photos The power came back when we hooked up the vacuum pump. Now the two power lines lay on top of each other for the entire run with the vacuum pump setup making slightly more peak power than the dry sump.

See all 22 photos The ported Wilson intake added power above 6,000 rpm. At 6,700 rpm the Wilson intake was 25 hp better than the baseline test.