2.4 DOHC race engine oiling issues

[RSCAracer]

I'm new here, and been searching the net for some help. For race applications, I trying to find out what the smallest size hole can be in the oil gallery in the back of the 2.4 block, just below the deck. The stock bullet shaped oil restrictor is .140. I'm trying to keep as much oil in the bottom end, without causing a upper end problem.

First a little background. I have a small machine shop and an oval track race shop building spec midget size cars asked me to R & D a 2.4 Mopar DOHC eng. to use in these cars. The idea was to keep costs down, while still trying to build a reliable engine for this budget class dirt and paved division. It is a hilborn alcohol injection - non turbo engine. Three years ago I built 2 motors and they tested them for the last two years at many tracks without any problems.

We used the 2.4 stock block, crank, and bare head. We used JE pistons, Total seal rings, Clevite bearings, Eagle rods, Crane cams and springs, Std. size SS Ferrea valves, Mopar lifters & followers, and oil pump. I assemble everything except the oil pick up and stock pan, since they seal it before it goes in the cars. The lower bal shaft assy. is not used and the speed shop built a windage tray and gated box around the pick up for better oil control.

This spring, after I built 15 engines, they started to race a weekly schedule. So far, 2 engines have blown - both with #4 rod failures. Oil PSI is 40 psi at idle and 60 -65 psi in the 7000 rpm range. After tear down - the rest of the bearings look like new. Now since their racing, many guys are turning upper 7000 rpms and I'm thinking the too much oil is ending up in the head and not getting back down to the pan. I feel its a lack of oil, since #4 is the fartherest away from the pump. (I had this experience with some wet sump chevy sprint car motors, where #1 rod in chevys usually go first - especially when the oil valley was plugged and screened too much which prevent oil from getting down to the pan fast enough at high rpms.) It only takes a split-second to starve for oil, while still maintaining oil psi.

The other reason I think it may an oil return problem is because they mounted the engines tilted slightly to the left in the chassis to clear the steering. This means more oil is probably returning down the single oil vent / return hole, than the two right side block return holes. Since their always turning left in the corners, I'm sure oil is returning down the right side - but is it enough?

What am I missing here? This is why I wonder if I can restrict the top end more? I'm looking for any other ideas before I suggest they remount the engine? Any help appreciated.

[puppet]

Have you tried using an accumulator?

[crazymadbastard]

darryl cox racing (dcr)sells a proven restrictor, maybe use that as a referrence.

[speeduphoria]

well I run a .108" in mine and know its safe from neon NA guys running 8500rpms with it, but some of the hybrid guys have run external oil feeds with .095" carb jets(the ones I asked had zero issues and never read about any issues). I just took the stock one and welded it shut, grinded it back down, then drilled the new hole.

The other thing that is good to do is chamfer the oil drains in the head and even drill them out a little to help it drain. On top of that opening up the oil pickup is good and porting/smoothing all of the oil passages in the filter housing/pump/block.

Another thing to look at is using the 2.7 v6 rockers as they a different hole in them and are strong. As well as making sure to use the newer lifters, or even a solid lifter if you want.

BTW how much oil are you running?

"neons dot org" is a great place for info on these motors.

[itoktoeatfish]

How about running one or 2 extra exturnal return lines like on a hybird.

[TonaChris]

Darrell Cox Racing (Powered by CubeCart)

2 links to his site in the past couple days...dcr should be giving me commission

[rfb6435]

Newer 2.7l V6 rockers are also an upgrade from the 2.4l ones and control the oil a little better since they have a smaller oiling hole where they contact the lifter.

-Rich