Marnel Cylinder Head Ported w/1mm OS Stainless Valves
Mitsubishi Oiling compared to Marnel and others
The upper two photos are of the Mitsubishi design. The oil from the block is fed through this hole as shown with the red tube inserted through it and passes around the bolt that fastens the cap to the head then enters the right side rocker shaft from around the sides of that bolt where is passes through the rocker shaft and feeds oil to that side of the valve train. The left side rocker shaft is fed from a hole in the right side rocker shaft and the oil passes through a galley that when drilled looks like a "V" and in the bottom of the "V" is the feed for the camshaft journal then onto the left rocker shaft. 8 Rocker arms, 8 hydraulic lifters (if present), 5 journals for the Camshaft and most importantly the 8 cam lobes are all lubricated with oil fed up from the block passing through this one small hole. Marnel bored the cap in the thicker bottom portion to feed oil to the right rocker shaft the same way Mitsu. did but they also feed the left side shaft the same way and the cam journal on its way there. Marnel didn't share oil from the right shaft to the left.
On the left side in the photos below is a Mitsubishi cap. The other is the Marnel version. You can see the cavity Mitsubishi has for the oil to get to the opposing rocker shaft but this is an early design.
This is the early 2.0l head below, there was also a 1.8l version and all three were chain drive. You can see there is no "V" cast into the cap to share oil between the shafts and they have that groove on the underside in the cam journal. You can also see the oil feed to each tower cap from the cavity that runs along the right side of the block that was later deleted in the 2.6 in favor of using the rocker shafts and also you can see the smaller combustion chambers. This head also has smaller ports and smaller valves.
Marnel drilled the passages differently. The part that needs to be addressed is shown in the two pictures below. The opening that feeds the entire valve train is VERY small compared to the Mitsubishi hole The red tube can not be inserted through that opening. This hole needs to be enlarged and where the two holes are drilled from each side that area in the center needs to be opened up to feed the cam. Many people are now building this motor for rpms exceeding the original factory limit and the oiling of the valve train is very important. One other thing to look at on your head I've noticed is that the spacing of the rocker arms is slightly different from OEM spacing, this means the oiling hole for hydraulic lifters may not be aligned as well as it could be. The thickness of the tower cap determines the rocker spacing and the springs on the shaft hold them again the tower caps. Check out that spacing as you assemble your rocker assembly, put the caps on with the shafts and leave the rocker arms off, now measure the distance from the cap to the oiling hole and measure the rocker arm inside and you may find a surprise.
These two below are from another Marnel head made a few years earlier. It appears their drilling just isn't quite deep enough at the center to connect the two bores and the feed is still the same small diameter bore.
Remember, this one tiny hole on the right in the above and below photos is supposed to feed up to 29 oiling points!
When someone buys one of these heads they usually are reusing their old rocker arms and shafts. Those parts usually have 100k+ miles on them and that means worn shafts and rockers and there is no way that tiny hole is going to supply enough oil to keep those lifters in the back or the cam lobes lubed like they should be. You can do a hard pull and go around a sharp corner at high rpms with a stock head and sometimes hear the lifters tick so imagine what happens when you cut the flow down and try to go racing using worn parts. Allot of your pressure goes out the first two rocker arms. Open up the points where they intersect in the center for the cam feed and enlarge that tiny hole!
Here is another cap from a much older Marnel casting. This head is at least 6 years old. Its compared to yet another early Mitsu. cap. Mitsu left/Marnel right
Although the two holes look the same they are not, the Marnel cap is closer to the camera lens
This is a different head labeled as M27. The red tube can be inserted through the oil passage and the raised bump on the cam has plently of clearance.
These early castings feed oil to the opposing rocker shafts through a cavity in the cam journal.
Look in the large hole with the bolt goes to hold the cap to the head, you can see where the other two holes intersect at an angle into the space around the bolt to feed the oil.
This is yet another casting- M29. The casting of the cap has changed to delete the common passage in the cam journal. You can see in the last photo the reason to line the raised bumps on the cam to the dots in the rocker shafts -the feed holes are only on the inner sides of the shafts.
Below are two rocker shafts -these are hydraulic style shafts. On the left are the slots that feed through the hydraulic rocker arms to the hydraulic lifters. On the right you see three holes in the shaft per rocker on the bottom shaft (exhaust) and one on the top shaft (intake). Of the three, one is to lube the rocker on the shaft and those are the two that have the horizontal lines to either side of the hole and that allows some oil to feed side to side. The hole that is above and slightly to the right of the exhaust rocker arm oil hole is to line up with a hole in the rocker arm to spray the exhaust lobe on the cam. The 3rd hole is not under the rocker arm but is out in the open on the shaft and that hole sprays oil onto the intake lobe of the camshaft. They didn't put the spray jet hole in the intake rocker arm or the hole in the rocker shaft to do that. I think they must have felt the exhaust rocker shaft would benefit from the extra cooling of that oil flow and it probably does.
In the picture below you can see the oil jet hole in the exhaust rocker to the left of the slipper foot that sprays the cam lobe.
Here's the rocker assembly. Don't forget your shafts will have the two raised points lined up with the dots drilled in the end of each shaft as an assembly check as shown below right.
Marnel head ready for assembly
Porting took about an hour -clean up took two. This is the cylinder head that was on Kurts car when he ran the 12.9 qtr. mile time. At that time it was unported, had the OS valves in it and was fitted with stock springs, a stock hydraulic cam and mechanical rockers. His motor now has the head he previous ported that was on the truck motor but the motor was never fired. This is the head that is to be on the truck motor now.
The intake ports were gasket matched to the Magna intake and the exhaust ports matched to the header
Left below an intake pocket, right is exhaust. I concentrated on the ports not the shrouds around the guides.
Stock replacement valves compared to Stainless
The benefit of using the stainless valves comes from the shape of their stem and the thinner back not the fact they are larger in diameter. Inside the port you can see the back side of the valve and how more flow happens immediately after the seal is broken with the design of the stainless compared to the stock replacements. Below on the left side of the 3 pairs of photos are the replacement valves and the stainless are on the right.
There is less material in the way on the stainless valves
Shown here in the pictures below are the valves side by side in the newly ported head. The cam was turned so both valves were closed then both rockers were both held down with spacers.
The same test was done as we did to see the air flow through the new intercooler we have chosen to use on the cars. A tank vacuum blowing smoke into the intake manifold to see the difference in flow.
Here's the proof in the two black spaces below. These are .avi files showing how much more flow there is using the stainless valves. The first one is using a yellow colored smoke but the second one using blue smoke shows the difference must clearer.
Move your mouse pointer over the space to play the file or right click and save it.
http://www.b2600turbo.com/IM000495.AVI
http://www.b2600turbo.com/IM000496.AVI
Here's one more .avi file below you can better see how the air comes out around the valve
http://www.b2600turbo.com/IM000502.AVI
Here's how I held the valves open
Below left is the stock replacement valve and on the right is the Stainless valve
Now what valves would you like to use in your head? Having the stock seats ground out for these is all we have done. it is not necessary to have new or oversized seats installed to use these so don't let someone tell you that BS. The porting was done using an air rotary tool and three different cutters; tear drop, ball and a cone shape and one flap-sander drum I picked up at a swap meet all 4 for 20.00 and the air tool you can get for about 30.00. When porting stay away from the valve seat because if you touch it you're sort of screwed and don't get crazy around the valve guide either. Enlarging the ports and matching those to your manifolds is where you'll see the most benefit for the work you put into it. First match the gasket to the ports, you can use spray paint over the gasket to mark where you need to remove material then enlarge the ports then go further into the pocket and a little around the guides and shrouds then to clean up use the sander drum. Don't press hard on the cutters or they will clog up with aluminum and dip in some used oil frequently to cool them and aid in cutting. I started with the tear drop shape, used the ball around the guide and the underside of the seat area where the flow turns up into the pocket and the cone shape just to touch up the guide edges. The hard part is cleaning all the ground up metal off before you can begin reassembly. I used a small parts washer filled with kerosene.
We did get the head assembled and the cap tower caps modified. Below are the two holes that were mentioned at the top of the page.
This particular valve train was assembled using Swivel Feet rocker adjusters. We drilled oil passages in the rocker arms to supply oil to them. You can click here to see how we did that, Swivel Feet.