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Front Cam Tower Oil Mod - Problem


importwarrior
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well for starters the front cam Tower has a oiling problem.

I first saw this from Indiana on his B2600turbo site.

 

http://i139.photobucket.com/albums/q299/I-W/Cam%20Tower%20Oil%20Mod/C8C8BAC9-2462-45EB-8B50-65BE71B99899_zps13fynwva.jpg

 

http://i139.photobucket.com/albums/q299/I-W/Cam%20Tower%20Oil%20Mod/9634E5E0-1545-4E29-85B0-9CB5E015AA08_zpsev8mempi.jpg

 

http://i139.photobucket.com/albums/q299/I-W/Cam%20Tower%20Oil%20Mod/31D3643A-8FF6-432A-A903-7CE97B6DB4B9_zpsofxkzb64.jpg

 

 

 

The front cam tower on the bottom has a oil feed hole from the block.

it passes around the head Bolt and through the head to the bottom of

the front cam tower. then as you look in to the oil feed hole that is drilled

in to the cam tower. The hole size is 2 extreemly different sizes.

 

as i measured using drill bits, primitive i know but all i had for sizing.

the first pic shows a 3/16th drill bit in the oil feed hole.

 

http://i139.photobucket.com/albums/q299/I-W/Cam%20Tower%20Oil%20Mod/119A328F-4E89-469C-A50B-FB1B1DF0EA85_zpsdulp0hqy.jpg

 

 

 

the problem is this hole is not drilled all the way through.

as you look in the oil feed hole, there is a smaller hole that

is about 3/32 in size.

 

http://i139.photobucket.com/albums/q299/I-W/Cam%20Tower%20Oil%20Mod/54008849-A24E-4438-9AF8-70580F4AD90B_zpse2i0l0wf.jpg

 

http://i139.photobucket.com/albums/q299/I-W/Cam%20Tower%20Oil%20Mod/E1B3ABBD-048B-4BD4-9A8F-0B63A99DB987_zpshjemtkjc.jpg

 

 

 

NOW if i am correct the engine oil flows from the front CAM tower

to all the lifters and rockers and CAM, this 3/32 hole is supposed

to supply oil to feed the entire CAM assembly.

 

i measured the oil feed hole in the head where the cam tower oil

hole alignes with the head feeding hole. the oil feed hole that passes

through the head from the engine was actually larger than the feed

hole in the bottom of the cam tower. it is 7/32 in size.

 

 

this is the third head i have seen with this same problem. 2 new

clearwater heads and now this magna head from australia.

 

i honestly dont know what the proper size these holes should be?

 

do i drill all the way through the 3/32 to make the feed hole all 7/32

to match the oil feed from the base of the head?

 

 

Thoughts?

Comments?

Suggestions

 

are Welcome.

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saw this from DAD as well he stated to drill the side oil outlet to rocker arm shafts

holes for the oil feed to the towers to 13/64. this is because they didn't align well

to the opening in the rocker arm shafts. this possibly could cause lifter tick.

 

 

in the pic below the right cam tower is the stock original Cam tower from an original head.

it measures 13/64

 

the left cam tower is the alabama or clearwater cylinder head. it measures 1/8 inch

http://www.enginemachineservice.com/cap1.jpg

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Only had an issue years ago with a batch of alabama heads but they were drilled offset blocking oil flow to rockers. I have to take a look but I think all the heads have the hole reduced. In the 4 or five years selling the M28, have not had any issues. got one on my shetland and My son has one on his now redquest.

 

 

Dad

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as far as the main Front Cam Tower oil feed in my first post.

is it supposed to be reduced?

 

the exhaust lifters oil hole is a whole different issue than the main cap feed.

be sure to check for proper sizing also.

Good point DAD.

 

Thanks,

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is it supposed to be reduced?

 

I think so, but in all honesty I have not looked into one of those holes in a long time, never seen an oiling issue with these heads., I'll take a look at a head tomorrow.

The oil holes on the Alabama batch would not align with the shaft, thats why you had to enlarge the hole, but it wasn;t the feed hole that you are talking about.

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My heads are the same. 3/32 hole. I have seen this on other heads, both new heads and old heads, been a while since I paid attention to it, that was back when I had the oiling issue with the alabama heads. I don't plan on making any modification to it. These M28 heads have worked fine for years this way, My theory is that it's a restrictor to keep from loosing oil in the bottom end as rocker shafts and rockers wear. Pull your oil fill cap and you will see tons of oil in the top end unless your rocker shafts are filled with crud. A lot of oil can flow thru a 3/32 hole.

 

Dad

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The stock head the larger hole drilled deeper. The aftermarket heads have the smaller hole. I enlarged my marnal head per indiana's website. I have not noticed any detrimental affects.

 

Where the oiling improvement helps is in the higher RPMs. It keeps the lifters more stable at 5k + rpm. The oiling system was designed by mitsu to have the larger hole. If you run the smaller hole then some of the extra oil that would have gone to the head gets spit out the oil pumps pressure relief valve. Oil flowing out the relief valve doesn't help the bearings.

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I drilled mine to the larger hole size to eliminate the step from the different sizes. That step could cause turbulence that could affect flow. I also drilled the passage between the two sides to eliminate the blockage found on some marnal heads that weren't drilled far enough. The oil port in the tower should be at least as big as the gallery coming from the block.
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Oil volume to the lifters is needed, but they require a certain amount of pressure to keep them pumped. My thoughts are that the reduced hole size is intentional to keep the required pressure to the hydraulic lifters since it is at the oil entry point and will affect the entire shaft assembly. I think the engineering is to also depress the lifter ball with pressure to always flush reservoir oil through the lifter hydraulic so the oil inside stays fresh. If the oil in the lifter gets dirty, they start to stick because the dirt gets between the little piston and cylinder wall that has tight tolerances to create the hydraulic.
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Oil volume to the lifters is needed, but they require a certain amount of pressure to keep them pumped. My thoughts are that the reduced hole size is intentional to keep the required pressure to the hydraulic lifters since it is at the oil entry point and will affect the entire shaft assembly. I think the engineering is to also depress the lifter ball with pressure to always flush reservoir oil through the lifter hydraulic so the oil inside stays fresh. If the oil in the lifter gets dirty, they start to stick because the dirt gets between the little piston and cylinder wall that has tight tolerances to create the hydraulic.

 

 

I guess my only question to that statement is,

Why was the original stock head from a stock car Cam Tower oil feed hole not have the restricted 3/32 hole in it like the new heads?

 

just wondering.

 

i wish we had more original heads to look at.

 

Thanks.

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I have a "T" casting jet valve head that belongs to Walker on the site. It is my understanding the T head is OEM. this head has the oil passage reduced to just under 3/32 also.

 

I have an 83 engine but not torn down yet that i will take a look at also.

 

Dad

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If you look at the rocker shafts, you can see how Mitsu engineers use the first hole to regulate pressure and volume. One hole in the first set is larger on the shafts than the other holes down the line. My point is that engineers have taken time to design this, and if it worked fine with balance shafts for over 100K miles, it should work even better without. No need to worry about hogging it out. Over the years, Mitsu made improvements such as the teardrop shaped divit in the oil feed hole to the head. So I do duplicate that on the aftermarket heads such as Marnal that don't have it. But drilling a hole just because I notice it is necked down, no way. There is a balance between volume and pressure. We are already increasing volume by removing the balance shafts, so there should be no volume concern after that. the large majority of machine shops will make the engine lose a little pressure on the rebuild, even with a new pump. Why? Because they must be more precise to put the tolerance on the tight side. It is easier to put it on the lose side (less main cap work, etc..). It really needs to be on the tight side to keep the pressure where a new OEM engine is.
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