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What Would Happen If Restrict Wrong Orifice

humz

By humz,
in Engines & Forced Induction

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humz Proficient

humz

Posted
Posted

From my readings it is recommended to block off the middle and restrict the rear orifice on a rb25/30 using vct.

Now what would happen if you blocked the rear and restricted the middle???

brief specs are as follows

standard oil pump

1.5mm restriction (in middle)

crank case breather on intake side of sump above oil pick up

from my understanding as the front only feeds the vct module, by blocking the rear wouldnt that give better oil distribution and balance in the head???

How many orifices does the rb26 have and where are they located in comparison to the rb25 block. ive read they have one blocked off standard so im assuming they have 2, and for better balance the middle would be blocked- makes sense

JonnoHR31 Grand Master

JonnoHR31

Posted
Posted

26s have 2. 25s have 2 head feeds in the same spot and a completely seperate vct feed at the front. you can block/restrict either of the 2 main feeds afaik, it shouldnt make any difference. but if you wanna be picky i would have thought blocking the rear and using the middle would be best for even pressure.

XKLABA Grand Master

XKLABA

Posted
Posted
  On 08/03/2012 at 9:52 AM, JonnoHR31 said:

26s have 2. 25s have 2 head feeds in the same spot and a completely seperate vct feed at the front. you can block/restrict either of the 2 main feeds afaik, it shouldnt make any difference. but if you wanna be picky i would have thought blocking the rear and using the middle would be best for even pressure.

both factory 26s I've opened have had one with a 2mm restrictor and one blocked off

KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted
  On 08/03/2012 at 10:57 AM, humz said:

Righto, thanks for that.

So you think there will be a significant pressure difference in the head?

What can this result in? Oil starvation to rear of head/cams?

Restrictors reduce flow not pressure. I have 2 x 1mm restrictors (and sump breathers) and hydraulic lifters work fine. So far no oil from cam covers into catch can v vast amounts with 1.5 restrictors and no breathers.

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