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Old 05-20-2013, 07:20 PM   #1
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Question 2.5 head question/observation

So I picked up a 2.5 and 2.3 head for my next turbo build, so I have a 2.0, 2.3 and 2.5 head to mix and match parts.
The 2.5 head is VCT as I understand, but I wanted one in my hands to see what exactly is different. I was curious whether or not I could simply use the cams from a 2.0 or 2.3 in the 2.5 head. From what I can tell I see no reason why I cannot.
Can someone please see if I'm overlooking anything? I see the first 2.5 cam cap oil circulation pathway is different than the 2.0/2.3, so the 2.5 caps would have to be used.

Here are some photos of the 2.5 head with a 2.3 intake cam. I have not removed the exhaust cam.








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Old 05-21-2013, 09:26 AM   #2
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I am thinking the sam thing. That 2.5 head is sooo meaty. So open. I would love to use it with stock 2.3L cams ( or even upgrades)

My guess is it might be a valve travel issue?

I am game to put the 2.5head back on this motor i am building - but a 2.5L head with 2.3 block under it would be super super interesting.
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Old 05-21-2013, 10:05 AM   #3
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How much bigger are the ports, int/exh? I'm asumming the valves are the same size= 35/30mm? Combustion chamber cc's ?
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Old 05-21-2013, 10:06 AM   #4
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Quote:
Originally Posted by MainiaxMotorsports View Post
I am thinking the sam thing. That 2.5 head is sooo meaty. So open. I would love to use it with stock 2.3L cams ( or even upgrades)

My guess is it might be a valve travel issue?

I am game to put the 2.5head back on this motor i am building - but a 2.5L head with 2.3 block under it would be super super interesting.
I believe the valves/springs are identical for the 2.0, 2.3 and 2.5. I need to get a spring compressor so I can get those measurements. This 2.5 head needs rebuilt anyway as it's obviously been sitting a while.
My primary concern is getting oil properly to that first cam cap. I know there is an oil regulation valve that controls how much oil gets fed into that cam to control the VCT, but I don't know exactly how that system works yet.
My initial assumption is there is 100% oil pressure feeding that location at all times, but the valve limits the pressure 99% of the time to limit how much oil is in that VCT gear.
Therefore if the oil pressure valve is not present the cam should get 100% oil pressure as desired. I need to find that out.
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Old 05-21-2013, 10:08 AM   #5
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How much bigger are the ports, int/exh? I'm asumming the valves are the same size= 35/30mm? Combustion chamber cc's ?
Much larger height, but the same width. I'll write down measurements sometime.
The combustion chamber appears identical. The diameter is the same (~87.5mm).
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Old 05-21-2013, 11:19 AM   #6
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much much much bigger on Intake



head size is identical though - so you might be right on valve length - just have to measure diameters
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Old 05-21-2013, 08:51 PM   #7
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I believe I have the 2.5 intake cam oil feed figured out (mostly).

The 2.5 head has an extra oil feed port that enters through the bottom and feeds that first intake cam area. There is an actuator/valve that controls the oil pressure from that additional feed port to the VCT.
My 2.0 block does not have that feed port, so as-is no oil would be going to that first intake cam cap.
That being said, the primary head feed line still exists in the 2.5 head, which runs directly under that first cam cap, it's simply not drilled through.

My plan at the moment is to
1) Drill a new oil feed down into the first intake cam area
2) Tap the existing 2.5 feed port and block it off to keep oil from draining to nowhere (against the head gasket and just sit there)

I'm in no particular hurry, this is just thoughts of the night and I'll likely come across other issues.

2.5 head with extra oil port (bottom left)


2.0/2.3 head (no port)


2.0 block (no port)


2.0/2.3 head (see tiny oil feed port in cam valleys)


2.5 head (no oil feed port in the cam valley - needs drilled)
There is a feed line that runs the length of the head to tap into.


2.5 cam with oil ports vs. 2.0/2.3 cam without


2.5 head


2.3 head
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Old 05-21-2013, 08:58 PM   #8
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Measurements

2.5L
Intake port: 41.6mm x 50mm (H x W)
Exhaust port: 37mm
Combustion: 87.6mm x 15mm (depth rough estimate)

2.3L
Intake port: 37mm x 50mm (H x W)
Exhaust port: 37mm
Combustion: 87.4mm x 15mm (depth rough estimate)

Now, the kicker is that my 2.0 head measures exactly the same as the 2.3 head I just bought. Either 1) I was sold a 2.0 head, 2) They do measure the same on the outside edge of the ports and the difference is on the inside, or 3) The 2.3 head isn't actually bigger that the 2.0, which I doubt.

If someone has a spare 2.3 head and would measure the intake port height I'd appreciate it!
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Old 05-21-2013, 11:01 PM   #9
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So the 25 has a higher int. port then the 23. How is the exhaust port size? Same size valves I take it, huh?
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Old 05-22-2013, 06:08 AM   #10
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Quote:
Originally Posted by felixthecat View Post
So the 25 has a higher int. port then the 23. How is the exhaust port size? Same size valves I take it, huh?
Exhaust ports are the same. I ordered a valve spring compressor but it's not here yet. I'll measure the valves when I get them out. Cross-referencing parts on RockAuto.com tells me they should be identical.
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