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Old 04-03-2006, 06:29 PM   #1
cyrus923
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Default Single cam heads

Maybe I should go into a little more detail. Yes I have a built motor and I am using wrx heads on my 2.5L. I would like to upgrade my heads and have heard of single cam heads on a wrx. What is the advantage to them versus dual cam heads? Maybe the moderator will not close this thread thread again and yes it does belong here.
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Old 04-03-2006, 07:45 PM   #2
banzai
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from what i understand, the single cam heads that came on the 01 or so 2.5 RS' are the best flowing heads and they are SOHC.

i also believe that they will bolt right on to a wrx/STi block.

I haven't been able to dig up any flow bench numbers to justify that claim however.
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Old 04-04-2006, 12:16 AM   #3
speed_freak27
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Cobb has flow numbers on those heads. The other benifit of these heads are that you can upgrade cams for half the money and you don't have to do a shim under bucket to get them to spin to 9k only valve springs and retainers. They will bolt right up to any suby block. I've had them on a ej22t and now my 257 w/no problems.
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Old 04-04-2006, 03:22 AM   #4
sick1.8t
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i'm not sure of the flow numbers, but i've seen dyno plots on here of stock to stock dohc RS motors and SOHC RS motors and the dohc's have more low end torque, the sohc's have more top end HP.
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Old 04-04-2006, 08:51 AM   #5
BensonRST
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Quote:
Originally Posted by sick1.8t
i'm not sure of the flow numbers, but i've seen dyno plots on here of stock to stock dohc RS motors and SOHC RS motors and the dohc's have more low end torque, the sohc's have more top end HP.
I think you're backwards. the benefit of the SOHC heads is response, they flow much air really fast, it's great for spool. but in stock form, they choke like a bitch up top. DOHC heads, make power later, but keep it going to the line. but with a little work, sohc is the bomb. you can get cams, spring and retainers for about 1250, iirc. Stock versus stock, they outflow corvette LS1 heads, according to cobb.
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Old 04-05-2006, 08:21 AM   #6
Sko
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Old 04-06-2006, 08:03 PM   #7
BensonRST
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good info, let's keep this going. let's find all the flowbench tests we can, to compare some hard numbers.
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Old 04-07-2006, 07:38 AM   #8
JonofScio
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I know that we cannot put DOHC heads onto a motor into a car with an ECU designed for a SOHC motor, but can we do it backwards? say for this example, a wrx (DOHC stock) but now is SOHC, can we bypass the extra unused sensor or two?
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Old 04-08-2006, 09:05 AM   #9
BensonRST
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i think the ecu would still be loking for it. a general rule of thumb, from what i've heard, is always match the ecu to the heads you are using, or go standalone. bottom ends, you can do whatever you want, as long as you have the ability to retune for changes in CR and displacement.
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Old 04-23-2006, 04:05 PM   #10
Hopper
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I have some flow test results of the WRX and SOHC intake ports, if someone would like to post? For some reason I canít post them?
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Old 04-23-2006, 04:41 PM   #11
VTsuby
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Well if you want to talk about the valve train end of things the rocker will initial out accelerate the dohc setup. Which is traditionally the way to go if you want torque. The dohc should hold on longer for high rpm usage. This is all depends on the flow of the heads. I would hope the sohc head port has less cc's than the dohc. This would creat more intake velocity down low and make the engine great on the asphalt dyno. I work with an eg33 so I have no idea. If your after a real streetable engine the sohc would be a good way to go. If you are using a 2.2 head on a 2.0 it will be under valved which will make awesome low end torque (which is really what make a fast car). Realize I'm talking about potential not what the heads do in their stock configuration.
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Old 04-23-2006, 05:05 PM   #12
Drac9
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It doesn't matter anyway though if you intend to use a wrx ecu. The trigger pattern on the SOHC cam gears is different than it is on the WRX heads. Only way to get around this is to switch to a standalone EMS. In 2002 subaru completely changed their trigger patterns.
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