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Old 09-03-2008, 03:43 PM   #1
frayz
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Default What machining to do on EJ207 heads going on an EJ257?

Hey guys,

Just thought id throw this around a bit and see what your thoughts were.

I'll be putting my EJ207 heads onto a new forged EJ257 build.

What mods should i do to my heads, combustion chambers, cc sizes etc for the best performance?

Anyone got any pics of machined 2ltr heads for a 2.5 build?

Cheers
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Old 09-03-2008, 05:54 PM   #2
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machining should be to have custom pistons made to match the combustion chamber and to get your targeted CR.
I'd also do a bit of valve deshrouding as you have extra bore, so why try and impinge flow?
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Old 09-03-2008, 06:12 PM   #3
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Should i not have the edges of the combustion chambers machined off to reduce the chances of det?
Do you have any pics of deshrouding baddy?
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Old 09-03-2008, 06:25 PM   #4
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+1mm or +2mm valves on intake and exhaust will really help flow tremendously, mark chambers with a 2.5L gasket for reference..... do a 3 degree cutter to unshroud around the valveseats and allow better flow for the larger chamber size, being mindful of the bore circle parameter that you marked using a 2.5L headgasket....

You didn't mention if these are large port V7 heads or regular V7 heads.....

smaller port V7 heads will benefit from pocket porting and mid runner and entry portjob on a 2.5L


What cams are you going to run?

Custom Kelford 280/274's I hope or something close....??

GOOD LUCK!!!
RYNO
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Old 09-03-2008, 07:01 PM   #5
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just have them mate the combustion chamber to the same size as the block no biggie. portin isnt needed just sharpen the intake runners and polish the exhaust side to a mirror finish...dont polish intake side leave it a lil rough
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Old 09-03-2008, 07:16 PM   #6
frayz
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Was gonna run with stock cams, and porting. 1000 for cams doesnt interest me lol

Theyre the small port versions.
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Old 09-03-2008, 08:05 PM   #7
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cams will get you a lot more than porting...
valve job is a sure thing to be done as well...

as for opening up the bore of the combustion chamber, I wouldn't. I'd make the piston match the combustion chamber...and yes, I'd knock the sharp edge off the chamber, as you should anytime you deck a head..

What kind of power are you trying to make? and how much of it?
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Old 09-04-2008, 02:04 AM   #8
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Want to make the best power i can on a GT3076R.

My limits will be 11mm head studs and an unlinered block.
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Old 09-04-2008, 10:12 AM   #9
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GT30R won't even phase the 11mm head studs...
At that power level I also see sleeving as to improve engine longevity via less cylinder deformation.

"Best" is still very vague for descibing power you want. I'll ask, where do you want your powerband to be? top end or do you need off corner "punch" for tight courses?

GST S2 cams should help you carry out the top end of the curve without hindering your bottom end too much. Aside from that, valves and I'd pocket port to, if you can afford it.

Down the road, I'd look into getting a medium sized intake manifold too.

-Micah
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Old 09-04-2008, 02:01 PM   #10
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The car gets used on the road and occasionally at the nurburgring, so i want strong mid to top end power.

Out of interest, how to you recomend fitting the head studs? i know there is alot of different views on how to fit them.

The cost is the only thing holding me back as the price of parts here in the the UK is rediculous.
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