im rebuilding my engine due to a cracked ring land #4 piston and I have a couple of questions #1 should I re use the stock rods and just upgrade the bolts with arp ? the rods have 115k miles already, I will not be going over 400/450 whp #2 should I get the whole rotating assembly balance since im replacing pistons and possibly rods with aftermarket ones ?
need opinions on my engine build
- Thread starter jsubaru04
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TK-421
New member
Don't stop short at just having the rotating assembly balanced, if your going to pay a machine shop to balance the crank, pay to have the piston ring gap file fitted, the deck clearance checked for both the cylinder heads and short block assembly, especially at that mileage. And also pay to have the cylinders honed and cross hatched to promote better ring sealing, it's never a good idea to just drop pistons in and call it a day.
The most common set up I build for customers is usually, K1 Technologies Rods (come standard with ARP bolts for the rod caps) King Rod Bearings, King Main Bearings, JE Pistions with a standard compression ratio if your going to run stock frame style turbos. And to be honest, what it will cost you to have your crank polished and balanced, you could purchase a brand new OEM heat treated one for a few bucks more. About the only thing I would re purpose would be the case halves, other than that if your going to build an engine, don't cut corners. Better safe than sorry in the end.
The most common set up I build for customers is usually, K1 Technologies Rods (come standard with ARP bolts for the rod caps) King Rod Bearings, King Main Bearings, JE Pistions with a standard compression ratio if your going to run stock frame style turbos. And to be honest, what it will cost you to have your crank polished and balanced, you could purchase a brand new OEM heat treated one for a few bucks more. About the only thing I would re purpose would be the case halves, other than that if your going to build an engine, don't cut corners. Better safe than sorry in the end.
Tk-421 I have a question about ptw clearance the spec sheet on the CP Pistons says .0030 thou but Iv seen other brands like Manley that they tell you for street use run xxx ptw for boost and nitrous xxx ptw but cp only gives you one size? Is .0030 enough for a car maybe pushing between 400/450 whp let me know what you think since you are an experience engine builder
TK-421
New member
Forgive me if I have been absent, as I was dealing with the stresses of a funeral and my family.
But [MENTION=4458]jsubaru04[/MENTION] in regards to your question about the specs, follow the instructions that come with your pistons, just because Another manufacturer states to run a certain spec, doesn't mean that should be the guideline for all builds. If CP states to use .0030 then that's what you should do. I would see the concern for something that was maybe 700 or 800 horsepower, with a power adder like nitrous or running excessive excessive amounts of boost pressure. But your looking at very conservative street numbers, you should be absolutely fine with ptw clearance of .0030. Just keep in mind that all cars with forged internals will have a small amount of piston slap until the engine warms up to operating temps. This is due to the fact that the forged aluminum alloy will not expand as fast or as much as a cast or hyperutechtic piston will.
But [MENTION=4458]jsubaru04[/MENTION] in regards to your question about the specs, follow the instructions that come with your pistons, just because Another manufacturer states to run a certain spec, doesn't mean that should be the guideline for all builds. If CP states to use .0030 then that's what you should do. I would see the concern for something that was maybe 700 or 800 horsepower, with a power adder like nitrous or running excessive excessive amounts of boost pressure. But your looking at very conservative street numbers, you should be absolutely fine with ptw clearance of .0030. Just keep in mind that all cars with forged internals will have a small amount of piston slap until the engine warms up to operating temps. This is due to the fact that the forged aluminum alloy will not expand as fast or as much as a cast or hyperutechtic piston will.
well finally got my block and heads back from the engine builder the deck of the block was resurface and they took about 0.002 thou and the heads were resurface as well they took 0.005 thou of each head that's 0.007 thou total between heads and block per side so now I need to figure out the thickness of the head gasket im gonna need I found tomei makes a 0.027 in or .7mm and cosworth has a 0.030 in or .71mm the oem Subaru gasket thickness is 0.023 in or .6mm so I would think I need the cosworth since is 0.030 in thick or could I use the tomei which is 0.027 in thick ? maybe someone can chime in and let me know what they think about the 2 choices I have which one is best . my personal opinion the cosworth would be best since is thicker than the tomei and it would put me back to oem specs ,but thats my opinion, but I always like to hear other's opinions as well. thanks in advance
HolyCrapItsFast
Drinks beer!
What is the static compression of the pistons? The gasket thickness is going to effect static compression. IMO these engines can benefit from a little extra compression but that would be something you would need to consider during tuning. If your goal is to remain as close to stock compression as possible then you would go with the thicker of the two. Consider getting OEM gaskets. Subaru makes different thickness gaskets and the OEM gasket is better in my experience. I know Cometic makes many different thicknesses but I don't really recommend Cometic.
the compression ratio is 8.2:1 CP PISTONS you said that Subaru makes different thickness heads gaskets ? I called my local Subaru dealer and they told me that they only show one size thickness head gasket for my engine which is an 04 wrx sti ej257, the reason I want to stay close to oem is cuz iv heard if I don't use a thicker HG the timing is gonna be off and sometime you have to buy timing gears and I don't want to do that so I would prefer to stay close to oem , and where would I be able to find a part # for a thicker oem head gasket that would work on my engine?
HolyCrapItsFast
Drinks beer!
Well I thought they did. I bought some OEM gaskets some years back or so I thought they were OEM. A few thousands of an inch is not going to impact timing at all or not noticeably.
I suppose if you had to then cometic would be one of your better choices for varied thickness. I know I said I don't like them but they do make a wide range of thicknesses and you can certainly find one that is ideal for your application.
http://www.jscspeed.com/catalog/Head_Gaskets_for_02_07_Subaru_WRX_STI-2056-1.html
I suppose if you had to then cometic would be one of your better choices for varied thickness. I know I said I don't like them but they do make a wide range of thicknesses and you can certainly find one that is ideal for your application.
http://www.jscspeed.com/catalog/Head_Gaskets_for_02_07_Subaru_WRX_STI-2056-1.html
HolyCrapItsFast
Drinks beer!
Do a little research before you make the final decisions. I "heard" that cosworth gaskets were merely rebranded cometic.
TK-421
New member
Yes cosworth is just rebranded cometic. And I agree as well cometic HG are not my top pick, I've seen many a big build with cometic MLS gaskets fail.
And yes Subaru has different thickness HGs. You just can't call your local dealer and tell them your model of car and year and expect them have a list of different thickness, the parts data list will only have the OE list replacement for factor part.
