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piston upgrade?or not?

Old May 4, 2007 | 10:19 PM
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piston upgrade?or not?

We did compression test last week. My 4th cylinder is reading 130psi and the rest are in 155+ psi. Ive been putting a quart of oil for every 1500 miles.(BTW 36000miles on the clock). My plan at first is to change the piston rings... but now Ive been thinking if i might as well change my psitons and rods.

My question is which pistons(size and brand?) and rods will give me more power using the stock crankshaft? my budget is only $1500 for parts thats why im not changing my crankshaft yet. Also my future mod will be upgarding my turbo in the next 6 months. (BTW this is for drag)

Last edited by evovin; May 4, 2007 at 10:46 PM. Reason: wrong spelling
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Old May 4, 2007 | 11:01 PM
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^help anyone!

Last edited by evovin; May 4, 2007 at 11:12 PM.
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Old May 5, 2007 | 05:34 AM
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First I think waiting more than 40 minutes for an answer is a good idea.

What are the goals for the car? Have you done a leakdown test yet? Just because your compression numbers are low does not mean the rings are to blame. Could be valve seats as well.
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Old May 5, 2007 | 06:02 AM
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^ my goals is to hit low/mid 11's on pump gas!
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Old May 5, 2007 | 07:00 AM
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If done right, the stock parts can handle that task.
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Old May 5, 2007 | 07:47 AM
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^ thats for stock turbo! but if you red my first thread...i will upgrade my turbo in 6 months and expecting to hit low 10's.
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Old May 5, 2007 | 07:51 AM
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when u did a compression test did u also add a drop of oil to see if that effected number in the the 4th cylinder- that will help rule out headgasket or valves. I would upgrade rod bolts when ur doing it and go with a smaller compression piston since u plan on running a bigger turbo (and more boost im sure)
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Old May 5, 2007 | 08:05 AM
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^ yup 130 psi at first then dropped oil and went to 140 psi.
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Old May 5, 2007 | 08:11 AM
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Originally Posted by evovin
^ yup 130 psi at first then dropped oil and went to 140 psi.

good man! now its just working around your budget and trying to figure out what kind of piston to run (seems everyone likes a different brand)
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Old May 5, 2007 | 08:24 AM
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With pistons and rods you wont notice any major power gains, just think of it as reinforcing your bottom end that is all. If you removed the balance shafts you could see a slight power increase. If you are only looking for a mid to high 10sec pass in the future, I would just throw some rod bolts on stock rods with stock pistons. As long as the tune is good you should be alright. Instead of spending that extra money on bottom end, I would spend it on good headwork, which will yield you greater gains that a built bottom end.
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Old May 5, 2007 | 09:28 PM
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Should i just change my piston rings rod bolts and invest the money for port and polish the head(in-exhaust manifold) Will I get more hp than changing the pistons and rods? I also want my bottom to be stronger just incase i put 35r or 37r later on.
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Old May 7, 2007 | 07:59 AM
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well if ur gonna keep the 2.0 instead of doing a forged 2.3- the benefit is its higher revving capabilities for turbos like the 35r and 37r- and when you port and polish the head and upgrade in valves and springs and retainers- you will be able to more safely bring the car to 9,000 rpms or so knowing the head can flow the big cams and safely not float a valve- but then u worry about the bottom end not able to handle the power- so i say why ur working on the bottom end its kind of logical to reinforce that first- why pay the money twice to fix something and regarding the head you can always tell yourself the old phrase "if it aint broke, dont fix it"
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Old May 7, 2007 | 09:54 PM
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^ higher revving...that's if i use short rods!
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