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Ok, ive only got 120-ish psi cylinder pressure in my 202. Seal is great, so it's lacking in static compression ratio. A faulty gauge at home made me think i had 150-ish (acceptable). This motor reads lower due to retarded cam timing (which i'm set to return to recommended)
I've been told to look for 180 to make power with all my other mods. Seems i have low-comp pistons, not the flat tops i presumed were put in. Doh! Call that one a major misunderstanding between a conervative engine reconditioner dad and an inexperienced me when first bulding the motor. I thought dished meant reeeeallly dished, and these flat-ish pistons were "flat tops".
So i've got 103hp at the wheels on somewhat low comp (standard is 9.4/1, +40thou bottom end, head shaved 40thou but with low comp pistons) My options are flat-tops in this motor, or a new bottom end with blue crank/rods and bigger cam to make use of my worked head and twin carbs.
I always use Vpower and i don't care about fuel prices. We choose to drive these, we pay the fuel costs.
Thoughts? |
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All normal 202 engines got dished pistons standard. GMH did this so they could still use the 186 combustion chamber, while keep compression to practical levels. The low-comp versions simply had a much deeper dish.
LJ XU-1s were the only ones which had flat tops & their comp was around 10.3.
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Ok, cool. So with the current over-bore and flat tops i could assume comp somewhere around 10.5/1, given that its an open chamber head but shaved nearly 40thou?
I know the only real way is to calculate properly by measuring CC, head casket, bore, stroke and piston to deck clearance, but im just trying to get a good idea before deciding on putting pistons in this motor or building a new, better bottom end.
Cheers. |
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I thought std CR for a 202 is 8.8:1?
So you are running red rods and std cam in this motor?
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Why are you reading this, you should be looking up there^^
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quote:
Originally posted by Mr Void
I thought std CR for a 202 is 8.8:1?
Stock comp ratios are 179 HC - 8.8 186 HC - 9.2 202 HC Red (pre ADR27A) - 9.4 202 HC Red (ADR27A) - 8.8 202 HC Blue/Black - 8.8 Dr Terry |
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Terry
Arent the HX/HZ/VB/UC 202HC engines 9.4:1?
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[quote]Originally posted by Mr Void
I thought std CR for a 202 is 8.8:1?
So you are running red rods and std cam in this motor?
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Stock red crank and rods, but cams a Crow 35665. 30/70 with .440 lift intake and 79/31 with .465 exhaust.
With compression and tune there could be 20-30 hp there.
But im thinking of a new bottom end and a slightly bigger cam, since id be building a better bottom end, may as well use it, but not go spastic. |
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