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Chevy with a cummins
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155 Posts
Discussion Starter #1
well its a little late to ask too many questions since its already in the car and running, but basically I freshened up a stock z6 block and topped it with a good a6 head I had, cause I didnt' want to mess with vtec, and it was a cheap way to lower compression.
1. so its in the car running, but the 1.5 I took out would run circles around this thing. I realize I now only have 8.6 compression, but geez. stock po6 computer though, timing belt set at a6 marks. is the lower compression killing it that bad?
2. will the lower compression hurt me in trying to tune for mpg once I turbo it, or should I just yank the head and put on a z6?
its n/a at the moment til I get it broke in. only planning to run a small turbo on it, and it hits 10psi at 2500 rpm. already had this turbo setup on another civic.
 

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Chevy with a cummins
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155 Posts
Discussion Starter #2
no opinions on leaving it the way it is or slamming a z6 head on it for 10lbs or less of boost? Hmmmmmm.
 

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Banned
My car...
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1,875 Posts
The "amount" of boost you run doesn't matter. What matters is what turbo, what powerband goals you have, and the overall set-up.
10lbs of air =/= 10psi.

If your only going for 200whp, I would run as much compression as my fuel allows. Which means you can probably run upwards of 11:1 Compression on 93oct if your chamber is decent and you have a good tune. But yeah, either mill the A6 head or run/mill the Z6 head and bump your compression up to atleast 10:1. There's no point in running low compression with "low" power goals.

But there's a number of reasons your NA motor makes less power/feels slower. The lower compression might be part of it, but it could also be the lack of a tune for that engine combo. Just make sure there isn't something wrong before you go changing things up.
 

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Chevy with a cummins
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Discussion Starter #5
guess I will play with the timing and maybe throw in my other chipped computer and try some different tunes for a few days. might still throw on the z6 head before its all done though.
 

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Classic Man
Civic
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16,355 Posts
if i was you, i would be more concerned with oil pressure.

you see, the A6 head does not have a restrictor jet in it like the Z6 head does. the A6's jet is in the deck of the block. the z6 block does not have provisions for this jet.


so right now you have a HUGE oil pressure leak, so to speak.... no oil jets at all!


id be interested in seeing how it plays out without any changes... and id really be interested to know what your oil pressure is like.
 

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Chevy with a cummins
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Discussion Starter #7 (Edited)
actually it was already drilled and the oil jet from the a6 went right in with a new o-ring!
I ported the oil pump as well before I put it together. haven't run a manual gauge on it yet but It seems to be fine. when I get my lift open where I don't have to lay on the ground to install the oil pressure gauge I will check it.
 
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