is it worth it?
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Elder User
Joined: Sep 2000
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From: Bay area
is it worth it?
current engine has about 6000 miles on it. I am thinking on finding a set of Aussie heads and building them up to bump the CR on the engine as I am going to EFI in the fall/winter this year. It is a 400 bored .030 over with a 509intake 519 exhaust cam in it. Running a edel 4bbl intake with edel 600 carb on it right now.
would it be worth the little extra power and get rid of any possible pinging issues these engines have or not?
would it be worth the little extra power and get rid of any possible pinging issues these engines have or not?
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
is it worth it?
There are many posts on this issue. Try the search function for some quick info.
Some basics:
-With std pistons there is no quench effect with the aussie heads. This required special pistons and engine machining.
-Aussie heads will up the compression to high for pump gas unless you detune the engine which hurts fuel mileage and performance.
So as far as the pinging issue -NO....
If you have pinging now either get your EGR system to work properly or re-curve your vacuum advance on the distributor.
Some basics:
-With std pistons there is no quench effect with the aussie heads. This required special pistons and engine machining.
-Aussie heads will up the compression to high for pump gas unless you detune the engine which hurts fuel mileage and performance.
So as far as the pinging issue -NO....
If you have pinging now either get your EGR system to work properly or re-curve your vacuum advance on the distributor.
Posting Guru
Joined: Aug 2000
Posts: 1,127
Likes: 3
From: (near) Denver USA
is it worth it?
jopes,
I don't remember which pistons you're running now, or what your current static CR is, but in my experience, anything over 9.5:1 is marginal in an M-block 400.
At that point, you have three choices:
1. Look for race gas (100 octane or more)
2. Severely retard the ignition timing
3. Drive like an old grandpa (and not one of those Santa Monica grandpas!)
EFI will not help with this limitation, except that if you install a knock sensor, the computer will severely retard the ignition timing for you.
A big cam (long duration, lots of overlap) can help reduce dynamic CR enough to avoid some pinging, but street driveability and offroad crawlability are significantly impaired.
I don't remember which pistons you're running now, or what your current static CR is, but in my experience, anything over 9.5:1 is marginal in an M-block 400.
At that point, you have three choices:
1. Look for race gas (100 octane or more)
2. Severely retard the ignition timing
3. Drive like an old grandpa (and not one of those Santa Monica grandpas!)
EFI will not help with this limitation, except that if you install a knock sensor, the computer will severely retard the ignition timing for you.
A big cam (long duration, lots of overlap) can help reduce dynamic CR enough to avoid some pinging, but street driveability and offroad crawlability are significantly impaired.
Thread Starter
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Elder User
Joined: Sep 2000
Posts: 936
Likes: 0
From: Bay area
is it worth it?
I am running stock pistons and I am guessing I am around 8.2-8.5 cr with the head milling that they have had over the years.
I know these puppies ping like mad, and I want to stay away from that.
if I have to run premuim ie 91/92 octane I do not care as I only run it when I take it off road.
I know these puppies ping like mad, and I want to stay away from that.
if I have to run premuim ie 91/92 octane I do not care as I only run it when I take it off road.
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