rebuilt smallport 4age with pinging issues

[webby]

Hi guys,

I've recently completed a rebuild of a Smallport 4age. All is good with the engine except i've had to retard the base timing back to b/w 0 and 5 degrees to stop detonation.

Just to give you some background

Stock Bigport cams
Compression ratio is ~12-12.2:1
running on a stock bigport ecu with no error codes.
the cam timing is correct.
running BP ultimate with nulon octane booster to try and help.
currently setting up a water injection system to prevent knock.
Now i'm running the stock ecu only for the short term to run in the engine before running bigger cams and aftermarket ECU.

I feel the issue is too much compression with these cam in the bottom end as it can detonate when free revved from idle in neutral when running 10 degrees base.

I need some thoughts, would altering the cam timing to bleed off some compression in the low end to enable the timing to be increased back to stock and then use the water injection under higher loads.

thanks in advance to any help.

[oldeskewltoy]

Stock Bigport cams
Compression ratio is ~12-12.2:1
running on a stock bigport ecu with no error codes.

WAAAAY too much DCR!

To run 12 to 1 compression you need to run a longer duration camshaft

[webby]

Thats what i've now realised.
whats a good DCR to be running on a 16V?
from using a online calculator its currently 10.9:1 would say 9.6:1 be reasonable

[the_random_hero]

CR needs to match everything else. First step - get a decent cam, then get an aftermarket ECU.

[Lachie]

Thats what i've now realised.
whats a good DCR to be running on a 16V?
from using a online calculator its currently 10.9:1 would say 9.6:1 be reasonable

Stock compression ratio is 10.3:1 from memory

[Casey-G]

CR needs to match everything else. First step - get a decent cam, then get an aftermarket ECU.

Please do this.


then come back with your insane power from that CR. aftermarket ECU and decent cams are a must, the power would be quite good i would imagine.