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Discussion Starter #1
What could be the timing for my 355 SBC under full boost with water injection.

Engine is 9.3 CR, 255°@0.050" cam with 0.630" valve lift.
22PSI with twin GT35R, 93 US octane and 30 Gph 50%wather / 50%meth direct port injection.

Last year I was runing 24° at 15PSI and 15 Gph water but seamed to be very low timing. Only managed 137 mph in a near 4000 lbs Chevelle.
 

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My setup is similar to yours. On dyno I found more power going from 28 to 30 and then 32 degrees. At 34 degrees power was same as 32. I stuck with 32. Been that way for three years. Did a freshen up last year and all parts looked like new.

I push 24psi on pump gas, 30psi on 100LL avgas.

I use 40 degrees timing to help it spool and once boost gets over 6 psi I ramp back to 32 and it stays 32 throughout the run.

I set an intake manifold temperature parameter to pull additional timing out if temp gets over 180, but it never does.
 

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What does the timing mark on the spark plug strap look like?
 

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What does the timing mark on the spark plug strap look like?
It's slightly on the electrode side of the bend.

Sometimes it is in the bend.

Sometimes you can't tell.

I am running NGK 7's right now.

I am not sure I buy into the theory behind reading timing from plug strap. Too many variables. I gave up on this and go by torque output. Good power output and no piston material on plugs works for me.
 

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Discussion Starter #11
One more question, what is your AFR with pump gaz and water. I have been told that you can run 12.5 - 13 /1 but I prefered to stay on the safe side with a 10.5 - 11/1. I think that so much fuel also costs me many HP.
 

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One more question, what is your AFR with pump gaz and water. I have been told that you can run 12.5 - 13 /1 but I prefered to stay on the safe side with a 10.5 - 11/1. I think that so much fuel also costs me many HP.
12.3 for me.
 
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