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Old 05-09-2014, 07:08 PM   #2
Board Member
Join Date: Mar 2014
Location: Tulsa

What it looks like to me,

Your wastgate allowed a little over boost notice the spike at the start then a drop. Notice a spike in the a/f ratio at the same time? You caused a momentary lean condition at that point. Not major, what boost controler are you using?

Always start tuning a car with stock cam timing. With the amount of smoothing and the choppiness of the graph, you may be have some issue in the cam set up or spark plugs getting blown out. A good a/f ratio does not always dictate no knock. Check the plugs for signs of pinging. Small pepper specks on the plugs.

Something else to add, if I remember right, the distributor on the 740 is attached to the back of the cam. When you changed the cam timing, did you reset the ignition timing? This is over looked often on these time of set ups. You advance the cam timing and advance the ignition as well(correct me if I am wrong on this could be retarding it)

You have a good set up. A little fine tuning will do wonders before throwing more parts at it.
1991 240 bone stock(for now)
adtendite et videte si quis confidit

Last edited by midnightsaint; 05-09-2014 at 07:22 PM..
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