Stroker engine "diesels" after I shut it down

airwoofer said
You guys are getting pretty technical on me but thanks again!! OMM may be onto the cause... It seems like this started after I opened up the idle (primary side) by adjusting the butterfly stop. I have not touched the mixture adjustments since buying the pro built and dyno'd motor (416). Same MSD mechanical dist as the top picture and the carb looks about the same too. There is a little flat spot just above idle at about 1500 driving with the throttle barely cracked open so OMM may be onto something. The carb is a NASCAR style Holley 830 jetted for the engine on the dyno (unfortunately no temp or density notes). When I first installed the engine I had the timing set (total) at 36* like the dyno run had it. After the over-run pinging I dropped it back a tad which was just after I put on the mufflers / X pipe and thought the increased power (lower ET) was due to less total timing or added backpressure. One day I may have to drop the 750 I have on the 340 on to see how it does as that carb was perfect on the little motor.

As for piston quench - dunno. It has 20cc dished KB forged pistons to get the 10-1. I have to assume that the builder has the quench right as they did a lot of measuring per the build sheet I got.

OMM is that a 4sp or manual VB? I have the kickdown for my 904 and have it set to make pressure when the secondaries start to open. Working pretty well as is the 904 in general when in DRIVE and driving like a cop is behind me. Kicks down nicely when the coast is clear also.

Well now that I know what you are running I will tell you what I have and why.

The motor is 428 with a solid roller and Indy heads. It is around 12.5 -1 comp. The distribotor is locked a 35 Degrees. It starts at 15 degrees and as the MSD digital 6 automatically retards the timing 20 for start up. When it reaches 800 RPM's it goes to 35 in run mode. So it shuts off at 15 degrees.

The motor idles a 1600 rpms. It has a 5500 stall converter. I shut it off in neutral and I periodically put in pump gas to make it home if I am running low.
If you turn your Idle down on the primaries and turn them up on the secondaries you'll see the dead spot off idle disapear.The proper way of making it real snappy is take the carb off. look at the underside of the carb primaries Open and close the primaries and you'll see the transfer slots. Close them up until as much of what your leaving exposed equals the width of the slot. If you need more throttle than this to make it idle you need to do this with the secondaries. This will let the primaries at the location they need to be for instant throttle responce. They will be able to use the transfer ports for the fuel application transition to the emulsion jets.

Next is the idle air bleeds you want to decrease or increase there size. If you can turn your air mixture screws in almost all the way without stalling you need to decrease the size. This will give you more fuel at idle and the motor will be more responsive with out adding accelarator shot. It will also help the motor to shut down.

I went through exactly what you are discribing. My motor shuts down with no problem now. Get rid of the X pipe , Just my oppinion, They are ok to block up exhausts on teeny motors for more torque. But it will hurt your stroker. Let the exhaust flow. use an H.