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Two problems I have seen referenced a lot is exhaust leaks throwing off the 02 sensor and dual plane intakes causing issues with fuel distribution.  Adding an open carb spacer may help.  Check for any exhaust leaks up stream from the 02 sensor and 18 inches after.  Hope you get it sorted out soon!

Scott Carpenter

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Update* accel. enriching didn’t change anything much. I Took it from the original setting of 49 and trying 2 lbs. at a time, went as high as 63 and as low as 26. So I took it back to 49 and left it there. 
I did notice though, that I’m getting a very rich smell when test driving. 
I’m going to try changing the a/f settings and see if that makes a difference. 

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Leaning out the a/f didn’t help either. Next step..I’m going to do a cylinder leak down test and see if something may have gone wrong on that first day out?

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200 miles is beyond the learning curve and you said it ran great, so if it ran well, once you can fix or eliminate engine problems, I'd really check the O2 bung if problems persist. Have you pressure tested the bung?

I know from the last bung that I've welded that it looked fine looking at it, but pressure testing showed it wasn't airtight as I thought it was at all. Air was able to pass very easy thru tiny passages that I could not even see, so grinded all again and made a second pass with higher welds and done entire diameter in one pass vs 1/4 which was prolly where the mistake came from.
If you use the provided thingy, after 200 miles of heat the insulation has become hard and if there is a weak pressure spot, it doesn't take much of gas pressure to create a false air gap.

It's annoying to remove things again, but as said above, it's been one of the most common source of probs on Holley forum for units starting to behave weird.

 

@scarpent1"dual plane intakes causing issues with fuel distribution.  Adding an open carb spacer may help."
I have 1 cm spacer on my Offenhauser dual plane on my 351, no probs at all, it follows the same logic as the venturies but on my 429, also having an Offenhauser dual, there is a different design for the split under the unit (right left vs 90deg split). I might need a taller spacer or remove bits of material at the split, time will tell. But no matter the model/design of the dual plane intake, a spacer certainly makes sense in combo with the Sniper.

73 modified Grande 351C. Almost done. 

71 429CJ. In progress

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So I was able to get thru to Holley tech. The guy was great and spent Some time with me looking at my datalogs. Didn’t find any issues though.  It does not matter how rich or lean I run the engine, the condition doesn’t change at all. 
my Leak down test was good on all cylinders, less than 4% loss.

 Compression is 180-190 on all cylinders.

I give up.  It’s going to go to a tuning shop.

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On 10/8/2020 at 7:01 PM, Fordboy71 said:

Update* accel. enriching didn’t change anything much. I Took it from the original setting of 49 and trying 2 lbs. at a time, went as high as 63 and as low as 26. So I took it back to 49 and left it there. 
I did notice though, that I’m getting a very rich smell when test driving. 
I’m going to try changing the a/f settings and see if that makes a difference. 

One of the big things I found was that opening the map in the software gave way more control of the Accel Enrich. When I played with it on the handheld it gives you one number to adjust. The point where I found I started making headway on the tune was when I added fuel right at the beginning of the curve. At the top of the graph you can see that its dumping a ton of fuel in, and thats where I was still able to lean it out a little bit. The problem with the handheld is i think it adjusts the whole curve together, so if you need more at the beginning then it means your also going to get even more later. That said, this has all been a learning curve for me, I was a little scared to start digging in but this is what I have found has been working for me. Now when I give her more throttle off a set of lights it picks up much faster, where before it wanted to die if you did that. 

This one is the curve at the beginning of when i started playing with it. You can see the first 2 points are at 12.5 and 19.7, but up high is 68. According to one tuner I talked about that is enough fuel in itself to make 140hp and thats not even including what the base map is giving it. 

Capture2.JPG.deb78d7745eb129c727ddd4698f1edf9.JPG

Now (revision 4) you can see it starts at 15.2 and 22.6 but has less up top. Now Im still going through and seeing how it looks on the datalog.

Capture.JPG.2b0c26ef1d1d5040d4381a039261231d.JPG

Someone I heard on here I think said that the self learning is like a carb still. The self learning will take care of the base map(jets) and will learn that part, but it wont learn all the tweaks(idle mix, accel pump). And that seems to have been the best description and I feel like when I started looking at it like that, it started making progress. 

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