Final post on this matter - after the ECU gave up, I in turn gave up on fighting 30-year-old tech. So I bit the bullet and got a Holley Sniper. It basically is the same as the GM TBI with a...

Always glad to help and let's work together wherever it helps! The backfire issue is mostly MAP AE vs. TPS AE, so tedious, tedious woring with the wideband o2 sensor to tune it out without going too...

Reporting back - getting there, even if tuning the TPS AE is a real PITA and involves more trial and error than I generally like. Thank you all for your input!

Thank you for the input! So basically, I have to check TPS AE in the affected TPS % range. Will do and report back (my girl told me to take the next weekend off from wrenching, so it'll take some...

Gotta bump this. Still at a loss. Any ideas?

Finally getting there! After lots of dabbling with the AE settings, she's running mostly great, with an AFR under AE between 12:1 and 13:1 - but the WB o2 tells me that starting from a standstill and...

As the owner of a late-70s Opel I an pretty good at acquiring Opel parts. Shoot me a PM what you need and I'll look around :)

I think I fixed it! Looking at ony's post about the MAP values again, I realized that cruising at low rpm the Ford 400 does not produce a lot of vacuum, leading to MAP values in the sixties....

I celebrated too early. The backfire's still there. You can find one in each of the logs attached. In the first one, it's easy to find right after the WOT run at the end of the log. In the second...

I changed the PE-RPM to 1200 while reverting to my guesstimated AE settings. A first drive looks like this has cured the problem.

But I won't know for sure unless I got a WB o2 under the car and...

MAP values definitly are different from a Chevy engine (and even from a Ford Windsor). The Cleveland/M-Block is an... interesting engine, to say the least (some people claim the M-Block plainly...

So, I tried two different things.
1. I first used the 5.0, 5.7 and 7.4 bins and an Excel sheet to find out where the approximate AE values for a 6.6 machine should be. The bin #34 attached was the...

I should try the cowboy hat thing some day! By the way, fuel prices over here are at their lowest since 9/11 these days with only around 5 Euros per gallon...

Well, now things get complicated....

Thank you for your reply!

One of the two aims of the cruise log you are seeing was to find out the real-world top speed of the car, so we pushed her hard on an empty stretch of Autobahn. In...

Thank you for the input, that makes lots of sense! :)

I will get the WB o2 sensor back under her after the holidays and test-tune the big block AE tables!

What I find interesting about people's...

After sorting out the general setup, my ignition timing and DFCO with the help of this community, I sill can't find a way to tune out an rather elusive backfire trough the intake.

The issue...