Yeah I saw an article in the WMF that made mention of so called J-7MF flights.

Also it’s not the J-7E but the J-7G. I think what PLAAF is trying to do is save as much funds to buy as many J-10s and Flankers as possible.

Problem of J-7 is that they’re a tactical handicap. In a Taiwan scenario you need range and loiter time, and short legs ain’t good enough for an offensive role. FC-1 has a more efficient engine than a J-7 thanks to its turbofan, which is a reason why the type can be considered. It also has a higher payload rating (3800kg vs. 1000-2000kg for a MiG-21 type) so you can carry more external fuel tanks and bomb loads.

Overall you can see right off, the FC-1 is a more versatile design. You get a greater range envelope and more payload possibilities.

Once again, no MiG-21MF and -bis is ever flown in the Vietnam War. I think you’re just engaging in too much wishful thinking.

And engines are not interchangeable, either, even with engines of the same size and different versions of the same aircraft.

Wrong again. The auxiliary air inlets are positioned just ahead of the engines. The fact they’re different on both the YE-152 and J-8I shows that the engines are positioned inside differently.

And I told you before, that’s not just an airbrake. It also serves as an opening to eject shells from the guns. J-6s also has that.

The F-18C and the F-18E/F still has a lot of direct fuselage commonality just as the F-16 and the Japanese F-2 does.

But in the case of the J-8I and the YE-152, there is no direct fuselage commonality at all.

And that means the Chinese got the blueprints out from thin air, right?

the Toolling is quit important because without it you can not build the aircraft, but the Chinese got the MiG-21 tooling so the based their J-8 mostly in it, you said that the calculations are different but also the MiG-31 is different from the MiG-25 but it does not mean it was not based the Foxbat.
The webpage you dislike from Test pilots Russia said the chinese only got the Blueprints but the J-8I got the R-11 from the MiG-21 and not from the Ye-152 so the Chinese were forced to change many aspects of the Ye-152 and also improved it and all this make the J-8 different from the Ye-152. It`s as the Lavi rumors in the J-10 development but this happened 44 yeasr ago so information on it is scarse also the Chinese designation erased many russian origins in their weapons

Bullcrap. The changes in the J-8I are not due to the tooling but because the design was a clean room.

Don’t let your illusions bite you.

The Chinese never even heard of the YE-152.

I don’t see how the Chinese would have changed the YE-152 as some of the changes do not necessarily mean they’re for the better. Just plain different. There was no other purpose in these changes—the inlet, the more slender body, the different wing chords—other than the simple fact there was simply no connection at all.

Let me tell you again, China does not have the blueprints for the YE-152.

The fact that the stress, airflow and aerodynamic calculations would be quite different shows you China had no access to the YE-152 at all, that the J-8I was developed with “clean room” engineering.