I changed to a 350 from a 305 tbi only upgrade is custom exhaust long tube headers going into a cherry bomb. My blm is stuck at 182. Do I need a heated o2 sensor. And which one would y’all suggest. I’m using a 747 computer asdu I think it’s the ecu that came with engine.

I asked this this question in exhausted and never got a reply. So I’m trying here. Sorry if wrong section

When installing headers, you should always run a heated O2 sensor. Headers may not allow the sensor to get to operating temperature so the engine is operating in open loop all the time. Your post indicates that you pulled the 305 and installed a 350. If your using the same bin then the programming is probably wrong for a 350. A 350 needs more fuel since it pulls in more air than a 305, thereby causing the 350 to run lean if using the same parameters as the 305. You need to tune or install the proper chip for your 350 application. Good luck.

I’m using 7747 with asdu chip. Should be plug and play. Only difference is no iat on 7747. Anyway also have moates adaptor. And a autoprom.

Any recommendation on what o2 sensor to use. With no back pressure now.

When idling, many times the exhaust gas temp is not high enough to maintain the sensor in a "ready" condition and maintain closed loop. Most sensors have to reach a temp of approx. 600*F to begin operating. "Operating" is generally defined as sensor being < 199 or > 699 mv. If sensor is not hot enough, there is no movement outside the required "ready" range and Open Loop results.

I ran a non-heated O2 for years without knowing any better and I didn't seem to have any issues. I was even using Hooker long tube headers. My O2 sensor always sent a varying signal. Since I didn't compare it directly with the signal from a heated O2 I can't say if there was a big difference. I did eventually switch to a heated O2 sensor before switching to a wideband but I didn't remember any huge change. A heated sensor is easy to install so I do recommend it. I would also recommend you sell the autoprom in favor of Rbob's EBL. I had nothing but trouble with the real time emulation feature of the AutoProm while every member praises the EBL. Discalimer: I've never used the EBL, in order I used MegaSquirt 1, AutoProm, MegaSquirt 2, MegaSquirt 3 Extra.

Yes, some have same experience as you. Unfortunately I and others are in the temp too low after idling a few seconds group, and the heated o2 solves the problem. Perhaps the reason for both chocolate and vanilla ice cream

You can use a acdelco afs-74 heated o2. Amazon has a good price for the o2 sensor.
https://www.ebay.com/itm/3-Wire-Heat...IAAOSw7aBVEVmQ
for the accessory power the fuel pump wire grey on a tan with a white stripe works well.