I'm helping a buddy with a new Weiand 671 blower on a 350 sbc and had some automatic transmission questions. He has a B&M TH350 with a BDS "transmission pressure diversion valve" installed inline before the vacuum modulator. Under 3/4 throttle and no boost, shifting 1-2 manually and the transmission shifts sluggishly soft. Under full throttle and with boost increasing, shifting 1-2 manually and the transmission shifts quick and chirps tires. We isolated the problem as an issue with boost or the BDS "pressure diversion valve". The BDS valve flows vacuum to the transmission vacuum modulator at all times, but once it senses boost the BDS valve blocks the vacuum signal and the vacuum modualtor increases line pressure accordingly. Because my buddy wants firm shifting all the time, regardless of boost, we thought of several to ways to alleviate the issue.
1) Install smaller blower pulleys so boost comes in sooner at a lower RPM
2) Delete the BDS "diversion valve" and get vacuum from above the blower and below the carbs
3) Install a full manual valve body...last choice as this is a street car
Any ideas as we are open all suggestions????
Thank you!!
1) Install smaller blower pulleys so boost comes in sooner at a lower RPM
2) Delete the BDS "diversion valve" and get vacuum from above the blower and below the carbs
3) Install a full manual valve body...last choice as this is a street car
Any ideas as we are open all suggestions????
Thank you!!