LD4B intake on a 1969 340CID

I never tested an LD4B but I did test an LD340 on a mildly built 340 in a street/strip duster with a 2600 stall converter. What I found was a very small increase in peak power but a significant loss in low speed torque. Cold idle quality was terrible compared to the stock intake. My quarter mile ET did not improve with the LD340.

Having said that, I have no doubt that an RPM intake would be an improvement. In my opinion, the LD340 and performer RPM intakes are nothing alike. Since I play with thermoquads, I have never tested an RPM but I have seen dyno comparisons published is some of the magazines.