I'm replacing my tired 289 with a 306 roller this month... and i will be running about 150 more HP and TQ than before... so do i need to upgrade the stall converter? what would that do? My cam is pretty mild... And for goodness sacks which one do i need, i looked on several websites and there seemed to be 10 different types and diameters just for a C4!

 

Your C4 tranny is a tough little unit it should be able to handle that 289 just fine. The reason their are many different stall converters is that they all pick up at different rpms. Judging by the new cam you put in you need to figure out what peak horsepower you will have at what rpms maybe 2,300 rpms? 3,000 rpms?
you need to find a stall converter designed to work in that power range of rpms of your engine.

 

Your Cam specs will tell you that.....post a link to the new cam specs from the manufacturer page...you might want to think about upgrading the tranny as well to handle the increase in HP and Tq...My C4 is at the tranny shop as we speak getting new cluthes, bands, spragues, shift kit etc etc....

 

If your c4 is pre 70,you are good to go with the stock one.The 2nd gear bands changed in 1970 to a flex band.Not performance oriented.They can be changed to 69 specs and will run great.I had mine rebuilt at a shop that specialized in muscle cars.They did the upgrade for me,including shift kit for $650.The torque converter wasnt changed because the guy said not to.My cam is acomp cams 268h.The biggest high energy cam I could get without going to a magnum cam.It works well.