What kind of difference will it make if I put a set of heads off a TPI 305 on my TBI 305?

thanks

Kyle

 

I'm not sure what kind of HP difference you will see but the 2 heads are SIGNIFICANTLY different. If we're talking about 305 motors in both cases they will both have 1.84/1.50 valve and 58cc chambers.

However, the TBI heads have a nasty "swirl vane" in the intake port that helps swirl but cripples flow. TPI heads have much more traditional ports- no swirl, but much better flow.

I would think that the TPI head would help power production quite a bit, but they would probably want more spark advance since they don't have as much intake motion helping to increase the burn rate. They would also probably appreciate a more aggressive cam with more lift and a little more duration. All this starts to get into the old "so you need to reporgram the chip to match the combo" area or the gains will probably be modest from the head change alone.

 

You would notice something, but its not going to amaze I don't think. If you had something other than the stock L03 cam, the gain would be significant.

 

Stock swap for stock swap your power gains will be minimal but notable (assuming you swap cams as well). The 416, and 081 heads really wake up with port work. Only then do the two distance themselvs even farther.