I did some reading on a Madmax thread of sometime ago where he took his stock manifold and ported + siamesed 5.5 inches off his intake.

I was curious if anyone else has done this to their stock manifold since then and what kind of results and/or success you've had ? Reason is I WAS going to buy and aftermarket base manifold (TPIS, ASM, etc) and after reading the DIY siamesing thread have to wonder why not just port out my factory unit and save myself the coin ? Same goes for the factory runners -- why not DIY port + siamese these ?

I have a slightly mod'd 305 (check sig) with some head and exhaust work on the way, 5-speed with 3.73s. The car makes 6k rpms now but anything over 5200 is flat. If I saw another 15-20hp out of a TPI porting project I would consider the work to be very successfull.

thx in advance for your comments,
RP.

 

i did the same thing to my stock base. ported the plenum. left the stock runners. using the lt1 cam, here are the results. also here are some other things i've done and the dyno results.

http://www.fl-thirdgen.org/mrr23-2.html

as you can see from 3000 it started to increase. but because of the stock runners, it still peaked at 4400.

 

yeah i see the peak in that chart...