I was wondering howto you figure out what size runnerare best for your engine. I'm building a 400 sbc, with forged flat top pistons, 6" H-beams, a forged crank, a single plane hurricane, and a comp cams Hi-Tech roller cam i believe its 256 duration and 630 lift 3200-6000 if i remember correctly. I had a set of bowtie heads but am now under the impression that they would not be enough to acheive my goal of reaching550 crank hp so i am considering aluminum heads 2.02- 2.1 valve size and 190 up to 235cc runners any insight on ahow to figure out the proper runner size or information on were to attain this info would be great, also is 550 reasonable? thank you GARRETT

 

That seems close to one we put together we havent fired it yet though. We went with the 230cc dart iron eagles we are planning on around 6800 rpm with a 3500 stall and floored down the strip though looking back on it I feel now that the 230 cc is to large as i rethink it 215 cc would have been a better choice. I believe you would need to look at each head individually and compair the flow the afr 190 cc flows great and you dont sacrifice the bottom end. Another thing I do question on our buildwas using the stock block a dart block will give you added insurance alot of machine shops dont even like dealing with stock blocks at that hp range anymore. If you do use the stock block you need to consider splaying (if its a 2 bolt) and studding the block then line honing you will also need to clearance it for the 6" rods . I would guess you would be in the $8000 range on a proper build up. We have around $6000 in ours but we used a flat tappet cam and the cheaper dart heads and assembeled the top end ourselves. If you want I could run your combo through desk top dyno but I would need specific cam info carb info and head specs(some head specs are on file but I dont have the newer ones)