anyone running these runners on a 355? i am working on getting my running and i will be siamesing the base quite a bit... hopefully 3-5 inches... and porting the pleneum as well... so would these runners be too much or would they work good?

5 inches is a lot.. I think I remember someone else doing that and blowing his engine by running too lean on a few cylinders. The idea is to allow each cylinder to pull air from the neighboring intake port if necessary, not join the ports. Do you think that much porting is needed?

280Z28 gained almost 5mph and about 4 10ths in the quarter mile from going almost 3". I'd suspect, based on his gains, that the amount he did would probably be about optimum. The thing is that you have it siamesed in two areas, and I don't really know how good that is based on how much potential siamesing has...I'm thinking having the runners fully siamesed into the base would be the best for higher rpm, higher power. Of course that's more difficult than just siamesing the runner tops and bottoms and the base.

5 inches may be too much... but i want to go with at least 3... cause i have heard good things about that...

the as&m runners i am referring to is the runners that they sell that are ALREADY siamesed... so no work to do...

I wouldn't go more than 3" into the base - I think you'll see a big difference with AS&M Si-Runners, and a 3" Si-Base. Just to let you know, 280Z28 has a mildly built 350 transplanted into a light weight 280Z (Nissan), so don't expect his gains to be typical. Still - I think you'll definitely feel more power as well as see a stretched powerband.

I siamesed my base 2 inches in at the head side. I made each cylinder pull from 2 runners. I dont really understand how some would run leaner than others with each cylinder having its own injector unless an injector was bad. Intakes 5 and 7 will kind of fight each other at idle with the lack of volosity. after i siamesed the manifold, ive noticed that the plugs are darker in color now. the car does seem to pull harder.