olds 307 and 403

Is it worth the time? I know all the issues with Thornton's 350 manifolds and since they need a lot of work to flow, I am thinking porting my stock exhaust manifolds might gain. Other than opening up the outlets, anywhere else worth porting? I already have the stock style dual 2.25"? exhaust without tail pipes, I may put the tail pipe expander in the glass pack outlets. I like the sound of the exhaust, just don't want to lose a bunch of power from the Sanderson shorties and machine bent 2.5" duals with an X pipe, those will stay on the G body.

joe_padavano

Other than matching the ports in the head, there is nothing in the exhaust manifold to "port". The SBO manifolds are simple open log manifolds, not individual runners like the BBO W/Z manifolds. Making those log manifolds larger isn't going to help flow. The aftermarket SBO manifolds aren't individual runner, either.

olds 307 and 403

I wonder if it is worth the bother? They suck and certainly don't blow SBO manifolds.

coppercutlass

Whats wrong with regular full length headers ?

olds 307 and 403

I may consider them in the near future, should not have given away my Flowtech 1 5/8" full length headers for the A body. Oh well the ceramic coated peeled and had major rust pits all over and the flanges were no hell. Same problem with a lot of header flanges and ground clearance too. I may just leave them as is, this car will see the track too.

coppercutlass

I personally don't have ground clearance issues . Car sits pretty low too. I'm just running an old pair of black jack headers. I do have to re paint them every 2 years. To keep them looking good.

olds 307 and 403

There always seems to be a gasket leaking some where and there are a lot of fitment issues no matter how much you pay. If I lose too much power I may use my Sanderson's or get the Herman shorties and use my 2.5" system. I think with a 3.90 gear upgrade, I will gain a lot. Plus running a more aggressive timing curve will help power and mileage.