Edelbrock streetmaster vs Offenhauser equa-flow high rise.

[dodge freak]

Right now I am using a offy equa-flow small port intake on my 318 with 3.91 gears and a Holley hp 750. Its great no flat spots and has good power. I can buy a eddy streetmaster 318 also small port for $65 and it looks fine. Should I do it? It looks like a torker but with smaller ports. Not sure why I want to change but like the fact the ports seem shorter. The offy is single-plane but has a plenum like a dual-plane thats good for low speed power but maybe with that 3.91 I don't need it. This is why I am asking, yes the best way is to just change it and see but though I ask first.

[grouseman]

Buy it, install it, and report.  It's fun!  I've swapped through 318 2v, 273 4v, SP2P 4v, factory 360 TQ, Offy Dual Port TQ, LD340, and Performer.  Each changes the engine's character noticeably.  Let us know. 

grouseman

[dodge freak]

It be more fun if I had a second mopar. Hate to change anything now but know it always can get better. I might just buy it and one day change it, always can sell it on ebay. Oh I had that performer on it, it stink, at high rpms it was no good and I get a better idle with the offy now, maybe thats why I am second guessing myself.

[grouseman]

No firsthand experience, but I'll guess anyway.     The streetmaster is an open single plane, but with a small plenum and short, small runners.  My guess is that it has good throttle response due to small plenum volume, but also decent mid range for a 318.   Long runners mean better low end torque, short runners move the torque peak further up. 

The Offy is a center divided single plane, with a much bigger plenum volume, so I'll guess that it has a soggy throttle response.  It probably runs best past the mid-rpm range.  It's got a weak point because 8 & 4 will inhale consecutively (right side of intake), and 5 & 7 inhale consecutively (left side, and the two are immediately adjacent ports). 

So my guess is these two intakes have very different characteristics on the engine.  Where do you want your engine to be most responsive?  Do you have a race engine in a light 4-speed, or heavy daily driver with automatic? 

[dodge freak]

Its a auto with a set of low gears added and 3.91's in the rear end. So my first gear is more like a 4.3 and second is like a 4.1 gear with a 3.91 third gear for a good top end. No its not a everyday car, just around the house here don't go more than 15 miles one way or so. Live 2 miles form the freeways , all 70 mph zones, and a nice 4 lane 55 mph zone that should be 70 also, but cause it has a few stop lights.  Its really nice I am sure you are right the best way is to install it and jet the carb for it to see how it is. Just thought maybe somebody here had it at one time.

[firefighter3931]

The streetmaster and sp2p series were pretty low performance manifolds back in the day. A stock 340 4bbl intake would be a step up from either of those. The ld4b is what you should look at for a 318....it's a dual plane with 318 sized ports and enough plenum to pull up top.

The short stroke 318 needs a dual plane for torque and throttle response. I don't see you being happy with a single plane on a 318 in a heavy street car. The ld4b is no longer being made but check e-bay.....they come up for sale often.


Ron