I know this has been discussed on here before but probably over 20 years ago. I just wanted to see what people are saying about cutting down the plenum divider on a Performer intake. Is it worth doing for a street car? Does it have positive effects on TQ or HP gains/losses? How much is too much, what else should be done to the intake to help it perform better like gasket matching maybe? Also please post up any pics you may have. I have a new Performer intake for my New build but I don't want to make any permanent changes that could hurt the way it performs. The Performer on my current engine IIRC when I swapped the holley 750DP for a 72 800cfm Qjet I recall noticing the rear part of the plenum divider was cut down about an inch and ground to a knife blade type edge.
Larry, that's what my current one looks like. Not sure if any port matching was done as I haven taken the intake off.
Also can anyone recommend a good bolt kit for the intake? I didn't get any hardware with it even though its brand new in the box and my old one looks like it was put on with hardware store bolts and washers.
I think depending on your year heads, the bolts are different sizes. TA has an intake bolt kit I think.
I did extensive dyno testing on this with several engines years ago On a 500 HP engine, lowering the center divider 1 inch, with the proper bull nose profile, added 10 HP to the peak, and subtracted 10 foot lbs at the torque peak. A one inch open spacer produced the same results or was slightly better, but the divider has to be bull nosed.. if left flat, performance was the same, or actually decreased. Any kind of "shelf" left in the intake path will reduce performance, generally. I rarely ever do it anymore.. as torque is more important for real world driving feel, than HP is. The notch in the intake that Larry showed, was usually done so that you could put a 950 Three barrel Holley on it, a carb which was popular back in the day. JW
Exactly the info I was after Jim. Sholud I round over the corners on the top of the divider to create a bullnose or just leave the plenum divider alone completely and gasket/port match the runners to help with the airflow instead?
When Gregg Tomlinson did my B4B he made the divider removable...great for testing. It seemed to do just what Jim said.... My removable divider spans across the primaries as well. One problem....don't lose divider piece!
I would go further toward primaries...if you are looking to top end power. Not going to kill much torque with a dual plane...just making it a bit more like a single plane.
Right Larry! I remember this exactly now and I just remembered I bought a set of bolts off a member here, now just to try and remember for what heads? EDIT: found the convo, I bought a set of the TA 7/16" intake bolts for aluminum heads off another member.
I wouldn’t make the notch any longer than an inch. You can’t make a dual-plane into a single plane. Some signal might get better,but some will get worse.
So here is my removable divider in my B4B. I tested with a Qjet and semi-open spacer (somewhat divided between primaries. Black is with center divider, blue is without divider. I lost 5 ft lbs and 2 hp from the peaks with the divider removed. The most difference is in the low rpm range, with the 2 trading elsewhere. Maybe the semi open spacer performed the same function as removing the divider. I did not test without the spacer.
