Modifying stock iron intake manifold

Any good articles on milling modifying the stock iron intake at the carb base? To make it more like a B4B, etc? Also, after doing mods, is it anywhere near the B4B?

Thanks,

Matt

 

The above supported 510 HP thru Qjet stock manifolds and iron heads

 

That's awesome

 

Thanks Ethan. How far down is the center divider from the carb base?

Do you have the cross over blocked?

 

Close to 3/4 in , crossover was blocked in the heads

 

Start here.

http://www.v8buick.com/index.php?threads/docs-dual-plane-mod-and-port-matching-stky.225437/

 

Awesome, thanks!

 

You will get better cylinder to cylinder power balance out of the stock Intake and power if you have room for atleast a 1/2" tall open Carb spacer as this helps to make up for the lack of turning radius into the shallow Plenum.

You still must grind out primary to secondary dividers on the iron intake , but this mod works better for the sake of drivability below 2500 rpm then just grinding down the iron wall divider on the stock Manifold.

The ideal spacer to work with will be a little smaller then what the stock Plenum is now, as on the shallow side of the Plenum this will allow you to grind in a radius from the entrance of the spacer ( top side) into the shallow side Plenum.

 

Thank you. What happens if I put on an open spacer and left the spreadbore intake for now?

Seems like that would be bad going from spreadbore to open (square bore) spacer then back to the original spreadbore on the intake.

Right now I just have a very thick spreadbore gasket below the carb and virgin intake manifold.

 

I did not post up to use a open square bore spacer, you use a open spread bore one if that's the Carb your running.
If you leave the stock front to rear dividers in place they will act like air flow restriction and you might as well skip using a open spacer and just run a 4 hole spread bore spacer.

 

Ok, that's what I thought.

 

Let me detail this more.
Adding a non open spacer will always help with the fuel distribution into the shallow Plenum and to a lesser degree air flow so these will help in terms of power production, but not as much on the top end rpm power production end of things as a open spacer.

 

It's worth about 9 hp and 12 ft lbs, I compared a stock one to a modified one on a dyno years ago.

 

Here you go!

 

A plot of the data from above.

 

Do you have pics or details of your mods to this manifold?

 

I don't, it was a long time ago that we ran that. Basically made it look like a B4B. No other porting or massaging. Similar to what Hugger shows but the divider was not lowered.

 

Marked it up with sharpies. The silver sharpie is the areas I propose to remove. The black and unmarked parts will be left original. Made a mistake the first go and didn't realize the center divide turned under the secondaries but just covered the silver with some black once it was dry. I'm thinking I'll keep the center piece its original height and add a notch by the secondaries like the B4B, unless there's any reason to lower it more for a mild 455?

Hugger, I noticed on the two outside edges, you kept a little "bump" of material. Is this for more gasket support?

 

Correct for gasket support, the notch on the B4B's was just for throttle blade clearance for the Holley 3barrel that was popular back then the newer B4B's and current ones just run the performer pad. The performance increase comes from adding plenum volume, with out dropping the center and running a 1/4in gasket no gains will be had IMO.