"Porting the stock intake" Is there any gain in opening up the intake just under the carb.? i red about it and seen some pictures but does it work? im talking a mild build 455 and 5300-5500 rpm.
I'd say the stock intake is perfect without mods for that rpm range. The factory invested a lot of time into that design, probably hundreds of dyno hours, more than any aftermarket intake. Acid porting could help but kinda expensive. I'm also swinging over to using the 4 hole or 3 hole carb base gasket that the factory used to deliberately separate the primarys from the secondarys, probably for better response in the lower rpm range. I could be wrong but it's worth a try and hardly costs any money.
The most simple and best thing you can do for a stock Intake is to get as tall a spacer under the Carb that your air cleaner will allow Hood clearance wise! Flow test show that the short / less deep Plenum loves a 1" inch spacer, but most times that calls for a non stock air cleaner. While on the subject of the stock air cleaner removing the heat riser tube during the warm season and cable tying that air cleaner flap open can be worth 3 to 5 hp above 4500 rpm!
Easier to remove the vacuum hose from the intake manifold, and plug the vacuum nipple. Re-connect the hose for operation in late fall, winter, and early spring.
Thanks to you all for replying. I really like torque so I go with the -as much spacer height as possible. I will block the heat passage as I have done on my 350. As I got a skylark hood (non GS) and an “open” air cleaner, will I gain anything noticeable from a “cold air” air cleaner/air intake (including tubing) like on e.g. Olds 442: s?
Yes, but the riser tube being connected is still increasing the temp of the metal air cleaner unit itself. Every little cfm of cooler air you can get into the motor the better!
I’ve heard 8-10 HP. It’ll cost you a couple sawz all blades and your time. I did that mod this fall but didn’t make it to the track after. Hopefully this spring.
It may have something to do with the configuration of the stock GS455 air cleaner, but I gain a tenth and 1 mph by running with no air cleaner and underhood air...
3-5 hp, 8-10 hp is such a small gain it is not good data unless the dyno test is 100% climate controlled and the engine and fluids are the exact same temps. Even less reliable on a chassis dyno. You'll gain 8-10 horse when the sun goes down. I don't think the factory spent hours of dyno time on the stock intake. In fact I'd be shocked if they even had more than a few prototypes. I know they had the wild experimental stuff but i doubt any of that went into the production intake. Otherwise i bet we would have seen something better for the stage 1 package.
Edelbrock vs stock intake on this 5300-5500 rpm engine (havent desided camshaft yet as the kenne bell "grosery getter" is't avaiabe). worth the monney or not? =any notisable gain to expect (other than weight)
Having the stock intake extrude-honed would be the only real way to port it,unless you want to slice it open,work all the runners,and weld it back up. If you are OK with running an aftermarket intake,just get an O4B or Performer. It will cost you less then porting your iron intake,and will also weigh less.
Installed my revised intake manifold and ran it this winter. No gains for a stock 455 motor. Running about 13.95 to 14.05.
