would that work? can you match up AS&M Runners, for example, to a siamesed, ported plenum such as in the pic below? if it can be done physically, what would be the technical and performance rammifications?

 

I see no benefit.

Everything should match. If your runners are not siamesed, no reason to have the upper plenum done.

 

If done with that plenum and non-Siamese runners at least knife edge the runners to smooth the air flow transition to the runners...

 

Think of it this way, you will expose the moving air to blunt sharp edges.
So yes, you need to knife edge the runners for smooth transition.

 

thanks all. the reason i ask is because i have been looking to buy a used plenum or two just so i can port them out and see if it nets positive results. and the preponderance of plenums for sale are the already ported, for siamesed runners type.

 

You are playing where most of us have played for many years. I have a ported plenum with port matched siamesed runners, no big gain. To realize much you need to use a large port base or port the factory base which has only so much room for porting. If you want more RPM ditch the long runner TPI. Then the L98 iron heads and peanut cam become your restriction. Headers and free flowing exhaust probably gave me the biggest gain. I need to do more but being married limits my interests.

 

Thank you for that well intentioned post. i guess this is one time it would have been useful for me to have a sig with a list of mods. My Formula has the following:

Stock L98, Scat Rods, KB Hyprtctc Pistons, Fluidampr, Cloyes Double Roller Timing, Edelbrock Vortec Lower Intake, Fast Burn Vortec Heads, Jegs 1.5 Roller Rockers, ZZ4 Cam, AS&M Large Tube Runners, Stock TB w/ Air Foil, Hypertech Cap/Rotor/Coil (black), MSD Wires (black), Accel 24 lb/hr Injectors, Walbro 255, Spectre Heated O2 Sensor, Ed Wright Chip, Dyno Don Headers & ORYP, Hooker Cat-Back w/ Monza Double Dual Tips, TA Performance Diff Cover, Alston SFCs, UMI Torque Arm, Hotchkis LCAs, KYB Shocks (black), one coil cut off front springs, TransGo 2, Corvette Servo. Hawks Fiberglass Aerowing

plus Wonderbar not installed yet. SSBC 1LE kit is in the mail.

 

YOu will see a lot of improvement if you ported the Base. The edelbrock vortec base sucks out of the box. But be careful, it is thin.

 

I'm not flaming you bro' just telling you what most of us have known for a long time. The TPI system was designed around the anemic 305/5.0 engine. Your ride with the mods listed would benefit from more (better) intake flow.

 

Right. I didn't take it like that. I only took it as you being under the impression that I was dealing with a stock or mostly stock power plant. I just wanted to clarify as the existing mods will likely change the parameters of what would work best for me.

 

Oh yeah, I kind of thought that after my last post. I like the looks of the TPI personally and would like to do more with mine on the top end but right now have bigger priorities. With my engine running 278,000 on the clock it would be a waste to do much with the top end and not the entire engine.

 

I thought for a TPI base the Edelbrock was pretty good. Didn't they make the TPIS Bigmouth and pattern theirs after the TPIS base? I would kind of like to use that base and keep TPI. Maybe build the motor up to ~ 375 - 400 HP. Hmm will TPI support that?

 

The Vortec base sucks. It is tiny, and the injector bungs stick way into the port. There is very little material, and you will go through it porting very quickly.

The Stock base is different. I have ported my stock base and there is a lot of material to take off.

My stock base is ported to match 146 gaskets, which are big mouth, 1 3/4" openings.

 

You can open up the vortec base a fair amount. You can cut away most of the injector bungs, and you can take a fair amount of material out of the short side radius. You may not be able to take it as far as a standard manifold, but you should be able to take it as far as an unported accel intake.

 

I ported a vortec base out to fairly large sizes. Decent meat there.

This is a base I got from a parts purchase then sold. (I now have a new one thats forsale.)

 

The opening is not the problem, it is about 2 inches inside the port,
it is as small as the stock manifold.

Edelbrock really dropped the ball on this one.

 

Yeah, there are other "issues" with this manifold but nothing that can't be worked to make a lil better.