I just purchased edelbrock high flow runners and am planning on porting the plenum and base along with those before putting them on, as my car will be off the road this winter anyway. Can you give me some advise on how much to port to maximize torque? I have seen some pictures of porting jobs on runners where the holes are connected at the beginning, should I do that if so how far?
Thanks

 

When you start porting, youre adding more airflow and increasing HP, not so much changing the peak torque as moving the RPM where it occurs up in the band.

If you do this with the idea to increase your off-the-line jump, you might be disappointed. Pretty much anything you do will move the peak up in the band, and may not really change the torque "number".

To maximize the HP, yes I would recommend siamesing the runners, but how far you go is up to you. There are tutorials around.

 

I would agree that there's very little you can do beyond port-matching everything (where hole-sizes match and line up).

You can "flute" the openings a bit to help load air into the tubes. Basically, put a nice radius on the top openings (like you ran a router around them). Match the plenum to the end-result.

The Edelbrock Hi-Flow runners don't allow much siamesing so don't bother trying to go down tube very far. You won't be able to affect the result enough to bother. That's because it takes a good 2-3 inches to move things more than 100rpms.

The runners can be honed to increase flow, but that is likely to improve HP more than torque. I used a combination of wire wheels and flap wheels to open the inside of the tubes as much as possible. This is an inexpensive alternative to honing.

 

Your starting off with desent heads anyway. I would just gasket match every thing and call it a day.

 

I have stock cast iron heads right now, and never heard them referred to as "decent".

 

can I achieve significant gains from porting the stock base manifold or would I be better off buying an aftermarket one?

 

Youd need a better runner to notice the difference. Doing the plenum is debatable.

 

If you aren't really looking to open up higher hp, just gasket match everything and get rid of casting flaws. Smooth as much as you can, and give it an 80 grit finish.

I had a really good article online somewhere, maybe have the link at home I can post up.

 

So is there no real gain going from stock to the edelbrock hi-flows? They where my top choice based mainly appearance and i got a good deal, but i thought they would still be significantly better than stock.

 

I meant workign on the plenum being debatable. Of course upgrading runners will help. On the base you need to really spend a LOT of time and go all teh way through the runner or its a waste of time. Quickie job takes me 8-10 hours, for a real nice job closer to 20.
Expect 1.7-1.8 runner dia, hard to do much more than that, youll run out of material. There are ways around it but it will get into a whole lot more time.

 

Before i get into this too much, If i do a moderate porting job on the base, edelbrock runners and plenum will I be losing any of my low end power?

 

nope

 

sweet, just what i wanted to hear

 

You can acheive a big difference in TQ by porting the front of the plenum to match the throttle body. If you open the TB blades you will notice that there is a ridge that runs along the botton of the plenum the severly restricts air flow even for the stock TB.Get you your grinder to clear and shape that path entering the plenum and open the plenum holes to match whatever TB you go with. You will see a bunch of area's that can be smoothed out.Just be carefull when doing the sides not to go thru as those humps aren't as thick as they look.That made a big difference on MY 88 IROC. Other than that just port match the plenum to the runners, open the plenum and cut it to match the runners.I did use long strips of sand paper to try and smooth out the inside radius of some SLP runners,kinda like using a towel to dry your back.Pulled one side thru the other and back and forth,but I don't know how much it actually helped.

 

Thanks for that info, i'll be sure to do to that.

 

You can do something similar and cut the divider wall out in the plenum to match,there are some obstructions behnd the piece removed that will help. You wont notice anythign huge but every bit helps with a TPI

AS&M runner

 

Nice !!!!!!!!!

 

Ok, got my runners in and looked at them, there are some slight indentations on the sides of both sets of runners. I cant tell if they where made like that factory or if something has happened to them, if anyone else has them are they completely smooth all the way around or is there supposed to be indented in places for mounting? my main concern is because the dimple is on the inside of the runners as well.

 

I have a set of the edelbrock runners, and they are round inside, no indentions. You have to use allen bolts to keep from cracking and breaking off the bolt holes as cast. If you have indentions, they were cast into the runners.
I port matched the plenum and the manifold, the biggest problem is gaskets. You have to modify the gaskets to match, or they are going to restict airflow.
I think there is no real difference since I don't flog my 24 year old engine that much, just smooth transitions from cruising to wide open, and maybe a short burnout or two once in a while.
In 110-115 degree heat, flogging means walking.

I think the runners are not really a benefit.

The heat sinks on the sides of the runners soak in the heat, and give up the heat to the incoming air that is cooler than the runners. This makes the runners a hot air intake mod. Not a cold air intake mod.
I think whatever flow you get from them is negatively impacted by the addition of heat to your intake air.
They just look cool with the ribs on the runners.
They might work better if you can keep them cooler or with a cold engine.

 

Are you talking about the (intential) indentations made for the injectors? A good clue would be indentations which exist on both set of runners and/or are PERFECTLY symmetrical.