Porting sbc heads?

[RCJ]

4412 holley ,150 cranking, 14 inch, the head won't be holding you back. 88%, 1.94 valve ,a good valve job is going to get you 95% there. Find somebody that has a cam and c/r combination ,put the best piston and ring pack you can afford. Heavily restricted rule are about low drag efficient motors or cheating

[steve cowan]

Hey Steve, please dig up a post on here where I ever eluded to being anywhere near the best ok?

There all stored on here to be looked back on so you find one, and until then stop your comments ok?

Mag,
Not directed to you sorry.
The Dave B guy is who I referred to.

[Tom68]

or cheating

How about a 12v vac pump mounted in the valley and passing the mandated 3/16 fitting (extended) right through a runner and onto the pump.

[88bluestar]

Mag, I appreciate your and everybody elses help and opinions.
I have to clean the 991s up and get them checked for cracks etc.
Would a slight gasket match be worth anything say a 1205 fel pro. 2701 intake can not be ported unfortunately.
Again it will be on 91 octane pump gas but eventually I will convert to E-85.

[mag2555]

Thank you for the clarification Steve.

[F-BIRD'88]

I say port the livin hell out of them save for the intake opening at the intake flange. Use common sense there based on the intake manifold used.
1.94x 1.50 valves (add a back cut?). Give 'em hell.
If the 991'have the twinned center exhaust heat risers like a 882. stuff 'em tight with HD balled up thick aluminum foil. (aluminum catering baking pan)

[SpeierRacingHeads]

Just for the record, your not getting anywhere near 290 cfm@28” out of any iron head that ever came out of GM / the factory
bolted to a production block.

Max ported with a 1.94” valve getting 260 cfm is a large challenge and had better have a flow bench at your disposal!

Why couldn't he?
We have heads laying here from 1970s that were factory production and raced in back then.Those heads had ports moved around and filled ,different valve sizes etc.They flowed over 290 then and still do.You think those guys had 1020 benches or cfd to work with then? It amazes me people waste their time with dinosaur parts when current tech will run circles around this stuff.Every day I see guys on here that have 383 or whatever that run 10.50s .We have a stock headed LS Vette that runs 9.60s @3500 plus so far with no flow bench ,no cfd blah blah. We don't have slicks or race tires or weenie bars, Just factory LS stuff and parts from jegs. I see Chad put all this effort into ancient tech that guys have beat to death for years.Why try to run a 60 yr old head design that guys go as fast with at 290 inch that you can with chads 358. I guess I don't understand living in the past or constantly going backwards.There are so many ways to polish a turd and it's been tried all ready, 1000s of times.Look up guys like Randy Wilson who ran mid 9s with this old tech and he did it years ago.He had iron gm bowtie heads,same port sizes,same epoxy blah blah.He ran lb per inch.So if he ran a 296 he weigh 2965 or so at 10 lbs.Like I have stated other times my father had these same small engs ,same dinosaur parts in 70s and made over 600 hp then.So what so exciting about doing the same now ,50 yrs later ? Same bat shit ,same bat channel..Some of you guys need to lose your 1950 tech reports and let your boys life mag subscription go!

Yea those ancient heads run faster now than they ever had. A set of ancient SS heads still bring $8000. I've never seen a fast LS in Super Stock. Maybe the COBO stuff. But that doesn't work for a 68 Camaro now does it!!

[SoCalDave]

Mag, I appreciate your and everybody elses help and opinions.
I have to clean the 991s up and get them checked for cracks etc.
Would a slight gasket match be worth anything say a 1205 fel pro. 2701 intake can not be ported unfortunately.
Again it will be on 91 octane pump gas but eventually I will convert to E-85.

Gasket matching heads and intake manifold won't make you competitive. Take off the intake and exhaust valves to see the bowls and valve guides. That's what you should modify.

[88bluestar]

I plan to clean up the guide boss(How much should be taken off?), and go by what recommendations I get from this site. I realize the intake and carb are already a restriction so I dont know about getting to crazy with a burr, but if I can gain something to help pull me to the flag stand than thats a plus.

[Alaskaracer]

Grind the ports until you hit water then back it off about .060"......

[Tom68]

I'm surprised there's no love for the 2.02 valve, since this engine will be 4412 restricted it will have high manifold vac at high valve lift, assuming a 2.02 flows more at low lift than a 1.94 (it bloody better) that's one way of getting some fill from a week port flow situation, I'd have thought.

[mag2555]

Everyone’s always looking for more high lift flow, but first how about producing more flow at a time when the compete intact is not saturated with whatever level of peak flow that it can produce?

When this is done any motor will hold on longer to the peak hp that it can make before it nose dives.

This is worth performance too!

It’s well known that the Valve D x .18 simple formula
Shows for example that with a 2.02” valve that up to around .360” lift that the amount of air flow produced is mainly in control of the valve job ( however many angles and there width) and the back head shape of the valve and it’s angles.

This requires flow bench time and the ability to test these parts and angles.

So like I asked at the start here why is this not optimized first so many times?

[rebelrouser]

I plan to clean up the guide boss(How much should be taken off?), and go by what recommendations I get from this site. I realize the intake and carb are already a restriction so I dont know about getting to crazy with a burr, but if I can gain something to help pull me to the flag stand than thats a plus.

Not an expert, but what I do is simply grind them like a airplane wing. Just radius the edges and blend them into a teardrop shape. One thing is air hates to go from a large cavity into a small cavity, so don't take too much off the guide bosses. I know performance heads are cast with very little guide boss but the port volume is designed that way. Also you will notice more space on one side of the guide boss, that is biased to provide swirl toward the spark plug, be careful about enlarging the small side too much it will reduce swirl in the port. The main place is the valve seat and the area right below and above the seat, you will get most of your flow there.

[Elroy]

I'm surprised there's no love for the 2.02 valve, since this engine will be 4412 restricted it will have high manifold vac at high valve lift, assuming a 2.02 flows more at low lift than a 1.94 (it bloody better) that's one way of getting some fill from a week port flow situation, I'd have thought.

With high vacuum in the manifold at WOT, which direction do you think that low lift flow will be heading?

[mag2555]

This works in conjunction with maximizing valve job flow ( D x.18, and the 85% rule .