Anybody know some good links to look at for porting some stock swirl ports? I saw the top posts, the guy talking about getting some extra HP out of them. Anyone know of what I need to replace if i take the heads off, just the gaskets, right?

 

The owner to whom you refer was (and is) Fast355 and his original thread was called something like garage ported 193 casting. If you search with his username and the terms 193 casting you'll find it. His flow numbers are listed along with the dyno results he obtained (267 rwhp IIRC which would be over 300 at the flywheel). A comparison of his flow data with other factory heads is included elsewhere on that thread if you scroll down through the posts.

"Yes" on the gasket replacement, but if you are going to the effort of head removal and then DIY porting, then you ought to replace the valve seals and clean up all the casting flash to help the oil under the valve covers flow more easily back into the engine.

 

When disassembling the head be sure to organize all parts so they go back exactly.

Do not use rolocs to clean the head surface (okay on intake). Use a scraper.

Open up the area under the intake valve seats (obviously do NOT hit the valve seats). You want to reduce any ridges, everything should be a smooth transistion. I choose not to open up the intake runner because it bottle necks to the swirl port soooo it is a waste of time. The surface finsh should be slighty rough to (smooth to the eyes) to help with fuel atomization.

On the exhaust, reduce the short side radius and polish the exhaust runner to mirror finish if possible.

My stock 350 heads did not have a valve shrouding issue, but my 305 heads had a major shroud issue. If you have shrouding, take your new head gasket and mark the bores. Than grind away until you have atleast 1/8 inch between the valve margin and the side of the combustion chamber.

You can also get your heads milled to minimum spec (your machinist will know) to get rid of some CCs to increase your compression ratio. If you do that polish your combustion chambers to reduce hot spots that can lead to detonation with your higher compression.

I have my heads done, and the valves are already in them or else I would show ya.

 

Looks like I need to do some more research. Does anyone have a book they read on how to do it or such, a solid tech article?

 

Its not really a task for an untrained person. I am still learning and it is much easyer on aluminum heads.

 

TWICEtheRICE, what are you running with the combo in you're sig... and if you haven't run it yet, tell me how she's running, 'all around'. Thanks.

 

Everyone is untrained the first time they port heads and you're right that it is easier on aluminum than iron just because aluminum is softer stuff.

As far as resources here's two.

1. David Vizard wrote a very handy book called Small Block Chevrolet Cylinder Head Porting that's not hard to find (try Amazon).

2. There is a very nice tech page linked if you start at https://www.thirdgen.org; there are some very handy Tech Articles. One listed is on head porting. There are also several head-porting threads, many with pix, that I linked into the 193 garage casting post that I mentioned above. Click on the highlighted regions in my post for the ported head flow examples.

The bottom line is that there are a lot of resources here at TGO -- but you have to look for them and then take advantage.

Head porting the swirl port heads is not much different than on any other head. The exhaust port flows ok for a stock head to begin with so even a mild cleanup on that side, along with smoothing the valve guide, will work fine. On the intake side, the swirl ramp isn't the obstruction many people think it is because the part of the port that it blocks is a low flow area --- any stock gen 1 sbc head flows poorly there because the airflow is already biased by how it enters the cylinder and by the intrusion of the pushrod wall. The bias isn't a bad thing because it helps get the mixture rotating (swirling) when it enters the cylinder, and the rotating flow will burn faster than it would without the swirl. So the swirl ramp gets smoothed during porting, but not removed, especially the last part of the ramp that is visible down the intake port from the manifold side. The rest of the usual porting stuff also applies. HTH.

 

Chevy SB 350, Bored .060, Stroker Crank, 454 TBI, Edlebrock Performer, Dart 200cc Platinums, 218/224 duration cam, .480 lift w/ 1.6 roller rockers.

Desktop estimates 400 ftlbs @ 2000-4000 / 330 hp @ 5500

See I just graduated from college now I have a job and I bought a firebird with a blown engine (3rd Gen F-body dream car since child) and I took the engine out of my truck (rust in pieces).

One thing that sucks about working full-time, you don't have any free time and weekends are for getting drunk and hangovers. My goal is to get this car running before the end of this month.

Heres my baby all grown up:



Going to the junkyard this week

 

Do a search for "Sitting Bull" on the boards, he has a great head porting thread listed in his sig. Or just do a search for Sitting Bull as the poster and "305 head porting" or something as the search term.