Hye guys I am runing what sin my sig right now, I was going to order a nitrous kit and spray it a little but I think i'd rather get my heads all done up first, What do you think I would get from my heads being port and polished and having 2.02 /1.60 valves put in? Would it benifit a whole lot?? thanks guys.... Also what does that kind of work usually run at a machine shop? thanks again

 

i wouldn't run anything more than 1.96/1.5 in Vortec heads. They need big time porting and whatnot to realize the benifits brought on by 2.02 intake valves.

Do a search on what Vortec heads like. I can tell you straight up right now, In many cases, its best not to touch the intake side and concentrate on the exhaust side, as the intake design is a pretty good one.

 

those small 64cc cc's shrowd the bigger intake valve a lot too... i say leave them 1.94's in there and spend the extra cash u have left over on better valvetrain parts or more time for porting - thos eheads have alot of potential!

 

As said earlier don't port the intake runners, just port the exhaust. The intake port is about as good as it can get, and porting will really screw up its refined design. Now on the other hand the exhaust on Vortecs really sucks. Port that sucker up nice and leave the valves alone.

 

Your Vortec's will respond to porting and larger valves.

Have verified this on a flow bench.

Went to 2.02-1.60's and completely ported the intake and exhaust port using standard porting techniques.
They were not "maxported" but were cleaned up and profiled. The chamber got minor relieving and contouring to accept the larger valves. Mostly to smooth out the cutter ridges from the new valve job. Nothing you can't do your self. I'd say less than 7cc's of metal was removed from each port. Flow increased from 228 to 245+cfm at high lift. (.500") Was hard to test because kept sucking in the
inlet radius putty on the intake port. We gave up at 245cfm@.500". (very good volocity)
The larger the cam lift the more benefit you'll see from "max porting" a cylinder head. You do not want to or need to make the ports huge. If you want a huge port then buy some big *** Dart 215's or 220cc heads.

Many people do not recomend touching the intake port.
its true if you're just going to get in there and monkey around a bit. The stock port is pretty good as is. You won't gain much with the stock valve. but if you going to move up to large valves and fully (moderately) rework the whole port, you'll get a good gain in flow.

The motor (406ci) seems to run real strong (very traction limited). No timeslips yet. The porting certainly didn't hurt any.

 

Really because Carcraft had a professional head porter who has been doing it for 300+ years port some 062 castings, and only gained 10cfm at .600".

http://www.carcraft.com/techarticles...rt/index1.html

 

Well I guess I just don't have as much experience as he.
He must be the all seeing lord of cylinder head porting.
Why with 300+yrs of experience. Imagine.
My *** if Car Craft says you can only get 238cfm out of a Vortec head, it must be so.

Give your head a shake.

I read that article. used it as a guide along with .....well less than 300years of my own experience.

It is not unusual to get 260 to 270cfm out of these heads with "professional porting."

238cfm is decent flow for a street head on a 327 or 350.
My effort was purposely not a "max port" effort. My cam only has .500" lift. Any improvment that would only help at .650" lift+ are meaningless. I do not want a set of heads with ultra thin port walls. (durability).
We did multiple test on the intake port. It keeped sucking in the radius puddy. Like I posted above we gave up at 245cfm @.500". It was well within my goals. There is definately room for more.

 

F-Bird

I didn't mean to insult you, if i did i'm sorry. I was just simply stating that if a professional can only get a +10cfm gain, what would the average guy get. Probably worse. There are other members on this board that ported up and installed bigger valves in some vortecs and lost a bunch of flow -50 cfm.

I know your peak flow numbers are awesome but what about your lower and mid-lift flow where the vortecs shine?

 

If you read the article closer, he didn't put much work at all into the intake ports, he focused all his time on the exhaust ports, as is shown with the flow numbers

 

also in that article i don't think they went to bigger valves did they? i think they just kept the stock 1.94/1.5

 

You both are absolutely right they did not add bigger valves or do anything to the intake port other then gasket match. They did port the bowl and chamber, and really port the exhaust. They also didn't hurt airflow at low and midlift either, which heavy porting will do.

 

i actually have the same heads on my engine, pulled them off a 96 truck mine are the crappy ones though, 906 casting i think, not sure off hand, but apparently those ones had something wrong with the exhuast port seat or some thing that hurt air flow? i was thinking about taking them off and porting them up. i probly should go that crazy on it though right? being as how my cam is only like .490's lift. I defenately don't want to change the valves though i just think that it isn't worth it for the money you'd have to shell out at the machine shop. how many people you know that have done it themselfs? do i have to worry about wrecking them, like how much can you take out before the walls get to thin?

 

Also, F-BIRD, if you would, could you elaborate as to where exactly you removed the ~7cc's of metal?

(I think we need a sticky or something on how to get the most out of Vortec heads or something, a thread that covers every aspect of Vortec head modification)

 

Generaly you can follow the article and pictures.
i didn't do or try to do anything trick or much different from the article. I did raise the roof of the port some.
if you look at a stock vortec head's roof there is a bevel
right near the port opening, Where the roof is lower than the opening. I basicly blended this back to the bowl, raising the roof slightly. I also opened up the pushrod pinch a bit. The rest was justt general cleaning up and contouring the guide boss and bowl below the new valve job.
If you follow this article and what David Vizard shows in his books on cylinder heads you'll do fine.
Same on the exhaust side.