Just wondering if the stock intakes flow good without porting. I've already got a 52mm tb. This intake and tb are going on a 383 setup. Some say that porting the intake is required for 383's. And some say it hurts performance. Whatcha all think?

 

I think the stock intake flows more than 300 cfm though each port which most ported heads don't flow anyway. So I say no.
The throttle body ports maybe a different matter though. It's my understanding that you want to keep the port velocity high and porting the intake would slow it down if the heads cann't flow the stock intake numbers anyway. Not an expert though. Just what I have read here in the past. Also, I believe the VE tables and tanny tables(A4) should be changed if the throttle body is changed any.

Jeff D.

 

i disagree-
at the least i think it should be gasket matched

 

Well, I don't have head flow numbers but my stage II heads did require the intake to be ported. I not sure is was neccessary but I like the fact that every was matched. They also had to be milled to fit the heads so it was done all in one shot.

 

I had to remove alot of material just to gasket match the intake. The stock casts are pretty sloppy both the intake and heads. Hold the gasket up to the intake and you will see what I mean.

 

Some folks don't gasket match their heads/intake. What is there reasoning?

 

Probably no need until your building a good set up. Someone who just had a intake leak usually doesn't match the gaskets until they get heads/cam etc.

 

The prevailing view is not to port the entire runner but only port match to the heads. If you need larger runners get a different manifold.

 

Depends.

If you're extending the rev range of the engine then yeah, it needs to breathe easier. The intake is just an extension of the cylinder head port.
Just a "port match" is really a waste of time... you'd likely gain as much hp as doing the tb bypass mod. To port the intake correctly, the entire runner volume needs to increase. I'd leave about 1/16 of mismatch at the head to account for misalignment once the intake is installed.
The larger the engine and/or the higher the rpm, the bigger the ports need to be. I'm using a heavily modified LT4 intake and I don't feel it's holding back on power.

-Mindgame

 

no offence-
but i really think its in poor judgement not to port match the intake manifold if its off already...

especially in a big motor where hp doesn't come easy

 

Smaller ports= higher air velocity throught the ports--HS physics. Smaller ports also equal greater bottom end performance but limit top end.

Read the Vizard book about porting chevy small block heads, it really clarifies about gasket matching. It seems that matching to the gasket doesn't do very much till the bowl and throat areas are seriously cleaned up since those areas already flow pretty well...and what does it matter if they are matched up if the port narrows down near the pushrods? Your top end power will be limited by the valve throat more than the ports, plus a little stip is alright to mix up the fuel/air mixture...

 

The intake ports are a hell of a lot closer to the gasket profile than the heads are. I didn't see any reason to port my manifold while it was off. My heads are gasket matched, and fully ported, but it was more of a mild to moderate job so I didn't touch the manifold.

John

 

Most people don't need to screw with it, as you can easily make over 400rw with untouched LT1 intakes. If you're trying to make more, then sure it should be given some attention. Ole 'game is right as usual & trey is ... yeah . If you're out to make lots of power, have someone port it, correct the taper etc. If you're most people with a budget & only want 400rw or so, I don't think it's worth the $ to port it.

Of course, I'm biased.. I hate porting manifolds

 

The gains are so minimal, I have a 383 and never touched the heads or intake, until you start building radical setups the gains are so minimal, you wont feel anything "seat of the Pants" for all that hard work of porting it all.

 

I am going to throw my 2 cents in on this thread for the heck of it. The problem with porting the LT1 intake is this: When porting any intake you want the runner to start large and slowly taper to the head. The LT1 intake does not have enough material up around the injector area to fully port it properly without adding material. If you do anything just clean out any casting flash and bolt it on. Obviously if you are looking to build an outright race engine and have the equipment to modify the intake and add material then have at it. Just my opinion.