Does anyone know the measurement to drill out the intake manifold? I assume the holes have to be the same size as the holes on the heads, correct? I guess I take a caliper to the measure what the size holes are on the heads and do the same to the intake manifold?
also Lets say I want to port my heads my self (obviously will need new springs and stuff) (with the help of guys at a machine shop where I work) any one know what the process of that would be? or the measurements?

Just trying to save some money, I got guys at my work who are good at this stuff (meaning working on the machines and very smart ppl) Just curious if i can do it.

 

What a lot of people do for the runners on the heads are take the gasket and line it up, take a marker and mark the openings. This is where gasket matching comes from.

 

I wouldn't touch that.

Intake ports should be slightly smaller then the heads. Leave that kind of stuff to the pro's, since you can easily ruin it by porting just a tiny bit too large and causing turbulence from the now protruding transition into the cylinder heads.

 

Unless you're a complete idiot, you can get this done easily. Score the ports and do not pass the lines you made, that simple.

As for porting the heads, just read up on the tips and where the power from porting comes from. If you feel comfortable with taking a carbide burr to your heads then go for it.

 

Thats what I did to port the intake holes to to open the TB to 58. I can do the same thing to the bottom of the intake manifold with the gasket i got?

 

You'll get mixed reviews at to port matching. You can go ahead and polish as much of the inside of the intake as you can reach though.

 

so how far do they go into to porting the bottom of the intake holes? I see that they go deep inside, it would be obvious to port that but just curious

 

I can tell you that the term "port matching" is a very elementary topic. You won't see or hear that phrase in many of the big wig engine builders vocabulary.

 

so your saying I shouldnt do it that way?

 

Most don't even bother with it.

 

why is that?

 

Because, if that is all you do to the runner it kills velocity?

The LT1 is not like the old school small blocks. The heads got a lot of developement before they went into production. They are actually better than the older Bowtie heads. Even with small valves.

 

If you "port match" without full porting you create a fat spot in the middle of the combined intake/head port which causes the air to change speeds TWICE wasting energy.

We have examples of unported stock intakes solidly over 400rwhp. What do you think you are going to gain with such a mild setup?

 

Definitely true, stock lt1 heads aren't the end of the world. No need to do work on them if it's not going to help you.

 

The other thing is depending on what intake and what heads you have the intake ports can already be bigger than the head ports.

 

Well using the intake gasket will solve the "over porting" issue if you don't go past it.

 

Most race engines builders who I'm aware of will flow the heads and, they will flow the intake with the heads. If the intake reduces flow considerably, they'll port the intake to improve flow, shape, etc.. Ideally, the intake runner is simply an extension of the head's intake port leading to the plenum. The 'bad' comes when the ports are matched but, mismatch once assembled. Always a good idea to check...

 

https://ls1tech.com/forums/8935624-post17.html
Most of you would consider Lloyd's opinion gospel so take it from him.

He has posted about a gasket match being a poor idea many times on multiple forums over the years.

Most other head shops wont get into details about their work like this so he is probably the only "LT1 professional" you are going to find written quotes by about this.


Things can change if the whole port is reshaped by a professional and as someone said earlier it can be useful to make the head port slightly larger than the manifold to stop miss alignment from creating a shelf that disrupts airflow.