So after coming back from a Slant Six Racing get together I am revitalized and ready to dive into some performance concepts.

I have read and watched quite a lot of information on port matching and polishing but I have a few questions.

It appears it is best to leave the intake port slightly rough. Is that correct?

On the exhaust port is there so such thing as to polished?

Do I want to polish the combustion chamber or leave it rough like the intake?

Is there any reason to also polish the intake and exhaust manifolds? If so how deep do I want to go into them?

Any other tips or suggestions?

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2006 Jeep Commander
2013 Chrysler 200

1964 Valiant 4 Door
1965 Plymouth Barracuda
1967 Chevy Camaro

Intake needs to be slightly rough to break up the fuel. I've heard mixed reviews for polished or rough chambers. I personally think same grit as intake. Exhaust can be polished, no reason to be like the intake. If you are going to port the head, then its a great idea to match manifolds. I would think as far back as you feel comfortable doing, aslong as its a smooth transition.

Its helpful to drill a guide hole to insert a locating pin to locate the intake and headers when you bolt them on and match your gaskets too. Since there is no way to positively re-install either when you bolt them on, if you cant line the ports back up with the intake or exhaust to align with the ports in the head, it really isn't going to be of a lot of benefit.

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There's no such thing as too much cam....only not enough engine!

When I see some folks gasket match what they do is blow out the port runners to match the gasket opening on the head and manifold sides. I don't know the benefit to having a runner of x volume, suddenly enlarging then contracting.
To get good flow, you want to be sure the intake port edges align.

You can do this by making a head port template.
Get a piece of light construction paper, rectangular size that would cover the head face with the intake and exhaust openings. Installl the center intake stud and two outboard intake studs in the head. Set the construction paper on the manifold face of the head, using the three studs as dowels to hold position of the construction paper. Using a light hammer,, tap the construction paper at the edges of the port openings,, they will preforate easily,

while still on the head, mark the construction paper,, intake manifold side..up - down etc....

Remove the paper template and set the side marked intake manifold side on to the intake manifold, using the center and outboard holes to align the template to the intake.

You can now see how that intake manifold aligns to that cylinder head.
If you see walls on the intake port inside of the cutouts, mark with a sharpie and open those to match the template.
If you see the cardboard overhanging the intake port opening, that indicates that metal from that location needs to be removed from the head.

You can save the template and if a year down the road, you find a different intake that you want to install on that head, pull the template back out and you know what needs to be done.

I would just dyekm the head and manifolds (bolted together) use the gasket to as a guide to scribe the ports. On the head side the studs will hold in place. For the manifolds, 3 bolts in the center of the intake will place it where it needs to be.

Gasket matching assumes the hole in the gasket is the proper size. That's a big assumption. If you examine the intake port face of a slant head you'll find it's a little bit larger than the manifold port to account for minor intake manifold misalignment. There should be a step up in size from the exhaust port of the head to the exhaust manifold/header. This again for misalignment, but also for anti-reversion. If you want to grind where it will do good you need to work on the valve bowl and valve guide.

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Joshua

What about casting imperfections? IE rough surfaces or nubs? I am trying to get the most I can out of my build.

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2006 Jeep Commander
2013 Chrysler 200

1964 Valiant 4 Door
1965 Plymouth Barracuda
1967 Chevy Camaro

and that is what many folks do when gasket matching ,,it makes sense to increase the runners to the gasket size, only if one was making the entire runner tract larger.If the runners are just being cleaned up,, why is a good thing to have the largest runner cross section in the middle of the run? That is what you get when you cut the port openings to match gaskets openings.

Josh's comments are on track
it is not helpful to have the gasket crossing into the port opening,, exhaust port openings in the head are typically smaller than the exhaust manifold or header opening, to help prevent flow reversion. I was speaking to intake port matching.

So what I am getting is that I should polish the exhaust port. Clean up the intake port and possibly increase to gasket size.

On the intake manifold I can match it to the head and again rough polish. On the exhaust. I should just polish and not increase the size.

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2006 Jeep Commander
2013 Chrysler 200

1964 Valiant 4 Door
1965 Plymouth Barracuda
1967 Chevy Camaro

I would not mess much with the intake manifold unless the runners have odd shapes or flashing. I wrecked one by gasket matching. You want the intake runners to stay the same size. You can clean up the intake on the head like Josh mentioned (bowl port) so it is bigger than the intake manifold runner. This really helps reversion when it's cold.

On the exhaust manifold runners I squared them up and cleaned them (lots of little casting bumps and ridges) out as far as I could reach. They are bigger than the head, again to reduce reversion. At the outlet I opened it up to a full 2.25" and went up about 4" at that diameter. On the head itself I just touched up the ports so they were square.

From dead cold to running temperature the engine pulls hard.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

It doesn't but if making a mild slant six for street and porting to the size of say a 'felpro' gasket then you really aren't losing anything on the intake side- about .045"?/exhaust size he might have some grinding to do(using a short stick the high vacc. will overcome this at any street speed, if he goes lots of compression and lots of cam for strictly race, this will change a lot- if he put a fat pak on neither the gasket or the head ports are large enough to match the manifold).

The real pinch in the stream of things is in the bowls and the valve guide boss as Josh states...

-D.Idiot

On my Offy intake manifold there is a reverse step necking down right at the flange. So by port-matching I basically made the manifold opening the same size as the runners.


And as DI pointed out the intake port opening and the Remflex gasket are the same size within .020-.050 on my head. I only really had to open a few spots to match the size/shape of the openings. The exhaust ports are a bit smaller than the gasket so I just made them even all the way around without enlarging them to match the gasket.

I did some minor smoothing on the inside radius and floor of the ports. A way to get all the floors alike is,
once you have an inside radius and floor that you are happy with, use a maleable wire, I used solder, and fit the wire along the contour of the floor.
Then remove the wire and make a trace of the contour on paper.
Then fit the wire to the floor of the port that you will work next and trace it on paper.
That will give you a visual on the differences.
Then work the port, re fit the wire to the floor and compare to the trace of what you are after. Repeat as needed.

Time consuming, but this gives you a shot at getting all the ports about the same, and consider the work mentioned here minor tweeks, the biggest gains will be in larger valves, multi angle seat work, bowl work...

I always open the intake ports to a minimum 1/8th of an inch bigger than the gasket. I mark the face of the head with a permanent marker. This creates a ram type anti reversion step.

Exhaust, I gasket match the sides and top. Smooth the bottom. Don't want a lazy exhaust.

Chambers get polished till they are shiny. I pay attention to the flame travel path from the spark plug hole towards the exhaust valve.

Lots of gains are in the bowls.

Unshroud even stock valves.

There is a small block Chevy porting book out there worth buying.

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

I would definitely be interested in the book if you can recall the title or any details. I have read a bunch and watched a bunch of youtube videos and EVERYONE has there on idea of how it should be done.

I think what I am going to do is rough finish and gasket match the intake on the head. While in there try and create a good flow path. On the exhaust side of the head I am going to polish to the best of my ability.

On the intake/exhaust I am just going to clean up any casting imperfections. Maybe polish the exhaust manifold and open the outlet to 2.5 inches.

On a side note nobody warned me the that mother weighed as much as a house. $#!+ I just pulled it and I think it must weight close to 100 pounds.

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2006 Jeep Commander
2013 Chrysler 200

1964 Valiant 4 Door
1965 Plymouth Barracuda
1967 Chevy Camaro