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Old 06-04-2006, 09:15 AM
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Exhaust port size on stock SBC heads?

I have a set of stock 14014416 heads on my 305 and need to to know the exhaust port size. Does anyone know, or know where I could find the size?

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Old 06-04-2006, 10:00 AM
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Port size

I usually take my calipers and make the measurement. If you are looking for just the general dimensions, the caliper is the quickest to measure the orifice. Plus, no stock heads are exactly the same. They are all close to the general casting, usually within a +/- .010" tolerance from the OEM specs.
Are you trying to match up headers?

Or are wanting the cubic area of the port?
Cubic area is quick and simple. Your valve must be closed first, pour some water into the exhaust port until it is full, next draw the water out with out spilling any of it and place it into a measured cup, or the use of a large syringe with CC measurements. Once all the fluid is drawn out of the port, then you should have an approximation of the port capacity. Some machine shops use fine granular sand to do the measurement. This is the best way to actually get a real close port capacity reading.

Last edited by LordMaximo; 06-04-2006 at 10:07 AM.
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Old 06-04-2006, 10:54 AM
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Quote:
Originally Posted by LordMaximo
I usually take my calipers and make the measurement. If you are looking for just the general dimensions, the caliper is the quickest to measure the orifice. Plus, no stock heads are exactly the same. They are all close to the general casting, usually within a +/- .010" tolerance from the OEM specs.
Are you trying to match up headers?

Or are wanting the cubic area of the port?
Cubic area is quick and simple. Your valve must be closed first, pour some water into the exhaust port until it is full, next draw the water out with out spilling any of it and place it into a measured cup, or the use of a large syringe with CC measurements. Once all the fluid is drawn out of the port, then you should have an approximation of the port capacity. Some machine shops use fine granular sand to do the measurement. This is the best way to actually get a real close port capacity reading.

For port size, the easiest way for a novice is to fill the port with windshield washer fluid using a large veterinary syringe. Ports are measured in CC's.

For port dimensions, measure them with a dial caliper.
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Old 06-04-2006, 02:11 PM
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The heads are installed. I can't pour anything anywhere. What I am doing is, I kinda got ripped off on some headers. They don't fit the stock motor mounts, which I didn't find out until installing them, and they have the round ports vs. the rectangle. So I decided to design some myself, and possibly build them when I take my refresher in TIG. So I need the width and height of the ports.
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Old 06-04-2006, 03:14 PM
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Quote:
Originally Posted by kringold
The heads are installed. I can't pour anything anywhere. What I am doing is, I kinda got ripped off on some headers. They don't fit the stock motor mounts, which I didn't find out until installing them, and they have the round ports vs. the rectangle. So I decided to design some myself, and possibly build them when I take my refresher in TIG. So I need the width and height of the ports.

I see. What I might suggest is to get a set of exhaust gaskets and put them up to the heads to determine the size needed. Headers can be oval or rectangular where they meet the head. Headers are usually larger than the port outlets of the heads themselves. As long as the header inlet is larger than the head outlet things are good to go. (the step is said to stop reversion).

You could also make a paper pattern of one port by holding a piece of paper over the open port and then rubbing your finger on the edge of the metal to make an indentation in the paper. That would give you an exact pattern to measure directly from the paper.

Unless you are adventuresome, I would suggest purchasing a set of headers for your specific application.
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Old 06-04-2006, 08:08 PM
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The heads are installed and on a daily driver. I don't want to tear the engine apart just to get the port dimensions.

Quote:
Originally Posted by xntrik
Unless you are adventuresome, I would suggest purchasing a set of headers for your specific application.
I did, that's how this started. The ones I bought don't fit, like I was told they would. They hit the motor mounts.
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Old 06-05-2006, 11:32 AM
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Quote:
Originally Posted by kringold
The heads are installed and on a daily driver. I don't want to tear the engine apart just to get the port dimensions.



I did, that's how this started. The ones I bought don't fit, like I was told they would. They hit the motor mounts.

Ah, I see. Is there a motor mount problem or just the wrong headers?
Try for a refund on those headers if they cannot be reasonably modified.

I suggest you use the gasket idea. Gaskets will always be bigger than the ports but will give you a dimension to work with.
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Old 06-05-2006, 05:13 PM
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Quote:
Originally Posted by xntrik
Ah, I see. Is there a motor mount problem or just the wrong headers?
Try for a refund on those headers if they cannot be reasonably modified.
Tried the refund shot. No go. They told me the headers fit on all the short blocks they know of. Told me I had to swap out motor mounts. Well that's not fitting then! And the headers have 1 1/2" diameter round ports, while the heads have rectangled ports.
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Old 06-08-2006, 08:05 PM
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What car? What frame? What kind of mounts? If they're the old style big "box" looking mounts, there are many applications that required the corner of the motor mount to the block to be cut out for header clearance. Done correctly there's no loss of strength or safety. I've seen this dozens of times. How bad does it hit? A smooth roll in the tube has no adverse effect on performance. You may be amazed at how little interference in one area grows to huge by the time it gets to the mounting flanges. Just some things to consider before jumping into header fab. Very time consuming, but fun if you like to fit and weld.
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Old 06-08-2006, 11:57 PM
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It's a 305 in a 1984 Chevy Caprice Classic. It has the old biga** mounts, which I think it would be a major pain to pull the motor to cut the mounts. Plus I think I may have to cut too much out for them to fit. See attachments.
Also I would be doing this for a welding class, so I should have everything I need to fab. them, including a tubing bender and a Bridgeport milling machine. I went with the gasket idea and came up with 1-5/16". I may go bigger later to allow for the tubing.
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Old 07-04-2006, 05:08 AM
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Yeah late reply but...yes those are the ones. You can remove a schitt load of mat'l off those with no problems. I had a whole corner whacked off a BBC with that mount and had no issues. It wasn't much of a motor tho. Only 477 cubes and just over 14:1 pistons The car had 1.40-1.42 60' times and ran over 400 passes...on the stock mounts! If you think pullin the motor's a pain, get started on the headers. I do understand the welding class angle tho.
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Old 07-04-2006, 02:42 PM
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I have a set of headers just like that on a 400sbc and they barley clear the old truck style mounts like 72 or older...Somthing else to consider if you havent already...are you sure you can get exhaust pipe on it after you do all the clearancing? It looks like there is a crossmember in the way..
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