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Old 10-16-2002, 07:01 AM
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Post intake gaket match?

I keep hearing different things saying that intake gasket matching is not necassary is this true? While i got my heads off my 350 i want to do something what should i do?

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Old 10-16-2002, 08:12 AM
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Gasket matching certainly does not hurt any engine, just be sure to match the manifold ports as well as the head ports. The only precaution that I would offer, is that you completely disassemble the heads before starting the port-match work. Otherwise you will get grinding grit into the valve guides/stems, valve springs/retainers, etc. Good through cleaning afterward with HOT soapy water is absolutely necessary! Have fun.
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Old 10-16-2002, 08:18 AM
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I've heard that it would be better to have the ports on the heads just a little bigger than the intake ports so that air can't hit a wall and cause turbulence.
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Old 10-16-2002, 12:24 PM
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Well, according to David Vizard (how to build & modify chevrolet heads from mbi powerpro series book)
making intake port as wide as gasket is indeed hurts flow. And it makes sense since air gets one more turn
at port. and that part of head is not usually even restriction.atleast before you make it restriction.
Very meny people does it but i think that flowbench does know better...
if intakeport in the head is a little bigger than manifold it doesnt really matter(it may even help sometimes because fuel gets back to airstream because of little turbulens that step creates) but if manifold is bigger it hurts flow.For obvious reasons.
You may disagree but its only what ive read and it does make sense...
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Old 10-16-2002, 07:01 PM
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Any abrupt change in the port wall will cause the air stall at that point decreasing flow on the outside of the port. I think this is very minor at the intake, and will only make a difference if the head is reaching its flow peak. Just my opinion from thing I have read, but you know what they say about opinions.

chris
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Old 10-16-2002, 07:40 PM
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It's important to remember where the restrictions are in a poppet valve engine, and that is the valve, and it's related components, namely the valve seat and valve guide. Generally, on stock heads, the intake port opening is not an area of restriction in comparison to the valve pocket area. Grinding the intake port opening to the size of the gasket doesn't enhance anything but the image of race ports dancing in the mind of the guy grinding away at the port opening. Enlarging the intake port is only recommended if the opening is causing an obtrusion from incoming air and fuel.
Now, enlarging the intake port opening to maximum is required when you are getting that last bit of volume out of the ports you have, once you've maximized the bowl area, and the rest of the port, you need to try and match the aperature to the rest of your work. This is what is done on a max effort race port on a competition engine. This leaves the head thin and fragile however, and prone to cracking.
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Old 10-17-2002, 04:07 AM
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I just have a hard time seeing where port matching (ONLY PORT MATCHING) could be a bad thing. I don`t get it. If you remove a restriction, you move a restriction. That equals increased flow. Now i do not think the aversge street guy needs to polish his heads, with todays fuels. I guess the hard part for me to get around is the flow bench thing!!! They don`t lie, how every , port matching has been done for years, and i can`t emagine it being a wrong think to do.. Baffled am i!!! I have all ways port matched. I`ll continue to monitor this thread. Maybe i learned something new. And that`s cool too!!!
Slider in Wa.
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Old 10-17-2002, 11:12 AM
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I think that polishing is okay and if I'm stripping the heads down anyway to port them, I might as well spend the time to polish them also.
I also can't see why port matching is a bad thing. After all, it will allow my engine to breath just a little better and at the same time remain streetable. Plus, it's something that almost anyone can do with a little guidance. Just check out <a href="http://www.sa-motorsports.com/diyport.htm" target="_blank">S-A Motorsports</a> site. They have an excellent guide on home porting.
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Old 10-17-2002, 12:32 PM
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none of the cars out of detroit have their ports matched. does that help you out. i would always port match tho if you want to spend the time, as it also creats uniformity/balance btwn the cylinders, but seems to me bigger hole=more air/fuel. every article on building says to do it. btw ont polish your heads if you run on the street, street motors need the turbulence.
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Old 10-17-2002, 12:52 PM
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Sorry to disappoint but polishing is also no no. polish chamber if you want(and that helps,beacouse heat is energy and it wont radiate as fast from polished surface.if you want to know more,buy or loan a book) but polished port will couse fuel droplets.(fuel and air separates). remove casting flash and other obstructions but leave it coarse.

slider :p ort matching isnt bad thing. what is bad is making port bigger than necessary.those gasket openings are too wide, you cant get port that wide where pushrods are so port must get narrower there. and there comes that restriction there wasnt before you made it. Normally intake ports arent restricted at that area anyway because it flows better than rest of the port. professional porters can get BIG valve heads flow better than pushrod area allows normally but it takes some skill and probably flow bench to get there. and even then its the pushrod area that is restriction,not gasket opening.
But all those who are attempting to port their heads,read a book or two. it isnt that simple as it looks. standard abrasives is just scrathing this subject at their web page and the benefits are well worth that 10 20 or whatewer those books cost there.
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Old 10-17-2002, 03:13 PM
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I always forget, is it no polish when there is fuel (i.e. intake ports on heads) or is it polish when there is just air (i.e. intake plenum on a fuel injected car)? Maybe I just had a brain fart or it's the lack of sleep, but I just can't seem to remember! <img src="graemlins/drunk.gif" border="0" alt="[drunk]" />
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