RPMS Posted April 27, 2004 Share Posted April 27, 2004 Hey, guys! I'm about to replace the intake manifold gaskets on an EFI chevy 350 block. The gaskets have metal knockout plates in two places, and I'm wondering whether I should remove them out or not? The aluminum 305 intake I looked at had a blank space in this area, the 350 intake seems to have a coolant passage there. Is there any reason I'd want to leave this in place? Of course, there are no instructions given with the gasket, and the repair manuals are silent as well. Thanks, I appreciate any help. Quote Link to comment Share on other sites More sharing options...
TOMAHAWKZ Posted April 28, 2004 Share Posted April 28, 2004 Leave them in place. I believe they began putting them in to somewhat restrict the flow thru the intake on fuel injected motors, for what reason is a good question maybe someone else can chime in but gm engineers usually have a somewhat good reason behind their thinking..at least the powerplant group. cant say much for their body design people.. Quote Link to comment Share on other sites More sharing options...
labrat Posted April 28, 2004 Share Posted April 28, 2004 You may want to make sure that it is a water passage and not exhaust passage through the manifold. To be emissions compliant and re-vaporize the fuel that falls out of the mix, in the 70's they started routing exhaust through the intake right under the carb to warm it up. This improves HC emissions, but robs power. There should be instructions with the gasket set as to which years need which restrictions (one, none, or both), but I usually block both of them if possible. What's the use of a cold-air intake if the intake charge is gonna be heated in the manifold by exhaust anyway? Go one better and get an Air-Gap manifold, that way the runners are not even heated by engine oil splash... my $.02 Bill Quote Link to comment Share on other sites More sharing options...
TOMAHAWKZ Posted April 30, 2004 Share Posted April 30, 2004 i may have mis understood your question. are the metal plates in the center of the gasket or at the ends where the water passages are? if they are in the center labrats suggestion is correct. Quote Link to comment Share on other sites More sharing options...
RPMS Posted April 30, 2004 Author Share Posted April 30, 2004 No, the knockout plates are at the end of the gaskets. The passage in question is at the very back of the block. Quote Link to comment Share on other sites More sharing options...
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