400 SBC Queustion
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Instructor
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400 SBC Queustion
OK so I want to build a new motor Ive built many SBC chevy motors. I have a 400 block 1972 out of a motorhome Standard bore nice, new pistons and rings 10/10 crank all new gasket oil pump recon stock rods etc I have a brand new set of aluminum heads from Summit. 76 cc I have heard different opinions on steam holes some say are not necessary. Do I need to have heads drilled 1/8 inch at 18 degrees at the right places or no? I have a pretty good drill press but not sure if I could handle it right myself. Thanks.
Team Owner
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Watch some of these videos. I use a world products intake manifold that is tapped for water flow from the back of the block. A good idea for over 400 ci SBC Are your pistons dished at all? Because my 427 and now 434 ci SBC use 64 cc heads to get compression.
https://video.search.yahoo.com/yhs/s...b&action=click
https://video.search.yahoo.com/yhs/s...b&action=click
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400 sbc
OK so I want to build a new motor Ive built many SBC chevy motors. I have a 400 block 1972 out of a motorhome Standard bore nice, new pistons and rings 10/10 crank all new gasket oil pump recon stock rods etc I have a brand new set of aluminum heads from Summit. 76 cc I have heard different opinions on steam holes some say are not necessary. Do I need to have heads drilled 1/8 inch at 18 degrees at the right places or no? I have a pretty good drill press but not sure if I could handle it right myself. Thanks.
Don't know rear diff ratio 336? 75 vette
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Oh I think maybe less than 76cc maybe 64 Makes a big difference I know
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FelPro head gaskets and yes they have steam hole I was going to us as template for cutting steam holes Nothing like a a 406 SBC!
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Dr. Detroit
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From: New Braunfels Texas
On my 406.......I drilled only the exhaust side steam holes for two reasons:
1)Air can actually get trapped in there due to the Siamese wall.....the other side air can just roll up the deck.
2)The exhaust is on that side.....so....hotter.
I also did the Fel Pro recommended block drilling mod between the center exhaust ports......(see pic). I recommend this as well.
I run Dart Aluminum heads.....10.5 to 1 compression and a stock water pump,fan,clutch......it never goes over 185 even in 105 heat.....with a stock Harrison rad.
Jebby
1)Air can actually get trapped in there due to the Siamese wall.....the other side air can just roll up the deck.
2)The exhaust is on that side.....so....hotter.
I also did the Fel Pro recommended block drilling mod between the center exhaust ports......(see pic). I recommend this as well.
I run Dart Aluminum heads.....10.5 to 1 compression and a stock water pump,fan,clutch......it never goes over 185 even in 105 heat.....with a stock Harrison rad.
Jebby
Drifting
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From: Port St. Lucie Fl
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
I would and have drilled the steam holes or should I say a machine shop did. Some of the holes have to be drilled at an angle otherwise you will drill though the waterjacket.
Angled steam holes should be made using a drill press equipped with an adjustable table
Angled steam holes should be made using a drill press equipped with an adjustable table
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I did a test on valves by putting heads on bench an spraying a bunch of WD40 into ports They didn't leak ANY so I guess they are good. Heads are brand new aluminum and say Summit Racing on the ends
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