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400 deck clearance? #1456978 06/22/13 11:35 PM 06/22/13 11:35 PM
Joined: Jan 2008 Posts: 4,258 Canada WO23Coronet OP master
WO23Coronet OP master Joined: Jan 2008 Posts: 4,258 Canada	Wondering how far down in the hole factory pistons are on a stock 1978 400 HP (kind of an oxymoron isn't it). I think I remember reading they're around .180" in the hole. Anyone ever measure a factory 400's deck clearance?

Re: 400 deck clearance? [Re: WO23Coronet] #1456979 06/23/13 09:15 AM 06/23/13 09:15 AM
Joined: Oct 2003 Posts: 21,345 Marysville, O-H-I-O 70Cuda383 Too Many Posts
70Cuda383 Too Many Posts Joined: Oct 2003 Posts: 21,345 Marysville, O-H-I-O	I don't see any reason why the 400s would be any different than the 383s and 440s, but I've never measured a 400 block. I can say that I built a 383, they cut the decks .015 to square them up. AFTER the cut, they were AT blueprint spec. (what was that spec again? 9.980"? Photobucket sucks

Re: 400 deck clearance? [Re: 70Cuda383] #1456980 06/23/13 01:03 PM 06/23/13 01:03 PM
Joined: Jan 2003 Posts: 4,395 The Pale Blue Dot Skeptic master
Skeptic master Joined: Jan 2003 Posts: 4,395 The Pale Blue Dot	The '72 block I tore down was -.125" down.

Re: 400 deck clearance? [Re: Skeptic] #1456981 06/23/13 04:18 PM 06/23/13 04:18 PM
Joined: Jan 2008 Posts: 4,258 Canada WO23Coronet OP master
WO23Coronet OP master Joined: Jan 2008 Posts: 4,258 Canada	Did the 72-78 400's use the same pistons?

Re: 400 deck clearance? [Re: WO23Coronet] #1456982 06/23/13 08:31 PM 06/23/13 08:31 PM
Joined: Jan 2003 Posts: 75,125 A Banana Republic near you. JohnRR I Win
JohnRR I Win Joined: Jan 2003 Posts: 75,125 A Banana Republic near you.	Quote: Did the 72-78 400's use the same pistons? probably something very close, a SMOGGER 440 would have a piston roughly .180 down. I JUST RAN SOME NUMBERS AND A 400 WITH A PISTON IN THE HOLE .180 AND A 90CC HEAD WOULD HAVE A 6.85 COMPRESSION RATIO , I DOUBT IT'S THAT LOW. Sorry for the caps lock , i'm not retyping that ...

Re: 400 deck clearance? [Re: JohnRR] #1456983 06/24/13 12:58 PM 06/24/13 12:58 PM
Joined: Jan 2003 Posts: 16,376 D dogdays I Live Here
dogdays I Live Here D Joined: Jan 2003 Posts: 16,376	And folks wonder why the 400 had a reputation as a dog....... So I went to Silvolite website and found 400 pistons stock replacement, 1.812" comp height, which puts the top of piston about 0.120 down. So maybe all 400s were the same. R. Last edited by dogdays; 06/24/13 01:13 PM.

Re: 400 deck clearance? [Re: dogdays] #1456984 06/24/13 02:39 PM 06/24/13 02:39 PM
Joined: Jan 2003 Posts: 75,125 A Banana Republic near you. JohnRR I Win
JohnRR I Win Joined: Jan 2003 Posts: 75,125 A Banana Republic near you.	Quote: And folks wonder why the 400 had a reputation as a dog....... So I went to Silvolite website and found 400 pistons stock replacement, 1.812" comp height, which puts the top of piston about 0.120 down. So maybe all 400s were the same. R. They are very close to that, .100 comes to mind. I looked at a rebuilt 400 a number of years back that was zero deck and I remember seeing that the intake had been cut .120 ...

Re: 400 deck clearance? [Re: JohnRR] #1456985 06/25/13 02:16 AM 06/25/13 02:16 AM
Joined: Dec 2003 Posts: 5,314 Carstairs, Alberta, Canada dave571 master
dave571 master Joined: Dec 2003 Posts: 5,314 Carstairs, Alberta, Canada	.100 is the ball park. Mine was .100" so I cut ,085 off the deck to give it a little more snot. The pistons were completely flat. No valve reliefs or dish.

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