A few 400 questions
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Senior User
Joined: Jan 2006
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From: northwest Georgia
A few 400 questions
I'm about to rebuild a 400 for my truck and needed to know a few things i couldn't find in researching.
1. For determining the dynamic CR i need to know the intake valve closing angle. I'm confused on how setting the timing chain straight up will affect this. for example, if the advertised ICA is 50 ABDC, is that already for straight up timing or will that change with a straight up set?
2. I've heard the stock valves bottom out at .480" lift. Is this true? Do i need new springs for .500" and higher?
3. just for laughs, how much weight would i save on an aluminum intake? like it matters.
thanks for any help
1. For determining the dynamic CR i need to know the intake valve closing angle. I'm confused on how setting the timing chain straight up will affect this. for example, if the advertised ICA is 50 ABDC, is that already for straight up timing or will that change with a straight up set?
2. I've heard the stock valves bottom out at .480" lift. Is this true? Do i need new springs for .500" and higher?
3. just for laughs, how much weight would i save on an aluminum intake? like it matters.
thanks for any help
Post Fiend
Joined: Mar 2005
Posts: 8,542
Likes: 5
From: Louisiana
I don't think setting the timing straight up changes the CR. It just lets the engine get rid of the retarded set timing and perform a lot better (by undoing the smog crap).
IF you put a RV cam, then you will need new valve springs.
The stock cast iron intakes are heavy, but you won't gain any performance for loosing 10 lbs with an aluminum intake, but with a 4v carb and an aluminum intake you will get more power.
I'm sure someone will come in and give some better info.
IF you put a RV cam, then you will need new valve springs.
The stock cast iron intakes are heavy, but you won't gain any performance for loosing 10 lbs with an aluminum intake, but with a 4v carb and an aluminum intake you will get more power.
I'm sure someone will come in and give some better info.
Senior User
Joined: Feb 2008
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From: Southeast Iowa
May I ask why you are worried about dynamic compression? If it's really important to you call comp cams. Are you going to run it 12:1 or something? Or maybe you're trying to figure out what compression to run?
Thread Starter
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Senior User
Joined: Jan 2006
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From: northwest Georgia
the reason i'm concerned with it is to get as high a dynamic CR as i can with 87 octane. I dont want to use 91 or 93 so i need to make sure i'm not making too much compression. The only thing that will be done is the heads will be milled .020"-.025" and the pistons will probably end up .020"-.030" overbore. so the Static CR will only increase by about 1/3 of a point. but the cam will determine the dynamic, and thats the one i need to know. I'm not too concerned with the weight of the intake. I was just curious. The trucks going from independent front suspension and a 302 to a solid axle and the 400. a few pounds wont make that much difference.
