decking causing questions
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Junior User
Joined: Aug 2004
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From: Huntsville, AL
decking causing questions
i've got a 400 block i want to deck .010 or .020 and bore .030 . my first question is how bad would this affect intake fit? second question is would this affect my pushrod length? third question is it a bad idea to deck the block and also use high compression pistons like badgers?
Postmaster
Joined: Aug 2001
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From: Delaware
1. Your machine shop will know how much to machine off the intake side of the heads, so that you manifold fits correctly after you deck the block.
2. Yes, it will affect your pushrod length.
3. It may be a bad idea to deck the block if you are using a flattop piston, because it will raise your Static Compression Ratio to >9.5:1 with a 0.030 deck and stock heads. That may be near to detonation with a short duration cam.
In general, I would not recommend it. The small increase in power from the increase in CR is not worth the expense and problems. Spend the money on head flow instead. The return is much better.
2. Yes, it will affect your pushrod length.
3. It may be a bad idea to deck the block if you are using a flattop piston, because it will raise your Static Compression Ratio to >9.5:1 with a 0.030 deck and stock heads. That may be near to detonation with a short duration cam.
In general, I would not recommend it. The small increase in power from the increase in CR is not worth the expense and problems. Spend the money on head flow instead. The return is much better.
Lead Driver
Joined: Nov 2000
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From: Albuquerque
You can probably go .010 to clean up the heads without changing anything else. Genereally speaking you wont get much compression increase from shaving the head, just go with the pistons and aim for 9:1. Any higher and you may have to work with it to avoid pinging. To go higher you will need a dished custom piston.
Hotshot
Joined: Dec 2003
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From: iowa
if I was decking in your case I would only deck far enough to square up the block, if you were going to put on aussie cc heads then yes you would need to bring it to zero deck but that would put your comp into the high 11s, and for intake fit it is on the 335 series engines it is 1 to 1 for decking the block, and heads to mill the same amount off of the intake face of the heads ie if you deck the block .010, and mill the heads .010 you need to take .020 off of the intake face of the heads to make them match up perfectly although in that example on most engines it won't make all that much difference.
New User
Joined: Oct 2004
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if you use 351C 4v heads on the 400,you must also use intake spacers,and valley pan to close up the gap left by the 400 heads,all must be port matched.and yes if you deck the block the pushrods will need to be longer.(these are the longest pushrods made)
Hotshot
Joined: Dec 2003
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From: iowa
hey fast59 don't you mean you will need shorter pushrods, you would only need longer if you were increasing the distance from the lifter to the rocker, decking the block, and milling the heads decreases this distance, and not real sure what you mean about bieng the longest pushrods made.
In any case you should check your valve train geometery even if you don't do any milling, you may or may not need different length pushrods, but the only way to tell for sure is check, I ended up with .050 shorter on my cleveland after milling a combined total of .055 from the block, and heads.
In any case you should check your valve train geometery even if you don't do any milling, you may or may not need different length pushrods, but the only way to tell for sure is check, I ended up with .050 shorter on my cleveland after milling a combined total of .055 from the block, and heads.
Last edited by monsterbaby; Oct 17, 2004 at 10:43 AM.
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