Re: How close is too close.
[Re: rebel]
#3046061
05/29/22 07:54 AM
05/29/22 07:54 AM
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Joined: Mar 2003
Posts: 2,495 PA
moparacer
top fuel
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top fuel
Joined: Mar 2003
Posts: 2,495
PA
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I ran an engine like that one time and didn't cause an issue until piston rock came into play. I think mine was closer than that though because it lightly scuffed the valve relief area exactly like yours is showing, but never hurt anything. Ran it for a couple years till we pulled it down I found it.
67 Barracuda street/bracket car 11.27-119 68 Dart 502 BB 8.70s-152 414 cid SB Dragster 7.65-174
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Re: How close is too close.
[Re: rebel]
#3046106
05/29/22 11:02 AM
05/29/22 11:02 AM
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Joined: Jan 2003
Posts: 16,923 NC
440Jim
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,923
NC
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... the edge of ghe fave face only misses the valve pocket side wall by 0.045. Would you consider that too close? Maybe I should advance the cam half a degree? Whats your call? I would just chamfer (bevel) the top edge of the valve relief to give insurance against piston rocking.
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Re: How close is too close.
[Re: 440Jim]
#3046162
05/29/22 01:44 PM
05/29/22 01:44 PM
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Joined: Aug 2019
Posts: 9,429 Super Spudsville
Mr PotatoHead
Half Baked
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Half Baked
Joined: Aug 2019
Posts: 9,429
Super Spudsville
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This would be my fix also. I would just chamfer (bevel) the top edge of the valve relief to give insurance against piston rocking. ... the edge of ghe fave face only misses the valve pocket side wall by 0.045. Would you consider that too close? Maybe I should advance the cam half a degree? Whats your call? I would just chamfer (bevel) the top edge of the valve relief to give insurance against piston rocking.
STOP POTATO HATE!
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Re: How close is too close.
[Re: Stanton]
#3046302
05/29/22 11:13 PM
05/29/22 11:13 PM
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Joined: Dec 2006
Posts: 4,647 aotearoa
rebel
OP
master
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OP
master
Joined: Dec 2006
Posts: 4,647
aotearoa
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What's your quench ?? Thicker head gasket would work. Quench is 0.039, right on the money i'm thinking. I dont think piston rock would take up the 0.045 side clearance I have. I think the fact that the block is Aluminium, the gap should increase as the heat expands everything. maybe?
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Re: How close is too close.
[Re: rebel]
#3046320
05/30/22 12:07 AM
05/30/22 12:07 AM
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Joined: May 2019
Posts: 712 Lake Villa Il
INTMD8
super stock
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super stock
Joined: May 2019
Posts: 712
Lake Villa Il
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Wouldn't you need to retard the cam to gain intake valve clearance?
Knowing nothing else I wouldn't be concerned but also inclined to use lighter weight/smaller diameter parts and higher spring pressures. My opinion may change with heavy parts, marginal pressures and aggressive ramps.
69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 650rwhp @7250 510rwtq @5700
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Re: How close is too close.
[Re: INTMD8]
#3046341
05/30/22 01:59 AM
05/30/22 01:59 AM
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Joined: Jul 2005
Posts: 707 California
BigDaddy440
super stock
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super stock
Joined: Jul 2005
Posts: 707
California
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I'd be fearful of running an engine with .045" clearance, especially if it were the exhaust valve which gets hotter an expands more. I've gone by the basic rule of .080" on the intake and .100" on the exhaust, but on occasion have run them slightly tighter than that. When it comes to advancing or retarding the camshaft, it depends on which valve you're having insufficient clearance on. In most problematic cases the the piston is chasing the opened intake valve and hits it before it can fully shut or hits it as the valve "bounces shut". To help reduce the risk of this situation you can retard the camshaft some and it will provide additional intake valve clearance as well as reduce your dynamic compression slightly. If your exhaust valve is the concern, retarding will only make that situation worse, and you'd want to advance the camshaft a few degrees to pick up some extra clearance on the exhaust valve. So you really need to know how much clearance you have on both valves before knowing if you have the room to advance or retard the cam -it's not always an option as it's a bit of a balancing act.
Different head gaskets vs optimal quench have been discussed here already.
You can also choose a camshaft that has a different intake closing or exhaust opening point to help improve your situation.
-Dan
1969 A12 Roadrunner 1970 Plymouth Cuda 1968 Dodge Dart
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Re: How close is too close.
[Re: 440Jim]
#3046664
05/31/22 07:54 AM
05/31/22 07:54 AM
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Joined: Jan 2003
Posts: 4,040 Shelby Twp. Mi
HardcoreB
master
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master
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Posts: 4,040
Shelby Twp. Mi
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... the edge of ghe fave face only misses the valve pocket side wall by 0.045. Would you consider that too close? Maybe I should advance the cam half a degree? Whats your call? I would just chamfer (bevel) the top edge of the valve relief to give insurance against piston rocking. X2!
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