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If If I change the quench what really happens #2820668
09/14/20 04:02 PM
09/14/20 04:02 PM
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MR_P_BODY Offline OP
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I might end up changing the quench height on a build.. what really happens to
the performance on a street engine.. I might have to go from .039 to like .080 so
my exhaust valve will get proper clearance(other than compression)
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Last edited by MR_P_BODY; 09/14/20 04:06 PM.
Re: If If I change the quench what really happens [Re: MR_P_BODY] #2820675
09/14/20 04:38 PM
09/14/20 04:38 PM
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On the parachute mount
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n20mstr Offline
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On the parachute mount
less quench slows the flame front


....BAD A$$ STREET CAR.....
Re: If If I change the quench what really happens [Re: n20mstr] #2820682
09/14/20 04:45 PM
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Originally Posted by n20mstr
less quench slows the flame front


So I just advance timing to help the slow front shruggy
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Re: If If I change the quench what really happens [Re: MR_P_BODY] #2820694
09/14/20 05:15 PM
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It might require less timing to prevent detonation. Ages ago I had some friends who both had very similar 360s. One was 10.5:1 with KB pistons and quench was paid attention to. The the other was 9:1 no attention paid to quench. The quench engine was almost a full second faster and could run more timing than the lower compression engine.


68 Barracuda Formula S 340
87 "Chrysler" Conquest
Re: If If I change the quench what really happens [Re: MR_P_BODY] #2820700
09/14/20 05:34 PM
09/14/20 05:34 PM
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The mixture in the quench volume will burn, but it may burn too quickly.


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Re: If If I change the quench what really happens [Re: Bad340fish] #2820705
09/14/20 05:41 PM
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Romeo MI
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Originally Posted by Bad340fish
It might require less timing to prevent detonation. Ages ago I had some friends who both had very similar 360s. One was 10.5:1 with KB pistons and quench was paid attention to. The the other was 9:1 no attention paid to quench. The quench engine was almost a full second faster and could run more timing than the lower compression engine.


Good to know.. right now I need to check the exhaust pocket depth to see if I can mill them deeper
and still have enough material in there before I can make any decisions.. might be easier to get
some other pistons if cheap enough.. I will sonic check them in a day or so
wave

Re: If If I change the quench what really happens [Re: MR_P_BODY] #2820976
09/15/20 09:44 AM
09/15/20 09:44 AM
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Tulsa, Oklahoma
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Mike,
In my opinion the engine will be more prone to detonation with that much clearance.
Bill

Re: If If I change the quench what really happens [Re: 340Cuda] #2820981
09/15/20 10:00 AM
09/15/20 10:00 AM
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Could you maybe find a ex valve with a hair thinner margin and cut the piston a tiny bit like you mentioned?

Just a thought, if you have a wide margin on your ex valve, couldnt you flat off .010 without issue, I know some of the ferrea valves I use have a very very thick margin that could give some room if needed.


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Re: If If I change the quench what really happens [Re: Mr PotatoHead] #2821064
09/15/20 12:53 PM
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Deckaids ago i used a cutter that you put in place of the valve , secure the head to the motor with a couple of bolts and use a drill to cut each piston. It made a mess but grease in the crevice of each piston/ cylinder wall allowed me to clean it up fine. Wow, that must have been 45 years ago now. Crane or Comp or Isky had the cutter, can't recall who.


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Re: If If I change the quench what really happens [Re: gregsdart] #2821155
09/15/20 03:54 PM
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Originally Posted by gregsdart
Deckaids ago i used a cutter that you put in place of the valve , secure the head to the motor with a couple of bolts and use a drill to cut each piston. It made a mess but grease in the crevice of each piston/ cylinder wall allowed me to clean it up fine. Wow, that must have been 45 years ago now. Crane or Comp or Isky had the cutter, can't recall who.


I did the same thing years ago but this engine is still on a stand and I can pull the pistons
to put on the mill
wave

Re: If If I change the quench what really happens [Re: gregsdart] #2821434
09/16/20 10:10 AM
09/16/20 10:10 AM
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RapidRobert Offline
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Originally Posted by gregsdart
Deckaids ago i used a cutter that you put in place of the valve , secure the head to the motor with a couple of bolts and use a drill to cut each piston. It made a mess but grease in the crevice of each piston/ cylinder wall allowed me to clean it up fine. Wow, that must have been 45 years ago now. Crane or Comp or Isky had the cutter, can't recall who.
that's what I did, I cut an old cyl head into thirds & got an intake & ex valve that were .100" larger than the valves & glued sandpaper to the faces & used a drill. I put tape around the perimeter on the piston to contain the debris & had the piston at TDC. worked perfect


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Re: If If I change the quench what really happens [Re: gregsdart] #2821442
09/16/20 10:21 AM
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Originally Posted by gregsdart
Deckaids ago i used a cutter that you put in place of the valve , secure the head to the motor with a couple of bolts and use a drill to cut each piston. It made a mess but grease in the crevice of each piston/ cylinder wall allowed me to clean it up fine. Wow, that must have been 45 years ago now. Crane or Comp or Isky had the cutter, can't recall who.


Isky still has them.

Isky Valve Pocket Cutter


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Re: If If I change the quench what really happens [Re: MR_P_BODY] #2821512
09/16/20 12:34 PM
09/16/20 12:34 PM
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Clanton Offline
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How much would a high swirl high velocity port help?


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Re: If If I change the quench what really happens [Re: Clanton] #2821675
09/16/20 07:10 PM
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It seems high swirl and high velocity don't matter much after all, they got 330 CFM sewer pipe heads on 345 CID truck engines now and they don't lack any TQ...

The term "High velocity heads" just means the heads don't flow enough


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Re: If If I change the quench what really happens [Re: HotRodDave] #2823317
09/21/20 02:40 PM
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Mike,
Years ago I had a 340 my Dad put together for me in a duster. It had 10:1 with very little quench. It would knock like crazy on pump gas.

Shortly after being put together, it ate a flat tappet cam, and all of the metal went in the pistons. Rebuild the motor with another set of flattops, but this time at 12:1 with very tight quench (.035"). That motor would run on 93 octane ALL DAY....

So I'm not sure what your plan is, but I was able to raise compression almost 2 full points, AND have it run better on 93.

Re: If If I change the quench what really happens [Re: dizuster] #2823429
09/21/20 08:05 PM
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I havent been out in the shop to do some measurement but I have thought about new pistons
wave

Re: If If I change the quench what really happens [Re: dizuster] #2823455
09/21/20 09:29 PM
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Quote
It had 10:1 with very little quench. It would knock like crazy on pump gas.

Rebuild the motor with another set of flattops, but this time at 12:1 with very tight quench (.035"). That motor would run on 93 octane ALL DAY....
So I'm not sure what your plan is, but I was able to raise compression almost 2 full points, AND have it run better on 93.
I'm convinced!


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