I knew the concept of decking the block, but then today I realized decking the head is another option. Decking the head would lower the combustion chamber volume and increase the compression ratio.
With a zero piston deck clearance how much can be removed from the head before the piston will come into contact with the valves? Yes, cam choice is involved in this because of valve lift.
Let's take the COMP Cam 68-232-4 for example, 0.460" intake and 0.476" exhaust lift. Now say I want to take 0.020" off the head, is this too much? How about 0.010"? What have you done?
My ultimate goal is to build a 4.7L with a SCR of about 11:1 and I will run on E85. Don't turn this into a discussion of E85 and politics, fuel economy, etc. I'm putting this out there because there is a method to my madness.
Decking the Head
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PolloLoco
- Donator
- Posts: 212
- Joined: March 8th, 2009, 6:39 am
- Stroker Displacement: 4.7L
- Vehicle Year: 1997
- Vehicle Make: Jeep
- Vehicle Model: TJ
- Location: DeRidder, LA
Decking the Head
4.7L Stroker, 4.88 Ford 8.8 w/Auburn ECTED, HP30 w/ARB, AX-15, NP231 w/RR SYE, 33x10.50 BFG A/T, 4" Skyjacker, 1" body lift, 1" MORE motor mounts, Kilby fuel tank skid, UCF ultra-high clearance 1/4" skid, HMMWV-style snorkel, 63mm TB
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SilverXJ
- Global Moderator
- Posts: 5790
- Joined: February 14th, 2008, 7:14 am
- Stroker Displacement: 4.6L
- Vehicle Year: 2000
- Vehicle Make: Jeep
- Vehicle Model: Cherokee
- Location: Radford, Va
Re: Decking the Head
I had my head resurfaced a while ago, but very little was taken off, something like .001". What I do know that when I checked piston to valve clearance (using the KB944s) I measured a piston that was .004" below deck. I used no head gasket, and even put a .020" shim between the rocker and valve (I used pumped up lifters and light weight valve springs). The valves didn't even touch the layer of silly putty in the piston dish (1/16-1/8" thick silly putty). This was with the Comp Cam 68-231-4 cam.
2000 XJ. 4.6L stroker
00+ Viper Coil Swap | CPS Timing Increase Mod | Fabricated Airbox | Dash bezel, Arduino Multigauge & RD Conceal
Eat, breath, drink, sleep, Jeep, drink
00+ Viper Coil Swap | CPS Timing Increase Mod | Fabricated Airbox | Dash bezel, Arduino Multigauge & RD Conceal
Eat, breath, drink, sleep, Jeep, drink
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johnhalabama
- I think I'll order a "tab"
- Posts: 42
- Joined: January 24th, 2009, 5:17 pm
- Stroker Displacement: 4.7
- Vehicle Year: 1936
- Vehicle Make: Dodge
- Vehicle Model: D2 Sedan
- Location: Chesapeake, VA
Re: Decking the Head
I'm curious to see what you come up with. I replied on your other post about the pistons. I want to run a high compression engine because I don't need the low end torque. It's going in a street rod that I won't drive every day so I don't mind buying the good gas. I just don't want to get it so I have to go find race fuel if I go out of town.PolloLoco wrote:My ultimate goal is to build a 4.7L with a SCR of about 11:1 and I will run on E85. Don't turn this into a discussion of E85 and politics, fuel economy, etc. I'm putting this out there because there is a method to my madness.
John
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seanyb505
- Donator
- Posts: 447
- Joined: February 16th, 2008, 9:34 am
- Stroker Displacement: 280ci
- Vehicle Year: 1997
- Vehicle Make: Jeep
- Vehicle Model: Cherokee
- Location: West Palm Beach Florida
Re: Decking the Head
I took .015 off the head and my pistons are supposedly .0045 down. No contact with .0465 ex lift. (.052 HG and .060 rocker arm shim, and a healthy piston dish)
Now I can be like all those other awesome people with more than one Jeep in their sig, but now I have to say one of them is sold:(
97 XJ 4.6
90 MJ 4.0 - sold
I want to have as many Jeeps as children. DD, offroader, drag MJ and another one. 4=4
97 XJ 4.6
90 MJ 4.0 - sold
I want to have as many Jeeps as children. DD, offroader, drag MJ and another one. 4=4
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