10:1 compression with GT40 heads - How much to shave & 5/64 vs. 1.5mm Piston Rings ? - Forums at Modded Mustangs
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post #1 of 2 Old December 30th, 2012, 10:20 PM Thread Starter
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10:1 compression with GT40 heads - How much to shave & 5/64 vs. 1.5mm Piston Rings ?

I want raise my compression from 9:1 to 10:1 in my 96 Explorer 5.0 with GT40 heads which is for street use only. I don't mind using premium fuel in my carburated 64 Falcon. I will be taking the block to the machine shop and have it bored 0.030 over and deck the block. I will also take the heads to the machine shop for new valve guides and a valve job. The machine shop should know how much material to remove to raise the compression to 10:1. I believe the GT40 heads are 65cc. In 1996, Ford switched over to thinner metric piston rings (for lower friction?) and for my Explorer Engine, I think I can use either the standard 5/64" or the 1.5mm piston ring pistons. All 302 up to 1995 used the 5/64" piston rings. The metric Explorer piston with 1.5mm piston ring has Compression Distance of 1.595. The standard piston with 5/64" piston ring has Compression Distance of 1.599.

Speed-Pro Hypereutectic Piston and Ring Kits (5/64" x 5/64" x 3/16") $170:
Speed-Pro Piston and Ring Kits Z8KH273CP30 - SummitRacing.com

Speed-Pro Hypereutectic Pistons (1.50mm x 1.50mm x 4.00mm) $118:
Speed-Pro Hypereutectic Pistons ZH816CP30 - SummitRacing.com
Sealed Power Plasma-Moly Piston Ring Sets ZE458K30 $71:
Sealed Power Plasma-Moly Piston Ring Sets ZE458K30 - SummitRacing.com

TFS Cam: TFS-51403001 - Duration at 050 inch Lift: 221 int./225 exh. Valve Lift with Factory Rocker Arm Ratio: 0.499 int./0.510 exh.:
Trick Flow® Track Max® Hydraulic Roller Camshafts for Ford 5.0L TFS-51403001 - SummitRacing.com

Can anyone please tell me how much material needs to be removed from the GT40 heads ?

Any issues with valve clearance using the Speed-Pro Hypereutectic Piston and Ring Kits Z8KH273CP30 with TFS Cam using 1.6 Rockers ?

Is it going to make any difference if I use the pistons with the 5/64" or the 1.5mm piston rings ?

The 5/64" version is cheaper since its available as Pistons and Rings set and was used on all 302 except 96+.


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post #2 of 2 Old December 30th, 2012, 11:58 PM
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5.0 HO engines had the 1.5/1.5/3mm rings way back in 85/86 I beleive! The Speed Pro pistons have the standard 5/64" rings & can be used in your application if you're boring your engine over. I found a compression calculator online & it looks like you would need about 53cc chambers to get down to 10:1.

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