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Technical => Engine Tech => Topic started by: 88XR7 on November 21, 2007, 10:57:40 PM

Title: HO vs SO pistons: Only higher compression?
Post by: 88XR7 on November 21, 2007, 10:57:40 PM
Along with being forged and is that it?
Just gathering a bit more information.
Title: HO vs SO pistons: Only higher compression?
Post by: grutinator on November 21, 2007, 11:03:01 PM
both are 9:1. SO's are dished and take up the same overall volume as the two reliefs in the HO's
Title: HO vs SO pistons: Only higher compression?
Post by: 88XR7 on November 21, 2007, 11:07:48 PM
Sweet, thanks man, no need to step up to HO pistons then :hick:
Title: HO vs SO pistons: Only higher compression?
Post by: TurboCoupe50 on November 21, 2007, 11:08:12 PM
The '86 HO has flat top pistons, with no valve relifs...
Title: HO vs SO pistons: Only higher compression?
Post by: Sick88Tbird on November 21, 2007, 11:13:48 PM
I found the specs for the SO to be between 8.4:1 and 8.7:1.
Title: HO vs SO pistons: Only higher compression?
Post by: grutinator on November 21, 2007, 11:14:00 PM
yes, with only a HO cam, you should be ok. anything bigger or better then a stock HO setup is when youll need valve reliefs
Title: HO vs SO pistons: Only higher compression?
Post by: thunderjet302 on November 21, 2007, 11:43:52 PM
Quote from: 88XR7;189071
Sweet, thanks man, no need to step up to HO pistons then :hick:


Unless you want to run a big valve head and a bigger than stock HO cam (like me ;) )
Title: HO vs SO pistons: Only higher compression?
Post by: grutinator on November 22, 2007, 12:00:58 AM
Quote from: Sick88Tbird;189074
I found the specs for the SO to be between 8.4:1 and 8.7:1.


83-85's were 8.4, when they went to sefi in 86, compression was raised to 8.9
Title: HO vs SO pistons: Only higher compression?
Post by: Innes on November 22, 2007, 07:32:16 AM
On the E7 pistons the eyebrow valve reliefs are -5.5 cc
Just some info don’t know if it helps.
Title: HO vs SO pistons: Only higher compression?
Post by: Sick88Tbird on November 22, 2007, 07:22:21 PM
Quote from: grutinator;189098
83-85's were 8.4, when they went to sefi in 86, compression was raised to 8.9


That explains my malfunction.
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