getting my heads ported out and he asked for compression ratio engine getting full rebuild cams 1mm oversize lifters 89mm pistons etc what do i need to tell him? just the std 8.5:1?
That is the standard comp ratio, though it is affected by deck height, how much has come off the heads and headgaskets. I would just deck and machine heads as per normal and take a raise in comp as a bonus.
Quench area is as equally important as compression. Have your builder calculate this properly, then comp can be set. To calculate quench he needs to know deck height and compressed head gasket thickness. Much more in it than just picking a comp number unfortunately. An 8:1 engine may be more susceptible to det than a 9:1 if quench is too tight. Correct quench has very large benefits in mid range power as well.
So how's it different between the pentroof style piston / head design of the Z32 compared to say a 2v hemi head? Both have remarkably different squish / quench areas. Is it a 'sweet spot' formula or a hit and miss sort of arrangement? ...For those playing along at home, the squish area is the tightest clearance between the piston at TDC and the matching surface on the head. It 'squishes' the mixture closer to the spark plugs and assists the flame front as it propegates down the powerstroke. The differences between 2 valve and 4 valve design heads and their pistons allows great variances in the possible squish areas of each motor.
It is dependent on combustion chamber type, piston type, head construction, desired fuel, boosted or not. Definately not one size fits all.
will be checking all 3 blocks i have and picking the best. its come to the point where i have all the parts now the machine shop just has do the technical side of it where gets bit confusing. just want what will work best but reliable. fuel is pump unless i get serious then e85. no nos or anything like that.
which 89mm pistons did you choose? (usually a custom order and you specify the comp you want) Are you going to match the chambers to the new bore size? (this will lower comp but allow better deshrouding of the 1mm valves).
yeah think i was dreaming when i said 89 meant to be 88 but still checking wall thickness anyway im going wisco 88mm that was 3 years ago i ordered them. and had different plans back then alot has changed.
yeah think i was dreaming when i said 89 meant to be 88 but still checking wall thickness anyway. chambers will be matched im going wisco 88mm that was 3 years ago i ordered them. and had different plans back then alot has changed. so im guessing they would just be std comp. says comp ht 1.2600 on the box. all info is great and ill relay it onto machinist and see what he can do.
have some questions on bowl work. the machinist wants to no what i want done before he can continue. if i remove material from the bowl this will lower compression right? the heads are not getting skimmed. standard head gasket height 1.2mm will be used 88mm wisco comp ht 1.260 is this higher comp than std piston? i want to up compression what i should of done is got different pistons. but with this set up will it be ok?
