Stealth-Z

My dilemma was similar. Apparently my RB30 originally was attached to an auto trans because it did not have a bushing. It did have a larger one fitted into the crank. This larger piece inner diameter almost looked like the smaller bushing would press in. The larger bushing does not fit snug around the input shaft of my RB25 transmission. My thought is to just leave it off and go with the smaller one only. On =premo='s picture, the area above the blue looks like the bush I removed.

Mine has been apart for some time now. I have measured the parameters for the compression calculators. My first set of custom Wiseco pistons were flat tops with -5cc valve relief cuts. They were suposed to produce a CR of around 9:1. After measuring, the CR came out to less than 7.

Ops, I transposd that one in to the post wrong. It should be 3.406 for the bore diameter. Inputing that number would give a 8.174:1 CR. Comp Ratio Calc For 4-Stroke Only Bore Diameter 3.046 Inches Engine Stroke 3.346 Inches Head Volume 64.00 Cubic cm's Gasket Bore Diameter 3.425 Inches Compressed Gasket Thickness 0.0510 Inches Deck Clearance 0.0000 Inches Piston Effective Dome Volume -16.00 Cubic cm's Gasket Volume 0.470 Deck Volume 0.000 TDC 3.399 Swept Volume 24.382 Compression Ratio 8.174 :1 Thanks for catching that error. Not counting the typo in my copying, my numbers entered into the calculator still yeild the same 9.969:1 Comp Ratio Calc For 4-Stroke Only Bore Diameter 3.406 Inches Engine Stroke 3.346 Inches Head Volume 64.00 Cubic cm's Gasket Bore Diameter 3.425 Inches Compressed Gasket Thickness 0.0510 Inches Deck Clearance 0.0000 Inches Piston Effective Dome Volume -16.00 Cubic cm's Gasket Volume 0.470 Deck Volume 0.000 TDC 3.399 Swept Volume 30.485 Compression Ratio 9.969 :1 I am still not understanding how it is possible to get around a 9:1 CR with flat top pistons. Changing the Piston Effective Dome Volume to 0 will yield a 7.968:1 CR according to the calculator. Comp Ratio Calc For 4-Stroke Only Bore Diameter 3.406 Inches Engine Stroke 3.346 Inches Head Volume 64.00 Cubic cm's Gasket Bore Diameter 3.425 Inches Compressed Gasket Thickness 0.0510 Inches Deck Clearance 0.0000 Inches Piston Effective Dome Volume 0.00 Cubic cm's Gasket Volume 0.470 Deck Volume 0.000 TDC 4.375 Swept Volume 30.485 Compression Ratio 7.968 :1 What am I missing here?

What is everyone using for a compression ratio calculator? Perhaps I am using the wrong formula? I have been using the four stroke version on Wiseco's website. http://www.wiseco.com/Calculators.aspx Here are the specs on the Wiseco pistons I have. 3.046 inches (86.5mm) 1.260 inch (32mm) Comp Height 16cc dome The RB26 head I have measures out at 64cc's. The head gasket being used is a Cometic MLS 87mm. Cometic rates the thickness at .051 inches (1.295mm). My block has been decked and the pistons sit at a zero deck. When I plug these numbers, Bore Diameter = 3.046 Engine Stroke = 3.346 (85mm) Head Volume = 64cc Gasket Bore Diameter = 3.425 (87mm) Compressed Gasket Thickness = .051 Deck Clearance = 0 Piston Effective Dome Volume = 16cc With these numbers I get a CR of 9.69:1 My plan is to shave nearly 11cc's off the piston dome to bring the dome volume to 5cc. According to the calculator this would give me CR of 8.490:1. I have to face the reality of 91 octane premium fuel in my part of the world.

I remembered seeing something about how to run the VCT/VVT setup with the RB26 head. When I first saw your post, I could not find it becuase I did not search for NVCS. http://forums.hybridz.org/showthread.php?t...;highlight=nvcs

Look at the plate in between the cooling lines on the center housing. There should be a plate with the part number. I have a set simular to yours. The numbers on mine are 14411-06U00. Information I have found is these are R32 Nismo type turbo's with a 15 degree cutback and a 270 degree thrust bearing. They are supposed to be capable of about 300ps each. As for Maximum boost, cannot help you there. I do not think you would want to go as high as ball bearing equivelents.

I have a set of these and emailed Wiseco about shaving the dome. This was the reply. If there is milling inside of the dome to hollow it out, I would say no. If it looks to be a solid dome, then yes. Minimum thickness for any part of the crown would be .150". Best Regards, Wiseco Piston Co. Inc.

I can confirm the off the shelf Wiseco's yeild low 7 CR. They sit .020 inside the bore. The valve relief cuts are a little over 11cc's. I was looking for a 8.3 to 8.5 CR. Alot of decking and shaving needs to be done to acheive that. I do not feel comfortable cutting that much off the block and head. They would be good for the high boost drag racer I suppose.