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Join Date: Aug 2021
Posts: 34
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Crankcase half thickness standard
Hello All,
I am trying to work out where the issue is with my lack of deck height. Could someone please tell me what the standard crankcase half to barrel register is? I am reading 112mm?? Also if someone knows the Piston pin to crown edge measurement on a standard 3.0 liter piston? I have 35mm from center of pin to crown edge, i think that is the issue... Thanks Christian |
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03-10-2022, 12:55 AM
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It's a 914 ...
Join Date: Jan 2008
Location: Ossining, NY
Posts: 4,706
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CP Carrillo lists the “compression height” of their SC aftermarket pistons as 1.335”, or 33.9 mm, for reference.
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03-10-2022, 03:53 AM
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Join Date: Aug 2021
Posts: 34
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Thanks for the info, I see JP are the same too... I am in contact with the piston guys now. If anyone can confirm the crankcase is standard that would be real helpfull.
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03-10-2022, 04:03 AM
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Join Date: Aug 2021
Posts: 34
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Piston company are going to adjust the pistons...
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03-10-2022, 04:55 AM
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Those spigot heights are all over the map measured to the casting. It's best to measure from the engine center line ( where the case halves meet) with a height gauge. Every old air cooled 911 engine case has probably been decked and line bored. All you can do at this point is shim the cylinders, check that the cylinder heads are planar ( all the same height) . Then you will need to place the cam tower in place with the chain housing mounted ( with the gasket in place), and make sure the camshaft retainer hole in the chain housing is concentric with the camshaft journal. If not you may have to either shim the chain housing OR flycut the chain housing to achieve concentricity. Your heads have been decked and that moves the CL of the camshaft journals closer to engine centerline.
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'77 1973 911RS Backdate, 2.7 liter w/webers '70 911ST , 3.2 liter '82 '74 911 IROC Tribute , 3.0 in progress '75 911 RSR street car in progress '77 930 Replica '75 993 GT2 EVO race car , 3.6 TT '79 928 5 speed money pit in progress |
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03-10-2022, 07:58 AM
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Join Date: Aug 2021
Posts: 34
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Hi, Thanks for your input.
Yes i did measure from the case halve to the cylinder register it is 112mm +/- 0.03mm. I think it is standard, not decked. Just wanted to know if someone could clarify that. I believe the problem is with the pistons. The compression height is higher than most. The company does not do them that often and mainly does custom race stuff. they were very very helpful, and will machine a little at tbe perimeter of the crown to make the "compression height" more inline with CP and JE pistons. I got European stuff so i did not get stung with customs and import fees etc, seemed like a good idea at the time... I would prefer to do that than shim the barrels and the timing chain housings. Thanks Christian |
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03-10-2022, 08:29 AM
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It's a 914 ...
Join Date: Jan 2008
Location: Ossining, NY
Posts: 4,706
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Make sure the dome of the piston won’t be too high into the combustion chamber. You wouldn’t want to have them cut the perimeter of the piston crown, only to find that the higher portions of the dome contact the head anyway.
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03-10-2022, 03:25 PM
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Join Date: Apr 2007
Location: OC
Posts: 824
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Yes , the engineered , stock dimension is 112mm .
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03-12-2022, 04:11 PM
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Join Date: Aug 2021
Posts: 34
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Thank you Sir.
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03-12-2022, 05:43 PM
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