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Registered
Join Date: Jul 2013
Location: Brisbane, Australia.
Posts: 2,586
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GT3 crankshaft - rod bearing clearances
This is the first time I've used an actual GT3 crank for building an aircooled motor.
The crankshaft is brand new. Rods are brand new Carrillo and the journal measures to 56.00 mm. Using new STD clearance bearings, my clearance measured with micrometer and boregaue is 0.07mm or 2.75 thou. Normally I aim for 2 thou. When micing the crankshaft rod journals, they measured 52.971mm where normally I see approx 52.98-52.984 mm. Are the GT3 cranks manufactured to give a greater clearance and is this suitable for a road car that wont be seeing 9000 rpm? Or should I get them resized to aim for closer to 2-2.2 thou?
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Always learning. www.aircooledporsches.com.au See me bumble my way through my first EFI and TURBO conversion! https://youtu.be/bpPWLH1hhgo?si=GufVhpk_80N4K4RP |
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06-21-2024, 01:46 AM
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Registered
Join Date: Oct 2008
Location: Nash County, NC.
Posts: 8,468
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Mike, the crank is marked with color dots that represent the desired bearings to use from Porsche
You might try coating the bearings if you need somewhat less clearance. Bruce |
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06-21-2024, 04:09 AM
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PCA Member since 1988
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FWIW, Smoky Yunick used to recommend 2.7 thou on his Chebby racing engines. He wanted oil flow to cool the bearings. I suspect Porsche did the same for the GT3 cranks.
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1973.5 911T with RoW 1980 SC CIS stroked to 3.2, 10:1 Mahle Sport p/c's, TBC exhaust ports, M1 cams, SSI's. RSR bushings & adj spring plates, Koni Sports, 21/26mm T-bars, stock swaybars, 16x7 Fuchs w Michelin Pilot Sport A/S 3+, 205/55-16 at all 4 corners. Cars are for driving. If you want art, get something you can hang on the wall! |
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06-21-2024, 12:32 PM
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Registered
Join Date: Jul 2013
Location: Brisbane, Australia.
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No idea who Smoky is (I only know of Smoky the Bear) but I reckon the larger clearance is probably right for high revving race cars. I aim to get the rods closed a touch.
__________________
Always learning. www.aircooledporsches.com.au See me bumble my way through my first EFI and TURBO conversion! https://youtu.be/bpPWLH1hhgo?si=GufVhpk_80N4K4RP |
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06-21-2024, 05:59 PM
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PCA Member since 1988
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Use your fave search engine or chatbot to look him up. He was the best known NASCAR mechanic/engineer, 1950's-1980's.
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1973.5 911T with RoW 1980 SC CIS stroked to 3.2, 10:1 Mahle Sport p/c's, TBC exhaust ports, M1 cams, SSI's. RSR bushings & adj spring plates, Koni Sports, 21/26mm T-bars, stock swaybars, 16x7 Fuchs w Michelin Pilot Sport A/S 3+, 205/55-16 at all 4 corners. Cars are for driving. If you want art, get something you can hang on the wall! |
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06-22-2024, 03:15 PM
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E-85 sippin drunk
Join Date: Jan 2002
Location: Warner Robins, GA
Posts: 1,554
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Hopefully Mike Bruns will see this and chime in. He is one of the only guys I trust when it comes to crankshafts, aftermarket rods, bearings, and related oil mods....
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Brad...930 gt-1 racecar, increased displacement to 3.6L, JB racing Cylinders, JE 8 to1 pistons, stroked crank, Carrillo rods, extrudehoned 3.2L intake, full bay Bell I/C, GT-2 EVO cams, Rarly8 headers, GTX-3584RS turbo, twin plug, P&P heads, Link G4 EFi system, G-50/50 with LTD slip and oil squirters/oil cooler, zork tube, full race coilover system, with carbon fiber body, full cage, E-85 sippin drunk |
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06-22-2024, 03:37 PM
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Registered
Join Date: Jul 2013
Location: Brisbane, Australia.
Posts: 2,586
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Quote:
__________________
Always learning. www.aircooledporsches.com.au See me bumble my way through my first EFI and TURBO conversion! https://youtu.be/bpPWLH1hhgo?si=GufVhpk_80N4K4RP |
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06-26-2024, 02:22 AM
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E-85 sippin drunk
Join Date: Jan 2002
Location: Warner Robins, GA
Posts: 1,554
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Quote:
Awesome!!!! 
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Brad...930 gt-1 racecar, increased displacement to 3.6L, JB racing Cylinders, JE 8 to1 pistons, stroked crank, Carrillo rods, extrudehoned 3.2L intake, full bay Bell I/C, GT-2 EVO cams, Rarly8 headers, GTX-3584RS turbo, twin plug, P&P heads, Link G4 EFi system, G-50/50 with LTD slip and oil squirters/oil cooler, zork tube, full race coilover system, with carbon fiber body, full cage, E-85 sippin drunk |
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06-26-2024, 02:28 PM
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| gt3 crankshaft |
