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Registered
Join Date: Dec 2001
Posts: 4,313
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heads coming loose on 3.3 turbo motor
This is my mildly modified 3.3 bus motor. The motor winds out so fast with the 5 speed I've never gotten past 1/2 throttle and .8 boost.
When I checked the head stud torque at 1,000 miles, the head stud nuts felt like they had about 10 lbs of torque. I re-torqued them down to 38 lbs. I recently re-checked them at 2,800 miles and again, the nuts feel like they have about 10 lbs of torque. I re-torqued them down to 30 lbs. I used ARP head studs. Cylinders 1,2,4,5,6 were loose, #3 was tight. Not sure what's going on, or what to do.
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Harold '79 930/DP935 (sold) '68 VW 3.3 Turbo Crewcab |
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04-02-2018, 04:28 AM
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Do you think the nuts are backing off or the studs winding out or pulling?
I have no idea but thought I would ask.
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Bill K. "I started out with nothin and I still got most of it left...." 83 911 SC Guards Red (now gone) And I sold a bunch of parts I hadn't installed yet. |
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04-02-2018, 05:05 AM
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Chain fence eating turbo
Join Date: Dec 2008
Location: Austin, TX
Posts: 9,125
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Did you use lube on the nuts? When I rebuilt my engine, I had severely undertorqued the nuts not knowing I should have a higher torque setting due to different studs than factory.
I put them on dry, and even though undertorqued, none were loose over 5 years of running lots of boost.
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Cory - turbo'd '87 C3.2 Guards/Blk, 3.4, 7.5:1 CR P & C's, 993SS cams, Borg-Warner S366 turbo @ 1.2-1.5 bar, depending on mood  , Treadstone full bay IC, 70mm TB, TiAL F46 WG, HKS 1 1/2" BOV, twin 044 pumps, MicroSquirt AMP'd w/GM smart coilpack, Bilstein coilovers, Tramont wheels (285's rr, 225's frt), Big Reds frt, 993 rr., tower brace, MOMO wheel
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04-02-2018, 05:19 AM
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Registered
Join Date: Dec 2001
Posts: 4,313
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I lubed the nuts, used lock tight on the studs. No hard boost. Since they are torqueing down, I’m assuming the head studs aren’t pulling out. ARP spec is 38 lbs.
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Harold '79 930/DP935 (sold) '68 VW 3.3 Turbo Crewcab |
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04-02-2018, 05:27 AM
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Registered
Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
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The root cause is your use of ARP head studs and I've seen a LOT more just like it since 1978.
ARP's metallurgy while very strong, doesn't match the CoE of the cylinders and thats why Porsche used Dilavar. The ONLY head stud we use are the 993TT Dilavar ones since these maintain proper clamping forces and head torque. While not cheap, its the best solution, hands-down.
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Steve Weiner Rennsport Systems Portland Oregon (503) 244-0990 porsche@rennsportsystems.com www.rennsportsystems.com |
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04-02-2018, 09:12 AM
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Puny Bird
Join Date: Nov 2002
Location: Port Hope (near Toronto) On, Canada
Posts: 4,566
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I don't totally agree with Steve, But I do agree with the ARP head stud bit.
First clue is they call for a greater than stock torque. I've seen issues on both NA and turbo so I don't use their head studs.
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'74 Porsche 914, 3.0/6 '72 Porsche 914, 1.7, wife's summer DD '67 Bug, 2600cc T4,'67 Bus, 2.0 T1 Not putting miles on your car is like not having sex with your girlfriend, so she'll be more desirable to her next boyfriend. |
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04-02-2018, 10:35 AM
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Registered
Join Date: Feb 2007
Location: Northeast
Posts: 463
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I had the same problem until I stopped using the Moly lube. The stuff never went away.
Using just oil I haven't had a problem since.
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Mark www.exotechpower.com 1981 Targa-messed with. 91 C2 supercharged track rat Radical Prosport-irritates the GT3 guys 40 years of rebuilding services |
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04-03-2018, 04:49 AM
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1983 Porsche SC
