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EFV-8 Club Forum / General Ford Discussion / Pressure plate bolts

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Posted By Discussion Topic: Pressure plate bolts -- page: 1 2     ole_Bill 09-10-2010 @ 4:46 PM reply profile send p.m. New Member Posts: 165 Joined: Dec 2009 What size are the bolts that secure the pressure plate to the flywheel? Do I use a flat washer and lock washer or just locktite? 51f1 09-10-2010 @ 4:59 PM reply profile send p.m. Senior Posts: 573 Joined: Oct 2009 5/16"-18x3/4" with lock washer. Richard flatheadfan 09-11-2010 @ 2:09 AM reply profile send p.m. Member Posts: 450 Joined: Oct 2009 ole Bill- I think you will find pressure plate bolts are not "ordinary" 5/16"- 18 bolts. They are hardened and more importantly they have a long shoulder. Tom TomO 09-11-2010 @ 7:27 AM reply profile send p.m. Senior Posts: 7252 Joined: Oct 2009 You can get them from Roy Nacewicz. http://www.fordscript.com/ Tom This message was edited by TomO on 9-11-10 @ 7:28 AM 51f1 09-11-2010 @ 7:54 AM reply profile send p.m. Senior Posts: 573 Joined: Oct 2009 There is nothing unusual about the bolts on my truck (no shoulder, etc). Maybe some of the older clutches used special bolts. I don't know which year he's asking about. My parts books list them as part number 350433-S, hex head bolt. They are listed for trucks, 1948-1955 and for cars, 1949-1953, which are all of the parts books I have. I would use grade 5 bolts. Richard This message was edited by 51f1 on 9-11-10 @ 8:01 AM kubes40 09-11-2010 @ 8:48 AM reply profile send p.m. Senior Posts: 3396 Joined: Oct 2009 The bolts were in fact case hardened and had a shoulder that helped locate the clutch plate on center. I can send you a close-up photo if you desire. I'll need your email address. Only a lock washer (split ring type) was used with these bolts. Mike ole_Bill 09-11-2010 @ 1:02 PM reply profile send p.m. New Member Posts: 165 Joined: Dec 2009 Sorry I forgot to mention the engine is a 1947 59A. I'm going with 5/16", grade 5 bolts with a lock washer. As always, thanks everyone for the great advice. 37RAGTOPMAN 09-12-2010 @ 7:39 AM reply profile send p.m. Senior Posts: 1960 Joined: Oct 2009 Ole_BILL You need to use the correct shoulder bolts like Kubes40 said, otherwise you may risk problems down the road, these shoulders center the pressure plate so it is dead on center, regular bolts leave a little side play, in each mounting bolt hole,and may not be dead on center,and if off set you will have problems, Just my 3 cents worth, 37RAGTOPMAN and KEEP on FORDIN ! flatheadfan 09-12-2010 @ 9:55 AM reply profile send p.m. Member Posts: 450 Joined: Oct 2009 old Bill- Pressure plate bolts are special bolts. Note the picture below. The three bolts (from different flywheels) all have a shoulder on them. If you look at the bolts holes on the flywheel you will see that the threads do not start at the surface. The top 3/16" has no threads and this is to accommodate the bolt shoulder. The purpose of the shoulder is to prevent micro-oscillations of the bolt by locking the shoulder to the flywheel. Without the shoulder micro-oscillations can become macro-oscillations which can cause oscillations in the pressure plate which in turn can result in you having a "bad day". You may want to think about that when you are turning 3000 rpms. Tom Stroker 09-12-2010 @ 3:42 PM reply profile send p.m. Senior Posts: 1460 Joined: Oct 2009 Ole Bill: You got excellent advice from many of the Forum contributors on the need to NOT USE common 5/16's cap screws. The clutch cover bolts act in the same way that alignment dowels do on many precision applications. It is very critical, given the mass of a clutch cover to get it absolutely centered. When I have had engines balanced, I always include the flywheel and clutch cover as parts I want balanced. A few thousands of eccentricity allowed by common hardware cap screws is like having an unbalanced tire spinning at 3000 rpm. The problem is; many generations of "parts-changers" may have simply substituted the parts they lost with stuff from the hardware store. Yes, the clutch will "work", but unless it is precisely centered, it will most likely create a vibration especially at high rev's.

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