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Nux Nux is offline
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3.2SS top end rebuild - compulsory newbie questions

I'm currently doing a top end rebuild of my 1978 SC based 3.2SS. This started out as a classic Max Moritz kit on otherwise stock engine. Since my purchase I've added EFI/ITB, 1 5/8 Headers and CDI+ignition (classic retrofit).

Car was running strong, no issues, no broken head studs.

I was going to clean up some minor oil leaks and wire work, so dropped the engine. I already knew the engine was "sweating" somewhat from the heads at the exhaust site. But when I took a closer look at it, I didn't even bother with a leak down:




It was pretty clear what I needed to do. So off with the heads



I must say, I'm amazed how easy the head bolts came off! I can't imagine these were torqued correct. Also, the previous builder didn't bother to change the lower studs - they are all Dilavar. None broken though.

What I also found was a wee bit of oil in the cylinders:



I suspect this is from leaking (broken) piston rings and/or leaking valve guides no?

So, I'm taking the top apart. I'm not going to open the case at this point.

Just a few questions...please bear with me:

1. I will install new piston rings (working on finding some for my 98.00 Mahle - NOT EASY) - but how do I check valve guides? Is it mandatory to change them?

2. The Mahle kit does not use a head to cylinder gasket. Do you recommend grinding the mating surfaces?

3. I'm changing Dilavar to steel studs. But should I change the old steel studs as well?

4. Do I torque down the head to 32ft?

Oh and last: I'm installing DC20 cams. There seems to be some conflicting timing numbers on these. I keep reading 2.2-2.4, but Joh Dougherty states 1.8-2.0?!?! Anyone with experience?

Thanks!!!

Last edited by Nux; 02-12-2018 at 11:00 AM..
Old 02-12-2018, 10:35 AM
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Quote:
Originally Posted by Nux View Post
how do I check valve guides? Is it mandatory to change them?
In the Technical Specifications booklet you can find the wear limits for the valve guides:

Old 02-12-2018, 01:27 PM
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To answer your questions, in general.

To accurately check your valve guides you should disassemble the heads, removing the valves. Then clean out all the carbon build up in the guide. There is more than one way to measure. The easiest is to install a new valve, dry, and measure how far it can be moved side to side. A dial indicator works. Your exhaust guides are more prone to wear. You can get an idea, just by using a screwdriver to see if the retainer can be moved with the valves and springs still installed. IMO, if they are not perfectly tight, replace them.

As long as the top of the cylinders and head sealing surface are not damaged and no sign of compression leakage, you should be good to go. No machining required.

Just replace the lower studs with steel. The uppers will still be good.

The torque is 24 FT LBS. 32 is newton meters.

no idea on the cams.
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Old 02-12-2018, 01:49 PM
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One shop I have used uses the dial indicator method. You set the dial against the tip of the valve stem and see how much lateral movement you get. They use 0.8mm as the max tolerance.
bear in mind only some of that will be the guide - the stem wears (tapered) too.
Gordon - do they do that test with the valve depressed at say 10mm, or closed?
Alan
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Old 02-12-2018, 06:13 PM
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The way I have seen it specified is to have the valve head 10mm off the seat. Use the dial indicator against the valve head.

One thing to keep in mind is the guide will wear more in one direction due to the forces of the rocker. The guide will have an oval hole.

Old timey mechanics will just put in a new valve, hold the head just off the seat, and give it a wiggle. Easy to tell if the guide is worn.
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Old 02-12-2018, 06:57 PM
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I called the local machine shop yesterday and asked for price incl cleaning, new valves and guides (with seat grinding if needed). Price = 1300$ auch!

So it would be nice to clean and check my self.
Old 02-12-2018, 09:29 PM
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12 new valves/guides plus machine work. Thats a good price. Depends what sort of job you want out of it - long term.
Alan
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Old 02-12-2018, 10:43 PM
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If you're getting DC20 cams, I would throw in a new set of John's valve springs in there as well. Sounds like a great build
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Old 02-13-2018, 04:36 AM
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Part of the problem with the head sealing is the cylinders are Carrera requiring a different torque value.
Off my memory, the spec is 15 #ft, first torque. Second torque is 15#, then a 90 degree swing
Lube the threads.
Bruce
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Quote:
Originally Posted by Flat6pac View Post
Part of the problem with the head sealing is the cylinders are Carrera requiring a different torque value.
Off my memory, the spec is 15 #ft, first torque. Second torque is 15#, then a 90 degree swing
Lube the threads.
Bruce
Yes, I have seen that technique described before. However, I do not understand the concept of "a 90 degree swing"?!

Can you elaborate please?
Old 02-13-2018, 04:51 AM
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Oh you mean swing the engine!? Torque down one side in two goes, and then do the other side. Got it.
Old 02-13-2018, 04:56 AM
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By the swing I mean a torque increase of 90 degrees on the torque wrench, not giving you an actual torque number but 15# + 90 degrees, +/- 2
Bruce
Old 02-13-2018, 06:30 AM
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Quote:
Originally Posted by Flat6pac View Post
By the swing I mean a torque increase of 90 degrees on the torque wrench, not giving you an actual torque number but 15# + 90 degrees, +/- 2
Bruce
Interesting that Wayne in his book does not mention this?

How would you check or retorque after 1k miles using this spec?
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Old 02-13-2018, 09:31 AM
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The spec book contains this info.
Bruce
Old 02-13-2018, 09:37 AM
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The spec book contains this info.
Bruce
I don't see a mention of re-torquing the heads after break-in in the Spec Book.

So do you back each nut off. Then re-torque according to the book?
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Old 02-13-2018, 09:58 AM
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I’ve never had a problem with loose heads or nuts loosening on motors I ve built. I do test the torque several times before closing up. I have had motors come in that were loose on the nuts but they were not my builds.
I did have an 82 turbo with all 24 dilivars in place and needed a 4 ft breaker bar to break the nuts loose of the dilivars.
Bruce
Old 02-13-2018, 10:36 AM
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Bruce - are you sure the 90 deg torque is correct for the head studs? Waynes book, and others I have all do a 2 step process, but to a final ft/lb value.
The angle torque is usually used for 'oncer' stretch bolts - eg rod bolts. I have not seen it used /recommended for head studs.
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Old 02-13-2018, 11:19 AM
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I'm pretty sure my leak was caused by loose bolts, but I also have Dilavar on the exhaust side.

The 90 degree swing must correspond to a second higher torque value, just like Wayne's recommendation.
Old 02-13-2018, 11:40 AM
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Quote:
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I'm pretty sure my leak was caused by loose bolts, but I also have Dilavar on the exhaust side.

The 90 degree swing must correspond to a second higher torque value, just like Wayne's recommendation.
Not exactly. Two different processes. Torqueing to ft/lb is just that - putting a defined load on the stud. Torqueing to an angle deflection is defining a certain amount of stretch. If the book says 23 ft/lb, then you torque to that load. there is no guarantee that a 90 deg deflection will give you that. It will have a ft/lb value - but that is not what you have torqued to - you don't know what the ft/lb value is. Not sure why you wouldn't use a ft/lb torque when that is the value specified.
Maybe I have been doing it wrong all these yrs. Just curious about Bruce's process.
He does more engines than me.
Alan
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Old 02-13-2018, 11:55 AM
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Butł

Quote:
Originally Posted by Alan L View Post
Not exactly. Two different processes. Torqueing to ft/lb is just that - putting a defined load on the stud. Torqueing to an angle deflection is defining a certain amount of stretch. If the book says 23 ft/lb, then you torque to that load. there is no guarantee that a 90 deg deflection will give you that. It will have a ft/lb value - but that is not what you have torqued to - you don't know what the ft/lb value is. Not sure why you wouldn't use a ft/lb torque when that is the value specified.
Maybe I have been doing it wrong all these yrs. Just curious about Bruce's process.
He does more engines than me.
Alan
Yes I agree. The final torque value will be unknown - just like Bruce said. Apparently both methods work? But how about re-torque after break in?
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