With a digital torque wrench (to accurately measure degrees of rotation) final torque WILL be known as it is displayed. Re torque is not mentioned in the spec book because it is not required.

Cheers

Perfect - thank you.

The new nuts are just coated with something different. Old were gray, probably uncoated, and the newer version were simply yellow zinc chromate (yellow passivated)?

http://forums.pelicanparts.com/uploa...1519054653.jpg
http://forums.pelicanparts.com/uploa...1519054660.jpg

Additional question:

All piston rings are good. Cylinders too with good cross pattern.

Should I replace rings anyway?

I think part of the confusion is between "re-torque", "re-tighten", or check tightness?

FWIW, After 150 miles on my new motor, I put a torque wrench on my head nuts and they all needed about a quarter of a turn to get them up to spec torque. BTW, I used VR base gaskets.

I had to pull the top end apart, don't ask, and when I reassembled I used OE base gaskets. This time after 500 miles I checked the torque on my head nuts and they are all still tight.

YMMV.

What size EFI/ITB were you running and with what cams previously?

43mm ITB's , 30LB injectors. Before was standard SC cams.

What kind of ITB? Are you bumping-up your injectors, and what led you to move to DC 20 as opposed to something a little more aggressive? Oh, what CR?

Always curious as to what drives particular choices, pro/cons.. other limitations etc..

Thx

It's the kit from Closed Course Motorsport (Clay's) which uses Triumph 43mm throttle bodies and Clay's manifolds. The 30LB injectors should be good for 280hp or so. Don't think my build will go beyond that (I wish....)

I initially went for 993SS cams, but since I'm not building a race car and since I got the DC20's dirt cheap, I though I would give it a go. Should be a "hot 964" cam.

I haven't measured the CR yet, but it should be 9.3:1 or 9.8:1 (Mahle made two different kits). I did consider gong for JE's or similar with 10.1:1 or even 10.5:1 - still single plug. Slippery slope. And again, very unsure about the high-comp-single-plug combi. I know guys who're running very high comp on their 2.7's - but not really anyone with larger displacements. So spend my money on some Wevo stuff and fresh paint instead.

So in total: Hopefully a street friendly 230isch rwhp (naive I know....) 1950lb hot rod Targa when it's all done.

You cam measure the angle (somewhat) with a simple torque wrench. From where you start the turn to when the wrench click's.

But the angle method is a lot more accurate. It removes all friction, wrench errors etc. 90° is 90°.

Biggest problem with these heads is making sure the heads don't collapse under the head nut washers.

3.2
 

Hi,on your setup with the weepy head seal I have found that the factory 3.2 head gasket repair kit works the best.I think the part # is 930-104-381-01 This works very well if your head surface has been machined.Use valve grinding compound & lap the cylinders to the head.Place in the oven & warm to 200 degrees.Wear a pair of gloves & wipe the surfaces with ATF on a rag as the pores are all expanded.The repair gasket is made of Inconel with a silicone like coating.Finish cleaning with Brakecleen.It will never sweat oil again.I use these gaskets on Turbo motors as well with great results.Good luck with your build.Oh,these are not expensive.Ciao Fred

My 3.2 had leaky heads (and one broken studs at the end).

I can't remember if I had the heads machined, I don't think so... Maybe I lapped them with grinding paste.

Then I bolted it up with Supertec head studs, no leaks 6-7 years and 30.000 miles later.

I used the same studs on my 3.6 rebuild too (that had leaks even though it had the updated seals), no leaks yet, but its only 2 years and few miles.

If I build another engine I'll use the same studs. No re-torque, set and forget.

Those gaskets are .020 thick work great to repair heads that have been cut to far too, to keep things stock height you will need to machine your heads .020 from the stock height of 84.5mm

https://uploads.tapatalk-cdn.com/201...de66b9cc46.jpg


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Fred & Craig make a very good point about those gaskets being beneficial if your heads have been machined. Because if you plug the added thickness of these into a compression ratio calculator, they have a considerable impact on the difference.

For instance let's say for the sake of simplicity and calculating, you have a dead on 98mm bore, 70.4mm stroke, typical 90cc combustion chamber volume (should actually be a bit less if the head is machined, but let's just use the original unmolested volume) and a measured piston dome volume. Dome volume is dependent on the piston type/shape and it obviously dictates compression ratio. Let's use a value of 33.5cc because it produces a typical Euro SC compression ratio of 9.3:1 when you calculate everything out.

Also in the compression ratio calculation is deck height. Let's say your cylinder base shim/gasket is sized good. Meaning, the original base gaskets that were used when the engine was first built at the factory are 0.25mm and let's say you increased them to 0.5mm to hit your desired 1mm of deck. Now by adding that 0.20" (0.5mm) head gasket because you'd like it to seal as best as possible, you're effectively going to be raising your cylinder height and that means you're now going to have 1.5 mm deck. That additional 0.5mm of deck height reduces the static compression ratio.

Here's the calculation

Bore (mm) 98
Stroke (mm) 70.4
#cyls 6

Bore radius 4.9 (cm)
Stroke 7.04 (cm)
Resulting displacement (cc) 3186.15 This is Pi x radius x radius x stroke x 6 cyl.
Single cyl. displacement (cc) 531.02 This is the above displacement divided by 6
Deck Height (cm) 0.1
V1 Swept V (cc) = single cyl. displacement = 531.02
V2 Deck V (cc)= 7.54 = Pi x radius x radius x deck height (0.1cm = 1mm)
V3 Head V (cc) = 90
V4 Piston Dome V (cc) = 33.5

Compression ratio = (V1+V2+V3-V4)/(V2+V3-V4) = 9.29:1

Now change the deck height to 0.15 in the above calculations and your resulting compression ratio is 8.83:1, which is a difference of 0.46.

So my point is you have to recognize using the gasket has a significant effect on deck height and compression ratio. Ideally what you should do is "cheat" a bit and use the minimum thickness cylinder base gasket (0.25mm) when you are using these cylinder head gaskets. Which is more important to you, deck height, cylinder sealing or compression ratio? 1mm of deck height is a general rule of thumb to make sure you have ample clearance from the edge of the piston to the edge of the combustion chamber. But there's nothing in the original engine specs that says 1mm is the absolute minimum to be adhered to. Folks who build race engines often go quite a bit below the 1mm.

Maybe also consider the volume that is around the fire band down to the top ring and the diameter of the fire band. This makes a difference to your numbers if used.

Often on these older pistons the fire band is upwards of 6.0mm tall and the piston OD there can be 1.0mm smaller.

Street engines with stock parts would make the compression ratio the most important. You do not have the luxury to establish a deck height as well as a compression ratio without one effecting the other.

Race engines should be as tight as possible with the piston "cleaning" the carbon off the chamber every time it reaches TDC.

My deck hight is currently 0.7mm with 0.25mm base gasket. I have no records of the heads or cylinders being machined. I believe it's the standard Mahle "max moritz" kit.

Using the above calculations, I have a CR of 9.6. However, I have previously read elsewere that the Mahle big bore pistons for the 3.0 engine (3.2ss) were 28.4cc and the 3.4ss piston was 33.5cc.

In that case, the CR is 8.94. I'll have to measure my piston domes.

Does the base gasket seal anything? I've seen posts from engine builders who claim they never use a base gasket?

.7mm deck height sounds like you are cutting it close. But yes you can assemble without the base gaskets. My old motor does not have them and it never caused problems or leaks.

Let us know how the CCing comes out.

The base gasket is to seal against crankcase pressure - nothing like the cylinder head pressure. If others can get away without them, you probably can - just make sure totally clean before seating. Else may get oil weep from crankcase. But dropping the gasket out will make your deck height worse (smaller)?
Alan

Yes my deck hight would be about 0.5mm. I need to verify my deck hight and measure the piston domes. Would like to have a CR close to 9.8:1

You better check your valve clearance first.
Alan

If you're going to go without a base gasket, i'd be sure to dress the sealing surfaces of the engine case and the cylinder to avoid any leaks. On my current '86 3.2 engine rebuild, these surfaces show a bit of corrosion. So I plan to lap them together with some valve grinding compound to smooth them out.

If no copper base gasket, I definitely would use some non-hardening sealant like Curil T or blue Hylomar to seal that area, just to be sure you don't end up with a pesky weep leak. With the new base gasket i'd leave it dry. In the one instance that i've seen base gaskets reused (heads were taken off, cyls left in place to do valve guide replacement) and they still don't show any leakage 20K miles later.

Neil makes a very good point about the fire ring zone that creates additional void space beneath the combustion chamber. Although over time this area gets partially filled up by carbon deposits collecting on the cylinder wall (actually considerably thick here) and a little bit on the periphery of the piston above the uppermost compression ring. What that means to me is a newly built engine has that void space which reduces the compression ratio. Then as the carbon collects it increases the compression ratio. The space never gets completely filled because the movement of the piston keeps the buildup at bay. So maybe account for 1/2 that void volume and call it 6mm tall by 0.5mm thick?

The same can be said for the carbon that grows on the piston crown and the cylinder head. This carbon on the crown & chamber is much more prominent than the fire ring carbon. So that too increases the compression ratio over time. Should we compensate for that as well?

Here's some pictures from the 80K miles engine i'm working on right now

http://forums.pelicanparts.com/uploa...1521211470.JPG
http://forums.pelicanparts.com/uploa...1521211470.JPG

I don't know if this is something that is taken into account with the original engine design. In other words, did Porsche slightly reduce the compression ratio in the design, knowing that the carbon buildup will eventually increase the compression ratio?

Or you can just let your valve guides leak and that'll keep things cleaner? ;) These pics are taken of the same engine at cylinder #3 that had a very leaky intake valve guide. Note the small pool of oil on the closed intake valve and the very fouled, but still operational spark plug.


http://forums.pelicanparts.com/uploa...1521211543.JPG
http://forums.pelicanparts.com/uploa...1521211543.JPG
http://forums.pelicanparts.com/uploa...1521211543.JPG
http://forums.pelicanparts.com/uploa...1521211543.JPG

Just to update:

Heads are now completely re-built. Cleaned (not blasted). 12 new high end valves, seats CNC machined. New retainers, springs and guides. Basically like new.

http://forums.pelicanparts.com/uploa...1524578792.jpg

http://forums.pelicanparts.com/uploa...1524578792.jpg

And I finally got my custum made rings as well. Naturally, Mahle does not provide replacement rings for their Max Moritz conversions. And to further complicate things, they are 1.2, 1.2 and 3.0mm - which no other company uses apparently.

So here we go: New 1.2mm compression ring, 1.2mm Napier 2nd ring and 3 piece oil ring:

http://forums.pelicanparts.com/uploa...1524578792.jpg

It does feel good knowing it's all in proper order though. Now it's time for assembly. Thanks again for help and guidance.

Good stuff. keep it up!

So I've CC'ed the heads to 89-90cc, pistons to 33cc isch, deck hight 0.9mm with base gasket.

http://forums.pelicanparts.com/uploa...1525239142.jpg


http://forums.pelicanparts.com/uploa...1525239142.jpg

So with somewhat crude measurements I have calculated my CR to 9.2:1 - which is pretty close to the 9.3:1 that Mahle states for the 3.2ss kit.

If I remove the base gasket, I will get CR around 9.5-9.6:1, but with a deck hight of only 0.6-0.65.

So unless you guys advise me differently - I'll stay with the base gasket. Correct?

Exactly what valves did you use?

Those are quality valves from Intervalves Technologies in Switzerland.

INTERVALVES TECHNOLOGIES AG