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Old 05-01-2018, 08:16 AM   #151
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Square tooth Gates belts are readily available in the USA and we stock them for $34.
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Old 05-05-2018, 07:25 PM   #152
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Quote:
Originally Posted by ROG100 View Post
Square tooth Gates belts are readily available in the USA....
I checked quite a few websites without finding it. All my faves (928 Intl, Pelican, Vertex, RM European) plus a half-dozen other Porsche and 928 vendors.

$29 through eBay, delivered.
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Old 05-05-2018, 07:48 PM   #153
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Default Intake tube polishing

Here's a few pictures and discussion on polishing the intake tubes.

This picture shows the first set of tools used on the tube. They're in order of use, left-to-right.

The first tool is a eye hook on a rope that drag either a Scotchbrite pad or rag through the tube. The trick is two large washers that force those against the sides of the tube. The tube is a bit more than 1 1/2" and the washers are 22mm.

With some mineral spirits on the scratchy pad, the inside of the tubes got fairly clean. Then the rag gets the solvent. When I first tried the sandpaper flap, it got gunked up really quickly and the working part had to get cut off. That's OK but I was going through the paper pretty quickly. Cleaning it first worked well.

The second step was to use the wire wheel on the ends. The wheel is 1 1/2" and fit the tube well. Lightly pressing up/down/left/right and the ends got nice and shiny. The nose of the drill fit into the tube so it'd get 4" in from the end.

Then comes the sandpaper flap. That's a "locally sourced" tool. The spring shaft is from a magnetic pick-up tool. With a finishing nail pressed into the end, it could get clamped tightly in the drill chuck. The sandpaper is a 1" wide sanding belt cut in half. Then the belt gets duct-taped to the shaft and it's ready to go.

I fed the flap in a few times from each end and worked in back-and-forth a lot. After each of the first two or three cycles the end needed to be cut off but after that it wasn't getting clogged with oily dirt. I was surprised how much gunk was inside the tubes.
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File Type: jpg PolishingTools1.jpg (139.4 KB, 0 views)
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Old 05-05-2018, 07:49 PM   #154
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Default Tube polishing, cont'd

The next step is to grind the inlet end. The tools are used left-to-right. The half-moon file was rarely employed but helped where the casting line was especially thick.

Which reminds me... I'm curious as to how the tubes are made. I always thought they were cast and there were mold separation lines. I'm starting to think they were cast in two or more parts and then welded together. From the inside, it looks like it may be welded. That'd explain why the "casting lines" are so thick. It might be cheaper to make that way, too. Anyways...

The goal of the grinding was to make the inlet end more circular and wider at the mouth. The tubes don't all line up with the plenum right and opening up the tube and rounding off the lip should help air flow.

The main tool is the barrel grinder. Using that, the inlet gets shaped more into a "V" or maybe a tulip shape. Takes a good while to do especially to make it circular and clean up the two weld/casting lines.

The ball grinder cleans up any unfortunate gouges and bumps deeper in the inlet. It's also good for smoothing down the bends right after the inlet.

The cone grinder is used to smooth the inside after it's been cut back and to shape the lip. The tube, as made, has a fairly square lip and a few passes at different angles makes it a quarter-round.

The rotary sander (110 grit) bit takes out a lot of course grinding marks. It's also good for reaching down the tube to the first bends.

Finally, some sandpaper (220 grit) is used to get the surface smooth. That pie-shaped piece is a section of self-adhesive sanding disk. Quite handy as I'd stick it to a gloved finger and could get some good action with it. All the preceding tools are rotary and this one goes across those. I'd do it on the inlet and then on the outlet where the wire brush left some scratching. The ends are nicely smooth to the touch afterwards.
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File Type: jpg PolishingTools2.jpg (139.3 KB, 0 views)
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Old 05-05-2018, 08:11 PM   #155
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Default Tube Polishing, Cont'd

This pictures show the before and after. The first pic is the inlet after cleaning with the eye-hook thing. Note the thickness of the lip and how square it is. The surface feels rough.

The second and third pics show the results of grinding and the flapper. The pics were taken before cleaning the tubes out with the eye-hook, clean towel sections and lacquer thinner. I'll clean them again and blow them out to ensure not grit gets sucked into the engine.

The texture is really exaggerated in the pics. Might be the lighting or smearing of the metal. (Check the bits on the grinders) It's a little "dimply" but very smooth. The third pic shows the inside and you can see the flapper has cleaned up the tube.

The tube inlet is about 1/2 as thick after the grinding and is rounded. The thinner lip blends smoothly with the rest of the tube about 2" in.
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File Type: jpg TubeOriginal.jpg (168.1 KB, 0 views)
File Type: jpg PolishedTube1.jpg (146.5 KB, 0 views)
File Type: jpg PolishedTube2.jpg (133.3 KB, 0 views)
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Old 05-05-2018, 08:23 PM   #156
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Default Tube polishing, cont'd

This is the debris that came out. The black pile is from using the wire wheel and the sandpaper flapper. Maybe 2 tablespoons of crud. The initial scouring took out most of the oily dirt. Note the sparkles of Al in the pile as those tools do work the surface back a bit and take off the tiny nubs from the casting.

The silver pile is the aluminum taken off in grinding. It's 1-2 teaspoonfuls.

The whole operation took almost an hour per tube. Maybe not the most valuable use of time. I've been mulling this over since I started modifying the 928 so 15 years. "Can ya port that intake manifold?" Just had to give it a whirl.

A friend asked how much power it'd yield. I had to be honest: "Something between 5 hp and 0.5 hp." I don't have high hopes but if it's 5hp, I'll be super happy. Assuming 300hp a 1% increase in air flow would net 3hp. Then again, I'll never know.

Just a few more pre-build things to get done, like fix the wiring harness, and it'll be assembly time.
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File Type: jpg TubeDebris.jpg (153.0 KB, 0 views)
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Old 05-07-2018, 03:54 PM   #157
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Quote:
Originally Posted by GlenL View Post
I checked quite a few websites without finding it. All my faves (928 Intl, Pelican, Vertex, RM European) plus a half-dozen other Porsche and 928 vendors.

$29 through eBay, delivered.
http://shop.928intl.com/Timing-Belt-...28-105-157-00/
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Old 05-21-2018, 10:26 PM   #158
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Moving along towards assembly. The block went back on the stand today.

Here's a couple of pictures showing how the block was drilled to allow use of a later oil pump. This '89 pump (discussed previously) has a different oiling path that pumps oil through the bearing and, from there, it drains back into the pan. Early pumps draw the oil from behind the seal and may suck in air through the seal. This is better (or simply "better") and the pump itself, although used, is likely tighter than the original one.

The first pic shows the drilled hole and the inside view of the pump. The drain is the oval area. The second pic shows marking the drain area on the block.

I also used Plastigage to size the rod journals. Using one rod and an old bearing, I checked the clearance each journal. All were in the range 0.045mm to 0.075mm which is in-spec (0.02-0.07) or real close to it. Considering the old bearing is a bit worn, it looks really good. This gives reassurance that the rod journals aren't worn and some guidance if the new bearings are too tight or too loose as to where to move the bearings to get a better fitment.
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File Type: jpg OilPump1.jpg (218.9 KB, 0 views)
File Type: jpg OilPump2.jpg (233.4 KB, 0 views)
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Old 05-27-2018, 07:04 PM   #159
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Default Crank in block

Moving right along...

The crank went in the block today. The Plasitgage numbers looked good but a little loose. They were close together with all between 0.07 and 0.09mm. The range is 0.02 to 0.098mm so in the upper range of acceptable. The crank turns very nicely with no hints of sticky spots.

The bearing set has all split bearings. These are NLA, last time I checked, and I spotted this on eBay a couple of years back. When cleaning the bearings, which were pretty tarnished, I found the marks "12 99" and presume these were made in December 1999. NOS trumps NLA every time!

It's not bolted in yet, though. I've gotta get the pistons in so I can fit the crank scraper kit. I got one from 928 Motorsports after giving up waiting for the one I ordered from Ishihara-Johnson.

I checked the ring gaps on the Goetz 97mm rings. One ring went into all holes to see if there are variations (not really) and then all the rings went into one hole. This way I can put longer rings into bigger holes.

As many people have found, the top rings are too short. The gaps are from 0.6mm to 0.83mm where the spec is 0.2 to 0.4mm. Rats. I'm going to look into getting some other top rings. The second rings are came in at 0.43 to 0.53 so not far from the 0.4mm max for those.

One confusing part was the the Goetz rings come in a three-part envelope that's numbered 1-2-3. I thought the rings were good until I realized that Porsche numbers from the top 1-2-3 and these were numbered backwards. (3-2-1) The #3 ring (oil ring) has a gap spec over 1mm so I thought the top rings were golden but the wide gaps I was finding bothered me into digging into it. The "tech spec" booklet has the gaps but doesn't say what 1-2-3 are. One of the exploded diagrams in the manual shows 1 is the top. Goetz thinks 3 is the top. Cripes. Other sources and the "rules of thumb" for gaps show that the top should be smaller and 0.4mm is appropriate.

Next up is figuring out what to do about the top rings and to get the scraper fitted. And check the rod bearings. I'll probably assemble and install the pistons using the rings I've got and hold off using the new rod nuts. Might need to take it all apart and I can move ahead while figuring out what to do with the rings, and while getting any new ones shipped in.
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Old 05-28-2018, 12:53 AM   #160
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getting there! You'll have a new old engine soon.
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Old 07-17-2018, 11:59 PM   #161
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Default Pistons installed

Starting with a picture of some progress. After some delays, the pistons are in the block!

The installation was fairly simple. No problems getting the rings in. Sometimes they catch on the cylinder top but I only needed to restart with one piston. Just gotta get the compressor cranked down straight and then seated well to the block.

It took a while to get the rings figured out. That follows.
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Old 07-18-2018, 12:17 AM   #162
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Default Working out rings

As mentioned previously, I got 8 sets of Goetze rings and they all had gaps that were too big. The spec in 0.4mm max and the smallest was 0.66mm with the biggest being 0.813.

All of the pistons were Tolerance Group 1. I put one ring into all of the bores and found only two sizes of 0.711mm and 0.762. I was only using single blades of the feeler gauge so that leads to "two sizes" but they were all pretty close. So, no real opportunity to move the Goetze rings around to address the gap problem.

So, what to do? There aren't a lot of rings offered in 97mm or close to it. There are oversized rings for other engines that are near 97mm and 1.5mm thick but pickings are slim.

What I settled on trying were Mahle rings for the 911 Turbo (3.8l). These are 97mm and 1.5mm for a Nikasil-coated bore. It's hard to find good technical data but the Goetze catalog says that the same ring is used for both the 928 97mm set and the 911 Turbo set. Only the top ring is usable in the 928 engine.

I ordered 1 set of the Mahle rings to check out. The one top ring showed a gap on 0.533mm. Still not in spec but smaller than any of the Goetze rings. Gambling, I ordered 7 more. Surprisingly, the 0.533 ring was the largest and the rest measured 0.431 to 0.483mm. This is in a bigger hole. (#1)

The numbers for the rings is below along with the Plastigage results for the mains.
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Old 07-18-2018, 12:21 AM   #163
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[Looking at the bore sizes and the rings on hand, I figured to put tighter rings in bigger bores and balance bigger gap tops with smaller gap middles. The oil rings don't really matter. The parcelling-out is shown in the next pic.
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Old 07-18-2018, 12:32 AM   #164
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Comparing the rings, the Mahle rings look to be a better option than the Goetze. The faces are both described as "tapered." The Goetze rings are phosphated and, while I couldn't find a spec, the Mahle rings look to be chrome plated. That's better for the Alusil cylinders, from what I read.

Another difference is that the Mahle rings smaller circles than the Mahle. This should mean lower tension in the bore and less sliding resistance.

Here's a few pics for reference showing the Part Numbers and rings.
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File Type: jpg RingPNs.jpg (180.5 KB, 0 views)
File Type: jpg RingPacks.jpg (259.1 KB, 0 views)
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Old 07-18-2018, 12:35 AM   #165
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Here's a pic trying to show the tapered face and another showing the coating.

The camera doesn't capture it well but the face is tapered the same way on both rings. An interesting difference is the bevel on the inside of the Goetze ring. Not sure what that does.

The Goetze rings are black and "powdery" while the Mahle rings are smooth and shiny. The second pic also shows that when out of the bore, the Mahle ring's ends are closer together. Lower tension rings take less power to slide. It might break-in more slowly, though.
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File Type: jpg RingsFlat.jpg (122.8 KB, 1 views)
File Type: jpg RingsOnEdge.jpg (186.4 KB, 0 views)
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