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Daddylolo
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Joined: June 05, 2007
Posts: 253
Location: Sintra, Portugal
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 Posted: Thu Jan 09, 2020 10:25 am Post subject: Con rod question |
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I'm rebuilding my type 4, 2L engine and have a issue identifying the up and down side for the con rods. Can you guys tell me if numbers face up or down? The rods seem to be original VW but as in type 1 there is no notch to see.
Another question I have: is there a figure for the force applied on fighting screws who fix the camshaft to gear? Bentleys manual is not specific on that
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SGKent 
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Joined: October 30, 2007
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Location: Citrus Heights CA (Near Sacramento)
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| Posted: Thu Jan 09, 2020 10:45 am Post subject: Re: Con rod question |
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type 4 have no up or down. I usually put them so I can read the numbers to verify that they match.
Those need to go to a reputable machine shop to be checked both big and small end. Make sure they read 360 degrees on the big end, not just about 300 like many machinists do.
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Wildthings
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Joined: March 13, 2005
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| Posted: Thu Jan 09, 2020 3:13 pm Post subject: Re: Con rod question |
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You should add the oiling notches as per the VW service bulletin. VW specifies a "V" notch, but I just use a small round file which gives a "U" notch.
Whoever supplied the timing gear and fasteners would be the one to ask about the torque for the timing gear bolts. I had to grind down a socket to get it to work with the very thin nuts supplied with the gear. |
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SGKent
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Joined: October 30, 2007
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Location: Citrus Heights CA (Near Sacramento)
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| Posted: Thu Jan 09, 2020 3:40 pm Post subject: Re: Con rod question |
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U is less prone to cracking than a V.
14 ft lbs on cam bolts with red Loctite is commonly used. A lot depends on the metric grade of the bolts, and whether lubricated or dry. Metric grade 8.8 is similar to SAE Grade 5, metric grade 10.9 is similar to SAE grade 8. Most of the bolts for cams don't have a grade marking on them whether they are the milled type or the domed type.
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Daddylolo
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Joined: June 05, 2007
Posts: 253
Location: Sintra, Portugal
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| Posted: Fri Jan 10, 2020 3:49 am Post subject: Re: Con rod question |
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Great help, thank you guys!
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Amskeptic
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Joined: October 18, 2002
Posts: 8568
Location: All Across The Country
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| Posted: Fri Jan 10, 2020 6:24 am Post subject: Re: Con rod question |
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| Daddylolo wrote: |
| Great help, thank you guys! |
Don't forget! Your new wrist pins must not fall through your fresh new connecting rod bushings like mine did yesterday! They are supposed to be a light press fit at room temperature.
Colin
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orwell84
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Location: Plattsburgh, New York
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| Posted: Fri Jan 10, 2020 8:38 am Post subject: Re: Con rod question |
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| SGKent wrote: |
type 4 have no up or down. I usually put them so I can read the numbers to verify that they match.
Those need to go to a reputable machine shop to be checked both big and small end. Make sure they read 360 degrees on the big end, not just about 300 like many machinists do. |
I don't understand what you mean about checking them 360 instead of just 300...
I'm currently getting my head around rods...Like many of those parts I didn't give much consideration, there are actually many things to consider. I have seen one rebuild thread where bent rods were found only after checking deck height. The basics:
Straight as well as parallel
Balanced with each other as well as big end and small ends
Piston pin bushing clearanced for each piston pin you have in hand
Proper bearing clearance with the journal
New nuts and bolts? New bolts require rebushing the big ends, when is replacing them required? I replaced the nuts on mine for good measure. The guys at at a local Porsche place had a good laugh when I told them my engine would probably never see 5k rpm
Side clearance-it's a huge range but can be a factor in maintaining oil pressure
Big ends-I have not seen specs for diameter or out of round, just for bushing/pin fit and that seems to be done mostly by feel...
There are a few sources I know of for "rebuilt" stock connecting rods, but it's not specified what they actually do. |
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SGKent
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Location: Citrus Heights CA (Near Sacramento)
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| Posted: Fri Jan 10, 2020 9:09 am Post subject: Re: Con rod question |
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| Quote: |
| I don't understand what you mean about checking them 360 instead of just 300... |
there is a part line where the bottom half and the top half connect. If that is tweaked/offset, or is not re-honed properly when the big end is sized, then the distance between one side and the other is larger one side of the part line and smaller on the other. That pinch can destroy a bearing or cause excessive internal wear that eventually results in a ruined bearing / spun bearing.
The human wrist does not rotate 360 degrees, Hold something and try to rotate it 360 degrees by turning your wrist. It takes a lot of practice, wind-up and shoulder movement to twist it 360 degrees. As a result when a rod is checked most machinists are only rotating it about 300 degrees on the dial that measures it for a final size. Unless you have a anal retentive machinist like I was re-machining high-quality connecting rods, the connecting rods only get measured 300 degrees instead of the full 360 + degrees. If you don't measure it 360+ degrees you will never know if it is pinched or way too big at the part lines.
The reason I decided to learn automotive machining was because at Road Atlanta we spun a bearing on an engine built by one of the top engine builders in the USA, Mac Tilton's team. They built Paul Newman's winning cars. When the bearing spun Mac Tilton and team could not figure why it happened. My mentor who was also a top engine builder was also at Road Atlanta that day for the finals so he came over and took a look. It took him 20 seconds of looking at the engine to determine that the rods were all pinched across the part lines and that is why they were in the process of spinning. (One rod was bent and ready to shrapnel when Leland sensed the engine was dying so he killed it on a practice lap.) I then went to work for my mentor learning the trade so I didn't have to rely on other shops to do the machining on the engines we were racing.
When the rod is measured the tool that measures it leaves a tiny scribe line on the inside of the rod. If you look carefully you can see it. There should be one on each inside side of the rod. It should go 360 degrees all the way around the rod and not stop short of the part line. One measures one side, flips the rod over and measures the other. The same machine is used for the big end and the small end, but the problem of being offset is only the big end.
This is what a tool might look like that measures the rod. A working machine like this is usually somewhere between $4000 and $8000 with all the mandrels. Owning one isn't a hobbyist thing unless someone has a place to store it and deep pockets. Machine shops are a losing business proposition these days because modern engines often outlast the cars. Finding a shop that does quality work is really hard because they can't pay more than minimum wage, and it is next to impossible to find top quality workers for that rate.
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Clatter
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| Posted: Fri Jan 10, 2020 1:16 pm Post subject: Re: Con rod question |
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Bearing tangs go down.
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SGKent
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Joined: October 30, 2007
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Location: Citrus Heights CA (Near Sacramento)
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| Posted: Fri Jan 10, 2020 5:42 pm Post subject: Re: Con rod question |
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| Clatter wrote: |
| Bearing tangs go down. |
The logic Steve (Clatter) is using is that the when the engine is rotating the tang is hitting the other half of the rod, stopping it from moving. The factory photos (including the German factory manual) show the tang down on the rod side and up on the cap side which agrees with that. The engine rotates clockwise, so the rod bearing tang will spin into the cap and the cap half will spin into the rod. If the rods are flipped over then the bearing shells can slowly work on the tang - unfortunately by the time that happens the engine is toast already. That said, the factory does not specify an up or a down (small end offset) like the type 1 engine but Clatter's advice is the best solution to prevent bearing walking.
type 1 engine
type 4
Type 4
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orwell84
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Joined: May 14, 2007
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Location: Plattsburgh, New York
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| Posted: Fri Jan 10, 2020 8:27 pm Post subject: Re: Con rod question |
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Something new everyday 
Thanks! |
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Wildthings
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Joined: March 13, 2005
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| Posted: Fri Jan 10, 2020 8:54 pm Post subject: Re: Con rod question |
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| SGKent wrote: |
type 4
Type 4
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I can read the number on the rod but seen none on the cap. Looks to me like they have the cap backwards.
If it were important that the bearing shells were all positioned so they were subject to the same forces then you would not turn the rods so the bearing tangs were all facing down or that the numbers on the rods were all facing up. Unless you had all the rods laid to the same side of the crank. Think about this !!!
Of note, the Vanagon Bentley makes no mention at all of which way the rods on a Type 4 go and the Haynes say to punch mark the rods so you can get them turned correctly on reinstallation. |
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SGKent
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Location: Citrus Heights CA (Near Sacramento)
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| Posted: Fri Jan 10, 2020 11:38 pm Post subject: Re: Con rod question |
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| Wildthings wrote: |
| SGKent wrote: |
type 4
Type 4
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I can read the number on the rod but seen none on the cap. Looks to me like they have the cap backwards.
If it were important that the bearing shells were all positioned so they were subject to the same forces then you would not turn the rods so the bearing tangs were all facing down or that the numbers on the rods were all facing up. Unless you had all the rods laid to the same side of the crank. Think about this !!!
Of note, the Vanagon Bentley makes no mention at all of which way the rods on a Type 4 go and the Haynes say to punch mark the rods so you can get them turned correctly on reinstallation. |
Good catch Mike. That photo is from the German printed English orange VWOG manual. I don't have a spare 2L rod to look at the numbers and tangs. If they are on the same side when the numbers are together it would still make sense to put the tang on the upper half in a position where the tang is facing the lower half in the direction of rotation because that is the side with most force. As I recall, and it has been awhile but I think on some engines the number side of the rod faces away from the camshaft or jackshaft if the cam is overhead. On some it is where the oil hole is in the rods.
Example of another engine type:
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Daddylolo
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Joined: June 05, 2007
Posts: 253
Location: Sintra, Portugal
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| Posted: Wed Jan 15, 2020 12:51 pm Post subject: Re: Con rod question |
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| SGKent wrote: |
| Clatter wrote: |
| Bearing tangs go down. |
The logic Steve (Clatter) is using is that the when the engine is rotating the tang is hitting the other half of the rod, stopping it from moving. The factory photos (including the German factory manual) show the tang down on the rod side and up on the cap side which agrees with that. The engine rotates clockwise, so the rod bearing tang will spin into the cap and the cap half will spin into the rod. If the rods are flipped over then the bearing shells can slowly work on the tang - unfortunately by the time that happens the engine is toast already. That said, the factory does not specify an up or a down (small end offset) like the type 1 engine but Clatter's advice is the best solution to prevent bearing walking.
type 1 engine
type 4
Type 4
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So you mean, even if on type 4 engines there is no "up" mark on the rod there is a position so the bearing is "hitting" the back of the other rotating clockwise? It makes sense.
My rods needed no machining but what you said previously makes me think as I thought the rod circle was machined to a certain level with them on the assembled position so this issue with 300ª only happens due a human error on measuring, right?
I have another question: Both piston and cylinders where also measured and are in tolerance all right. The engine had no oil burning problems so I believe I can just put everything back in place, rings included...what you think?
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Wildthings
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| Posted: Wed Jan 15, 2020 1:02 pm Post subject: Re: Con rod question |
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Not educated as to why a Type 1 engine has offset rods as center to center will always be a straight line. Maybe there is a clearance issue?
As for Type 4 rods preferably being installed one way or another, if you installed them so that all four rods had the notches for the bearing shells pointed down, then TWO of them would be in backwards. There may be a reason for having all the tangs pointed in one direction, but this can not be accomplished by pointing all of the notches down (or all up) when the rods are aligned in their installed positions.
New rings are pretty cheap. |
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FreeBug
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| Posted: Wed Jan 15, 2020 2:04 pm Post subject: Re: Con rod question |
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| Wildthings wrote: |
Not educated as to why a Type 1 engine has offset rods as center to center will always be a straight line. Maybe there is a clearance issue?
As for Type 4 rods preferably being installed one way or another, if you installed them so that all four rods had the notches for the bearing shells pointed down, then TWO of them would be in backwards. There may be a reason for having all the tangs pointed in one direction, but this can not be accomplished by pointing all of the notches down (or all up) when the rods are aligned in their installed positions.
New rings are pretty cheap. |
One of the reasons is to reduce piston slap. Formula V guys would install them the other way, supposedly getting something out of that. It's really the piston which has that offset, the rod's little end is offset to be centered on the pin. |
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SGKent
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Location: Citrus Heights CA (Near Sacramento)
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| Posted: Wed Jan 15, 2020 4:10 pm Post subject: Re: Con rod question |
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any rod changes shape on the big end as it is used. It enlarges and ovals over time. They get cracks and so do the bolts. Before any rebuild they should be properly torqued in a soft vise so the cap and rod align, then measured and inspected carefully. If they are in tolerance then run them. If they are out, the cap (and preferably rod too) get clipped and then re-honed to the spec size. It takes some skill to keep the hone straight because the stones wear faster than the rod. If someone doesn't know how to keep the stones wearing evenly then the rod gets an hour glass figure which allows the bearing to flex. I lost count after resizing about 5,000 connecting rods of all types, and boring blocks of all kinds. One thing to carefully watch is for the bolts stretching as they are torqued. They just feel funny coming up to torque. Racers often torque by measuring the bolt stretch.
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RWK
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| Posted: Sun Jan 19, 2020 10:19 am Post subject: Re: Con rod question |
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Ok, school me on rod honing/rebuilding, from a toolmakers eye,I would, for example, surface grind .015 from each rod flat parting line, set up to the new parting line split, (new rod center), from small end, previously measured, split to small hole dia. center then bore large end round again, hoping it cleans up on the parting line undersize to what ever I needed, and then hone to size. Is that the general idea? having limited experience with a hone I wouldn't expect it can hone to/on center from a previously oblong or distorted hole, another words how does the hone know its at on the rod split? I have done some jig grinding,boring in tool work and we know where everything is at, and typically only used a hone for hole sizing, other then the jig grinding of course.
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SGKent
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Location: Citrus Heights CA (Near Sacramento)
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| Posted: Sun Jan 19, 2020 12:47 pm Post subject: Re: Con rod question |
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| Quote: |
| surface grind .015 from each rod flat parting line |
you hone the big end after clipping it. The clip is done on a special machine like the photo below so the clips are perfectly flat. I don't recall how much to take off but .015" on the cap and rod each seems like too much. I used to just bring it up to where it lightly toughed to be sure it was flat and then two passes just a little each. Inspect and if it looked even stop. Then put the rod bolts back in after inspecting them. Normally somewhere in there before clipping the rods are glass beaded, washed in a hot water based parts washer, dried with compressed air, and inspected, and weighed. Any differences or cleaning up are done before honing. The small end gets pressed out using the new bearing to press it out, any oil holes drilled, and the small end honed out to custom fit each individual pin. The cross hatch is controlled by the operator.
You set the measuring tool to the size you need with a well calibrated mic. Then you hone with a rough stone to just less than that size, and finish with a fine hone. The measuring tool is what the arrow in the photo is to.
When you stroke each stroke has to go partially off the stones, and linger or the center (inside of the rod) will get more honing than the outside of the bore. This will wear the stones uneven and also hourglass the bore. It is an art form that someone who has done it many times needs to watch you and teach you the first 100 or so connecting rods that you do. There is a rhythm to the speed of honing it and one can't teach that. As you measure the rod every few passes one has to adjust the rhythm to keep the bore straight. You also need to learn how to measure the full 360 without wiggling the gauge. Last you will need a high quality honing machine set up for rods, and not just a drill driven hone. The mandrel and stones also need to be the right sets. Most important you need to know how to read the stones to be sure they are wearing even as you hone.
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Last edited by SGKent on Sun Jan 19, 2020 1:05 pm; edited 1 time in total |
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Wildthings
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| Posted: Sun Jan 19, 2020 1:05 pm Post subject: Re: Con rod question |
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This is an operation best left to an experienced shop.
The only Third World fix on this that I know of is to figure out how much of an oval you have and then remove only that amount of material from the mating surfaces and the go with the rods as is, say if you have a 0.0005" oval remove only 0.0005" from the mating surface.
For the cost of having someone else do your rods, doing it yourself just wouldn't be worth it to most though, as the consequences of getting things out of whack just wouldn't be worth it. |
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