Type 4 Rod Bushing Clearance..?

[Desertbusman]

[SGKent]

2 bit course on rod rebushing and big end sizing.

from the experience of doing thousands of these during my racing years, stock, street and drag. The pin should never be tight. It should never wiggle. With oil on the pin and at room temperature the pin should be a soft smooth slide through once you get it started. It may fall out under its own weight but it will be a slow controlled slide that takes I'd say at least 5 seconds. If the pin can almost freefall through the bushing you will probably feel wiggle in it. To feel the wiggle, hold the rod flat on the workbench and slide the wrist pin until one end also sits on the workbench. Then try to wiggle it. If it is good there will be no wiggle and you can gently turn it with your fingers. If there is any binding it is too tight.

As a bit of additional info. Not all cars have wrist pin bushings. Some hold the wrist pins in an interference fit. On those they are installed by heating the rod small end until it is startiing to blue then the piston is slid over it in the correct alignment and the pin is pushed through and centered before the rod end cools. You only have about 3 or 4 seconds to get it right and there are no easy do-overs because when the rod shrinks onto the pin it really grabs it.

Also - the wrist pin should slide through the piston about the same as it slides through the bushing. Make sure that the wrist pin clips are installed correctly and if they are the snap ring style that the square shoulders face out and the rounded ones in. I put a little pressure on the clips to collapse them and make sure they rotate freely to be sure they are in their grooves. Teflon buttons in lieu of clips or snap rings are junky IMHO. I have seen them fail and the wrist pins pound the cylinder walls.

If you aren't sure about the shop, ask to see their equipment and test a few samples they have completed recently. On the big ends, when you get them back you want to look at the inside area that is honed. The crosshatch should be even and steady. There should be two (2) lines on the inside going all the way around where the machinist measured them. It takes a little experience to rotate one over 180 degrees in each direction or 360 degrees when measuring to read the numbers for roundness. Many machinists will only measure about 150 degrees on the top and bottom however that can cause a failure if the rod cap is pinched from side to side as it will only show up during the last 4 to 5 degrees or arc. It is hard to explain but if you don't see those two lines going in a full 360 - and if they end before the split between the cap and rod, you may want to ask the machinist to remeasure or find a new machinist.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[fusername]

when you have mahle slugs, the wrist pin will nearly lock in the piston if it is cold, say 60 deg or less. you hold the piston in your hand a few minutes and you will be able to push it out with finger pressure. with a set of AA pistons the wrist pin will slide VERY easily through the piston, thats just how they make em. sign of quality. not to knock the AAs, they have a high success rate and have really improved thier quality. thier balance often exceeds that of a set of mahles, however they lack the steel expansion inserts and use a looser wristpin fit. maybe its actually because of a different alloy used in the slug, I don't know.

there should be no slop in a wrist pin in the rod on a VW. They should be hard to start, and then slide with very moderate presssure through the bushing. I am going to say THE WRONG NUMBER AND CONFUSE YOU HAHA is the clearance spec, and as you can guess measuring equpit like that is expensive. I sold a mic that would measure that for over 800$ on ebay about a year back. A lot of very experienced shops simply fit the small end by feel. takes skill and a supply or replacement bushings.
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FORSALE: Thrust cut T4 and 1.9 main bearings

[Amskeptic]

VW wrist pins are supposed to have a clearance of .0008" to .0012"

A nice almost snug clearance is nice. That is a tough place to live in an engine. Early BMW M10 engines had a problem with wrist pins giving their famous intermittant double-knock at idle, mine never got any worse. It is extremely unlikely that your wrist pin clearances as you now describe their fit, will give you a lick of trouble, if you do not feel any rocking with oil on the bushing. Do make sure your oil holes are lined up. Notching the rod big ends is also helpful to wrist pin longevity, not to mention piston cooling for the 93/94mm pistons.
Colin
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[whip618]

This is my set up for reconditioning rods, a sunnen rod and pin hone and like most of the oldtimers on this site I have been doing these things for thirty plus years. My rule of thumb is if the pins falls through the bushing even wet with oil it is to loose and should be rebushed. I have all the precision tools to measure the clearance but years of fitting pins has taught me that feel is the best way to go.

This is a type IV rod

Phil
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Samba Member No. 3307

[foxtail1]

whip

I am impressed also that there is still some old timers still around that know how to do quality work.
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As they say, "You never know until you ask the question."

64 bug
64 bus
59 ghia
71 bus

[SGKent]

Phil that sure brings back memories.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[fusername]

That is an intersting holder for the oil spray. the one I am learning on uses rubber hoses on nipples clamped to the parallels. really fun machine to run, still haven't even tried small ends, but I have the big end down pat. And I can press out an old bushing like nobodysbuisness
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[email protected]
Need something custom bent up? shoot me an email, maybe we can make it work!

FORSALE: Thrust cut T4 and 1.9 main bearings

[whip618]

[SGKent]

[fusername]

phil remind me not to bother you. you didn't make this rod as a prank either, did you?

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[email protected]
Need something custom bent up? shoot me an email, maybe we can make it work!

FORSALE: Thrust cut T4 and 1.9 main bearings

[SGKent]

that is a unique way to lighten a rod. Haven't seen that one before.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[Hoody]

Live and learn.In Canada send them to Scott.