piston to block contact in trial fit 2332

[fl59bug]

Hi everyone,

On my 2332 I'm taking my sweet time to make sure I get it right the first time out

While carefully checking for free rotation of this engine, with the long block fully assembled and the engine perpendicular to the ground while on the stand, with #1 and #2 facing straight up I am getting a very slight contact (resistance, small thunk really) at around 90 degrees before #1 BDC. The contact seems to be most pronounced in this vertical position, but happens to a lesser extent with the engine horizontal to the ground in its normal running orientation. There seems to be no contact when I have 3 & 4 pointing up. I've noticed this for a while now but have been busy with other facets of the build. I'm now ready to give this contact my full attention, find out and remove what is causing it.

With the engine in the "worst" position for the contact (1 & 2 facing straight up) I disassembled the 1/2 side down to just the piston and rods and still noticed the small "thunk". I removed #2 piston and still felt the contact, so then the #1 piston was removed from the rod. With both #1 and #2 pistons removed the "thunk" was gone. So it looks like piston skirt to block contact. I don't believe it is the piston contacting the connecting rod at this point. From what I see the contact is between the #1 piston skirt and the block reinforcement on the #1 cylinder. The block is the CB Rhino Aluminum block, and the pistons are the CB 1082 combination P&C, which have longish skirts ie they are not "slipper" skirts if I even correctly understand what slipper skirts are.

I will add pictures shortly. I unfortunately can't see exactly what is contacting with the #1 piston so close to BDC, but it must be the left side of the #1 piston (when looking down from above, on the opposite side as the arrow pointing to the flywheel) since that is where the block reinforcement sits.

Again pictures coming, but if I'm right about what is hitting, how do I fix it? Should I grind the block reinforcement (not too much to avoid weakening it), or just whack off the #1 piston skirt and its twin on the other side, which will lead to me having to do all 8 piston skirts since I currently have all pistons balanced to within 1 gram of each other?

thanks

Ted

[mark tucker]

is the fly wheel on and end play set? if not that may be the issue. other wize you can do some blueing, or clay. or eyeball to see whats up.and dont forget about camshaft to rod contact.and rod to case contact.thus the need for end play &flywheel on as that stuff is dam close and if the crank is going to the rear bumper side of thing that may be the issue. are the rods long enough for the stroke? vw or chevy size? a or b pistons. ???
you can also have 1/2 the case off and see whats going on. the crank counter weights also can come in contact with case with rong end play...rods can contact the oil pickup too as well as the cylinder in some applications.

[fl59bug]

[modok]

[fl59bug]

[Ohio Tom]

If there was contact, you should be able to see a contact mark on something.
Whatever is hitting, it's leaving a mark that you can find if you look close.

Now you know where to look.

Agreed that 90deg is likely cam hitting rod.

Can be hard to see as you have to hold the rod centered on the studs as you look for contact points.

[txoval]

You could remove the heads, pistons, and cylinders, and then use rubber bands between the studs to hold the rods centered. Then rotate and visually see if the rods are hitting the cam.

[evanfrucht]

I have some pictures of the process on page 11 of my build thread. In my case they were not hitting BUT I had less than .04-.06 clearance which is what you need there to be safe. Less that .02" is pushing your luck as far as I know. Your's may just be barely rubbing against each other. Also the cam gets clearanced in 8 spots BTW so make sure you get 'em all. Just mark the areas that need clearancing with a sharpie or crayon, then a grind a slight flat spot in those places with a file or dremel, I used an air file which worked great if you happen to have one. https://www.thesamba.com/vw/forum/viewtopic.php?t=743961&start=200
_________________
1967 Bug ( the daily rod )
1964 Fury Wagon ( the pavement shredder )

[Rome]

[fl59bug]

Thanks guys. I unfortunately saw no smoking gun when I spread clay across the case reinforcement and rotated the rod w/ #1 piston attached up and down, so its further down, probably the cam and rod like ya'll mentioned.

I'm disassembling the right side of the engine, including removal of the case half itself. Just sighting down in the case with the head, cylinder and even the piston removed didn't turn up anything. The contact also goes away when I point the left side of the engine straight up but is present with the engine horizontal and with the right side straight up. My fear is that removing the right case half will also remove whatever weird contact is there and I'll never find it lol. I almost wonder if I need one of those boroscope things that I can rig up to my phone or something.

The very (I mean very) slight amount of contact/resistance/thunk/whatever is also making it very hard to track down. I want to remove the right case half and leave the flywheel, crank, cam, crank pulley, and left side of the engine assembled and try to rotate it and see if I can observe anything hitting. If it still plays hardball I may reattach the #1 and #2 pistons to their rods while rotating, though without the case half that may just be dumb and pointless. I'll update with what I find, thanks again.

Ted

[evanfrucht]

The shaft of the cam might be barely touching the rod caps/bolt area. That is the most likely so check that first.

It should be pretty clear when you rotate the crank over with all rods attached. I have pictures in my build thread of the process. It's easy to see if they touch or get very close.

Once you take the case apart you can check for rub marks also.
_________________
1967 Bug ( the daily rod )
1964 Fury Wagon ( the pavement shredder )

[txoval]

Worst case, reassemble without the cam and see if it goes away

[fl59bug]

[fl59bug]

[fl59bug]

Ok ya'll were right, its rod to cam contact. Looks like the corner of the big end of the #1 h-beam rod is contacting the center cam journal. Although in the photo it looks like there is clearance, although a very small amount, when the rod is in just the right position I can see and feel the contact. It is VERY slight, but it is there, and it happens when the #1 rod is at 90 degrees before bottom dead center BDC just as I noticed when the engine was fully assembled.

Now I need to fix this in the most efficient means possible. I believe I'll want to grind off the cam and not the rod so as not to open too big a can of worms!

Let me know if you want to see more pictures/detail and I'll take more photos.

Thanks everyone

Ted

[evanfrucht]

One thing to make sure of before the clearnacing is that the crank is where it is supposed to be. As in, not pushed forward or back.

I would the cleanrace the cam personally. Some people prefer do the rods. It is easier to do it that way but the rods are a more heavily stressed part so I avoid messing with them.
_________________
1967 Bug ( the daily rod )
1964 Fury Wagon ( the pavement shredder )

[fl59bug]

[RickS]

I would chuck it up in the lathe and take a small 45 degree cut off the cam journal. Looks like there is plenty of journal before you get into the bearing contact surface.

[ekacpuc]

Mine had to be clearanced same spot. I just hit it with a burr grinder and followed with a sanding drum to smooth it out. Didn’t take much.

[fl59bug]

Thanks RickS and ekacpuc. I have the sanding drum bits and burr grinder. I've marked the contact area with a sharpie and removed the cam. I'll try to get to it tomorrow. I'm happy to have located the contact points.

Ted