Xu9j4 Rebuild With 8v Crank And Rods

[unariciflocos 49 1 Cars]

I decided to rebuild my Mi16 after it spun a shell on a stage last year.

 

I want to make it surge proof so I'm thinking of using an 8v crank I have and 8v rods. I'll also be using the 26 tooth sprocket for the oil pump, longer chain, windage tray, spacer with tin sump, extended pickup and some home made baffles.

 

I don't know which pins to use or how to mate the 16v pistons to the 8v rods. I took apart the 8v pistons yesterday and the pins are badly scorn and I was told they are not usable. I still have to take apart the 16v pistons and see how the pins on those are.

 

My question is what kind of pins do I use now? Do I use 8v type pins locked in the rod and allow the pin to float in the piston or do I use 16v pins with the circlips at the sides and machine the rods to allow them to float on the pin? Don't know if i made myself clear enough so I'll try to rephrase... Pin locked in rod floating in piston OR pin locked in piston floating on rod?

 

I am doing most of the work in the machine shop at Uni with the help of the technicians there so please bare with me if I'm not that knowledgeable with these operations or engine rebuilds, this being my first one.

 

Next I will be decking the block and liners but first I need to match the pistons to the rods so that I can measure how much I can take off.

 

Thanks in advance for your advice gents,

Andrei

Edited May 26, 2010 by unariciflocos

[S@m 156]

I can't believe you used the term 'surge proof', you are asking for trouble with that one! Especially around here, given all the things we have tried to deal with surge (and there is still an ongoing and lengthy {a decade at least} discussion about it as we speak). And im not going to be much help aside from suggesting you check out a build thread that deals closely with the 8v rods in an Mi16,

http://forum.205gtidrivers.com/index.php?s...t=0&start=0

There, its not clicky but it will do!

Sam.

 

EDIT - Maybe it is clicky!

Edited May 26, 2010 by Sam306

[unariciflocos 49 1 Cars]

A little bit of an update, I disassembled the 16v pistons and the pins on those are ok.

 

I'm thinking of press fitting the 16v pins into the 8v rods and not have the circlips anymore so that there is some side to side travel.

 

The question is now how much the rod needs to travel from side to side and how much do i need to machine from the inside of the pistons for this. After my measurements 0.8 mm need to be machined (0.4 on each side) for the small end to be a perfect fit, but in the 8v piston there is an extra 4 mm for the small end to travel in the piston. So... how much do I machine on each side of the piston? And could it be possible to machine the rods and not the piston?

 

Hope I've made some sense...

 

LE:Noticed your post after i submitted mine, I read that topic several times, but will give it another look over. Now that I've actually had the parts in my hands and measured everything up I may find something new that I may have skipped the first times.

Edited May 26, 2010 by unariciflocos

[A2TheA 0]

A little bit of an update, I disassembled the 16v pistons and the pins on those are ok.

 

I'm thinking of press fitting the 16v pins into the 8v rods and not have the circlips anymore so that there is some side to side travel.

 

The question is now how much the rod needs to travel from side to side and how much do i need to machine from the inside of the pistons for this. After my measurements 0.8 mm need to be machined (0.4 on each side) for the small end to be a perfect fit, but in the 8v piston there is an extra 4 mm for the small end to travel in the piston. So... how much do I machine on each side of the piston? And could it be possible to machine the rods and not the piston?

 

Hope I've made some sense...

 

LE:Noticed your post after i submitted mine, I read that topic several times, but will give it another look over. Now that I've actually had the parts in my hands and measured everything up I may find something new that I may have skipped the first times.

 

 

if you machine the rod you will have problems with different bearing sizes wouldnt you?

i asked the 'how much to machine' question earlier to a member and awaiting reply.

 

if im following correclty, your planning to machine the mi pistons by .4mm? is this a snug fit? you may have to take into account the heat expansion. im sure you wont be far wrong if machining such a small amount, you can always take more off if you find its not enough.

 

this may or may not help you as its not a direct answer, sorry.

 

Aaron

[Alan_M 66 1 Cars]

if you machine the rod you will have problems with different bearing sizes wouldnt you?

i asked the 'how much to machine' question earlier to a member and awaiting reply.

 

if im following correclty, your planning to machine the mi pistons by .4mm? is this a snug fit? you may have to take into account the heat expansion. im sure you wont be far wrong if machining such a small amount, you can always take more off if you find its not enough.

 

this may or may not help you as its not a direct answer, sorry.

 

Aaron

 

 

He's only planning on machining the little end of the rod, hence to fit the 16v piston.

 

I was planning on doing this mod too, but can't be arsed now.

 

I was going to replicate the clearance on the 8v rod/pin/piston using the 16v piston and press fitting the gudgeon pin. Basically, running the 8v piston located setup with the Mi16 piston (and crank in my case).

[A2TheA 0]

He's only planning on machining the little end of the rod, hence to fit the 16v piston.

 

I was planning on doing this mod too, but can't be arsed now.

 

I was going to replicate the clearance on the 8v rod/pin/piston using the 16v piston and press fitting the gudgeon pin. Basically, running the 8v piston located setup with the Mi16 piston (and crank in my case).

 

 

but you could also machine the piston and leave the rod standard no?

[ifcho 0]

You could do both.

I am more into machining the rod, as if ever you have to remove the piston from this rod, the piston will be most likely damaged, and you will need to use new pistons, which will need modification again. While, if the rod is modified, you will be able to fit new pistons directly, without modifying pistons again.

[A2TheA 0]

You could do both.

I am more into machining the rod, as if ever you have to remove the piston from this rod, the piston will be most likely damaged, and you will need to use new pistons, which will need modification again. While, if the rod is modified, you will be able to fit new pistons directly, without modifying pistons again.

 

 

very good point sir!

 

this is why im still learning

[unariciflocos 49 1 Cars]

I don't want to mess too much with the pistons because the 16v pin is shorter and I'm worried about its resistance. In order to replicate the clearance of the 8v piston I'd need to machine at least 2mm on either side of the 16v piston and with the 16v pin being a good 10mm shorter I'm afraid there will be too little material left in the piston where the pin is.

 

I don't know much about the resistance of materials but I'm tempted to machine both the small end of the rod and the piston.

[ifcho 0]

Well I am as well. I am doing a similar build now, and by the end of the week I will have some more time to check which would be the best route to go for.

[welshpug 1,623]

as the gudgeon pins are a press fit, and the piston effectively has a bearing surface in it, I'd be inclined to only machine the rods, as you would be reducing the bearing surface area in the piston.

 

martin price (crf 450) and Colin Satchel (eeyore) can help you with the machine work, probably a few others on here too.

[nick 3]

It was my engine that me and Martin fitted the 8v rods to. Machine the 16v piston to the same dimensions as the 8v (this will obviously give the right amount of rod/piston clearance because it is the same as the 8v) use the 16v pin with no circlips. The pins need accurately pressing in as they are a VERY tight fit.

 

It's all in the thread mentioned earlier.

 

Nick

Edited May 26, 2010 by nick

[unariciflocos 49 1 Cars]

Thanks welshpug, I was referring to the bearing surface when I was saying there will be too little material left. I'm not actually worried it will break but the less bearing surface there is the more prone to wear it will be as the forces are spread on a smaller surface. I will have to do the machining work here as I'm a good 1500 miles from the UK in the opposite corner of Europe. Ifcho is just south of me.

 

Nick, how is the engine holding on? Any surge or reliability issues?

 

I've decided to machine the small end of the rods to a safe extent, 0,5 mm on either side, and then 0.5 mm on each side of the piston and do a trial fit in the block and check if the clearances are ok.

 

Thanks for the help so far.

[nick 3]

Engine is holding up very well. I have put about 10k on it since the build with no issues whatsoever. As for surge, things are looking good, bearing in mind this engine used to surge on the road and surged itself to death at Donington on road tyres, I haven't seen any pressure drop anywhere. Ultimately I need to do a trackday in it to see how it behaves, but I am confident that it would be fine.

 

Nick

[roote 0]

nick, cheers for a link to your previous thread, very good info on ideas ive been thinking, only thing is ive just finished my mi engine all std and wish i had read it about a month ago ! but life would be boring if it was all to easy.

[unariciflocos 49 1 Cars]

1mm taken off each side of the small end of the rod

 

1mm taken off each side of the piston

 

Machined rod in 16v piston

 

Machined rod in 8v piston

Edited May 28, 2010 by unariciflocos

[ifcho 0]

Nice. Did you do the rod with the angle grinder or you took it to a machine shop?

[unariciflocos 49 1 Cars]

Is there a rule to how you put the rods back in? What I'm asking is, if I have the pistons with the arrows pointing at the distributor, to what side should the notches in the big end point to? Hope I'm making sense.

 

LE:Machining was done on a vertical mill and then the faces were skimmed on one of those benches with a big grinding stone (sorry don't know what they're called). Pics were taken before the skimming.

Edited May 28, 2010 by unariciflocos

[Batfink 201]

What tollerance is that compared to the mi16 fitment?

Edited May 28, 2010 by Batfink

[unariciflocos 49 1 Cars]

I don't understand what tolerance you're referring to.

 

Speaking just about the 8v rod - 16v piston assembly, the rods small end was 0.8mm wider than the opening in the piston and a total of 4 mm were taken off, so that should leave 3.2mm side travel for the piston with the rod crank located.

Edited May 28, 2010 by unariciflocos

[welshpug 1,623]

arrows should point to the timing belt side.

 

I can't remember about the bearing tangs.

[unariciflocos 49 1 Cars]

Piston and rod assembly for those interested:

 

Decked block and liners:

 

Mi16 piston on 8v rod (you can't really see much difference to the 16v rod):

 

Took both the mi16 and 8v crank to be measured and seems the 8v was scrap and the mi16 was all standard except the journal with the spun shell that will need an R1 regrind.

 

Anyone know where I can buy only one pair of shells? I'd like to avoid buying two sets if possible.

[petert 554]

Nice work! How did they hold the liners to machine them?

[unariciflocos 49 1 Cars]

Thanks Peter, I'll be needing one of your stage 2 inlets IF I get this running. If somehow I mess smth up, this being my first engine build, I can't get spares for an Mi16 in Romania as they are extremely rare and will be dropping the project. At the moment I can't even find rebuild parts here.

 

The liners were done on a lathe.

 

0.6 mm taken off the block and 0.55 mm off the liners.

Edited June 9, 2010 by unariciflocos

[DrSarty 90 1 Cars]

I'm just about to do this too. Very handy your work and thread. Thanks.