weight matching pistons and rods

SXSENIS · May 1st, 2005, 08:56 AM

Just a note. The connecting rod and pistons wiegh about 820 grams each.
cylinder 1= 827g
2= 817g
3= 816g
4= 822g
I thought they would be closer together. I'm installing new rings and have a digi scale and was courious. I'm going to leave 2 and 3 alone but am going to lighten no#1 to match no#4 by removing materal form its rod. There is eadges from its casting so it shouldn't be to hard to shave 5 grams. I've already started and its leaving the shaved area polished. I've got like 3 more grams to go. I'm being very careful not to lesson its integrity,and I'm rewieghing often. If I could I'd like to get all 4 within a gram of each other. A blanced rotating assembly leads to a smoother running engine and longer lasting engine. The strange part is no#1&4 are grade 1 and no#2&3 are grade 2. Id figure since they(2&3) are larger they would be heavier. All bearings; rod and crank look to be in very good shape. No signs of wear

**wes** · May 1st, 2005, 10:12 PM

Quote:

Originally Posted by SXSENIS

Just a note. The connecting rod and pistons wiegh about 820 grams each.
cylinder 1= 827g
2= 817g
3= 816g
4= 822g
I thought they would be closer together. I'm installing new rings and have a digi scale and was courious. I'm going to leave 2 and 3 alone but am going to lighten no#1 to match no#4 by removing materal form its rod. There is eadges from its casting so it shouldn't be to hard to shave 5 grams. I've already started and its leaving the shaved area polished. I've got like 3 more grams to go. I'm being very careful not to lesson its integrity,and I'm rewieghing often. If I could I'd like to get all 4 within a gram of each other. A blanced rotating assembly leads to a smoother running engine and longer lasting engine. The strange part is no#1&4 are grade 1 and no#2&3 are grade 2. Id figure since they(2&3) are larger they would be heavier. All bearings; rod and crank look to be in very good shape. No signs of wear

Interesting data. Accoding to Mike K. most of the Nissan motors are pretty darn close to begin with. How accurate is that scale out of curiosity?

Anyway are you going to polish the journal's as well?

landlord · May 1st, 2005, 10:40 PM

yeah i thought nissan's pistons were withing 2-3 grams of each other. or maybe that was just the rods?

SXSENIS · May 8th, 2005, 07:20 AM

My digi scale was gotten from a Fuson Inc. they make swissmix and ibprofin. They also have a gov. contract to make food supplments for the miltary. so I assume its very acuate(per food standards).It can read grams past 100th thous. And has a level to set it striaght.

All pistons were within 2g of each other. the rods were what was off. The no#1 rod had a bit of over cast(ridges form casting left from finishing?) I got them to within 1.6g of each other and stoped there.

the wieghts I showed were from the rods weighed with the pistons and rings still installed. after removing the rings and cleaning it got a little closer.

The rod journals looked to be in great shape. However I was thing of sending the bearings to swain for coating. But I'd need to now how much materal that will add to the bearing thickness. I saved the old ones and have yet to install the new ones. So when I find out 1 set is off. The old 1's look good but after cleaning I noticed a bit of corrosion wear, but no pits or heavy scratching. If the journals are polished do you think that would make up the diff from the coated bearing? I could not do that myself and have to tap a local shop for that. The diff between the new and old bearings are both in fac spec with the used 1's on the max side. I've e-mail swain about a week ago with no responce so I'll most likly call next week to find out. There prices for small parts is not bad at all. The less friction the better.

SXSENIS · May 8th, 2005, 07:47 AM

Added note jethot quoted me 145 to coat my intake manifold(upper and lower)in sterling thermal. About half of swains list. And according to swains price list the bearings would be about 30 for thr rods and the crank would run around 45 plus shipping for there low friction coating. Which is Very Good.

JetHot sent me some good info with there quote. According to them a big block headers of the same design were tested. The non coated headers temp was around 525 f and the coated was at 200 f. Thats over 50% reduction in temp. They coat inside and out so the heat stays in the tubes or out for my intake manifold in my case. And if the part is new they will warrent it against cracking(header) for 2 yrs. And have several colors to choose from.

SXSENIS · May 10th, 2005, 10:46 AM

Swains bearing coating adds about .002 to the thickness of the bearing. Which would be not marginal at all. I could send them my new ones and still be in fac spec on my clearance. fac clearance for standard is .0006-.0015 for the rods and .0007-.0017 main with both having a limit of .004. with the coating my new bearings would be close to the limit at .0035 rods and .0037 main. The old one needing to be repolished would have a clearance of .003 rods and .0032 main roughly. My ? now is I've read by keeping the clearance so tight to the limit that this will raise the oil pressure a bit. Not a bad thing but in a good way because it makes for a better lubricated bottom end. Is their truth to this?

IanH · May 10th, 2005, 11:39 AM

Quote:

Originally Posted by SXSENIS

Swains bearing coating adds about .002 to the thickness of the bearing. Which would be not marginal at all. I could send them my new ones and still be in fac spec on my clearance. fac clearance for standard is .0006-.0015 for the rods and .0007-.0017 main with both having a limit of .004. with the coating my new bearings would be close to the limit at .0035 rods and .0037 main. The old one needing to be repolished would have a clearance of .003 rods and .0032 main roughly. My ? now is I've read by keeping the clearance so tight to the limit that this will raise the oil pressure a bit. Not a bad thing but in a good way because it makes for a better lubricated bottom end. Is their truth to this?

No I think you have the tolerances the wrong way round.
fac clearance for standard is .0006-.0015 for the rods and .0007-.0017 main with both having a limit of .004.
So you have +0.001 clearance new +- 0.0005
If you coat the bearing with 0.002 of coating then your clearance will be 0.001 -0.002 -0.002 for - 0.003
This will be an interference fit with no clearance. The engine will not turn over if you are lucky and will spin the bearings and maybe break something big is you aren't.

So to make this work you will have to have your crank ground down by the coating thickness x2. This is because the crank is measured as a diameter, and the coating is specified as a film on one side, and there are two sides.
I hope you see what I am saying here.
Good luck.....

BTW the only time I got into piston weights was an a 3.4 Jaguar engine in the UK, I needed one replacement piston, to match to a replacement set. The manufacturer said they were balanced to +- 1 g when sold by them, ALL of them are the same for that engine and size, so no weight matching was required within their brand.

SXSENIS · May 10th, 2005, 04:53 PM

Oh The tatal thickness increase is .002 so .001 per side. Acorrding to swain. Your second sentence is the same as mine. I'm not sure what you are telling me.?So I figure its wrong? I thought you would add the coating thickness to the bearing thickness which would lessen the clearance by that amount; add .001 to rod to crank side and .001 to bearing to rod to calculate the new clearance for the bearings. Right?.The actuall bearing thickness is nominal with the coating added. What I implied by saying resufacing my old bearings was to make up the differance for the added thickness. If coating the new ones would lead to resizing the crank journals. I haven't proceeded yet so help me understand what I have read and been told by other people.

I heard nissan engines are very close from the factory. Balance wise. So I was just curious to see so I wieghed them. Besides It would not hurt for them to be closer. That was the whole reason behind me wieghing them in the first place.

SXSENIS · May 10th, 2005, 05:49 PM

Sorry I read and reread your reply. I understand now what you were telling me. Tell me if I'm right.

say my clearance is .001 add.002 twice(once for each side). which would put me at .005. which is too much..Being .004 is the limit or min. amount of clearance. I guess I did not say it right. the total thickness added is .002 which I stated last post is .001 per side. which would still put me in the green. Right?. I over looked the thickness specs not thinking. Example: my no#1 rod has a fac spec of .0593-.0594 (grade 0). Add .002 to the tatal thickness and I get .0613. Subtract the min fac clearance of .0015 and you get .0598 which is .0004 too big for the journal. But still within clearance spec by .0005. I was told that was not a factor because its to small of a differance to cause interferance? Wouldn't be easier to simply thin the bearing to adjust for the coating. See I know that the journals on the crank are hardened. Is that true for the bearing surface as well? I think I need to do some more math.

IanH · May 10th, 2005, 07:59 PM

Quote:

Originally Posted by SXSENIS

Sorry I read and reread your reply. I understand now what you were telling me. Tell me if I'm right.

say my clearance is .001 add.002 twice(once for each side). which would put me at .005. which is too much..Being .004 is the limit or min. amount of clearance. I guess I did not say it right. the total thickness added is .002 which I stated last post is .001 per side. which would still put me in the green. Right?. I over looked the thickness specs not thinking. Example: my no#1 rod has a fac spec of .0593-.0594 (grade 0). Add .002 to the tatal thickness and I get .0613. Subtract the min fac clearance of .0015 and you get .0598 which is .0004 too big for the journal. But still within clearance spec by .0005. I was told that was not a factor because its to small of a differance to cause interferance? Wouldn't be easier to simply thin the bearing to adjust for the coating. See I know that the journals on the crank are hardened. Is that true for the bearing surface as well? I think I need to do some more math.

If you add metal to the bearing shell you decrease the clearance.
You are adding to the clearance not taking away.
Since the clearance is a nominal 0.001 your clearance goes away to nothing.
ie 0.001 take away 0.001 take away 0.001 = less than zero !!!!

A 0.002 thickness coating is 0.002
A 0.001 coating will be spec'ed as 0.001 not 0.002.
You are going to need to remove the same amount as the coating adds. Remember journals are speced as a diameter. So twice the layer.

Whoever told you this was ok without major surgery is not to be trusted.

Yes you can have the journals re-ground, and most hardening is more than a few thou thick. I am not sure the crank is hardened anyway. If it is, it is likely to be 0.020 + thick.

If it is hardened you can get it re-treated IF that is required for a nominal 0.010 dia undersize.You can ask a machine shop, they have handy guide books. remember a 0.010 under size is 0.005 metal removal from an unworn surface.

Whatever you do here you must check the clearances with plasti-gauge to make sure someone didn't screw up.

The bearing shells are strip metal that is pressed and chopped up in one operation. The coating is soft and engineered in a two step layer. This is normally plated on and cant be easily removed. ( OK I am assuming we have Lead Cu lined shells) My best guess is the lead is about 0.001 thick, the Cu about 0.005

Wes we need your input here !!!

lshadoff · May 10th, 2005, 08:22 PM

The main and rod bearings are listed as 'Grades'. The crankshaft is marked with the bearing grade required.

The FSM lists the bearing grades by their thickness. What you need to do is get a thinner grade to be coated so that the final product has the correct grade.

Lew

SXSENIS · May 10th, 2005, 08:51 PM

I got it. I was adding to the clearance. Makes more sense now. I sniffed too much paint today.! haha. Actually Richard at swain said it would not be marginal. I had a feeling Somthing else would need to be done. I also knew I'd have to wait and use plasti gauge to get my final no#'s. I was just tring to grip what I'm tring to complete. As for the crank I Ass.u.me d it has hardened journals as the other engines I've overhauled (3 prior)has had them. I thought it was like a manditory thing when it came to that. Why is it somethings seem right until you hear someone elses opion or view then they go wrong until you understand what they are saying. Yea, that was my idea. To get a thinner bearnig to coat.Well that and maybe thin mine to coat, but that seems out sense there is more to a bearing than a thin peice of metal with a oil groove in it. Much more doable for me to buy a custom bearing. My crank is fine, and I don't want to fool with it unless I have to. Man i just reread what I wrote and I must have been? I see my error. I need to talk with a auto machine shop and see my options to fit my ideas. I'm in no hurry. Thanks

IanH · May 11th, 2005, 09:32 AM

Thanks Lew.
Looking at the bearing color chart this will not help much. the total difference from Plain to Green is only 0.0002

Assuming your bearing color was green you would only gain this much, 0.0002 and you need 0.002 IF the coating is 0.001

So lets back up and ask why you want a coating ?
I believe you said it was to reduce friction.
The bearing is Pressure Oil fed and floats on Oil at all times except for starting.
So to reduce Friction run a Thin Low viscosity Oil Like Mobil 1
These Engines do not have bottom end problems even when making almost obscene amounts of power.

The Other Engineering concern I have is the durability of what you are trying to accomplish.
If this coating sheads what happens ? New Engine ?

The bearing is Engineered with a soft shell and hard Crank pin.
The reason I have read for this is durability.
Any hard abrasive particles not swept away by the oil can be and are hammered into the soft shell out of harms way and will not rapidly wear the crank pin (hardened or good grade Iron or steel.)
If you change this surface to hard and hard or medium and Hard then the whole wear dynamics changes.
If you are doing this because you can and nobody else has, then good Luck.

SXSENIS · May 12th, 2005, 07:53 AM

It was manyly because It was apart anyway to replace the rings. I bought another block cheap with its rotating asssembly in place to play with and prep. I could just throw it all back together and go. Witch I am now. Just wanted to see what has to be done. And to see if my thoughts were credible. I've done a basic overhaul but not to this degree but always wanted too. Like every other member(most) I've got the boost bug. I want to build it right. I upgraded the sespension and brakes all in a vain attempt to bring my car to a level of preformance I want. Not a dyno monster but a quick spooling street terror that will hum all day in traffic for another 100k. Your points are great help. I don't want to change the bearing make up. I figure since you can buy a piston in any spec you can buy a bearing in any spec. Which I am right. I just need to give them the spec and they can order a set. They can not make a bearing thinner. That is because of the reason you state. It ruins the bearings durablity. I noticed no wear at these points the journals all look brand new. However the bearings on my block showed signd of corrosion wear, and the slug at the bottom of the oil pan explains why. That and the rings carrying fuel down into the oil and the anifreeze mixing in causes a very nasty change in the oil making it like a mild acid eating softer metal until a point of falure. If I could why not? improve and have better piece of mind that this would not happen again because of steps I take now. Thnaks for the info on bearings and how they are made.

SXSENIS · May 15th, 2005, 08:01 PM

Anyway i got it back together. Haven't started it yet still need to check over every thing one more time and put oil in it. Added note. the factory rings are a gapless design. The rings I replaced it with were from sealed power. they are ductile iron with a moly coating on the edges. I didn't need to gap them or anything. they fit the first time. I installed the new bearings and all went well. A machine shop said they could get bearings in any spec but the wait for custom bearings is like 3 months. So the spare block I got will see them hopfully in a few months maybe as a x-mas present to myself. When it goes that far I'll post specs and prices.