If you have any kind of a ridge at the top of the cylinders, I personally would bore it. So, how hard was it to get the pistons out, break any rings? Reason I ask is if there is a noticeable ridge, there will be a taper, and it will need boring. Just my opinion.....
318 Difference?
- Thread starter 04 Diesel
- Start date
-
txstang84
Well-Known Member
I would also recommend moly top rings...lower friction than standard cast rings...arguably seal better.
txstang84
Well-Known Member
Those aren't bad.
But the ones that he has from the "70 motor" in the top picture may be higher compression than those.
I'm not knocking your suggestion, but he may have a better piston already, why not save the money and use it. It seems like he's trying to put a cheap runner together with minimal cost.
I try to avoid cutting the block and heads if possible so you don't have to also tweak the intake manifold fit. Just personal preference to me.
Pistons all came out just fine on both blocks, didn't break one ring. Not much of a ring at all on both blocks.
I am going to measure the pistons and use the tallest set, both sets are in good shape.
txstang84
Well-Known Member
The only thing that may be an issue is if cylinder taper is too far out...regardless of how good the pistons look, if the taper is more than [I think] .006-.008", the block will need to be bored unless you're OK with increased potential for blow by.
Simply not having a ring ridge isn't the only indicator. This is where you may need to bring both blocks to the machinist and see which is the better of the two, unless you have a set of mics and can do it yourself.
Simply not having a ring ridge isn't the only indicator. This is where you may need to bring both blocks to the machinist and see which is the better of the two, unless you have a set of mics and can do it yourself.
nm9stheham
Well-Known Member
Were the bearing shells on the #4 main bearing in place with the tabs intact or had they moved or been worn off? Question being if it spun the bearing or just melted the bearing. How'd the crank journal look on that bearing?
BTW, on the ring ridge, it is just not a wear indicator but can possibly break a new ring. The main bearings wear and the crank will settle a bit downward, and the rod bearings will wear and do the same. Over time, the pistons and rings will not come up quite as far as when new; it is just a tiny amount, but the bottom of the ridge wil move lower a bit over time. When you put in new bearings and rings, the top ring wil try to to go back up the the orginal top of the travel, and hit the ridge, and there you go, with a broken ring or land or 2.
Just want you to be aware if you are not already. There are reamers to remove it if you do not rebore.
BTW, on the ring ridge, it is just not a wear indicator but can possibly break a new ring. The main bearings wear and the crank will settle a bit downward, and the rod bearings will wear and do the same. Over time, the pistons and rings will not come up quite as far as when new; it is just a tiny amount, but the bottom of the ridge wil move lower a bit over time. When you put in new bearings and rings, the top ring wil try to to go back up the the orginal top of the travel, and hit the ridge, and there you go, with a broken ring or land or 2.
Just want you to be aware if you are not already. There are reamers to remove it if you do not rebore.
A38Valiant
Collector Of Rust
As was previously mentioned, the 70 pistons are more compression height, but the 77 has beefier rods. Catch is, I'm not sure what is involved in combining the two. The 70 is floating pins, while the 77 is pressed pins. Bad things happen if you use the pressed pins and beefy rods with the pistons designed for floaters. My brother-in-law did this 20 or so years ago. The pins end up being that tight in the pistons that they will not move.
On a side note, having been around a few hundred 318s, and a few dozen 360s, some of each that were dirt track engines, the rod failures I have seen have almost always been at the shoulder of the rod bolt. The "645" later rods have no significant increase in meat in this area, just the beam section. The early lighter rods will bend in the beam section when exposed to 7,000 RPM plus. I can show you a set of eight bent rods. But for a good, solid, street engine, the early rods, floating pins, and higher compression pistons is the way I would go.
Oh, by the way, those 70 pistons look 100 percent like the stock 70 pistons laying in my shop.
On a side note, having been around a few hundred 318s, and a few dozen 360s, some of each that were dirt track engines, the rod failures I have seen have almost always been at the shoulder of the rod bolt. The "645" later rods have no significant increase in meat in this area, just the beam section. The early lighter rods will bend in the beam section when exposed to 7,000 RPM plus. I can show you a set of eight bent rods. But for a good, solid, street engine, the early rods, floating pins, and higher compression pistons is the way I would go.
Oh, by the way, those 70 pistons look 100 percent like the stock 70 pistons laying in my shop.
You cannot interchange press fit pins into floating pistons or vice versa.
You have to keep them together, either both floating, or both press fit.
******************************************************************
I would use the 70 pistons with the same rods that they are pinned on.
One good way to check the compression height between the two is to remove one retainer clip from the floating piston and use it to line up the wrist pin bores on both pistons, then compare which one is taller... Bingo!
Make sure to replace the clip after you are done comparing.
******************************************************************
Also, make sure that you can spin the rings freely in their grooves by hand. Your rings need to be free to spin. If they don't you need to clean the ring grooves and or rings or replace the rings.
******************************************************************
When you install the rings, you should check the ring end gaps for the two compression rings and make sure that they are a minimum of 90°, the same also applies to the two thin oil ring gaps, they must be 90° or more apart from each other and free to spin by hand.
******************************************************************
To measure taper on your bore, the maximum side load for the piston is when the crank is at 90°, which is exactly mid stroke. If you measure the bores half way down the stroke from top to bottom and side to side (up and down, and across) with the micrometers and then at the top side to side, and up/down, you should get a good idea if they are tapered.
Or hone your cylinders, and check the ring end gap halfway down the bore with a new ring. If the ring end gap is in spec, you should be ok.
You have to keep them together, either both floating, or both press fit.
******************************************************************
I would use the 70 pistons with the same rods that they are pinned on.
One good way to check the compression height between the two is to remove one retainer clip from the floating piston and use it to line up the wrist pin bores on both pistons, then compare which one is taller... Bingo!
Make sure to replace the clip after you are done comparing.
******************************************************************
Also, make sure that you can spin the rings freely in their grooves by hand. Your rings need to be free to spin. If they don't you need to clean the ring grooves and or rings or replace the rings.
******************************************************************
When you install the rings, you should check the ring end gaps for the two compression rings and make sure that they are a minimum of 90°, the same also applies to the two thin oil ring gaps, they must be 90° or more apart from each other and free to spin by hand.
******************************************************************
To measure taper on your bore, the maximum side load for the piston is when the crank is at 90°, which is exactly mid stroke. If you measure the bores half way down the stroke from top to bottom and side to side (up and down, and across) with the micrometers and then at the top side to side, and up/down, you should get a good idea if they are tapered.
Or hone your cylinders, and check the ring end gap halfway down the bore with a new ring. If the ring end gap is in spec, you should be ok.
The ridge at the top will be cleaned up when he hones it.
In addition to the bores, check to see what condition the cam bearings are in for each block.
I am going to put new cam bearings in, would like to do it myself.
I don't know what happened on #4 main bearing, when I bought the motor it had new bearing in the motor. Crank does not look bad.
Pistons look the same height too me, not sure what to do.
If they are both the same height, then it doesn't really matter which ones that you use. Maybe the ones with the eyebrows will have a little more valve clearance if they are the same height. Either one will work if they are both in useable condition and the same compression height.
Some advice on installing cam bearings:
You need to get them right the first time. If you have to push them out, they will not have the same retention force if you use them twice, and may spin easier.
MAKE SURE THAT YOU GET ALL OF THE OIL HOLES LINED UP!!! The cam bearings have an oil hole in the bottom and one or two to send oil to the heads. You must make sure that you get ALL of them lined up with the oil holes in the block.
A quick easy check that they are lined-up is easy. Just get a wire coat hanger (the thicker ones - not the real skinny ones), straighten the coat hanger, and stick it in the oil holes in the main bearings in the block and make sure that it goes through to the cam tunnel - then the passage isn't blocked. Then stick it down each oil hole for the heads to make sure that the bearing holes for them are also lined up (the wire goes through to the cam tunnel).
Good Luck, we're all counting on you....
[ame]http://youtu.be/aB2yqeD0Nus[/ame]
Get a wire coat hanger and straighten it out. Then stick it through the oil hole for that bearing to make sure that there is no dirt/debris in the oil hole from the old bearing. Just in case some of it got in the oil passages, you need to clean out all of the bearing material that may have fragmented into there when the other bearing failed.
If you find any crud in the oil passages, then take it to a pressure wash do-it yourself car wash and blast the oil passages clean (wear a raincoat, to do it properly you will get lots of "splash back"). Or just be ready to get wet and dirty... Argh.. Argh... Argh.... (Grunt like Tim Allen...)...
Still, either ones will work. Unless one set is forged, but chances are that they are both cast. If you're going to build a basic daily driver motor for your truck, they will work fine.
Nothing wrong with the Canadian pistons. Either set will work.
It would be a good idea to check piston to valve clearance when you build the engine just to make sure that you're ok.
I wasn't saying that Canadian pistons are bad, just that its not stock.
-
