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Today i checked the ring gaps on the first (#7) cylinder. Pushed the ring carefully in with the piston and evened it with a caliper depth gauge.
Top ring gap is a very bit less than .020, that means with a bit pushing i would get the .020 feeler gauge completely between the gap. .019 and .018 feelers are getting in light.
2nd ring gap is the same.
.015 feeler goes in the gap with some slight pushing, .014 feeler goes in the gap a bit lighter.
so i guess, these ring gaps are good to like this?
i will definitely check it like this for each cylinder/piston.
As instructions are saying "all marked rings are facing with the marked side to top of the Piston (second groove rings are having a dot, top groove rings arent marked), is it right that the top groove ring has no installing direction?
Top groove ring (it has no bevel or marking):
2nd groove ring (dot marking and bevel):
One last question. The top ring has a moly surface i guess, so is it right to just apply a very thin coat of engine oil onto the cylinder walls before piston installation and no oil soaking the pistons and rings?
i heard this is necessary to help the moly rings seating properly.
Good turn around time on your block, especially these days. It looks like you are pretty close for ring gap. I know some say ATF is better to coat the cylinders with, I am going that route. Either way do some first gear up and down throttle on break in. Good luck.
Good turn around time on your block, especially these days. It looks like you are pretty close for ring gap. I know some say ATF is better to coat the cylinders with, I am going that route. Either way do some first gear up and down throttle on break in. Good luck.
Yeah, winter here is the best time to wrench around on your summer car stuff.
do you mean the gaps are pretty close? Or pretty close to a good goal gap? 😁
I have heard that too to use a coat ATF in the cylinders. Maybe some others have some expieriences with that.
What is the final bore? Your top is plenty, the second looks tight, going off a major piston manufacturers recommendation for a Street engine. http://blog.wiseco.com/everything-yo...about-ring-gap
The reasoning for ATF is no chances of leaving deposits and potentially have the rings stick in the pistons.
Take all of your piston rings and lay them out and select fit all of yours rings to each bore. You will find that you will get a nice fit when you do this.
I tried all 8 top rings in bore #7 and found 2 of them with the gap very slightly larger than the others. Theyre still pinching the .020 a bit, but no that strong than the others. But, the rings are definitely slightly differen to each other.
I have used ATF on the cylinder walls as a lubricant and cleaner on a fresh bore. No matter how well you have cleaned the block, seems like the bores are never clean. I take a common facial tissue like Kleenex and fold it into a small square, soak it with ATF almost to the point of dripping and proceed to wipe the cylinder bore. If the tissue remains clean, it is ready for a piston to be installed. If the tissue comes out dirty, take another and repeat until clean. The ring positioning diagram you show is fine. I feel that making sure the top and second ring gaps are opposite each other on installation works fine for me and be sure the oil ring scrapers gaps are not in line with each other and not in line with the expander. It is said by many builders that the rings will seek their own position upon run in, I have never checked for that myself.
I have used ATF on the cylinder walls as a lubricant and cleaner on a fresh bore. No matter how well you have cleaned the block, seems like the bores are never clean. I take a common facial tissue like Kleenex and fold it into a small square, soak it with ATF almost to the point of dripping and proceed to wipe the cylinder bore. If the tissue remains clean, it is ready for a piston to be installed. If the tissue comes out dirty, take another and repeat until clean. The ring positioning diagram you show is fine. I feel that making sure the top and second ring gaps are opposite each other on installation works fine for me and be sure the oil ring scrapers gaps are not in line with each other and not in line with the expander. It is said by many builders that the rings will seek their own position upon run in, I have never checked for that myself.
Thanks a lot for your help and ideas! I will clean/prepare the bores exactly like this with ATF 👍
Originally Posted by joesw31
ATF works great and that’s what I always use.
Your diagram for ring position is fine as well.
I have found variances in ring fit and therefore hand fit all my rings.
Keep up the great work
Ok, so it is common to to file fit "non file fit rings" if a gap is slightly too tight?
What i find odd is that sometimes, even here in this forum, people say that the top ring gap needs to be slightly larger (.020) than the second rings gap (.015), which makes absolutely sense to me, since the top ring gets more heat than the second.
In the same case, in some other forums/informations/instructions i found around the internet, it says the opposite. Second ring gap larger than top ring gap. Just curious...
What does Speedpro recommend? These pistons were introduced many years ago, the info should be available through them. I using the Mahle recommendation and Mark's expertise because I am using Mahle pistons, which he used in multiple builds. This link explains why more gap is good on second ring. It will ask you to open or download. https://www.google.com/url?sa=t&sour...YaF1gvLVgMn5H7
Last edited by olds 307 and 403; February 4th, 2022 at 06:15 AM.
What does Speedpro recommend? These pistons were introduced many years ago, the info should be available through them. I using the Mahle recommendation and Mark's expertise because I am using Mahle pistons, which he used in multiple builds. This link explains why more gap is good on second ring. It will ask you to open or download. https://www.google.com/url?sa=t&sour...YaF1gvLVgMn5H7
with a little resesrch, i found this:
I dont know if the 'speed pro - rings' in this instruction are still the same as my sealed power rings, but it recommends a wider end gap - multiplocation factor for the second ring too.
Now i dont know which way is the right way to go 🤔
if i would go with the 'larger 2nd ring gap', i would definitely have to file the 2nd groove rings, and the top rings would be on the larger side (0.004×4.087 = .0163 and mine are out of the box in the .018 - .020 area).
Look in your service manual and use those specs. Remember your using a stock replacement ring pack.
Personally, I have not had to file rings that were ready to install.
1971 CSM says: ".. the gap measurement should be .013" to .023" for compression rings and .015" to .055" for oil rings."
Its not saying "this gap for top, and this gap for 2nd.
So just for my understanding, if you recommend to use the ring gap tolerances of the CSM, ring gap (specially in this case with stock style sealed power rings) has nothing to do which pistons are used? I ask because stock pistons are cast and mine are forged?
While the rings are a stock style, these pistons are not as you said. Remember you were told to get the machine shop to hone an extra .005" of clearance due to these pistons expansion? A modern piston requires half that much. They show their reasoning for the larger second ring gap, your call.
Are you going to be spinning your engine at max rpm all the time as on a road course? If the motor is not being built only for flat out racing , don't worry about it; I doubt you would see any difference regardless of which way you choose to gap the second compression ring. Your choice; do what makes you feel best!
Are you going to be spinning your engine at max rpm all the time as on a road course? If the motor is not being built only for flat out racing , don't worry about it; I doubt you would see any difference regardless of which way you choose to gap the second compression ring. Your choice; do what makes you feel best!
While the rings are a stock style, these pistons are not as you said. Remember you were told to get the machine shop to hone an extra .005" of clearance due to these pistons expansion? A modern piston requires half that much. They show their reasoning for the larger second ring gap, your call.
Yeah, i informed my machinist about the expansion of those pistons, and he agreed.
I measured a few bores with a caliper (i know, not very accurate, but sadly i have no bore micrometer in my garage) and got as a caliper measured result 4.090 - 4.091, which is approximately .004 over 4.087, so this should be ok.
Originally Posted by 67OAI
Are you going to be spinning your engine at max rpm all the time as on a road course? If the motor is not being built only for flat out racing , don't worry about it; I doubt you would see any difference regardless of which way you choose to gap the second compression ring. Your choice; do what makes you feel best!
Originally Posted by joesw31
Totally agree
Yeah, thats the point. Its a street car, which will operate 95% of its running time at cruising rpm's.
So your opinion is just to check the gaps for .020 on top ring and 0.15 2nd (which is barely like they are out of the box) and call it a day?
Im maybe just a bit "over-careful", because im still a newbie to engine building with not that much self-expierience and i really would like to avoid the case of ruining my build just because of small (but important) steps like ring gaps.
again, i very apprechiate all of your help, expierience and knowledge!
Last edited by 71OldscutlassS; February 6th, 2022 at 10:43 AM.
Finally i was able to put my rotating assembly back together. Its easy to turn the engine over with a short wrench by hand, so i assume that there should be no binding or some other problems.
i plastigauged the rods too and got something between .0020 and .0030, i think this should be fine. Torqued to 42 ft. Lbs. With oil on threads as the CSM says.
I used the diagram i posted for ring clocking (see marks on the pistons).
Cam is already in too. I put green Lucas assembly lube for cam bearings and red line red assembly lube for the lobes, this sticks ways better than the lucas lube.
What makes me a bit nervous, is the orientation of the rods. Now, i have all the 'noses' on the rods pointing to drivers side/engine front. I mean, this rotating assembly was assemblied that way and ran without problems in my old block, and i havent took the pistons off the rods (all arrows on pistons pointing to engine front and all pistons are numbered in their right bore).
i couldnt find any information anywhere what is really right and whats wrong. 71 CSM says note the spit holes for orientation, but my rods dont have spit holes.
No binding and adequate side clearance tells you everything is good. Oldsmobile did away with the spit holes sometime in the mid to late 1960s or early 1970s. Found they are not necessary.
I got beat to it but yes if the rods are the wrong way it binds stuff up. Learned this many years ago the hard way lol. If you have second thoughts pop a cap off and see where the chamfer on the rod sits. It should face the cheek of the counter weights. Meaning then the rods are in place you will have chamfers away from the parting line of the rods where you check for side clearance.
No binding and adequate side clearance tells you everything is good. Oldsmobile did away with the spit holes sometime in the mid to late 1960s or early 1970s. Found they are not necessary.
Today, i checked the side clearances of all rods. I have .015. CSM says .002 to .011. Ive seen a post of cutlassefi somewhere, where he wrote he shoots for .015 to .020, so i guess im fine with this.
Check the oil pump pickup screen as some debris is visible. Most debris is under the shrouded area and hard to see.
Check the crankshaft endplay.
Good luck!!!
Originally Posted by Sugar Bear
Tried to confirm from the pics but wasn't certain, are all the piston arrows on the top pointing forward?
Yeah, ive seen the debris, i have to check that, it looked first like old oil hanging in the pickup screen.
Do you mean 'crank thrust bearing clearance' with 'crank end play'? My thrust bearing clearance is about .005 to .006.
Yes, all piston arrows are pointing forward. the pistons/rods has been assembled and ran like this in my old rust pitted block. I havent disassembled the pistons from the rods.
I will take better pictures of the rods next time in the garage.
No binding and adequate side clearance tells you everything is good. Oldsmobile did away with the spit holes sometime in the mid to late 1960s or early 1970s. Found they are not necessary.
Ok, thanks for the information, good to know.
my '71 CSM still shows the version with spit holes.
I got beat to it but yes if the rods are the wrong way it binds stuff up. Learned this many years ago the hard way lol. If you have second thoughts pop a cap off and see where the chamfer on the rod sits. It should face the cheek of the counter weights. Meaning then the rods are in place you will have chamfers away from the parting line of the rods where you check for side clearance.
Thanks for the information, maybe i just thrusted on the way how the pistons and rods was assembled in my old block. I have to say that for me, there wasnt really one side of the rods "more chamfered" than the other side. I once assembled a mopar engine with my brother, and there the one side of the rod witch is facing to the counterweight of the crank was a LOT more chamfered.
I think i havent looked well enough, because i thought it will be just fine because it was installed lile this in the old block.
Looks like the larger chamfer is pointing in the wrong direction.
#5 rod seems correct to me:
well, i guess my previous owner installed some of the pistons wrong on the rods, since #6 pistons arrow is pointing forward. Sometimes, this hobby just sucks :/
I cant believe how this was running without an issue?
Edit:
I took all caps off to check, and found out that
Nr 1, 3, 5 and 7 are installed correct,
Nr 2, 4, 6 and 8 are with the larger chamfer facing to the wrong (not the crank side).
Edit 2:
maybe i think it ran without binding (and its easy spinnable by short wrench without binding) because my crank has an undercut on the journals.
Last edited by 71OldscutlassS; February 17th, 2022 at 11:38 AM.
Im not sure if i can leave it like that or if i should disassemble the pistons on 2,4,6 and 8 to turn the rods for "the good feeling that its done right" because im afraid of damaging the pistons while pressing out wrist pins.
The pistons have an arrow due to the location of the wrist pin. They should be removed and taken to a competent machine shop that can complete this task. And as I previous advised your pistons should be pin fitted.
My $.02 , there is no way I'd leave it incorrect. Pistons should be able to be pressed without a problem if done in a holding fixture.
Good luck!!!
Originally Posted by joesw31
The pistons have an arrow due to the location of the wrist pin. They should be removed and taken to a competent machine shop that can complete this task. And as I previous advised your pistons should be pin fitted.
Today, i pulled piston 2,4,6 and 8 out again and disassembled the rings to get them ready to turn.
Its true, they have been installed with the larger bearing offset towards the front of the engine. That means, this larger offset was pointing towards the odd numbered rods 1,3,5 and 7, not to the crank side.
I really think that in my case, it would be fine to run it like it is (and it runned like this) because of the undercut crank journals. I read somewhere that some people disassembled bone stock never opened engines (with non-spithole rods) which have had all the rods assembled with the larger offset pointing to engine front, but i dont know if thats true.
but for me, it would bother me just of knowing that its wrong, so the 2,4,6 and 8 rods will do a 180° turn.
The bearing tang and spit hole are located on the same side of the bearing when so equipped, thus the location of the bearing tang when properly installed will point toward the center or camshaft. Also the bearing sits in the connecting rod slightly more to one side than the other because of the larger chamfer on some connecting rods to allow adequate clearance for the radius of the crankshaft journal. #5 is correct, #6 is not.
Don’t forget to recheck the side clearance as you re-install the rod/piston assemblies. Whoever did the original engine assembly didn’t pay attention to the details. Now everything is suspect. Let’s do it once, do it right. All of us are pulling for you. Keep us updated on your progress.
Don’t forget to recheck the side clearance as you re-install the rod/piston assemblies. Whoever did the original engine assembly didn’t pay attention to the details. Now everything is suspect. Let’s do it once, do it right. All of us are pulling for you. Keep us updated on your progress.
today, i was able to re-install pistons 2,4,6 and 8 after they made a visit to the machine shop to turn the rods. Now, all rods are pointing to the direction they should.
I torqued all rod nuts evenly to 42 ft. Lbs and everything can be turned over freely by hand with a short wrench.
My rod side clearance is .016 to .017 which i think is good, refering to mondellos article posted here.
Installed the oil pump too and torqued to 35 ft. Lbs.
February 1st, 2022, 10:32 AM
