1G cylinder ridge - photo

[sacrileger]

is there a quick and dirty way to tell what i can get away with regarding a cylinder ridge at the top of the compression ring travel in order to put new rings on and not use ridge reamer?

 

[90laserRSfwd]

Not sure I'm understanding the question... could you rephrase? Are you concerned about the 1/4 - 1/2" top of the bore where the top piston ring doesn't reach? As far as honing it or what are you asking exactly?

 

[sacrileger]

Not sure I'm understanding the question... could you rephrase? Are you concerned about the 1/4 - 1/2" top of the bore where the top piston ring doesn't reach? As far as honing it or what are you asking exactly?

thanks for asking to rephrase for clarity:
the block has 160000 km on it. the rings worn off the side of the cylinder all the way up to the end of the ring travel forming a tiny ridge at the top (TDC) where the 1st compression ring stops. the ridge would have round corners.

my concern is that with new rings, the sharp corners of the new first compression ring would crash into the radius of the ridge which most likely will result in damage to the top of new ring and bending or breakage of second ring LAND.

the proper way to remove the ridge is to use ridge reamer. i dont have one. plus, there is a credible source that says dont use one: https://tinyurl.com/jhcvog4

 

[1990TSIAWDTALON]

If there is a ridge, you are probably going to have excessive Piston To Wall clearance issues leading to piston slap. It isn't something that I would want in my motors. And you are right, that ring will end up butting up to the bottom of that ridge and possible break the ring. I would get rid of the ridge, check PTW clearance and make an informed decision on what to do next.

 

[donniekak]

Have it honed. Either it's going to clean up and stay in spec, or it'll need bored to the next oversize. Either way it'll need honed for rings.

 

[sacrileger]

If there is a ridge, you are probably going to have excessive Piston To Wall clearance issues leading to piston slap. It isn't something that I would want in my motors. And you are right, that ring will end up butting up to the bottom of that ridge and possible break the ring. I would get rid of the ridge, check PTW clearance and make an informed decision on what to do next.

perhaps i should have mentioned it earlier - i did check the PTW as this was the topic of discussion in another post. i am 0.007 under the service limit. in other words, within tolerance; thus not warranted to take the block out of the car, have it re-bored to the next size, getting over-sized pistons and rings.

i am just wondering if there's some reasonable method to blend the ridge with the piston wall. the ridge is not huge. it is tiny. nevertheless, i dont want to take the chance. perhaps there's a reasonable test, like, put the new rings on and see how much; or with what force, they catch on the ridge when manually pushed up past the ridge. obviously, i am just grasping at straws here.

 

[sacrileger]

Have it honed. Either it's going to clean up and stay in spec, or it'll need bored to the next oversize. Either way it'll need honed for rings.

the ridge is only on one side of the cylinder, i would say about 40%, about 140 degrees. i am concerned that if i dont get the ridge out first, i'll just make it worse. also, the cross-hatch is not too bad at all. you can even see it in the pic i posted.

what is the trade-off if i dont rehone the cylinder and run it with new rings? i am not sure how to make that judgement or, informed decision.

 

[donniekak]

You have to have the cylinder honed for new rings. Otherwise they won't seal properly.

 

[sacrileger]

You have to have the cylinder honed for new rings. Otherwise they won't seal properly.

my plan was to use "bottle brush" hone technique just to prep the cylinder surface; but that obviously will not take care of the ridge. the cylinders are in pretty good shape except the ridge. i'd like to avoid anything too aggressive if i can help it. the block is still in the car adn 'bottle brush" hone appears to be appropriate here.

 

[1990TSIAWDTALON]

Just the one cylinder or all of them are this way???
Wondering why it would put a ridge on just part of the cylinder wall and not a complete circle pattern. Did it have any broken rings when you took it apart?

 

[goodbye]

The bottle brush should take away the ridge as well. Sounds like all you need with a set of new rings.

 

[sacrileger]

Just the one cylinder or all of them are this way???
Wondering why it would put a ridge on just part of the cylinder wall and not a complete circle pattern. Did it have any broken rings when you took it apart?

that's a very good question! because that pattern (partial ridge) is only on 1st and 3rd cylinder. Cylinder #2 and #4 are perfect, no ridge at all. there appear to be no broken rings, but the pistons are still in the block. i am in the process of taking them out as i type. btw, this question is related to this post: https://tinyurl.com/hvh4pqr
just to add color to my current question.
basically, as the pics show, the timing belt jumped, the piston hit valves and put a hole into the piston. i have taken a good piston out of the turbo donor engine, put it on the connecting rod of the broken piston, measured PTW distance, and am ready to re-ring it. but i can guarantee (99.99%) there are no broken rings on 1st and 3rd.

 

[1990TSIAWDTALON]

I am hoping that @BogusSVO will chime in. He can add his 2 cents on the reason why it wore irregularly. I have a half a** solution but it isn't the right thing to do. I have had many many years of engine building and ran across a lot of things but never a ridge that didn't go all of the way around. Bogus runs his own machine shop so maybe he will get on board.

 

[1990TSIAWDTALON]

Do you think the two different pistons weighed the same or are very very close? I wouldn't want it to be unbalanced and shake the engine apart. I would weigh a good piston from the engine and then weigh the "donor" piston and see if they are close to the same weight. I did mine on a paint scale at the local parts store. They weigh the paint when they mix it, but the scale can be used for anything like I used it for on one of my Chevy builds.
Come on @BogusSVO, I'd like to hear from a machine shop man.

 

[sacrileger]

Do you think the two different pistons weighed the same or are very very close? I wouldn't want it to be unbalanced and shake the engine apart. I would weigh a good piston from the engine and then weigh the "donor" piston and see if they are close to the same weight. I did mine on a paint scale at the local parts store. They weigh the paint when they mix it, but the scale can be used for anything like I used it for on one of my Chevy builds.
Come on @BogusSVO, I'd like to hear from a machine shop man.

again, great question. i did weigh it just now after you asked and what i got was 365gr for the non-turbo piston and 390gr for the turbo piston. the connecting rods are the same, of course. and the wrist pin as well. the difference is 25 grams. i am attaching pics of the pistons w/ on the w. scale.

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[donniekak]

How are you going to wash the honing grit out of the block if it's still in the car?

This seems like a project destined for issues. Pull the block, have it washed and honed.


You'll need 4 Pistons and rods that are within 2 grams of each other to keep it reasonably balanced.

 

[sacrileger]

How are you going to wash the honing grit out of the block if it's still in the car?

i was going to follow a method where each cylinder is de-greased and then on the bottom of each cylinder is taped to the wall a "cup" made of thick plastic to protect the crankshaft. the bottom of the plastic cup is covered with damp paper towels. once the honing is done, the cylinder walls are wiped clean from the bottom up. then remove the plastic cup, cover crank with damp cloth. wipe cylinders dry.

This seems like a project destined for issues. Pull the block, have it washed and honed.

i may have to do that

You'll need 4 Pistons and rods that are within 2 grams of each other to keep it reasonably balanced.

i had no idea it needs to be that close in weight. needless to say, i cannot find the link anymore; however, one method of balancing each complete piston is to cold weld and/or spot weld balancing weights inside the wrist pins. has anyone done that here?

 

[1990TSIAWDTALON]

Well I can't say for a DSM but for my SBC builds, I would match all of the pistons to the lightest weight and then check the big and small ends of the rods for weight, then match each piston to a rod that got them all close to each other then work on the final balance when I don't have access to a balancer (which is over 2 hrs away one way). My DSM motor was balanced on a machine tho.

 

[sacrileger]

Ok, laddies, spring is here and I just wanted to give you an update on my project before we get to a new issue: putting 2g head on 1g 7bolt block.
But I warn you, what I have done with this project here is sacrilegious to the perfection you laddies strive for; nevertheless, please remember that this car is not intended for a track; it's
just to go to the store to get a case of beer and hardly ever the car will go faster than 120km/h which gave me the room to be silly and experimental with this motor.

This project started with a timing belt that jumped on me and resulted in piston #2 kissing an exhaust valve, breaking it and putting a hole into the piston head:
https://tinyurl.com/jgpzvw6

At around the same time I purchased a 2g 4g63T motor:
https://tinyurl.com/jy8rgjh
so I took one of the turbo pistons (63DTEV) out to replace the damaged 63DK piston head.
Here I ran into a bit of a challenge and a few mistakes were made. First of all, the 63DTEV cylinder head was much heavier than the 63DK as well as the wrist pin from the turbo was heavier. Not realizing this, I mounted the 63DTEV on the 1g rods using the 63DTEV wrist pin which resulted in a total weight of 1152 grams for the entire piston..compared to about 1128 grams for the other three 63DK pistons. Since there was no way I could lighten the 63DTEV piston (but I tried), I had to add weight to all three pistons to make all pistons the same weight. I added weight to the three 63DK pistons by making the wrist pins heavier.
At the end, all four pistons ended up being exactly 1152grams sans new rings. Here they are; all ringed:

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Once the pistons were taken care of, I honed the cylinders - but not too much; just enough to have a nice scratch pattern so the rings could seal nicely. I am already very close to service limits on PTW so I left a bit of the ridge at the top which I dont think will cause any problems. BTW, these cylinders were extremely well cleaned with detergent, varsol, gasoline, TSP, Acetone and carb cleaner after honing. They squeak.

Here it is, #4:

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Here's cyl #3:

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Here's cyl #1:

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And here are all four pistons installed:

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[jking29]

If you are changing one piston to a 2g, you need to change them all. The 1g and 2g 7 bolt motor have different compression. Also If you can catch a fingernail on the ridge, you may have problems with breaking a ring.

 

[joemamma]

If you are changing one piston to a 2g, you need to change them all. The 1g and 2g 7 bolt motor have different compression. Also If you can catch a fingernail on the ridge, you may have problems with breaking a ring.

if u can catch it with a fingernail it needs to be bored over

 

[sacrileger]

if u can catch it with a fingernail it needs to be bored over

The ridge is tiny and is only 1,5" long. I tested it and the new rings don't even move since they appear to slide over the ridge instead of into the ridge and get caught in it. It's not proper way to leave the ridge; however, given that this car will not be raced it should be ok. I certainly will keep this thread up-to-date if there will be negative consequences to my not removing the ridge.

 

[joemamma]

well don't say we didn't warn ya