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tony barnhill
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What would happen if the machine shop mounted 1098 pistons on the rods backwards?
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Midget Rod Question
- Thread starter tony barnhill
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tony barnhill
Great Pumpkin - R.I.P
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Yep. Pistons have a 'front' mark....& when I install it with the 'front' to the front, one of the cap studs hits the block as I rotate the crankshaft.
<span style="text-decoration: line-through">I use a very good machine shop but they focus primarily on modern street and race engines - Midget engines aren't brought to them every day</span> - NOT THEIR FAULT!!
_________________
I'm a <span style="font-weight: bold">DUMMY!</span> Midget engines are different than other engines....the rods are offset & you have to put the correct offest in the correct hole!! I apparently didn't!
In a MGB engine all I worry about is the oil hole is facing in the correct position - it doesn't matter which rod goes in which hole!
In a Midget engine, the #1 rod offset faces to the rear, the #2 offset faces to the front, the #3 to the rear, & the #4 to the front....I just learned that - after breaking all 4 of my bottom rings (in a 5 ring set!)....man, these engines are nowhere as easy as an MGB engine to build!
<span style="text-decoration: line-through">I use a very good machine shop but they focus primarily on modern street and race engines - Midget engines aren't brought to them every day</span> - NOT THEIR FAULT!!
_________________
I'm a <span style="font-weight: bold">DUMMY!</span> Midget engines are different than other engines....the rods are offset & you have to put the correct offest in the correct hole!! I apparently didn't!
In a MGB engine all I worry about is the oil hole is facing in the correct position - it doesn't matter which rod goes in which hole!
In a Midget engine, the #1 rod offset faces to the rear, the #2 offset faces to the front, the #3 to the rear, & the #4 to the front....I just learned that - after breaking all 4 of my bottom rings (in a 5 ring set!)....man, these engines are nowhere as easy as an MGB engine to build!
racingenglishcars
Darth Vader
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Not as easy, maybe, but certainly a much better engine.
regularman
Yoda
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Now I doubly wish I had stopped by your shop. I have fooled around with a bunch of the A series. Yep, they are a bit different.tony barnhill said:
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tony barnhill
Great Pumpkin - R.I.P
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I just don't mess with them - I've got several but I just drive them...this is my first time to really spend any time with one.
Now I've gotta find a new set of .020 5-ring set rings! To go on my new 5-ring .020 pistons! To replace all the ones I broke today!
Now I've gotta find a new set of .020 5-ring set rings! To go on my new 5-ring .020 pistons! To replace all the ones I broke today!
Trevor Jessie
Yoda
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See. Isn't it fun to do the work and learn new things (even if it causes a bit of headache and a few $)?
regularman
Yoda
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Easy does it Tony. Hopefully the rings are the same as other pistons and not special for the 5 ring kind. I bet those pistons were $$$tony barnhill said:
regularman
Yoda
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Longer leak down time maybe?Jayrz said:
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tony barnhill
Great Pumpkin - R.I.P
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Okay, I don't know alot about these little engines, I'm an MGB guy....however, & hopefully I can explain it until one of the experts on these little engines comes along.....As I understand it, the 5th ring is a wash ring that cleans the cylinder walls, pushing oil back down into the pan quicker....&, instead of 1 oil ring, there's 2....mine originally had a 3-ring setup - but 5 just seems more protection & higher compression for longer time.regularman said:
&, yep, they were a dollar or 2!!
regularman
Yoda
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Mine had only 48K miles on it and had 3 compression rings and then the oil ring. I have seen this a bunch on BMC type cars, where most of the other cars only have 2 compression rings and then the oil ring. I don't know if they count the 3 part oil ring as two rings or what. How many grooves in your pistons Tony?
regularman
Yoda
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Does it look like this Tony?
regularman
Yoda
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Also Tony, just me asking a dumb question. Do you have the right ring compressor? The one for the bigger pistons won't go small enough and keep a perfect round shape good enough to work. I went and bought a small engine ring compressor, like for a lawn mower engine. Its what you need for this little babies, or the rings wont go in. Should just tap in with the wooden but of a hammer real easy like.
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tony barnhill
Great Pumpkin - R.I.P
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5regularman said:
No...mine are all solid except for the 4th ring:regularman said:
compression ring in 1st groove
compression or oil ring in 2nd groove (thicker than #1)
compression or oil ring in 3rd groove )ticker than #1)
oil ring in #4 groove (has little springee thing inside it)
sweeper ring in #5 groove
(I think)
&, before you ask, they were made in the UK.
That might be part of the problem...I have 2 ring compressors: 1 for MGB's & 1 for larger engines....I used my MGB ring compressor....when I get back from Puerto Rico, I'll buy a smaller ring compressor.regularman said:
regularman
Yoda
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Oh, Ok then. That sounds different. I hope you can find some more rings and get it figured out. I know that has got to be frustrating.
regularman
Yoda
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Be careful and have fun man. One of the smaller ring compressors should be pretty cheap. If you can't find it at an auto parts place, then check a small engine parts place. I had lost my old smaller one that I used on small engines and the occasional motorcycle engine that assembled that way and tried to use one I borrowed from my dad that was for Fords and Chevys and it was not right. I knew something was wrong and one place was pooching out and I knew it wouldn't work. Good thing is that once you buy one, its good on any engine like that.tony barnhill said:
jlaird
Great Pumpkin
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He has the late model pistons for a street engine, low compression, all is well but he has a learning curve.
Yep all the rods are numbered for the cylinders they go in. Never thought much about the front or back but they have to clear the block. Think they will only really go one way if you plan to attach them to the crank, as you are correct they are offset.
I know those are moss pistons so came with rings, I expect Moss can get the rings by number.
Oh yea, compressor just snug, not tight, they should tap in easly. Lots of nice lub.
Yep all the rods are numbered for the cylinders they go in. Never thought much about the front or back but they have to clear the block. Think they will only really go one way if you plan to attach them to the crank, as you are correct they are offset.
I know those are moss pistons so came with rings, I expect Moss can get the rings by number.
Oh yea, compressor just snug, not tight, they should tap in easly. Lots of nice lub.