importance of checking the end gap

[newaccorddriver]

i was helping my friend rebuild his D16 motor, and he has new pistons and such for his motor build. he never actually checked the end gap of the rings before he put in the pistons. and now that his engines altogether and motors in the car, its kinda hard to check it at all now

his main arguement for not checking the end gap is that 'a stock replacement piston with rings ordered to a specific size shouldnt need to be checked at all. they are made to have a specific end gap, and clearance as from the factory'

my question is, from not checking his end gap, did he just ensure his motor doesnt live long?

['89AccordLX(Rus)]

There truly is no way of knowing now. His ring gaps might be within spec, or they might not. Its pretty foolish to expect things like ring gap to be perfect from the factory. No matter how tight the manufacturing tolerances, it is still very likely that the gaps would need to be adjusted before installation. There are just way too many variables between the manufacturer and the point at which the rings are installed (storage, shipping, temperature changes, etc.) I wouldn't go as far as to doom an engine to early death just because ring gap wasn't checked, but its reasonable to assume that the risk is now increased.

[newaccorddriver]

so if i plan to go upgraded pistons and such, and i used the gapless seal rings that total seal offers, would that be more risky?

['89AccordLX(Rus)]

Gapless rings are usually used with pistons with gas channels to allow for gases to escape from between the rings. So as long as you use a combination of gapless rings and pistons designed for them, you should be good from a technical standpoint. I'm sure someone on here can tell you whether the gapless rings are a worthwhile upgrade for whatever build you intend to do.

An article I found talks about ring and piston design: http://www.carcraft.com/techarticles...ng_technology/

[AccordEpicenter]

dont use gapless rings in a performance build and always always always check the ring gap. Chances are that the ring gap will be on the big side if he replaced the pistons with standard size pistons and rings and didnt overbore and go with bigger pistons because the bores are already worn a bit

[88Accord-DX]

The first thing that needs to be done before purchasing stock rings & pistons, is to measure the cylinder bores in the block. To check for out-of-round, taper & to see if they are in tolerance for stock rings & pistons. Using telescoping gauge with outside micrometer/ or dial bore gauge.
The worst thing that could happen in his situation, is blow-by & possibly low compression. He can check his compression to specs w/ compression gauge & that will pretty much will tell if his end gap is too far out. Checking end gaps are real important for a successfull rebuild. Too little end gap & you take the chance of breaking the rings. End gaps are in place for the ring to expand under hot temperatures. Placement of the end gaps are just as important too.

All I know about gapless rings, is they aren't recommended for performance applications.

[newaccorddriver]

dont use gapless rings in a performance build and always always always check the ring gap. Chances are that the ring gap will be on the big side if he replaced the pistons with standard size pistons and rings and didnt overbore and go with bigger pistons because the bores are already worn a bit

its odd cause when i checked over mine yesterday, my gaps were out of tolerance on 2 of the rings. they were well over the biggest gap allowable. mine you i went with oversized pistons and rings that go with them. these werent a hair off, since i can fit 2 of the highest allowable tolerances in them

im just wondering what the machine shop i bought them from is going to say.

wouldnt a bigger end gap mean more loss of pressure during combustion?

as far as my friends engine goes, hes not having many problems with them yet

[newaccorddriver]

ive just read the clearances thread on the how-to section. it says that a bigger end gap isnt something to be worried about unless its at 0.040". my service manual says it should be within a certain amount of gap when new, but my rings are new and are way off that point. im not sure if its bigger then 0.040" since i didnt check after i saw it was out of tolerance, but is it normal for rings to have that huge of a gap when new?

[cygnus x-1]

When I did my rebuild I used stock size (82.7mm) Honda pistons and Sealed Power rings. I bought rings that were the next size up because I wanted to set a tight end gap. Obviously I had to file them down but that was the point. Then I discovered that the oversized oil control rings just didn't fit quite right so bought another set of standard size rings and used just the oil control rings from the standard set. Just for giggles I tried one of the standard size top rings to see what the gap would have been had I used those. It was much larger than I expected. Not 0.040" but more than 0.020".

Anyway I don't know if it's normal but the "stock" size rings I tried had a pretty big gap with a stock size cylinder bore. Oh, and the cylinders were bored to 82.7mm because the block started out as an A18 (1.8L).
Too large a gap won't be a big deal unless it's WAY huge. Then you'll just get more blow-by gases into the crank case. Make sure the PCV system is good.

C|

[newaccorddriver]

i talked to the machine shop today about the end gap, he says that its normal for engines to have a 'big' gap since it lets more pressure out higher up in the rpms. also, when factory makes rings, they tend to stay on the large size for that reason, the main reason for filing it down is for expansion. if there were no room to expand, or not enough room, it would create a big mess. it might have a problem when your doing a compression test, but overall, when driving normal, it shouldnt matter. he actually recommended a bigger gap for me mainly since i was going forced induction and it would give the rings more room to expand.

[cygnus x-1]

Right. A larger gap is safer than a smaller gap. Too small a gap means wrecked rings and cylinders.

C|

[rjudgey]

ring gaps, i run mine to a set figure given on a table written by a performance tuner, they are tighter than stock but big enough for clearance for expansion, on a N/A engine this is critical can mean a big difference in compression i typically see 210-220 readings on my cylinders and each one is hand filed per cylinder using std oversized rings, tried the total seal ones, they give great bhp and torque increases more than you would expect from just a set of rings but the downside is they create so much extra suction that the valve guide seals can't cope and the engine burns oil so would be difficult to pass emissions, also uses a lot of oil for road use as they were for race use the throttle stays open most the time so isn't so much of an issue i did 200 miles on a trip and it used 4 litres up and then destroyed the bearings before i realized it was empty!!

Also makes sense that turbo app is bigger as the extra heat created from the turbo would make rings expand more.