66 Riviera 425 cid engine bored .40 over : New pistons rings less wide as

[FrenchRiviera64]

Hi guys, I'm refreshing a 66 Riviera 425 engine bored 0.40 over, after pistons removal I checked rings gaps and found .055' at bottom of cylinders wich is more than twice as specified, so I decided to change rings and ordered new rings. When I received new rings (Enginetech R43128-40), I checked the gap on the cylinders and measured it right and also checked their width and found it right (5/64') but I immediatly saw the 1st and 2nd rings were less wide than those I removed on all pistons.

The first and second rings removed are 5.2 mm wide, the Enginetech are only 4.7 mm wide. 

As I don't expect to put back olds rings and keep those pistons I'm a little bit bored !!!

Does anyone here already encountered this kind of situation on a 425 nailhead ! 

I don't think the rings I ordered are wrong but I'm not sure, they are specified for 66 425 nailhead

Perhaps some aftermarket pistons manufacturer made wider rings ? 

The only information I have about pistons is 228X on one side of each piston near pin.

Thank you in advance for your help !

Philippe

 

[DFeeney]

You can find several expect piston ring vendors thru  this site.  Perhaps other members can send you a reference.  As you know it is important to get the right ring.

[joe_padavano]

Sorry but I'm confused. Didn't your new oversized pistons also come with new rings? Are you saying that these rings are the ones with the excessive gap? To be honest, you should be measuring gap at the top of the bore, not the bottom, and if it varies excessively the cylinder is tapered.

 

[Oldtech]

I think we are confused which measurement you are asking about.  There are 3 things. The end-gap of the ring when in the cylinder, and yes it should be measured at the bottom - the tightest part. The width of the ring which is how it fits in the groove. This MUST be correct. and the depth of the ring as in the depth of the groove. This does not have to be precise.  It sounds by your post that the ring with is too narrow, if that is the case they will not work. If it is the depth it should be no problem.

[FrenchRiviera64]

Thank you for your answers, the new rings are too narrow, compared to the rings I removed, you can see it easily on the picture ! The ring above is what I removed and the ring under is the new one ! 

I was wondering if the piston manufacturer (that I don't now) made special rings for their pistons ! I still not  find who made those pistons...

My objective would be to keep those pistons because they are in good shape but if I can't find matching rings for them there would be no other choice than buying a new set of today pistons with new rings ! 

Those 425 nailhead pistons are very expensive cast pistons compared to others (even compared to 401) and in my case there's not really technical interest to put new ones

 

 

[PAV8427]

Many ring suppliers out there. Instead of looking for rings for a 66 425, its going to be easier to find by bore size and thickness. And width would be something to factor in also so you dont bottom out in the ring grooves. 
Just measure your bore. Use a micrometer to check thickness and width and go shoppin. 
Probably would be best to convert to inch dimensions for ease of searching. 
 

[joe_padavano]

Sorry, but I'm still not understanding the issue here. You bored the cylinders 0.040" over. That means you needed new pistons for the larger bore. Didn't the new pistons also come with matching rings?

[Oldtech]

In my opinion a difference in what I see - the horizontal thickness of the ring is not an issue. As long as it fits the groove snuggly and the end gap is correct ( important)  it will work. Be sure  that when the ring is in the bore at the tightest spot, which will be the bottom, that you have approx .015 gap between the ends.  Modern rings have less pressure on the cylinder walls and that is likely the reason for the narrower ring. 

[FrenchRiviera64]

Thank you for your answers. In my first post I told I was refreshing this 66 425 nailhead engine, not rebuilding it, that's why I only want to change piston rings. So no boring /honing, I got the engine .040 bored over and intend to let it like this as the taper it still in tolerance and pistons are in good shape ! The only things that are wrong here are rings gap ! Too large ! So I ordered new rings for 66 425 Buick but got too narrowed rings (less horizontal thickness)

I took a look at others V8 engine with about 4.30 inch diameter bore (440 chrysler, 403 Olds, 429/460 ford...)

Finally I found the solutions, in fact those 425 nailhead pistons have Cadillac 472-500 cid rings (and cadillac 472-500 ring land depth). Those rings are wider ( horizontal thickness) and perfectly match with removed rings. 

But I still don't know piston manufacturer at his time ! 

As my engine is 4.3525' (4.3125' bore+.040), I ordered 472-500 Cadillac 4.30 +.060 ring (4.360') and file fit rings to get correct gap at bottom travel of piston, will use .015' gap.

Hope it might help others guys ! 

 

Edited October 12, 2022 by FrenchRiviera64 (see edit history)

[Ben Bruce aka First Born]

22 hours ago, joe_padavano said:

Sorry, but I'm still not understanding the issue here. You bored the cylinders 0.040" over. That means you needed new pistons for the larger bore. Didn't the new pistons also come with matching rings?

I think he tore down an engine that was ALREADY bored and is using the pistons he removed.  

 

  Ben

[joe_padavano]

1 hour ago, Ben Bruce aka First Born said:

I think he tore down an engine that was ALREADY bored and is using the pistons he removed.  

 

  Ben

I THINK that is correct, based on the most recent posts, but simply stating that would eliminate all confusion.

[Larry Schramm]

Even if that is the case, he needs to check the piston clearance to the wall. If more than if my memory is correct is .003", he will have multiple problems.