I've been running a 1911 with stock cam and L-Jet for some time now and its ready for a refresh. I've been looking at a set of NPR 96p 1.8 P&Cs as a replacement big bore kit. Are there any comments out there regarding this particular manufacturer's product? I'd like to know before I purchase something I don't want because of something I didn't know.

Thanks, Marty

I put in a set of those same NPR's about '85, with an "Eagle" mild carb cam. That engine is still running with close to 100k miles on that rebuild. I don't know what kind of quality they are today though. I'd probably shop Jake's online store.

bump

Try posting of Jake's forum. Someone will respond.

NPR is fine.
if they are the 1.8 variety and not the 1.7 you will be happy.

Japanese

And what would be the difference between the "1.7 variety" and the "1.8 variety"?

The Cap'n

Other than the quoted question, I'd like to know if they are a "thrust" piston design.
That is, are the pistons directional to the power stroke. The Keith Black pistons I've been using are not and they have developed a lot of noise (piston slap) later in life.
I don't want to head back down that same street again, if possible.
Marty

The 1.7 P/C's are meant for the 1.7 heads.
The outer diameter of the cylinders is smaller than the 1.8.
So, you get a very thin walled cylinder with alot of warpage that can happen.

The pistons, at least stock, do have the wrist pin offset a bit...not sure how much. Its so at BDC you dont get to much lateral force...thus piston slapping.

I have no idea if anyone aside from Mahle makes them this way anymore...you would have to measure the centeline of the wrist pin from side to side to confirm.

Rich

I've been doing this since 1973, and I don't recall any 1.7 configured 96mm P?Cs ever being available. Not to say there aren't any, but I've never seen/heard of them. The Cap'n

Probably because you would never have touched them. You would have run away quick just looking at them.

There was a big bore kit by NPR ( I think) for the 1.7 about 15-20 years ago...
I have not seen them new in a long time.
They were 96mm but the walls were so thin it was a real serious problem getting them to seat.
They also warped quite a bit right out of the bag...just from honing.
I dont think anyone sells these new anymore, but I have seen a few used ones kicking around on here and ebay...
At least one set was on here last year..I called, he measured, I said no thanx

Rich

I used a set of the 96 on my 1.7 case.

Made by NPR and bought from European Racing in about 1989.

You DO understand we're talking about the head end of the cylinders, right? All the bottom ends are the same, at least for any that don't require boring the case spigots.

Remember, ALL the T4 cases are essentially the same. The Cap'n

Ahhhh...

Nippon Piston Ring 1.8's..... No chinese rejects for me.... I gots two NOS sets of the little devils. A little more compression than stock if I recall -8.3:1 or 8.5: 1 vs the stock 8.0:1

The cast iron cylinders are quite consistant in diameter, taper, and concentricity, use good cast iron with no voids and porositys, and are good stuff when you can find them.

The pistons use a ring set that is a bit wider than normal and not as easy to locate.

Ken

That proves that the Cap'n doesn't know it all!!! :-)

These were made by both Mahle and Kolbenschmidt, and also by NPR.... Probably the reason he never saw them is because they are a really bad idea and generally cause issues..

Nothing wrong with NPR, they are nice pistons but the Grant rings they cam with were not my favorite.

Why so? And do you have a replacement?

Hastings makes rings that will work. I can help you find some if you wish, or just call their 800 number and have a set of calipers handy to measure the rings.

Here's why the 1.7 kits are a bad idea...

Click to view attachment

The green arrow is a second crack beginning to form...