Hot Rod Forum : Hotrodders Bulletin Board

Hot Rod Forum : Hotrodders Bulletin Board (
-   Engine (
-   -   Pistons dont fit in block. (

darce 10-07-2012 01:05 AM

Pistons dont fit in block.
Hello i decided to re ring my chevy 350. I honed the cylinders with 400grit stones and bought new sealed power moly rings ze251k, now i tried to install the pistons in the block but couldnt. i bought the piston ring compressor and applied light oil to both the piston skirts and cylinders.

I noticed that piston stopped at the second compression ring. I hit it alittle hard and forced all the piston in but stopped, i didnt want to break anything. I then decided to pull the piston out. now there is a grey mark on the cylinder wall were the piston rings were.

I made sure i had boots on the bolts and not hitting the crankshaft. Also i made sure the rod wasnt hitting anywhere. And there was plenty of oil on these parts.

Help is really appreciated.

poncho62 10-07-2012 04:13 AM

Sounds like your rings are too large....Try a ring in the bore by itself, without piston and see what the gap is at the end of it

Irelands child 10-07-2012 05:16 AM

Most after market piston rings are 'file to fit'. To say that, they are manufactured .015 to .020 oversize to fit differences in the way each cylinder is bored.

I don't have photos handy, but you take each cylinder individually and each piston (I use that cylinders piston) and a set of the three rings that you intend on using in that cylinder. I then push the top two, one at a time, about an inch into the piston bore, using the top of the inverted piston itself and measure the end clearance with a feeler gauge. This should end up being be.005/.007 per inch of piston diameter(4" piston would be .020 gap) for the top two rings AFTER YOU FILE TO SIZE. This may entail several 'trips' into that cylinder and several passes with a file or special filer tool (Summit and others will have that tool). The bottom and usually 3 piece ring doesn't get any fitting (normally) and is installed as supplied.

There are many write ups on the internet, but if you have conventional cast/moly rings, will all use this kind of assembly. There are other kinds that are installed differently, but are specials with those 'special' high buck prices.

Dave W 10-07-2012 06:46 AM

251k rings will not fit GM factory pistons. Factory pistons require a "Shallow groove" ring. Consult an automotive machine shop or REAL auto parts store for correct cast iron ring set for the different VIN codes.

CNC BLOCKS NE 10-07-2012 09:02 AM


Originally Posted by (Post 1596758)
251k rings will not fit gm factory pistons. Factory pistons require a "shallow groove" ring. Consult an automotive machine shop or real auto parts store for correct cast iron ring set for the different vin codes.

x2 !!!!!!!!!!!!!!

darce 10-07-2012 11:50 AM

ok guys so i decided to go with cast iron rings. would i need to re hone the cylinders? 10-07-2012 03:31 PM

No, cast rings are very forgiving. Thats why they are used in worn bores. Never Chrome or Moly!

darce 10-07-2012 04:54 PM

so what rings would you guys recommend?? 10-07-2012 05:04 PM

Sealed Power, Hastings, Perfect Circle, Mahle, are all quality stuff. Cast iron for best results in your situation.

cdminter59 10-07-2012 06:48 PM

Pistons don't fit block. Help

Originally Posted by darce (Post 1596945)
so what rings would you guys recommend??

Check your piston on the inside for a number. Call Hastings or Speed Pro with the number. They will tell you the correct ring part number. Is the number #10128249, and have 6106 on it? If it does it uses Hastings #5615.

Silver Surfer 10-07-2012 07:32 PM

It is probably worth mentioning that you need to ream the ridge off the top of the cylinders. If you put new rings on and leave the ridge, it will break the new rings.

tboneb4a 02-27-2013 07:38 PM

i seen this thread is a bit old but if ur tryin to put them in a 350 it not gonna work thats a 4.00 inch bore. l2477 pistons are for a 400 small block whitch has a standard bore of 4.125 hope that helps ya out.

prumora1 02-28-2013 08:10 AM

just like other post stated you need to file fit the rings, unless they are gapless, there should be a paper with your rings that give you the equation for figuring on your gap. it will have a multiplier for different applications such as street, racing, supercharged and even your types of fuel you plan to use.
all of these things make a difference when your putting your motor together. also there is a top and bottom to the rings, the top will be indicated by either a dot or a taper on the ring its self

All times are GMT -6. The time now is 07:44 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999 - 2012. All Rights Reserved.