I know this is not right but... I want to get new piston rings and not have to over bore at all. I know it wont be a perfect seal since bore will not be a perfect circle by not over boring it a tad. But i think the new rings will comform to the bore with in a few hundred miles of driving. thus creating a good seal. Do any of you concure?

my motor does have 94k miles and the rings look like they have a perfect seal. I cant move the piston back and forth like i could with my 95 olds 3.1. that thing let me move it about 7-8 mm by hand. talk about burning oil. with this i mean i dont think there is much wear at all in the motor. I can also easily see the cross hairs in the bore.

Thanks
Derek

 

I'd at least hit it with a hone a bit.. for the new rings to break in..

 

Why replace the rings? leave the stockers in there. if you decide to put new rings, you will need to bottle brush it so the new rings will seat.

 

two tools I recomend ridge reamer and a hone.

 

So why do it at all??? Did you take the motor apart already and for what??? Okay ... let me get this right, your gonna do all this work and get new rings but you don't wanna do the bore job? I don't understand this in the least.

 

Nah im not that nuts, I plan on stroking it using a 396 crank to get about a 390 cubes. Clearancing the crank is not a prob for me, but getting the block to the shop plus boring it is out of my budget.

 

In order to use the 396 crank you're going to need new rods and pistons and ballancing, the price of an overbore will be nothing compaired to this.

Ben

 

Well shoulda mentioned that my man . But anyways...if a bore job is outta your budget you should really reconsider the whole project cause that is the least of your worries.

 

I agree here, and am not trying to be a smart ***. But if you are going to go through all that trouble and money to storke it to a 396 - the bore, why wouldn't you build a really good 383 instead? The 383 would probably be cheaper(from what I have read) and then everything would be new. I used to cut corners, but now I know better. There are somethings you just don't want to skimp on, especially on a short block.

If you do want to keep your stock bore take it to a machine shop and have them check the taper on it, if its in spec get better pistons, HOWEVER, you need to check your sidewall clearences for the new pistons. Nothing would be worse than putting new pistons/rod/crank in and start the engine and have it seize when the pistons warm up and lock in the bores. Thats why most machine shops, i know mine does, bores the block off the set of pistons to make sure the right clearence is acheived.

If the taper on the block is ok, then ridge ream it, which you really should do before you take the pistons out, and hone it so the new rings will seat properly.

Building a short block is one of the things that most worrys me when I build an engine because there is so much labor involved. I am about to to a 355 build up for a friend of mine and the engine isn't even out of the car yet and I am nervous.

Can you get by with not boring it? Maybe. Are you going to get as good of ring seal? Maybe. But I can honestly say that a block that has been bored with the correct pistons and rings is going to have less leakdown and blow by than a budget hone job. but thats just my .02.
Good luck.
Jason

 

I've read that GM engineers found that LT1 rings "flutter" at higher rpms, thus the LT4 rings had a redesign to correct this problem. I didn't read what your total project was but just to answer your question, get an LT4 design ring, (something about a chamfer on the inside of the ring that helps prevent the ring from deflecting with higher cylinder pressureand rpm) or a design thats better than the stock anyway. Get a hone from an autoparts store, it only requires a drill for use, and try to (lightly) recreate that cross-hatch design you see in the bores, thats a must with new rings.

 

The 'ridge reamer' is only needed if there is actually a ridge at the top of the bore.. if not ,you don't need to do that.. but again at least hone it[mussers suggestion of the 'bottle brush' hone is a good one as opposed to the regular stone type..
Conforms to the bore better for a faster honing, especially when not boring..

 

Another thing to consider is that stock rings for an lt1 are not cheap.....$120-$160. For that price you can get a set of 30 over pistons and rings and come close to paying for the boring.