73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Stewart G Griffin on June 21, 2007, 01:07:19 pm
-
Let's say that a block is being rebuilt/remanufactured/overhauled etc. And the cylinders need to be re-honed.
Does this mean that the new pistons (if new pistons are required) must be slightly larger in diameter than stock because the cylinder is now slightly larger in diameter than it was originally?
How does this process work?
-
Yes, if the bore is groved or worn and honing won't clean it up enough, it must be machined to a larger size and new pistons must be purchased to replaced the old ones.
-
Right, what i was trying to get at is, how do we determine what size pistons to use? Do they come in predetermined sizes or do we have to go custom?
-
Piston size is determined by the machine shop doing the machine work. They will tell you what it mic's to and the size to get.
-
Sometimes they can hone the cly's and Knurl the pistons. Car lots did this years back instead of buying new pistons. (Much cheeper so they made more $$ at the sale ) The way I see it, If you got it down that far spend the extra $$ and bore the block & stick in a new set of pistons.
Unless you plan on selling the auto.
Check with your machine shop, they can give you a price list on machine work.
-
A machine shop can typically safely bore the cylinders up to .060" larger than factory without sleeving or replacing the block.
To determine how much needs to be removed check bore diameter, taper, out of roundness, and scoring.
It's a good idea to have your new pistons when the engine is bored also as most machine shops like to mic the pistons.
-
1) Describe Knurling.
2) I guess, in the case of say a 350, that the pistons come in stock, .30 over and .60 over? So, if an original 350 needs an overhaul and the cylinder walls are worn to the point where they need to be honed out(?)/rebored, the machine shop can bore them out 0.30 because that is the next standard size that they make pistons for? So it makes it simple for the machine shop?
3) If custom pistons are needed, how they cut them down to size?
-
Knurling in where you expand the piston skirt back to the size of the bore to reduce piston slap. I don't recommend it.
Pistons can be had in any oversize. .020, .030, .040, .060.... In general people pick the mass produced sizes of .030 and .060. Pistons have to be cast or forged to size...
The don't cut them down, the hole is getting bigger. If the stock pistons in your vehicle are worn they have to be replaced with new ones.
-
Can you give me some sources and manufacturers.
Let's say i have a non-popular engine such as pontiac 265 or even the chevy 262. Can i get pistons for them i guess was my whole purposes for starting the thread.
-
* Arias Pistons
* Clevite Engine Parts
* Crower
* Eagle Specialty Products, Inc.
* Federal Mogul
* Fel-Pro
* GM Performance Parts
* JE Pistons
* Keith Black/KB Pistons
* Lunati
* Mahle Motorsports
* Ross Racing Pistons
* Sealed Power
* Speed Pro
* Summit
* TRW Automotive
* Wiseco Piston
http://store.summitracing.com/egnsearch.asp?N=700+4294925232+4294839001+115+4294891096
The Chevy 262 V8 was only made for basically 2 years, 1975 and 1976 and could only be found in a Monza or a Nova. They were also WAY underpowered... Finding a piston set for it will be expensive, if not impossible.
The Pontiac 265 is the same way, it was offered only in 1980 and 1981.
-
I agree Knurling is a big no no. Great temporary fix and that's it. Use a reputable company like Summit that will back their stuff too. SBC engine kits are cheaper than dirt. Literally - I need top soil and I'd rather spend the $ on pistons :P
-
northernautoparts.com will have most of what you need, not to mention their kits include a cam.