ReHone & run -When & How would you rering & build an engine off of an existing bore?

[StreetSleeper]

I come across good deals on stock bore pistons, some Keith black hypereutectic, some forged, not the old forged pistons that expanded with heat, modern forgings.

I have 2 standard bore blocks, & many are for sale standard bore at the moment. (318’s) /

There are forged pistons for sale, discounted, that are standard bore pistons.

What do you look for to consider building an engine with its existing bore?-when is it worth it, with high (street) use expectations?

As I hear it, the magnum blocks are often low on cylinder wall wear.

A ridge at the top-if it does exist, would a three stone hone remove that enough without hurting other places on the bore besides the common top ridge line?

You want to catch it with a finger nail if you question the ridge correct?

(Can I measure top, middle, & bottom bore thickness accurately myself?)

Cylinder straightness -can I measure that?

I understand that one wants diagonal cross hatching to catch & retain oil.

I have heard conflicting information regarding how fast to insert & retracting the honing setup as you hone-any advice there would be appreciated. Thank you


Besides cleaning, magnifluxing, decking the block & Aline honing the crank journals, what other services would you concern yourself with

Regarding a 300 + hp street build.

This concept applies to other enthusiasts that might come across a used .020”, .030”, .040”, .060” set of pistons and block as well.


Or do you think trying to cut corners with the bore & cheap pistons is a waste of time?

The ‘good’ pistons for a 318 run a premium, I am on a budget, and am trading time for money if I try to do everything perfectly.

Thanks for your input.

 

[RustyRatRod]

"Modern forgings" expand more with heat than cast pistons. That's an attribute of forged aluminum. It doesn't go away with "modern" technology. If the cylinders measure good on taper, roundness and bore size, hone it for ring seat and run it. Otherwise, bore it. Same rules as it's always been.

 

[66fs]

I come across good deals on stock bore pistons, some Keith black hypereutectic, some forged, not the old forged pistons that expanded with heat, modern forgings.

I have 2 standard bore blocks, & many are for sale standard bore at the moment. (318’s) /

There are forged pistons for sale, discounted, that are standard bore pistons.

What do you look for to consider building an engine with its existing bore?-when is it worth it, with high (street) use expectations?

As I hear it, the magnum blocks are often low on cylinder wall wear.

A ridge at the top-if it does exist, would a three stone hone remove that enough without hurting other places on the bore besides the common top ridge line?

You want to catch it with a finger nail if you question the ridge correct?

(Can I measure top, middle, & bottom bore thickness accurately myself?)

Cylinder straightness -can I measure that?

I understand that one wants diagonal cross hatching to catch & retain oil.

I have heard conflicting information regarding how fast to insert & retracting the honing setup as you hone-any advice there would be appreciated. Thank you


Besides cleaning, magnifluxing, decking the block & Aline honing the crank journals, what other services would you concern yourself with

Regarding a 300 + hp street build.

This concept applies to other enthusiasts that might come across a used .020”, .030”, .040”, .060” set of pistons and block as well.


Or do you think trying to cut corners with the bore & cheap pistons is a waste of time?

The ‘good’ pistons for a 318 run a premium, I am on a budget, and am trading time for money if I try to do everything perfectly.

Thanks for your input.

To measure accurately bore and straightness, you will need an accurate dial bore gage to .0001 of an inch, plus a setting ring, gage blocks, or setting tool. If you have a very good block (very low wear), you can make good power without boring. If you have a "known" good block from a car you ran or heard run, you can skip a lot of expensive machine work. Forged pistons are stronger and will "grow" with heat. This can be a plus when trying to prep a standard bore block, since more piston to cylinder clearance is required.

Before you do anything, check the bores of the block you want to use. Use the block with the least wear. If you have more than .005 clearance, I'd buy oversize pistons and bore and hone (with torque plate if you can) with the torque plate and main bolts torqued to the assembled values you will use in final assy. Install the crank and check for smooth operation. Put a dial indicator on the middle journal to see how straight the crank is. Next take a rod and piston assy and install it in the #1 bore, check the deck hight near the center of the pin along the pin axis. Take the same piston and rod assy and do the same for #2, #7, and #8 bores. Now you know how square the deck is. If all is well, you don't need to align hone, deck, or magneflux the block, now you can start to work. The stock 318 pistons to look for are 68-69 @1.77 pin height or 85-91 @ 1.76 pin height. If any of the newer pistons have any dish at all don't use them. Make sure the ring grooves are clean with little to no wear. Use premium ductile iron, molly rings.

 

[Dart Frog]

Good results can be had if and if and if which is a lot of ifs. Nothing will compare to a fresh cylinder bore and hone my opinion I've been through it had decent results with a good refresh. But wear patterns are what they are in the bores and will only continue as new miles roll up. My experiences is RPMs will be a determining Factor as the ring struggle to seal at high RPMs.. results may very.

 

[66fs]

If you hone with a Sunnen hone and use torque plates with the mains torqued the wear is taken out and the bores are straight and round. The engine will run very good, better than new.

 

[Dart Frog]

If you hone with a Sunnen hone and use torque plates with the mains torqued the wear is taken out and the bores are straight and round. The engine will run very good, better than new.

Definitely the way to do it if boring is not in the cards but what about piston fitting and Rock do you consider that less than optimum?

 

[66fs]

Definitely the way to do it if boring is not in the cards but what about piston fitting and Rock do you consider that less than optimum?

I have done this and have 2 more to go. A 340 and a 273. Theoretically it is not the best, but I've had some really fast engines that were not the optimum. The 273 block has almost no wear, or miles on it by the looks of it. The 340 should clean up with less than .005 clearance. I'll run them both and I am sure they will last me for as long as I am able to drive.

 

[toolmanmike]

If you hone with a Sunnen hone and use torque plates with the mains torqued the wear is taken out and the bores are straight and round. The engine will run very good, better than new.

As long as the bores are straight to begin with. Taper is often an issue. You can't straighten a bore or remove taper by honing. Honing is a finishing operation. But you knew that. The OP doesn't though.

 

[Murray]

Rehone and run- when? When it measures well. If you have enough ring ridge to feel then need a bore job. Putting new pistons in an old bore is a waste of money, knurled your old pistons.

 

[66fs]

As long as the bores are straight to begin with. Taper is often an issue. You can't straighten a bore or remove taper by honing. Honing is a finishing operation. But you knew that. The OP doesn't though.

Yes, to a certain point, but a Sunnen hone will fix both within reason. I had a friend that worked for a Chevy Dealership. It was acceptable to have .010 clearance between piston and cylinder. I just laughed when he told me that, but I didn't tell him why. It is amazing what an engine will tolerate, but will loose power and run hot if clearances are to tight. Efficiency and power will be down if clearances are too much, but there is more leeway with a looser engine than a tight engine. I'm not racing or building a "Class" engine.

 

[NC Engine Builder]

The clearance is typically built into the piston. They are designed to have proper running clearance if the bores are finished to the nominal size. So a new std piston in a worn bore is definitely going to be looser than its intended to be, but they will run loose.

 

[junkyardhero]

So a new std piston in a worn bore is definitely going to be looser than its intended to be, but they will run loose.

loose is fast baby!
*takes drag off unfiltered camel*
*goes back to spraying MEK on carb parts*