Inliners International Forums General Discussion Hi Performance Chevrolet 261 build and head questions

SilvoLite used to make .080 stock replacement pistons.An 1/8 over is max,.110 is safe according to Pat Smith.
I just had a 261 block bored .080 to clean out some rust pits in the cylinder bores.It has Ross pistons,9-1 compression.
I will know pretty soon if the cylinder walls are too thin........

I'm begining to think... stay away from clifford... they seem to have good intakes, poorly fitting valve covers, single pattern cams, an overbundance of 390 holleys and overzealous suede-shoed sales personell!

I bored 2= 261s to .060", only because of cost. Cheaper pistons, and cost of multiple boring passes (.060 can be cut on just one pass).

My experience with Clifford years ago was overzealous salesmen!
I got the 261 .080 block back from the machine shop yesterday. The block was bored .080 to clean out previous cylinder damage.It's sitting on the engine stand and using a variety of homemade tools I tried to measure cylinder wall thickness by poking through the water pump hole and various other cooling passage holes.This is crude at best but it appears the thinnest spot is the front of number one cylinder at around .140 inches
Ok,what does .140 mean in relationship to cylinder wall strength? On this engine I have no idea.....But...on Chevy 350 V-8's used back in the 1980's for circle track racing,this was when they still used actual production engine blocks. Minimum wall thickness was considered to be about .130.These were long duration racing engine making 70 hp per cylinder for hours at a time.
Maybe this comparison isn't realistic but it's something in a sea of questions............

I would think no problem with that thickness. 'cause no 261 is gonna meet those revs, or hosses, or that kind of beating, you only removed .040" from the wall- thats only 3/4 of one sixteenth, or barely 1 mm in Weber talk.

I recently talked to Patrick Dykes in Arizona about the .080 bore business.Patrick has his opinions but he has seen a lot.He says it was a common overbore years ago with stock after market pistons,no problem.The machine shop thermo cleaned this block then took a good look through the various core plugs and holes to look for excessive cylinder wall corrosion before boring.Sonic testing will reveal wall thickness to a certain degree but a small pits of serious corrosion can go undetected.

should you discover a pit in the cylinder wall, I would suggest sleeving.

BUT BE SURE to have the machinest to leave a lip at the bottom of the bore for the sleeve to bear, then the machinest will plane the top of the sleeve flush with the deck and all will be right. 'cause without the bottom lip the sleeve can/will be able to slip down, and the head will do a suitable job preventing slip in other direction. If the machinest uses the wrong amout of interference fit this slippage will occur. Now the machinest will protest and say thats not necessary and never seen it happen in his blah-blah years etc.
well he's been lucky but he cant/wont fix if it does happen.

I've had two sleeves and had 50% luck. And the unsucessful one was only fixed by a $1500.00 replacement block, Twice it was "glued"(gasso"ed or some other miracle cure)back in place. Three times it slipped down 'til a rod would hit it and the tapping would put you on the side of the road again, by some act of faith, no broken pieces.

The sucessful sleeve had the bottom lip, again protested by the machinest as not necessary. This was my block, not his, and if he didn't want to "square" the bottom of the sleeve to rest on the lip, and put a slight champher on the o.d. so it could be driven in place--then he would not be doing the job. Lots of times there is not a complete wall left after the boring to have, or to trust to a simple interference fit. The sucessful sleeve was in a '62 327 block that lasted until a fleeing rod left the scene. This sleeve never slipped.

Eh Tu cnc dude?

This 261 block had a lot issues and if I had to do it again another block might have been cheaper.Bad main bearing cap,line honing,big overbore added 600 bucks to the cost.
Now I'm assembling the engine and I noticed the 6 top rings do not match,3 of one type,three of another type.The rings were supplied by Ross with their pistons,Hastings Plasma moly. Just more stuff to deal with.

Your right preacher,that is the best effective method to install a sleeve and the only way we did it. With the sleeve trimmed off flush with the deck, the cylinder head traps the sleeve from moving up or down, and eliminates any comebacks from the customer, and make them happier.