Inliners International Forums General Discussion Hi Performance Aftermarket 261 pistons

Has anyone recently purchased pistons for their 261 from the aftermarket? Was wondering what alternatives may be available other than the stock type units and what cost would be involved. I know Patrick's and Egge sell stock pistons, and I see stock sets occasionally come up on eBay, just don't know what else may be available.

Ross advertises in 12PN.

http://www.rosspistons.com/products/index.php#cid=3&acc_id=0&type_id=34&vehicle_id=0

I know Venolia has a forging for them also.

I got a set of forged pistons from Ross last year for a 261 build.About 550 bucks.
Before ordering make sure you know what compression height and ring width beside the oversize and compression ratio.

Try Keith Black Silv-O-Lites. Part no. 1422

They are good for a stock 7.5 compression engine....These and other replacement cast 261 pistons sit .050-.070 below deck at TDC.

Tony p, i did not know that they sat so far down. I did know the compression would be less then 8.0 but always attributed it to a 95.5cc combustion chamber. This is the issue. There does not seem to be any replacement pistons, at like $250, off the shelf. What a pain.

Yes, a pain. 235 pistons generally sit .015-.020 below deck with a piston compression height of 2.030. 261 piston compression height is 2.030. I have measured stock engines in the past to verify this.
I built a 261 years ago with stock pistons and the block deck cut down .050. It ran well and caused no problems.....But I don't think cutting so much off the deck is the best idea...The 261 build last year has 600 buck Ross pistons at zero deck height.The engine is very responsive with the tighter quench and actual 9-1 compression.
I checked a uncut 848 head to find 80 cc chambers,I believe a 261 head is around 90 cc's. When doing the math and with known combustion chamber volume and piston height below deck ,the GM advertised compression ratio is about .5 more than actual.

You need a rod stretcher. You should be able to get .050 to .070 out of them.

Edit,235 piston compression height is 2.060.....

The Ross pistons you used, were they flat tops or did they have lumps?

You are pretty close on the 848 head. They are spec'd at 79.1 but I have never had one actually come in at that number. The heads that i have cc'd have been like 81 82cc. My 261 heads are different castings with one spec'd for 86 cc and the other at 95 cc. If I was a betting man I would bet if i actually cc'd them both would be bigger. There is just no way I can build a 261 with stock pistons sitting so far down the hole. I have one 261 going together with gmc rods and venolia pop up pistons. Having trouble with the pop ups hitting the head. In the process of making a combustion chamber mold for venolia so they can see what the problem is. The second 261, which is the back for the first I wanted to do the 292 rod with cad pistons but the pistons appear to be very hard to come by now. So I was sort back to a 261 rod motor but could jot for the life of me come up with a substitute higher performance off the shelf piston instead of the stock 261 pistons. No luck. I will have to start saving my pennies. Want a little snap, not just dump truck performance

Flat top with a "depression" for intake valve clearance.It was a design Ross has on file.The pistons are about .005 below deck at TDC,the 848 head was shaved only .010,the valves are not sunken in. This gives an actual 8.9 compression ratio with a .050 compressed gasket.
This engine using a 2 barrel carb on a modified stock intake,home made short tube header and a reground cam of .430 lift with 212 degrees duration at .050 lift runs nicely with sharp throttle response.

I wonder If Egge Machine could move the wrist pin bore .030-.040" on their cast pistons? Then the difference can be made up by decking the block.

I have a 261 in a basket that will be my next build, so I'll be watching this thread LIKE A HAWK!!! I haven't had the bores miked, but they only have a slight ridge, pistons are STD. If the ring lands look good, I'll reuse them with new rings. Engine looks to have had really good care.

Is there a safe limit to decking the block?

Has anyone here found a source for MOLY rings? All I've seen is listings for cast and chrome. No problem for a 235...
Maybe Total Seal?

I met Isky at the GoodGuys - Del Mar show last year. I asked him if he still had Mcguirk's old cam masters for his dual-pattern cams. He does, recalled how he worked with Frank on them! I need to talk to him about those grinds before he leaves us, and get mine reground to a stout 3/4. REALLY nice guy...

Sorry to hijack this thread, and TIA!!!

Best Wishes, Tim

If possible,also tell Egge or whoever makes the pistons to cut the piston for 5/32 rings..
I have read and been told some used to deck them .070.....I measured the deck in several places on a 261 and it was less than .500 and thinner than a SBC.

You know, I can call egge and ask. The question I have, if egge is willing to make up pistons with the compression height altered, and cut for 5/32 rings, what are the actual ring sizes for .010, .020, .030, .040, and are they actually a common size, in other words off the shelf. Second, if egge is not willing to do this on an order by order basis but would on a few sets, is there any interest by others in a cast piston, with a compression height that would place the piston in the hole similar to a 235 for a 261.

I talked to them about this a year or so ago and they have absolutely no interest in doing anything other than OEM replacement parts. They would have to make another piston mold to create the different pin height, and wouldn't even consider it even for 50-60 sets at a time. Maybe when Bob was still around, but not now.

Maybe you could do what Bill Jenkins used to do with TRW 100 years ago - they wouldn't make him a different piston, but they would sell him a partially finished piston, and he added the details himself.
How about a piston with a blank pin hole - since it's not cast-in?
Yes, it would be stronger if the entire pin boss were moved but I'm sure there's enough metal for NA apps.

Would they have to make another piston mold? The difference is like .030. I will have to look at a stock 261 and see if there is enough meat to offset the pin

It would be worth a phone call to see what they say. The worst they can say is "yes"....then how you gonna bore the holes.

They probably grind the cam profile on the skirts after the pins are machined so they can attach fixturing to hold the piston to do it.

Yeah,and when all is said and done,a 500-600 buck set of Venolia or Ross pistons might be a better deal unless you want a cast piston.And with close to zero decking the intake valve to piston clearance might be an issue.

Is there any way the stock pin hole be machined larger and an off set bushing (.030-??) be pressed in the oversized pin hole. I'm not a master machinest- Just asking????? Sounds like goofy tricks tried yesteryesr. 1 OL REDNECK

If your using a GMC rod you could do that to the S/E of the rod. You would just have to make a set of custom OD bushings. But if your using the Stovebolt rods, its not going to work because of the pinchbolt design.

Good thinking! Thank you. 1 OL Redneck