Inliners International Forums General Discussion Engines 261 rebuild

I picked up a 261 that had sat for several years and upon opening it found some pitting in some of the cylinders.
I have read we're some people suggest if the pitting is minor to leave it alone. Some claim it fills in with carbon deposits and it won't be noticed. Others say to sleeve it since it is already bored out by 0.080 and others say to buy pistons that are 0.100 over and start clean.
This is all very new to me and would appreciate any advice.
I would post pics but not sure how on this site.


Thank you

Where are the pits?

What is it that you are looking to do with this motor?

The pits are not in all cylinders but in one case the upper portion of the piston about 3/4 of an inch down around most of the circumference.

It will be a weekend driver predominantly and perhaps an occasional local car show. I dont intend on any real long drives. Actually thinking of a offy intake for a couple carbs and maybe a bulldog cam from Langdons.

Your best bet for a successful reliable rebuild is to bite the bullet and have the critical parts properly machined. For the block, the machine shop can measure the size and taper of each bore which will tell you how extensive the machine work will need to be. I have yet to have a 235 or 261 that did not need an over bore and hone. besides, you will be much happier with bores that are clean, straight and round as the building block for your motor. In addition, the deck will likely need to be machined just to make sure you have a nice flat deck to keep the head gasket from failing. The stock pistons on a 261 sit pretty far down in the cylinder at top dead center, I think something like .115 or more so pleanty of meat for machining.

Crank, have it checked, you might get lucky and it may not need anything more then a polishing and new bearings. More likely it will need to be ground on the rods and mains. While you are at it, you can, if you want, have the crank balanced just to make sure no out of balance running vibrations. Also, have the snout of the crank drilled for threads and a balancer bolt, mr. Gasket, small block Chevy. The threaded snout will also allow you to install the balancer with a balancer install tool instead of a block of wood and a hammer that can and frequently does result in damage to the crank thrust bearing. Do not try to have the mains align honed or align bored. I have never had a 235 or 261 that needed it, and when it does have to be done, it plays havoc with the timing gear clearances.

Head rebuild, standard stuff, have the deck machined for head gasket seal. Rebuild the rods, new rod bolts are near impossible to find now so you will have to use big block Chevy bolts and have bolts shaped to 261 shape after they are installed (for cam clearance).

Any 2X1intake will work. Consider using adapters and a pair of 1974 ford pinto Holley Weber 5200 carbs. They are a progressive two bbl with a small primary and a larger secondary and run really well. The 74 version of those carbs has threaded fuel inlet which makes fuel line hookup easier and cleaner. Run hot water to the bottom of the manifold if you are going to run Fenton’s or Clifford headers. Weld a plate to the bottom where the stock exhaust would go with fittings. I used a bolt on plate and gasket, it always leaked. If the underside of the manifold has sheet metal plugs staked in (and the offy will) you have to weld aluminum plugs over them or they will leak water. I ran a Weiand intake with adapters and these carbs for many years and the combo runs really well and very reliable.

You can step up the the Clifford 2x2 Weber dgev 38/38 carb. It s pricy but will really wake up the motor. That is the set up I am currently running.

Finally, spend the money and have the distributor rebuilt. You will be surprised at just what a difference it will make. I just had one of my old spare distributors running on my sun 405 distributor machine where i discovered that the advance is coming in way way late so all gummed up under the point plate or a broken spring. No way will a motor run at its best like that. I also put an nos distributor on the machine and it is also not quite right. The rebuilt unit I did for my 261 is spot on and starts and runs great.

This is my son running my car down the dragstrip at this year’s trifive nationals. It was his first time driving the car so dad told him to take it easy. The motor is very modified but you get the idea. Nice careful machine work, good quality parts, you will have a nice runner on your hands.

https://youtu.be/lMVz66tyrKQ

why would a line bore of the mains raise havoc with the timing gears.
Jay D.

Because it moves the crank centerline closer to the cam centerline making the timing gears mesh tighter together and making them be in a bind. It also causes timing chains to be sloppy in engines that have timing chains.

What CNC-Dude said!! It takes a really competent machine shop to perform a proper align bore, or "line bore" as we call it. Most shops just grind the main caps and then bore the crank bearing surfaces to a new center line. A true align bore is done by boring along the correct original center line spec. There are VERY FEW machine shops equipped to do this or even willing to do it correctly, and many blocks are too damaged to repair in this fashion!!

One of the shops that I used back in the late seventies and through the eighties in Nashville has long since closed. The old machinist is still around. He particularly hated to see me bring him a Chevy six because of the problem mentioned above.

I don't know ANYONE around here that does it correctly anymore!! We also used to bore the cam galley so we could use camshafts with much larger lobes. Not sure if anyone does this anymore either!!

Absolutely correct. The gentleman who showed me how that job is correctly done was Jim Fox who ran the Frantic Ford Mustang funny car, and John “Radar” Henry, both out of the famous east coast K&G Speed Associates machine shop. Jim fox was a man of few words so when he and radar showed me how time consuming it was to get a gear driven 6 block properly set up to correct a main bore problem, and the associated costs involved, I listened. They were both unbelievable machinists and engine builders. Of course, the machine shop is now long closed, Radar passed away a good number of years ago, and Mr. Fox retired, I heard he may have gone back to California. They were great days. Try to find a machine shop that can do such work. Few and very far between.

That is why with these early 6 motors, if the mains are fine, and they usually are, leave them be (I have over thirty of these 55-62 motors under my belt and I am nothing more than a hobbist and have never had to re align the mains. That is not to say it never has to be done, only to say that it is pretty rare in my experience).