Inliners International Forums General Discussion Engines Interesting 261 Story

A few years ago I saw an ad for an old Chevy engine and I went out to the guy's place. He was a Buick nut, and didn't want the engine. I was looking for a high oil pressure 235 to rebuild for my '53 Chevy 210 convertible. I wanted this car to be a driver/fun car, so I wasn't interested in matching numbers, besides it is a 3-speed car, and I didn't want to waste time on the old low oil-pressure 235.

When I got there the only engine he had was a 1961 261 and it looked weird. Instead of being covered with 1/2" of black sludge, like I had expected, it was perfectly clean but rusty--there was no oily residue on the outside of the engine at all, nor evidence of any paint whatsoever. So that got me curious. I pulled the oil pan, and the inside of the bottom-end looked clean enough to eat off of--no black sludge at all. I pulled a couple of bearing caps and the crank looked very, very shiny. I pulled the head and the cylinders were only slightly rust-hazed. So we struck a deal for $400. The engine came with a stock 261 oil filter and an intake but no valve train.

I loaded it up into the back of my truck and took it home. That night about 3:00 a.m. I was awakened by my truck alarm going off, immediately followed by the sound of an old Chevy with dual-glass packs roaring away (You know that sound--it is very distinctive) I got up and checked my truck out--evidently some morons had seen my engine in the back of the truck and decided to try to steal it! They didn't get it--and I drove to a friend's house then and unloaded the engine into his garage.

However in trying to disassemble the engine I found out it was VERY stuck. I couldn't even rotate it enough to get the upper pressure plate bolts off--I had to cut the darn bell-housing off with a Sawzall!! That was work! I squirted a lot of #2 diesel all over the engine and let it sit for a few weeks, and eventually loosened up the varnish. The engine was really glued together from sitting for so long.

When I was taking the oil pump off, I discovered that one of the brass fittings, which hold the copper oil pipe was cracked. In this state it would not have tightened & sealed the oil supply pipe at all, and the engine probably would have showed low oil pressure.

I took the engine to my machine shop and everything mic'ed out really good. I was able to use the stock pistons, and it didn't need the crank turned either. One cylinder had a tiny bit of rust going into the cylinder wall far down on the stroke, but it was only about a thousandth off and my machinist said to just ignore it.

So my guess is that this was a factory warrentied engine. My guess is that because of the cracked brass nut, the oil pressure would never come up to normal, and instead of fixing the problem the dealership just replaced the engine. What do you guys think?

I haven't started this engine up yet, and I'm a little worried that the rotating assembly might be out of balance--I didn't have it balanced at the machine shop. Does anybody know whether that is likely? I mean, to my way of thinking this engine must have been warrentied for some reason--I am hoping it was just low oil pressure from the cracked fitting on the pump-to-block oil line. But how likely is it that an unbalanced engine got through the building & inspection process back in 1960. Anybody know? Am I just worrying for nothing? Ideally I would just start it up and see how it runs, but I can't do that for about 4-5 more months.

The story could be as you say,sounds likely.The factory balancing was good enough for what the engine was designed to do.If you have any doubts,now's the time to disassemble the rotating parts and have them checked out.

Dear Mr. Rausch;

Toney is correct.

If your going to operate it within factory limits, you'll be just fine.

I only ballance my 'Hot Rod' models as they turn 5500 RPM & more.

Be sure to check the camshaft/bearings & rockershafts/rockers for excesive wear or damage and inspect the oil passage from rocker feed downward as well.

Good luck.

Thanks Tony. I may get it balanced just to be safe, since the engine is still out of the car.

Thanks John, my machine shop put new camshaft bearings in at no charge, because they accidently damaged one of the old ones, but the old cam bearings looked fine. In fact, the old crank and rod bearings looked fine too, but I went ahead and replaced them just to be safe. I had the ends of the rocker-arms ground at the same time I got the machine work done. I'm using a set of rocker shafts & arms from a 1960 235.

The oil passage from the rocker feed downward--how is the best way to check that?

I also posted this question on ChevyTalk, and Gene Schneider, who worked in dealerships from the time he was 14 until he retired, and who was a Chevy Parts Dept. Manager for many years, posted the following reply. I add it here as it gives some good information.

Posted by Gene Schneider:
"The first truly balanced Chevrolet engine was the 1955 8 cylinders. They were "spin" balanced after assembly.

The 6 cylinder engines were balanced by select weighing of parts that went into one engine. A select set of rods,pistons, etc. would be put into one block. The crankshaft was balanced by its self before assembly. Same with the clutch and flywheel. This was all done to about a 1/2 ounce - give or take. Due to the heavy weight of the rotating parts of the 6 cyl. engine the 1/2 ounce would be a very slight amount of unbalance.

If the engine was installed as a complete assembly (with head,pan, oil pump, water pump, rocker arms and valve cover) it would have been painted.

What we called short blocks (no head,pan, oil pump, lifters) would have been unpainted. Or if it had a problem under warranty a block only would have been installed (no lifters,etc). Thats why I doubt if the engine was a warranty exchange unit. Also the warranty parts had to be returned to the Chevrolet Warehouse for inspection. In the later years the Zone Service Rep. would inspect them at the dealership and he would take a sledge hammer and make a hole in the side of the block. This happened to about 90 percent of the warranty engines. If he didn't show up in the 60 day time frame we were supposed to destroy the engine...I think we may have hid a few.

Once a part is replaced in an engine, say one piston or one conn. rod it could be farther out of balance. Same if the pressure plate is replaced. Its no longer perfectly balanced to the flywheel.

Just drive it and don't worry. I am sure that there were millions of 216-235 and 261 engines out of balance by more than an ounce and lived a long life. That was the advantage of the generous main bearing surfaces and a heavy flywheel."

"...he would take a sledge hammer and make a hole in the side of the block..I think we may have hid a few."

Oooouch! That hurts.

Gene is one of the last "major old hands" and his grat knowledege knocks me off my socks any time I talk to him.

Frank

Dear Mr. Rausch;

Simply blow air through the oil pasageway from the top of the block downward, making sure It's clear.

We ballanced the 216/235 engines down to 1/2 a gram in the 50s. Today they go even closer. I can't emagine anything out of ballance by ounces (28.3495g) +/- etc.

So; assuming that info is correct, go ahead & ballance like you said if you plan to keep the vehicle/engine.

I had an II. member tell me his rods were within 4 grams a few years back, so you have to be really carefull on advice here (internet)sometimes.

It's NOT the weight of the parts, but the speed at which they will be moving that's important. So on a 'stock' (3,500 RPM) engine, 4g rods would be okay.

Good luck.

C-Dan, I completely agree about Gene. He is the BEST!

John, thanks for the info. I'll blow it clear.

Well, I'm not going to be street racing with this car. The truth is I'm not a youngster anymore, and I've done enough racing. So I doubt the R's will ever get much over 3,000 or so.

Back in 1969 I had a '58 Corvette with a 327 with big valve heads and I did enough racing, (and got enough tickets) that I kinda got it out of my blood. I once missed a power-shift in that car and jammed it back into 1st gear when I was aiming for 3rd, and saw the rpm's go to 6,000--but not for very long!!