Inliners International Forums General Discussion Engines 261 Torque Specs?

I just got my 261 back from the machine shop and when my new parts come in from Patrick's, I'll be bolting it back together. Problem is I do not have an engine manual for the 261, so I do not know the various torque specs I will need. I would need specs for: mains, rods, head, intake and exhaust manifolds, timing cover, oil pan, valve cover, water pump, thermostat housing, flywheel, bell-housing to block, trany to bell-housing, pressure plate, motor mounts, starter. Did I forget any? Does any one know if there is a source for new head, main, and rod bolts for my 261? I'd heard that you should always replace them on a rebuild. I also read that if you have the head decked that you need to shim the head bolts by an equal amount with washers. Is this true?

Torque specs are the same as for the 235.
You have to shim only if milled down more than 0.06
Never used new bolts, never had any problem (did 8 engines til today)

hope this helps, Frank

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LIVING IN THE PAST TODAY
http://www.TheSavoy.de

I do not know the torque specs for the 235 either. This engine came in my 54 GMC pickup when I bought it. I have the shop manual for the GMC truck with the 228/248 engine, but I'm sure these specs will be different than the 235/261 chevy specs.

reproduction shop manuals are around $20 from several sources, like FillingStation.com They should have all the info you need

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'50 Chevy Fleetline DeLuxe ('55 235)
'48 Chevy Fleetmaster coupe ('60 235)
Chicago
http://www.geocities.com/hellfish122

A Motors or Chilton manual that covers the year of your engine will also give you enough info for reassembly.

You should be able to reuse the bolts in question without a problem. It's the late model stuff with "torque to yield" bolts that need to be replaced everytime.

How much was taken off the block and/or head?
If it was just a re-surfacing of a few thousands, don't worry about it. If they took alot off, say .030 or more, then shimming the rocker shaft stands a similar amount would be a good idea. Never heard of needing to "shim" the head bolts.

I believe the shop only removed a 0.002 - 0.003" when they decked the head. I assume the reason you would have to shim the rocker stands if they took too much off during the decking process, would be because you would not have any room left to back up the valve adjusters. Is this correct? The reason I'm asking this is that I might not have been the first one to have taken this head to the machine shop. More likely I'm the 2nd at least, since I know this is not the original head for my 261 (casting # tells me it's a 235 head). Thanks.

Okay, here is what I got:

Head bolts 90-95 foot pounds - make sure you have the right sequence and do it in 3 steps.

Engine mounts 25-35
Connecting rod bolts 40
Main bearings 105
Timing gear cover 6-8
Rocker assembly 25-30

anything else?

many greetings from sunny southern Germany,

Frank

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LIVING IN THE PAST TODAY
http://www.TheSavoy.de

Dear Cujo;

If your using a 235 head on a 261 you have to drill the vent holes.

JM, #3370

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Thanks for all the input. I did have the steam holes drilled in the 235 head when I had the head reworked.

If you milled your head .060" to .125" I can give you a part number on new fresh bolts that will work that you can pick up at your local Chevrolet house. I used them on my 261 with a .060" milled head and decked block. They worked great and I felt much better using fresh bolts that weren't stretched no telling how far. They are head bolts from the old 5.7 liter Chevrolet-Oldsmobile diesel. The short bolts are Group 0.293, part number 22510580. They are 3" long, the 235-261 bolts are 3 1/8" long, but if you have milled your head, they will work fine. The long bolts are Group 0.293, part number 22510579. They are 4" long, the 235-261 bolts are 4 1/4" long, but, again, if you have milled your head, they will work fine. The heads on these bolts are 13/16" heads, not 3/4" heads, but clear without any problems. If you want to mount an accessory on your engine, Group 0.293, part number 22520637 is a short (3" long) bolt with a 1" x 3/8" stud on the top of the head. Two of these bolts can be used at the left front corner of the engine head (above the generator spot) for an accessory mount alternator or A/C compressor. Being used on the 5.7 liter diesel, these bolts will torque up to 125 lbs. If you can't find them at the Chevrolet house, the Olsmobile also used the the 5.7 liter diesel engine. I have successfully used these bolts and have been satisfied with them!

Yes, the spacers are to help keep correct valvetrain geometry.

To tell if it's been milled enough to worry about using stand spacers, there is a triangular area right under the middle intake port. If this is gone, then you should consider shims. If its still there, don't sweat it. If you don't need to shim the stands, then you aren't going to need to worry about the head bolts. A set of hardened washers is alot cheaper than new head bolts. .060" off is the max for the later 235/261 engines, and usually requires recessing the intake valve and shimming the valve spring a like amount to prevent the valve from hitting the piston, especially when using a high lift camshaft.

My '55 factory shop manual says 90-95 lbs. on the mains, but my '61 Motors says 100-110. Be sure to chase all of the threads before assembly and oil threads. No sealant required. I went with 90 on mine. Studding the mains is not a bad idea, either.

You should know the year of the engine because I believe the '54's were using shims on the mains, which might mean different torque specs.

Cujo,
Please look in the tech column for the corect head bolt torque spec AND tightening sequence! The 261 is a siamezed block while the 235 is not.This does affect the tightening sequence, and final torque value. This information is presented to the club members free in the tech tips area. Chiefoldephart

I am aware of the different torque sequence for the 261 compared to the 235, which I did find out here in the tech tips section. I am not sure what you meant when you said "The 261 is a siamezed block while the 235 is not." Could you elaborate on this point?

The cylinders of the 261 are cast such that there is no cooling passage between them.The larger bore required the larger cylinders. The 235 has smaller cylinders, allowing coolant to encircle each cylinder completely.

So is that why the 261 has steam holes and the 235 does not? I'm guessing the steam holes were they're attempt to try and dissipate some of the heat, now that there was no longer room for a full water jacket around the cylinders.

OK, now for catch 22, is your torque wrench calibrated? I worked at a calibration lab for a couple years and learned that most torque wrenches out of the box 'new' are way off. With maybe the exception of Snap-On and other expensive units. The cheapos, forget it, don't waste your money. Don't rely on Dad's old torquer to be even in the ball park.

Where does one get his torque wrench calibrated? I'm sure its not the same place I get my johnson rod adjusted.

One of the folks over on the Stovebolt page gave me this link on Torque Wrench Calibration and proper care. http://www.sts.sae.org/servicetech/july-2001/tech-tidbits-04.pdf