The Stovebolt Site Forums The Shop Area Engine Shop 250 manifold bolts

Should the 4 bolts and 2 nuts that secure the manifold to the head have lock washers? Mine don’t and I’ve had a problem with gasket leaks after a few thousand miles.

Did you retorque them after the engine heated up? My 235 doesn’t have lock washers but good mechanical practice calls for a retorque.

My 216 doesn't have any, either.

Recently replaced an exhaust manifold on another vehicle. Torqued it to specs and then took it on a 20 mile drive. I re-torqued it upon return. Definitely a little more movement in the bolts after the heat-up process.

I replaced the gasket probably 8 years ago and don’t remember if I re-torqued them or not. I’ll do it this time and see what happens. What should they be torqued to?

216/235 specs as follows:

Manifold center clamp bolts: 15-20 ft lbs
Manifold end clamp bolts: 25-30 ft lbs


Did you use any exhaust sealer with the gaskets?

My 250 didn't have lock washers. What type of gasket are you using? The 250 has a lot of weight pulling on the gasket, so its not surprising they leak. When I change gaskets or manifolds, I hold the weight up with one hand and tighten all the uppermost bolts first, then the lower bolts. Even though they are almost straight across, this seems to help mine seal better and having two manifolds with flat faces really helps. If you have the two separated, snug them to the head first, then to each other, then tighten to the head, then tighten to each other.
Joe

Although this doesn't answer your question on if lock washers are required or not, I did come across this possibly helpful info about the torque specs for the manifolds.

According to this list (see Note 1 below chart) the torque values are indicated as:


Also found this previous Stovebolt conversation on 250 torque specs. There is an old but still active link in there to GM I6 engine torque specs for 1966 that should also apply to your '67 250. See the screenshot below for details.

I don't have a Chevy shop manual covering the '67 250 engines, so can't confirm if these are accurate or not???

Anyone else have that resource to confirm???

Dan

Those numbers essentially confirm what I posted from the 1947-1952 shop manual.

1966 Oldsmobile online service manual, engine section. http://oldcarmanualproject.com/manuals/Olds/1966/Chassis/06-Engine.pdf

Thank you for the information and recommendations. I’ve never used exhaust gasket sealer before but I’m going to give it and loosen the exhaust from the intake then torque them a try. It will probably be a few days before I can do this but I’ll let you know how it went.

Okay, went to the auto parts store yesterday to get exhaust gasket sealer. The guy behind the counter was about as helpful as my cat. What do you guys suggest?

CRC Maniseal Exhaust Cement


https://crcindustries.com.au/products/maniseal-exhaust-cement-145g-5061.html

Here's the one I actually used most recently on a 1956 Cadillac.

Walker Exhaust Putty 35958

https://www.amazon.com/Dynomax-35958-Hardware-Muffler-Cement/dp/B000CQHVLI/ref=sr_1_4?crid=27VZJ2NFTHI9V&keywords=muffler+cement&qid=1685318149&sprefix=walker+muffler+cement%2Caps%2C12715&sr=8-4

Copper silicone seal.

blue67fleetside My 235 ratmobile got a donut leak,just corked it with furnace cement. Shouldn't probably do that to better equipment!!