lock washers for manifolds?

[Llay R. Rac]

I am replacing my exhaust manifold. i had lock washers on the two back bolts (the bolts were loose anyway), but no lock washers on the rest. i made a french lock for the rear bolt but that didn't hold for long.
googling whether lock washers are necessary or not gives me mixed results, some say definitely, some say not a good idea.

loose bolts and exhaust leak from the rear has plagued this engine (stock 292) for 40 years, i really want to solve that.
does anyone use lockwashers?

[TJ's Chevy]

I never have needed to. I did a two time torque method and never had problems. If both surfaces are flat and clean, and with a good gasket....torque then once cold....drive it and get things hot....let it cool....and then torque them again. Once that's done you should be fine. Lock washers won't Hurt, but vibration is vibration....they'll still probably loosen a bit. I'd use lock style nuts....better chance of them staying tighter that way.

[bpmcgee]

Loctite blue is rated to 300F, which is in the ball-park of normal running temps. Or they also make a high-temperature green, which works up to 450F


B

[shp4man]

I put lock washers on mine. no problems so far.

[Heater63]

Belleville washers, got mine from McMaster-Carr

[Llay R. Rac]

i have done the twice torque method every time i replaced the gasket.

The second and fifth holes are actually studs with fine threads, so lock nuts may help there,the others are bolts. I have the dowels at each end and have thought about replacing with studs, but decided i didnt want to do that.

the studs and bolts are original to the engine, would new bolts have a better chance of holding? i've been searching for new bolts but cant find any yet, anyone know a source?
i've also thought about replacing the bolts with fine thread studs, but i am trying to do things the way chevy did.

I have to move the truck by saturday so i think for now i will do locktite and lockwashers and see how it goes, i have a lot of other work to get my truck road worthy, when i get all that done i can go back and redo the bolting.

does using locktite affect the torquing of the bolts?

[TJ's Chevy]

Not enough affect if any to hurt a thing, if you have a store around your area like a True Value, Lowes, or Building Supply where they have tons of misc bolts you could always get them there for cheap. Stainless to if you wanted. I have a local building supply with rows of nuts and bolts and that's where I get most of mine from.

[cg285]

i will sometimes use lock washers but because i want a thicker washer not because they give any benefit from loosening. there are studies that suggest fasteners loosen easier with lock washers than with flats or nothing.

[andyh1956]

Originally Posted by cg285

i will sometimes use lock washers but because i want a thicker washer not because they give any benefit from loosening. there are studies that suggest fasteners loosen easier with lock washers than with flats or nothing.

He's correct, it is a proven industry standard that in a properly torqued situation that a lockwasher is useless.
However a grade 8 lockwasher does a great job of spacing and keeping a bolt head from fretting into the base part it is securing.
The v8 engines had lockwasher SIZE solid (Bellville?) washers under the ex manifold bolts on some engines.

[vince1]

Belleville or star or grade 8 maybe. I don't think a regular mild steel lock washer will have enough bite to hold.

[cg285]

Originally Posted by Llay R. Rac

loose bolts and exhaust leak from the rear has plagued this engine (stock 292) for 40 years

shouldn't need any washers on this. ASSUMING your setup is stock you may need to separate the intake from the exhaust and replace the center gasket. snug it up but do not final tighten it. bolt the assy to the head then final tighten the center bolts. you could also put a straight edge across the assembly. there have been times past were we needed to surface the two together.