69 396 - 350 Hp I read in a previous post that the locks only go on the end bolt pairs... is this correct, or do they go on all??
french locks on all bolts?
utility5
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I don't really understand what you're asking. I've never heard of french locks of any sort having to do with an engine.
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I agree more detail is needed. On the end bolts of what? (heads, intake, manifold, exhaust manifold, control arms, etc..)
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Lock washers perhaps? I'm trying to imagine what he could be refering too. Kinda like fenders are mudguards, and a hood is a bonnet...if you're English.
Sorry guys - french locks are a curved piece of metal that is used on the exhaust manifold bolts. They are designed to bend over the bolt head and stop the bolt from becoming loose. The question is, how many locks are used per side??
I think you are looking for these
http://www.rickscamaros.com/cgi-loc....exe/cgi-local/smpagegen.exe?U+scstore+jvsh3286ff7b317b+-p+-c+scstore.cfg+RC-60
It appears as though they are only used on the two bolts on each end port.
http://www.rickscamaros.com/cgi-loc....exe/cgi-local/smpagegen.exe?U+scstore+jvsh3286ff7b317b+-p+-c+scstore.cfg+RC-60
It appears as though they are only used on the two bolts on each end port.
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Yes - the "French" locks go only on the end bolt sets.
Shaped like a half-hoop with two sets of bend down tangs on the bolt circles.
Chevy used them on small blocks from the mid 60's until the late 70's. GM part #3880844 (group 3.604).
Some mid 60's 409's also had them but, used a different part number.
Usually hit the spare parts drum the first time the heads or manifolds were removed...
One of those secret points thingys in Corvette scoring...
Shaped like a half-hoop with two sets of bend down tangs on the bolt circles.
Chevy used them on small blocks from the mid 60's until the late 70's. GM part #3880844 (group 3.604).
Some mid 60's 409's also had them but, used a different part number.
Usually hit the spare parts drum the first time the heads or manifolds were removed...
One of those secret points thingys in Corvette scoring...
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hrmph, learn something new every day
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One parts book I have mention that BBs only had them from 65-67.
The Classic catalog says 67-72. (..But then Classic sell Mustang Fan Caution decals labelled as 1st gen Camaro decals, so I already doubt the 67-72 info.)
The Classic catalog says 67-72. (..But then Classic sell Mustang Fan Caution decals labelled as 1st gen Camaro decals, so I already doubt the 67-72 info.)
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I just went through the same thing with mine. I know I read in one of the "bibles" that all BB's and SB's recieved french locks. Then I read all Camaro BB's had smog. Try getting french locks on a BB with smog and air. I'm sure I'll use them for something someday. How about spark plug shields on a BB Camaro. Anyone know the rule there?
I've heard conflicting facts about all b/bs having smog. The definitive book, If i remember, stated they all have them. I also hear no shields - and see in the A/m that no shields on b/bs... but they don't show french locks on any manifolds - mysteries so far unsolved.
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Okay, after a couple of questions, I had better clarify what I said...
I said lots of SBC's used them - not BBC's didn't
I had, and worked on, several BBC's that also had "french locks".
My 1971 BBC Corvette had them, as well as half-cup shaped Heat Shields for each plug hole - so Yes, BBC's had French-Locks & Heat Shields also... at least some of them...
SBC's & BBC's used the locks on the front and rear bolt pairs only. The reason GM put them there, is that the end bolts aren't torqued to the same spec.s as the centers from the factory and the end pairs would loosen in service if the locks aren't in place.
This fact is not known by many and it is the reason manifold cracking is such a problem - not from the factory, but after someone services the engine and retorques the end bolts to 30~35-ftlb's same as the centers. Next thing you notice is the manifold is cracked at one of the ends a couple months later.
GM fiqured this out after they took the gaskets off the exhaust manifolds back in the early 60's and went to just surface to surface contact on the heads/manifolds.
So, if you are using the stock manifolds and want them to last. Torque the centers to 30~35-ftlb and then torque the end-pairs to 15~20-ftlb and bend over the french-lock tabs to keep them from loosening. This will allow the manifold to 'grow' a little towards the ends when hot and not crack...
Hope this clears things up a little;
John
I said lots of SBC's used them - not BBC's didn't
I had, and worked on, several BBC's that also had "french locks".
My 1971 BBC Corvette had them, as well as half-cup shaped Heat Shields for each plug hole - so Yes, BBC's had French-Locks & Heat Shields also... at least some of them...
SBC's & BBC's used the locks on the front and rear bolt pairs only. The reason GM put them there, is that the end bolts aren't torqued to the same spec.s as the centers from the factory and the end pairs would loosen in service if the locks aren't in place.
This fact is not known by many and it is the reason manifold cracking is such a problem - not from the factory, but after someone services the engine and retorques the end bolts to 30~35-ftlb's same as the centers. Next thing you notice is the manifold is cracked at one of the ends a couple months later.
GM fiqured this out after they took the gaskets off the exhaust manifolds back in the early 60's and went to just surface to surface contact on the heads/manifolds.
So, if you are using the stock manifolds and want them to last. Torque the centers to 30~35-ftlb and then torque the end-pairs to 15~20-ftlb and bend over the french-lock tabs to keep them from loosening. This will allow the manifold to 'grow' a little towards the ends when hot and not crack...
Hope this clears things up a little;
John
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Very informative info. Thanks for sharing it. GT
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Makes perfect sense when you think about it!
Thanks!
Thanks!
well now I'm really confussed - I tried to install the frenck Locks on my BB and they won't fit - the curvature isn't tight enough. They are from Classic, made by Paragon (if I remember correctly). The exhaust manifolds are numbers matching.
They are very nice when you are running aluminum heads and cast iron manifolds/steel headers; the different expansion/contraction rates work the bolts loose if you don't have french locks. A stock Buick 300 with factory aluminum heads and cast iron manifolds........ask me , I fished mine out of the spare parts barrel.
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Utility -
They bow out over the manifold tube, like this...
![Image]()
They bow out over the manifold tube, like this...
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