Carburator torque spec to manifold
What is the correct torque spec's for attaching carburator to manifold on a 1967, 327/350. (all stock)
THANKS
THANKS
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Re: Carburator torque spec to manifold
Joe, I checked all my books but could not find the information. Thanks for your help.
DaveComment
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Re: Carburator torque spec to manifold
65-80 INCH lb. from shop manual and Holley book. 16 FOOT lbs. is way too much.
Hope thiws helps,
Bill FordComment
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Re: Carburator torque spec to manifold
OK, now I'm really confused. Big difference between foot & inch lbs.Comment
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Re: Carburator torque spec to manifold
David:
Although I like to torque most bolts on my 1967, I have never torqued the carb studs/nuts......ever. I use either a 1/4 inch drive ratchet or a small box end wrench and simply snug them down. I do this in a few steps so that everything is tightened evenly and gradually.
After running the engine for a few hours, I go back and snug up the studs/nuts.
To me the important things are to use a new/fresh gasket under the carb that will seal without a lot of force, and to snug the carb studs/nuts down evenly. Based on my experience, I would guess that the 65-80 inch-pounds (5-6 ft-pounds) is probably closer to correct than the 16 ft-lbs for the L-79 engine with aluminum manifold.
I am willing to bet that most auto mechanics and owners NEVER used a torque wrench on the carb holddown studs/nuts.
LarryComment
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Re: Carburator torque spec to manifold
Larry, I never have torqued them either but after having had my carb rebuilt it stated how very important this was. So I thought I would get technical & do it wright this time. I just called the Holley tech line & they said it should be 60 in. lb. I'm going with this.THANKS ALLComment
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Re: Carburator torque spec to manifold
I think just one grunt is adequate, from a backyard mechanic's perspective.
Stu FoxComment
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Re: Carburator torque spec to manifold
Joe,
Hate to argue but 16 ft. lbs. is not the torque for carb to manifold-that would be 192 in. lbs.-you'd warp the carb or pull the studs out . Maybe you're thinking of other nuts rather than carb mounting.Comment
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Re: Carburator torque spec to manifold
The 16 ft-lbs Joe mentioned (actually 14-18 ft-lbs) is shown in the 1967 AIM for the 390 HP engine with the cast iron manifold. This carb installation has the manifold, gasket, metal spacer/heat plate, and then the carb.
Later in the same AIM, there is the torque spec for the 435 HP engine with the aluminum manifold. This installation has the aluminum manifold, gasket and carb only. It is shown as 84-120 inch-pounds (7-10 ft-lbs). Nothing is shown for the L79 engine (327/350 HP) with the aluminum manifold, as far as I can see.
I would say that the L-79 torque spec should be the same (or closer to) as the 435 HP engine with the aluminum manifold rather than the 390 HP engine with the iron manifold and the metal heat/spacer plate.
LarryComment
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Re: Carburator torque spec to manifold
The attachment is the Holley Torque Chart from the Holley Illustrated Parts Catalog of a few years ago:
https://www.forums.ncrs.org/attachme...0&d=1227479595
It is in a pdf format, so you have to open it with adobe reader.
It says 60-80 inch pounds for the carb to manifold nuts.Jerry Fuccillo
1967 327/300 Convertible since 1968Comment
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Re: Carburator torque spec to manifold
Larry, William, David, et al------
While there is no torque specification for the 1967 L-79 carburetor attachment which is specifically called out in the AIM, if one looks on the "non-illustrated parts" page for the L-79 option, next to "carburetor", one will note a symbol. This symbol, a half filled-in circle, denotes "installs same as production". This means the carburetor installs in all ways the same as the carburetor on the base engine, for which torque specs are provided. Those torque specs are 14-18 lb/ft. By the way, GM SERVICE torque specs are almost always the middle of the PRODUCTION torque range and, in this case, would be 16 lb/ft.
If one takes another example of a Holley 4 barrel carb mounted on an aluminum manifold for which specifications are provided in the AIM, one could use the case of 1971-72 LT-1. The final torque specs here are set at 120-168 lb/in (10-14 lb/ft).
The fact that there is aluminum, in this case the carb throttle body, in the clamped system does not necessarily indicate that much lower torque specifications must be used. For example, the same torque value is used for intake manifold bolts for either cast iron or aluminum manifolds. The same torque value is used for exhaust manifold bolts regardless of whether the heads into which the bolts thread are cast iron or aluminum. The torque value for cylinder head bolts for small blocks is the same whether the heads are aluminum or cast iron. A slightly lower torque value is used for big block head bolts, though, when the heads are aluminum versus cast iron.
The "standard" torque for a 5/16-18 or 5/16-24 stud of SAE grade 5 is 14-15 lb/ft.In Appreciation of John HinckleyComment
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Re: Carburator torque spec to manifold
Bill -
See the Assembly Manual, UPC 6, sheet C2, item #8 nut, torque symbol 2, which is 14-18 ft-lbs. That's a Holley 4-barrel (which is why the L-79 section references "same as production"). Doesn't matter whether the intake manifold is iron or aluminum - it's exactly the same carburetor, and the torque on the nut is the same (it's the same nut).Comment
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