Was over a friends shop today while he was finishing up a Chevy 350 Vortech rebuild using the Edelbrock Top end package.
First time I have been around the Vortech design and the 4 bolts at each end of the intake manifold made me think why would Chevy go to something screwed up like that?
How do you maintain a good seal for the center ports with all the torque on the ends?
He told me the torque specs for the screws were 25-35 ft. lbs. which sounds like a lot for those going into aluminum heads!
Chevy 350 Vortec intake torque specs?
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Re: Chevy 350 Vortec intake torque specs?
On mine on gm cast vortec heads I just tightened thenm down by hand with a wrench, using common sense... You will need to go back later and retighten the bolts. after heat cool cycles... Again by hand do not get carried away. the bolts are small.
All new installs will need hand retightening... 25 ft lbs is more than plenty.
The key is re tightening on new installs.. Watch the length of the bolts you use.
If when not using gm bolts and oem gm vortec gasket.
All new installs will need hand retightening... 25 ft lbs is more than plenty.
The key is re tightening on new installs.. Watch the length of the bolts you use.
If when not using gm bolts and oem gm vortec gasket.
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Re: Chevy 350 Vortec intake torque specs?
1. "Vortec" is a GM trademark. Add an "h" to make "Vortech" and you've got an aftermarket supercharger company.
2. The big secret to Vortec bolt pattern and torque spec is the silicone-enhanced gaskets with a hard carrier. You think GM retorqued the intake manifold on the bazillions of production-line engines? Torque it and forget it...until the silicone rubber on the gasket carrier deteriorates. That "was" a big problem for GM, although I think they improved the gaskets to remedy the situation. If the silicone isn't damaged, the gaskets are re-usable most of the time
3. Why are you torquing to 24--35 ft/lbs when spec suggests 11--12 ft lbs?
http://paceperformance.com/p-3981-gm-en ... specs.html
2. The big secret to Vortec bolt pattern and torque spec is the silicone-enhanced gaskets with a hard carrier. You think GM retorqued the intake manifold on the bazillions of production-line engines? Torque it and forget it...until the silicone rubber on the gasket carrier deteriorates. That "was" a big problem for GM, although I think they improved the gaskets to remedy the situation. If the silicone isn't damaged, the gaskets are re-usable most of the time
3. Why are you torquing to 24--35 ft/lbs when spec suggests 11--12 ft lbs?
http://paceperformance.com/p-3981-gm-en ... specs.html
Re: Chevy 350 Vortec intake torque specs?
The torque is 3 then 12 then 15 Newton-meters, with blue Loctite on clean bolts and clean threads.
More than that will destroy the gaskets and they will leak!
The idea is, the iron block and heads will want to move around differently compared to the aluminum manifold, so LET IT. The "gaskets" are plastic with rubber O-rings and when you torque the bolts, you're basically just snugging them enough to kiss the O-rings down so the metal is on the plastic, just barely enough torque for the bolts to not back off. Overtorquing makes the plastic break.
Age and many heat cycles of manifold and head fretting the gasket with motion also make the plastic break, which is why you should be using the updated aluminum-backed gaskets which are way more expensive but are a "forever" part.
More than that will destroy the gaskets and they will leak!
The idea is, the iron block and heads will want to move around differently compared to the aluminum manifold, so LET IT. The "gaskets" are plastic with rubber O-rings and when you torque the bolts, you're basically just snugging them enough to kiss the O-rings down so the metal is on the plastic, just barely enough torque for the bolts to not back off. Overtorquing makes the plastic break.
Age and many heat cycles of manifold and head fretting the gasket with motion also make the plastic break, which is why you should be using the updated aluminum-backed gaskets which are way more expensive but are a "forever" part.
Re: Chevy 350 Vortec intake torque specs?
My recomendation is for the felpro 1255 intake gasket. Ya you want to retorque on new installs..
Re: Chevy 350 Vortec intake torque specs?
I wasn't doing anything but observing his work and drinking a nice cold beer! I believe he was using the FelPro aluminum backed gasket.
Just thought it was a strange setup with bolts on the outer corner and none in the middle. He claimed from his info that 25-35 was the torque which I thought was really high for 5/16th screw into aluminum heads.
Personally I prefer studs for all my manifold installations on aluminum heads.
Just thought it was a strange setup with bolts on the outer corner and none in the middle. He claimed from his info that 25-35 was the torque which I thought was really high for 5/16th screw into aluminum heads.
Personally I prefer studs for all my manifold installations on aluminum heads.
Re: Chevy 350 Vortec intake torque specs?
You can be sure the intake and gasket setup was for production time. I have a set of the bolts from Edelbrock, and one of the heads snapped off flush at the intake surface, right under the power steering booster. The intake bolts from a mid 70s Buick 3.8 V6 work really well on these. Nice big flanged head bolt with plenty of length.
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So much to do, so little time...
Re: Chevy 350 Vortec intake torque specs?
I wasn't doing anything but observing his work and drinking a nice cold beer!
This is the way to be. I can do this all day.
This is the way to be. I can do this all day.