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Username Post: re torque intake        (Topic#356590)
995jim 
Contributor
Posts: 456
995jim
Loc: Ohio
Reg: 12-17-06
05-29-19 05:32 PM - Post#2767294    

Hello, I had a 402 rebuilt approx. 10 yrs ago . I was putting a throttle return spring on using 1 of the intake manifold bolts and noticed that all of the bolts are around 5-10 ft lbs instead of what I believe should be around 30-35 ft lbs. The heads are cast iron and the intake manifold is aluminum. There are no leaks and runs fine so should I leave the bolts as is or will tightening make problems. Is this because of dissimilar metals?Just don't know what to do.
thanks jim

Jim

65' Impala SS, 65' Belair, 89' Silverado Z71, 95' Silverado Z71, 12' Silverado, 15' Silverado LTZ, 16' Tahoe LTZ


 


YOUNG57 
Frequent Contributor
Posts: 1128

Loc: Tennessee
Reg: 12-06-10
05-29-19 06:05 PM - Post#2767298    
    In response to 995jim

BBC intake manifold torque values
25 Ft/Lbs - Aluminum Heads
35 Ft/Lbs - Iron Heads

Always torque bolts in three equal increments




Edited by YOUNG57 on 05-29-19 06:06 PM. Reason for edit: No reason given.

 
grumpyvette 
Senior Chevytalk Moderator -- Performance Subject Matter Expert --
Posts: 17348
grumpyvette
Age: 71
Loc: FLORIDA USA
Reg: 03-16-01
05-30-19 11:17 AM - Post#2767333    
    In response to YOUNG57

yes ,especially if aluminum heads are used on an iron block, as the engine heats and cools in thermal cycles the bolts tension tends too allow the bolts over time too loosen up, so checking and re-tightening, the manifold bolts to about 32 ft lbs is a good idea every few months , if you find them significantly loosening over time

IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!


 
Ray P W 
Contributor
Posts: 426

Reg: 09-30-15
05-30-19 01:04 PM - Post#2767340    
    In response to grumpyvette

"so checking and re-tightening, the manifold bolts to about 32 ft lbs is a good idea every few months , if you find them significantly loosening over time"

Grumpy,

The stainless steel bolts attaching my Edelbrock "Performer" aluminum intake to Edelbrock aluminum heads on a Gen 1 Chevy 350 do loosen over time as you mention. There are flat washers under the bolts but no lock washers. Can you suggest something to prevent that loosening?

For what it's worth the stainless steel socket head bolts that attach the headers to the heads on that same engine have not loosened at all after the initial installation about 15 years ago and a couple of retightenings back then as the header gaskets from a Felpro set fully compressed. The header bolts do have lock washers.

Thanks!

Ray W




 
grumpyvette 
Senior Chevytalk Moderator -- Performance Subject Matter Expert --
Posts: 17348
grumpyvette
Age: 71
Loc: FLORIDA USA
Reg: 03-16-01
05-30-19 05:41 PM - Post#2767363    
    In response to Ray P W



under the bolt head over the washer

loc-tite on threads certainly wont hurt





but I generally use thread sealer on the threads and it works fine


IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!


 
Ray P W 
Contributor
Posts: 426

Reg: 09-30-15
05-30-19 07:25 PM - Post#2767379    
    In response to grumpyvette

"under the bolt head over the washer

loc-tite on threads certainly wont hurt"

Thanks so much Grumpy. I'll give that a try. I used anti-seize when installing the intake bolts so Loc Tite probably wouldn't stick but I'll give the star washers a try.

Ray W



 
Crusty66 
"7th Year" Gold Supporting Member
Posts: 349
Crusty66
Age: 59
Loc: Albany, eNZed
Reg: 11-04-12
05-30-19 08:55 PM - Post#2767383    
    In response to Ray P W

the loosening is usually the gasket compressing over time, not the bolts actually undoing. Many intake gaskets are a fibre gasket - flash paper really and the gradually crush. Also the heat cycles with the different metals cause a very slight movement at the joint, which also crushes the gasket.


Steve
1966 Caprice 396 496 496mkII TH400


 


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