Loose Intake Manifold Bolts

[Grumpy]

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

yes , thats very common, especially if aluminum heads are used on an iron block,
as the engine heats and cools in thermal cycles the bolts tension tends to change and the cycle allows threads to slowly loosen,
that expansion & contraction, due to heat 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. you'll generally find that in most cases after 3-4 re-torque sequences, it becomes far less frequently needed.
gaskets compress and bolt tension gets more consistent

http://garage.grumpysperformance.co...stalling-the-intake-manifold-distributor.464/

https://www.grainger.com/product/FABORY-3-8-16-x-1-3-8-22TR30

grade 8 socket head screws and star lock washers, or ideally studs and loc-tite on stud threads, tend too, reduce problems

https://www.almabolt.com/pages/catalog/washers/star.htm

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
yes part of the issue is the intake gasket compressing over time,if some style gaskets, and gasket materials are used,
but that generally stops being a factor after the first or second bolt tension check and re-torquing sequence