I guess this did not get posted last night  OK. Here wes gos again. 1) 1981 GTSi. 2) Engine is IN the car (and not coming out). 3) Trying to get the plenum risers off for cleaning re-painting, etc. 4) Got all nine (9) nuts off each riser where they attach to the heads. 5) Gaskets appear to be the original think black type (may also be a grey gasket sealant in there too). Even hitting with a heavy plastic covered dead-blow hammer . the plenum risers will NOT BUDGE. Any suggestions?
Make sure all the washer are off for penetrating lube to get down around the studs. I really wanted to make a puller for this because I couldn't get it to budge without jamming a screw driver in between the manifold and head where I knew there was no water jacket to bugger up. Even after I got it to budge it was still tight the whole way off due to build up around the studs not letting the runners "rock" while you're working them back and forth. Hope it gets easier. cheers
Could be one for some penetrating oil around the base & the gaskets & then find some way to exert some constant sideways pressure on the thing & leave overnight. Have you got some kind of a ratchet strap you could rig up around the manifold?
If you haven't already gotten it off, be extra careful when you remove the plenum. On each stud is a metal spacer that keeps the thick rubber gasket at an even thickness across the intake chamber. If the gasket comes off with the plenum, inevitibly some of the spacers will fall down into the engine. Fortunately they are too large to fall into a cylinder through an open intake valve, but they can be a PITA to find and get out. Don't ask me how I know this.
I have not done this on one of these cars but is there sufficient stud length sticking up to double-nut them and pull the studs first? It would make it a lot easier if you can. If the length is marginal it might be possible to grind a couple of nuts to half-thickness and use those.
Plenum is off. All spacers (8) within the thick rubber gaskets are accounted for. I do look at the parts manuals BEFORE I pull things apart JUST for that purpose. HOWEVER, good on you for saying this as others will read this thread........