I took the heads off the 400 today to remove some twisted off exhaust manifold bolts. First question, should I plug the exhaust holes that run through the intake manifold? I don't have an X or H pipe on the exhaust yet, but plan on installing 1 when I replace the exhaust system probably this winter. Next question, I'm putting all new stainless steel exhaust manifold bolts in. I can't remember where they all came out of, except for the 3 extra long ones (the last one on the passenger side and the one in the very middle on each side). The new ones have 4 different sizes, although some have a minor difference in size. Will it matter much where the rest go in? Last one for now, the head gasket set didn't have any intake gasket. Can I re-use the valley gasket by putting some sealer on it? I was told the motor was rebuilt @15 years ago, but only has @ 12k miles on it. It has virtually no ridge at all on top of the cylinders. I can't say how it runs yet, although it starts better than my daily driver. Guess thats it for now. Dan:3gears:
Hi, I would watch the bolt lengths. I bought a stainless kit for my 455 and noticed some bolts too long. You might be ok, but double check them as you install them. Buy a new valley pan. The old one will have a good chance developing a leak. I would also reccomend an X pipe over the H. Some H systems actually lose power over standard duals (according to some dyno sheets I have seen online). All this IMHO, of course. Good luck.
I'd planned to run manifold heat on my 462" powered roadster due to the winters here in Central California can get a touch chilly. Granted, nothing like the northern states and Canada, but we have people from Alaska get off the plane and bitch about the cold. Ended up I couldn't run heat because I was running an early style intake manifold on later heads. With both chokes operating as a manual setup on the dual quads and an electric choke on both a Holley and Carter single carb setup, the car is pretty civilized as far as starting and low speed runing goes when it's cold and the amibient is in the high 30's. All you have to do - specially in cold weather - is give the engine some time to warm up and especially don't rev it very high when it is cold. I don't do the driveway warmup, just fire the engine, check for oil pressure and drive away at an easy pace. What worked for me in blocking the two circular holes in each head was to cut some hot-rolled steel down close to the hole size, clean the hole in the head out with lacquer thinner - or acetone - and JB Weld the plugs in. Hot rolled steel was chosen because it usually finishes up with a rough surface in the lathe and that gives the JB a lot of 'tooth' to grab. 41,000 miles later, no probs.
The first time I plugged the cross overs in my heads, I used 9/16" bolts. I sealed the 2 bolts together by filling the area above the head w/ample amounts of JB Weld. Should have known the failed when my intake paint started cooking in that area. When I tore the motor down the bolts were all lying outside the holes and the JB Weld was gone. Exhaust temp was too high. I installed 18mm freeze plugs in the heads yesterday. Can't tell you if they will work as the motor won't be installed and running until tomorrow or Monday. But most of the advice I got on this board was to use this method. I had to drive them pretty deep before they got any bite so I am not sure these won't end up outside the holes too. These passages in my 72 heads are machined but in the 75 heads they are rough castings with no uniform shape. Looks like Buick was trying to lighten the castings the last 2 years. I will be reusing my valley pan for the 4th time today. I clean it with lacquer thinner then place a solid layer of RTV Black High Temp on the water passages and a very thin layer on the Intake ports. If it leaks, which it hasn't done yet, I'll order and new one and replace it in the car.
Will it matter if I plug the holes and don't install the X pipe until this winter? Another question, when I pulled the head bolts they all had a thick layer of silicone sealer on them. Why is this. I've done a few head gasket replacements before, but never remember using a sealer on the head bolts. Thanks, Dan:3gears:
I am plugging mine and not running an H pipe. I think these are 2 unrelated improvements. It has been my understanding that the primary benefit of an H pipe is not pressure equalization, but rather to creat a scavenging effect between the right and left banks of the motor. I only sealed 5 bolt holes on the motor I assembled yesterday and they are around the timing cover to block water passages. If the head bolt does not go into a water passage, (such as small block Dhevys) sealing is not necessary and could possibly cause bad torque reading. I use "gorilla snot" 3M super weather stripping on bolt that do need sealing.
Don't worry about sealing the bolts unless their in water passages like the above post said. Also, I ran a dual exhaust (no X or H) for many years with the crossovers plugged in my heads. The reason I replace the valley pan is for peace of mind. It is easy to pick up at the parts store and not expensive. So, why take a chance on using it? At least, that's my opinion.
