248 engine miss

[tony]

Hi I am having problems with my 248 straight 8, at idle there is an irregular miss, the head was reconditioned in 1997, but had little use for some years, it blows a lot of carbon out the back when first started in mornings but seems to go when warmed up. The compression seems to be low with readings of between 65-80 being the highest reading, should i be looking at valve problems
thanks

[rcull]

I would eliminate ignition spark problems first. Buick liked to put all their wires under a plate tight together. This is just not good! Could you be just having a problem with crossfiring because your wires are not in perfect condition and running too close and parallel to each other?

[39CENT]

Ive had problems with several of my buicks with an 'irregular idle', but the car would run ok otherwise. have heard it can be corrected with longreach plugs, but i havnt tried it out yet.

[39CENT]

ohh and if it hasnt run in a long time the exhaust pipe will have lotta rust pieces flaking off, and then when you fire up again it blows out.

[Straight Eight]

Tappet adjustment if you have solid lifters will make the idle you describe as a tappet adjusted too tight is held open just a tad, and that is the poof you are hearing.

Also if carb idle is set too lean the same kind of poofy idle. Try turning the mixture screw out just a tad and then go listen at the tail pipe. If no change in sound try a little farther, if no change put it back and try the other mixture screw.

[Aaron65]

With that low of compression, there's a good chance of some valves being held open...go back and check your valve adjustment...

[tony]

Hi thanks to all the help given, i have readjusted the valves and this seems to have inproved the idle problem .