Re: 23rd series Eight Tail Pipe Diameter

Posted by Owen_Dyneto On 2007/7/2 11:39:37

The engine pulls a rock-steady 19 inches of manifold vacuum when idling, and other than overheating at idle even on cool days runs extremely well. I'm beginning to discount the tail pipe restriction for another reason - logic would seem to say that at idle with so little exhaust product to move, it couldn't be the problem; a restricted exhaust might be expected to manifest itself more at higher speeds though I do recognize that the heat exchange from the better air speed over the radiator would counteract that. As to the heat riser, its broken but I'm told it's wide open (counterweight down). This one really has me baffled, block exceptionally clean inside, water distribution tube perfect, timing OK, new 4-row radiator and water pump. I hate to use an external electric fan, that's generally not a good idea, it just masks the problem, kind of like taking a pain killer after you sprain you back so you can back out and split some firewood. Open to any ideas, no matter how far-fetched.