I bought a 1976 440ci motorhome engine with only 48k miles. As I was taking it apart I discovered at the very top of the cylinders, in all 8 cyls, there is a ground out or machined out area that runs about a quarter inch down into the cylinder, ( top to bottom ) and just guessing is maybe .040 deep. (The last one of these engines I worked on was back in 1979. I do not recall the top of that cylinder block having a recess, but back then that would probably would have been a 60`s model block I was working on.) Does any ony know the purpose of these recesses in the later model 1976 model blocks? Thank You Ed
A picture would help, but I'd guess a valve relief in the bore (odd for a factory engine). Any signs its been rebuilt before?
Most likley someone rebuilt before and the ridge reamed the top of cyl but pics would be good so there is no ***uming
I'll second (third?) that; from the description it sounds like a ridge reamer is the likely culprit. Seen plenty of blocks wrecked by overzealous ridge reamer use. I never use 'em. The ridge reamer at the shop I work at hasn't moved from it's dusty corner of the tool box in at least 20 years.
I do remember hearing that some blocks did have that done, and befroe i heard this i did have a block that may have been done this way
I agree. If you have a mishap with a ridge reamer, you'd have one hole with a shaved segment on the wall, or a dig in here and there. But uniformly across the board, it was intentional. Bob
Sounds like it was machined for a valve relief. Is it close to where the valve would be when opened? Tommy
on the Max wedges they did cut the relief in there due to large valves A 1976 440 was well on its way to being choked down for emissions no large valves and bore size would be large enough to miss anyway
That's valve clearance. If you run large valve heads on any wedge head Chrysler, the valves run into the cylinder wall. You have 2 choices. Make offset dowel pins and move the heads towards the center of the block or relieve the cylinder. Are all the areas the same? I haven't owned a motorhome block but I have been around industrial blocks which I thought had the same heads. I don't remember the relieve on the 413 industrial block.
Anyone besides me notice KY509 hasn't been back to this post or that he says he's a retired auto shop owner? What kind of retired machanic don't know machine work from damage? What do you suppose KY stands for? The Wizzard
Sorry about neglecting this thread, but there are some health issues that will cause a feller to shelve his projects for months on end and re-evaluate his prioritys. I should have been more clear as to the info I was after. The notches I was refering to are no doubt machined in by the factory, these are not an error made by some wannabe mechanic or machinest. They definitley are not done by a poor attempt at ridge reaming or smoe other slip of a tool. It`s just that there could be more than one reason for them to be cut into the cylinder wall. Are they just to unshroud a valve to improve flow efficiency? To lower the comprssion. Clearance for the valve? To cool a valve? Combination of the above. I guess I ***umed that some one working in the automotive machinest trades may have seen a tech bulliten and already know the details on the notches. As far as photos, I will take some when I bring this block back out of storage, but right now it is coated with preservitive and wrapped in heavy plastic.
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