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old buicks

boring 27 engine blocks

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Have a friend that has a block for a 1927 Lincoln that needs to be bored and new pistons - the whole 9 yards. He was recently told that on those blocks you could only bore .030 oversize and then the block is no good anymore. Anyone else ever heard of this? Why can't you sleeve the engine and rebore to standard size if it's already .030 oversize?

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I don't know much about the old blocks, except that they were heavy. However, a competent engine shop should have some sort of sonic tester, or maybe you could rent one. This should give you an idea of how thick walls are, and how much machining they could take.

Abe

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The loose spare block I have is from a mid-production 1922 engine. There are threee large water jacket holes in the top face, plus a smaller hole of about an inch diameter at each end. These ar all large enough to make a very good estimation of the material thickness of the cylinder bores. For this I used a narrow strip of 22g panel steel, a scriber, and a digital caliper. I put a right angle bend in the strip mso I could conveniently hold it against the cylinder wall below any radius, and scribed the outline of the hole. Then placing the mark on top, alighned with the hole, gave a visual and measurable representation of the wall thickness. The wall thickness through the major holes was from 0.230 to 0.250 approx. Through the smaller holes at front of #1 cylinder and the back of #4 cylinder were a little over 3/16". Even if the later 3 1/2"bore blocks were cast with the same cores as the earlier 3 3/8"blocks, 30 thou oversize only amounts to 15 thou a side, which is miniscule. Lelands were fastidious with their castings, and many of their key people were ondoubtedly still there five years after they had moved away. Stutz changed the coreing of the straight eights to maintain the wall thickness when they they increased the bore 1/8". It would be surprising if Lincoln did not likewise. A model Duesenberg are the engines with very thin cylinder walls that you have to watch.

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