Greetings from Spain. Last year I bought a 1937 Special Coupe from the US, with engine and transmission completely overhauled some years ago, 7.000 miles on the clock since that was done. I have all the invoices from that job which unfortunately was poorly done. After driving the car some 300miles I noticed the occasional knocking from lower end in the engine, pulled out the oil pan and the oil was full of fine metal chips that probably had come off over the year. Main bearing shells showed serious signs of wear (thus the chips) and we decided to take the engine out. What we found was:
- pistons with very little clearance, .0022 to .0025 (2 pistons had seized), pistons pins were almost stuck and not moving freely at all
- all bearing areas on crankshaft showed wear and require regrinding
- all main bearings show wear and can only been thrown into the bin
- no shims were used neither with rod bearings nor with main bearings. Main bearings are .10 undersize
- a modern replacement rear bearing seal was fitted into the groove (wrong for series 40 engines in 1937 I understand)
Both rod bearings and main bearings were already converted to insert type. Here's my question: since going back to babbit type bearings is too much of a hassle here in Spain (hardly any shops left who can do that) I will need to go for the next size of insert type mains. Those they sell are all for 1939 and later type of 248" engines I understand. The rear main bearing looks too wide in diameter and probably needs modifying it in oder to not obstruct the oil passage. Attached are 2 pictures showing what I found in my car and how the rear main bearing looked like
This thread in the forum from a few years back was already dealing with some of these questions but it would be great if you guys could confirm what I should do best with the rear seal and rear main bearing: no bearing seal and modifying the new bearing to the same look as in the picture (cutting out just a small hole for the oil passage)?