I have an early '67 Swedish domestic market B18A in my Amazon to which I have fitted a D cam, B18B spec head, twin SUs and a four branch manifold & Simons exhaust. The engine has 230,000 km on it (144,000 miles), runs well, has plenty of power, does not burn oil or produce any visible smoke and has compression readings that are even and well within spec. When I swapped the head, I noticed that the bores were smooth but had no wear lip. I know that it would have been a better idea to measure the bores for wear and at least have them honed at that point before matching a higher compression head to old rings but I didn't and here I am.

The engine has the old style breather setup where the crankcase is vented through a steel gauze at the side of the block and then down a small pipe that vents to the atmosphere near the sump. There is no recycling of gasses for emissions purposes.

The problem I have is that there is an exhaust pulse from that pipe and the gasses from it are entering the cabin. This has been an issue since I fitted the new parts. At first, I assumed that there was a broken ring on one cylinder or just general wear and that this was causing blowback. It struck me recently that the B18B always had exhaust gas recirculation and that the pulse from the crankcase vent pipe on my engine might be just because of higher crankcase pressure created by the higher compression head. That said, exhaust gasses shouldn't be escaping past the rings into the crankcase should they?

Anyway, I have no means of doing a leakdown test so the only way that I can truely verify the condition of the rings is to strip the engine. Before I do that, I thought that it might be a good idea to ask for other perspectives.

Do you think that the issue with my engine is likely to be rings/bore wear and that I should tear down the block or if I need to consider fitting the later breather system?
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1967 131, 1977 Volvo 245 DL, 65 VW Bug, 71 VW Westy

Make sure your oil filler cap is perfectly clean. You only need the basic smooth cap but one with a pipe to the front filter will work too as it is sucking air IN from the filter. If the cap is bunged up, the side pipe will try to suck and blow. Clean that one out as well. Single or twin carbs makes no difference. The very early side pipe didn't even have an "ear" with a mesh flame trap.

Certainly somebody near you can give you some kind of compression test cheaper than a teardown!
You could certainly get later components for the PCV system.
Sounds like too good an engine to teardown just on suspicion......
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George Downs Bartlesville, Oklahoma

The poster mentioned he has even compression--within specs. That being said it is no guarantee the motor is totally sound---as I found out on disassembly of my B20 (two pistons with broken top rings)--but that also doesn't mean the motor can't go many more miles before really showing signs of wear/breakage.
I'd go with your suggestion--devise a positive crankcase system--either the B18 PCV type or the B20 restricted orifice system to eliminate the engine compartment fumes. Then see if there is any oil consumption--although the original post says there is not. If none--drive the car till there really is evidence of wear. As you said, George--sounds like too good an engine...Dave

Thanks to you all for your responses. I've already taken the filler cap apart and soaked the mesh in paraffin/kerosene. I'll double-check that I put it back together properly in case that I blocked something but next step will be a proper gas recycling system. Its a lot easier and cost effective than a rebuild.

I'll keep an eye out for someone who'll do a leak down test for me and that might decide things over the longer term.

Thanks again
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1967 131, 1977 Volvo 245 DL, 65 VW Bug, 71 VW Westy