weeelll.... lets throw my experience on the engine's i've played with in here
so far to date, i've toyed with at least 8 different blocks.
But, citing River's mammoth Diagram thread.....
Note the following 18R-G block:
... see the breather thing is fully blocked up on the exhaust side. This is synonymous with the TWO genuine 18R-G blocks i have in my garage.
Now note the following 18R block:
... see the breeather on the exh side is actually open, suggesting a breather pipe is fitted to it. This would make complete sense on an 18R where the intake is also on the exhaust side (non-crossflow). It would make NO sense on an 18R-G cos the intake is on the other side of the engine.
Some further evidence.......
see these 18R-G diagrams... the crankcase breather is on the exhaust side. This is correct with ALL the 18R-Gs i've played with.
Compare that with the 18R block below
... see how the crankcase breather normally found on the intake side of an 18RG is blanked off......
And now for some annecdotal shit
.. this tends to make me think that the lump on the exhaust side of the block indicates the block to be an 18R-G item, and the lump was ditched when they became the 18R-GU.
- 18R-GEU engines have the crankcase breather blocked off on the intake side of the engine too.
- later 18R-G blocks that have come from KNOWN '77 engines do not have the lump on the exhaust side as shown in the diagrams above. These blocks have always had the 8.7:1 pistons.
- The two blocks ive pulled apart with the lumps on the exhaust side have had 9.7:1 pistons.
I think it's also pretty darn same to assume that the "U" in 18R-GU is indicative of Exhaust Gas Recirculation (EGR), as shown by diagrams 55 and 56.
Also looking at diagrams nearby to that, you can see all the EGR stuff is ONLY on the "u" designated engines.
Mammoth diagram thread is here: http://www.toymods.net/forums/showthread.php?t=22911
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