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Uh........yeaaaaaaaah. i went through it this past summer and pretty much wasted the whole summer. Will provide details soon, but it relates to my thread in the engine section.

But one of the first rabbit holes i went down was:

Smoke billowing out of the right exhaust pipe only (true dual exhaust with no crossover).

i actually took the right side head off thinking it was a blown head gasket and replaced the gasket. Still doing it.

Tried another engine i had in the shed. Same problem. Is this a problem that affects small block chevies? The right side head gasket goes bad???????

Somehow, i had either knocked the vacuum modulator line off/or i did not attach it securely. During another road test i noticed that the trans wasn't shifting right, but there was no more smoke coming out of the exhaust pipe.

It turns out the vacuum modulator was bad---it was allowing trans fluid to leak and be drawn into the intake, and if you look at most SBC intakes, the vacuum connection for the modulator is usually on the right/passenger side of the intake----which likely causes the fluid to eventually go to cylinders 6 and 8, which would cause smoke to come out of the right side exhaust IF you have dual exhaust.

Proper diagnosis is the first step in fixing a car right.
I had the same problem years ago on my Blazer! It wasn't until I tore the heads off for new gaskets that I saw the transmission fluid sitting on the number 8 intake valve. After some choice words at myself and the truck I went and got a new modulator too. Whole weekend shot for a five minute fix.
 

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Another one of my dummy moves was when I built a 350 for my 1977 Chevy Concours. My friend needed a new engine for his Camaro, so I sold and installed one for him and kept his old one. Upon teardown of his core I saw a low mileage rebuild with four spun rod bearings. (He had a lead foot). His block was excellent and I wanted to do an engine on the cheap with some used parts I had laying around. Threw a different crank rods and pistons in it with a new cam and put it in the car. While breaking in the cam I noticed the oil pressure going away. Okay, 10 psi at idle is not good. The oil pump was used so figured that was the culprit. Out came the engine. cut the oil filter and no real glitter to worry about so replaced the oil pump and put engine back in. Okay, better, but not great oil pressure. Took car for a drive and oil pressure started going away and started getting a lower end knock. out comes the engine again. No glitter in filter, so off comes oil pan again. Rods are tight and no spun bearings. WTF? Then it finally dawned on me. I assumed the crank was standard. Upon checking it was actually 0.010" under. WHOOPS! Ever pull a crank with the heads still on? I don't recommend it lol. I gave myself the "dummy of the month" award for that bonehead move.
 
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