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Discussion Starter #1
Started and broke in my rebuilt 396 about a month ago. It is the original engine for my 68 RSSS so it is very close to stock (mild cam because it is an automatic and I didn’t want to install a stall converter). The cam break-in went fine considering the timing was rough and the carb hadn’t been adjusted properly since its rebuild. Ran the motor for about 45 minutes that day without any major issues. Got all of the transmission stuff hooked up this weekend and wanted to make sure it would go in and out of gear. Cranked the motor and got it up to temperature. The transmission worked fine. The motor was idling way too fast and it would almost die when I put it in gear but the engine hasn’t been properly timed and I’m sure the Q-jet is out of adjustment. No big deal because I have someone coming to tune it up in the next couple weeks.

Here is the latest issue: I did notice a rattling sound, not a knock, on the passenger side/towards the rear of the motor. It only rattled when the motor was idling. When I would give it gas it would quit. I thought it may be a valve out of adjustment (hydraulic lifters) or the heat riser chattering. The next time I crank the engine I plan on opening the heat riser up or hold onto it and see if it chatters. If it stops that is my source but if it continues I’ll have to look into the valve adjustment. Wouldn’t a valve out of adjustment peck not rattle? Could it be the heat riser and if so what can be done to correct the problem? Sorry for the long post!

Tim
 

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Heat riser, you nailed it. That's almost certainly the problem. They make a lot of noise sometimes, usually only in warm-up conditions. Once warmed up, the spring tension should keep it solidly open.

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Discussion Starter #3
I hope that is the case. Scary to hear something like that after a complete rebuild. Just doesn't sound like a lifter/valve problem. I'll post what I find.
 

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Yeah, I know what you mean about scary noises. I just got my fresh engine (454) back in and running a couple of days ago and it had a horrible noise. Turned out to be a water pump, which made me VERY happy, LOL.

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Discussion Starter #5
Cranked the engine and it was the heat riser. What a relief! Believe I will replace it with the spacer. Wish I had known that before spending $50 for a GM riser. Oh, could have been worse.
 
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