I recently fired up my 61' with the rebuilt motor. 283 c.i, solid lifters. It runs great, but it has a noticeable "hiss", that sounds like it is coming from the dual carb set up. I have good vacuum, and I don't think it is a vacuum leak. My other question is, why does the solid lifter engine use a non vented oil filler cap? Does it make any difference if I use the vented oil filler cap? Thx Phil
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Re: 61 engine noise
Check/verify vac leaks by carefull spritzing carb cleaner here/there. If there's a leak, RPM will jump slightly when you hit the leak site. On non-vented oil fill cap, that's the way Zora and the boyos designed the high-horsie SA cars. MANY prefer to run on the street with conventional vented caps and save the 'rare' non-vented, factory original caps for show.... -
Re: 61 engine noise
Phil -
Chevy got lots of complaints (starting with '57 solid-lifter engines) from racers about blowing hot oil vapors out of the vented breather cap all over the top of the engine (high rpm, high power settings, high blow-by/crankcase pressure under race conditions), so they responded by releasing the non-vented oil fill cap for solid-lifter engines to stop the complaints. As a result, these engines no longer had even crude crankcase ventilation - they just relieved crankcase pressure through the road draft tube, as there was no longer a fresh air intake point at the filler tube. The bottom of the road draft tube is shaped such that it creates a negative pressure area when the car is moving, and with the vented cap, that drew in some fresh air through the cap which then flowed through the crankcase and out the road draft tube.
You need two caps - one (vented) for normal driving, and one (non-vented) for judging. I ran a vented cap on my '57 270 for four years/5,000 miles, never had any oil drips or mist anywhere on the engine; swapped it for judging.Comment
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Re: 61 engine noise
May be a silly question, but is the Air Cleaner on the car?
Some carbs get pretty noisy without the air cleaner in place.Comment
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