Low vacuum

Perfromance and Technical discussions about C3 Corvettes
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rbryce1
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Tell us about your Corvette: 2001 Targa Top Coupe, Stock 350/350 hp Automatic,
1968 Full Custom Mako Shark Convertible, 454/425 hp, Muncie M20 Transmission. 1965 HP Resto-Mod Coupe, 350/390 hp, Kiesler 5-Speed, FiTech FI, Hedman headers, Edelbrock heads, Comp Cam.
Location: Pinellas Park, Florida

Re: Low vacuum

Post by rbryce1 »

Can't open the video. Could you check it?
Love_69
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Joined: Jun 23rd, 2014 6:23 am
Tell us about your Corvette: 1969 L68 4sp Corvette
Location: Australian Capital Territory

Re: Low vacuum

Post by Love_69 »

Try it again now.

https://www.youtube.com/watch?v=SZ7KR_T ... e=youtu.be


PS: I will also have to check/adjust the timing to see if the vacuum reading can be improved upon too. 15in Hg seems to be a little low.
Love_69
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Posts: 47
Joined: Jun 23rd, 2014 6:23 am
Tell us about your Corvette: 1969 L68 4sp Corvette
Location: Australian Capital Territory

Re: Low vacuum

Post by Love_69 »

...by the way, when holding steady revs at, say, 1500 rpm, the vacuum needle is bang on 20in Hg, and is solid as a rock.
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rbryce1
Corvette Addict
Corvette Addict
Posts: 1210
Joined: Apr 8th, 2010 4:35 pm
Tell us about your Corvette: 2001 Targa Top Coupe, Stock 350/350 hp Automatic,
1968 Full Custom Mako Shark Convertible, 454/425 hp, Muncie M20 Transmission. 1965 HP Resto-Mod Coupe, 350/390 hp, Kiesler 5-Speed, FiTech FI, Hedman headers, Edelbrock heads, Comp Cam.
Location: Pinellas Park, Florida

Re: Low vacuum

Post by rbryce1 »

How much cam overlap do you have? Does the engine lope at low idle? Bigger cams don't hold as much vacuum at lower idle speeds but do much better in the 1500-1800 rpm range.
Love_69
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Posts: 47
Joined: Jun 23rd, 2014 6:23 am
Tell us about your Corvette: 1969 L68 4sp Corvette
Location: Australian Capital Territory

Re: Low vacuum

Post by Love_69 »

Not too sure about the cam specs and it no longer has a slight lope at idle. Today, I used the vacuum gauge to set idle mixture and set ignition timing. As a result it now idles nicely/smoothly at 800rpm at a steady (no more shaking vacuum gauge needle)...17in Hg.

Also, whilst playing with the centre carburettor, I corrected the accelerator pump actuation as well, and this has resolved the bog/stumble when stomping on the gas pedal. I know I didn't mention it before, but hey, one thing at a time :)
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rbryce1
Corvette Addict
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Posts: 1210
Joined: Apr 8th, 2010 4:35 pm
Tell us about your Corvette: 2001 Targa Top Coupe, Stock 350/350 hp Automatic,
1968 Full Custom Mako Shark Convertible, 454/425 hp, Muncie M20 Transmission. 1965 HP Resto-Mod Coupe, 350/390 hp, Kiesler 5-Speed, FiTech FI, Hedman headers, Edelbrock heads, Comp Cam.
Location: Pinellas Park, Florida

Re: Low vacuum

Post by rbryce1 »

On a Corvette Tri-power setup, do the outside carburators have accellerator pumps?

I had a friend in Corvette Charleston back in the 70's who had a 427 w/ tri power, and I thought he didn't have an accellerator pump on the outside units?
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