Vacuum Advance Tube Support
During recent NCRS meet, I was told by a judge that my 1970 Corvette (350/350 HP) was missing a support that supports the vacuum advance tube running from the carb to the TCS valve. Most of the literature that I have does not show this support as being original for an L46. I will, of course, go with the judge's decision, but wondered what other 1970 owners have on their cars. I was also told that the distributor tag should be red rather than "aluminum" colored. I thought some could be red and some could be bare aluminum. Can someone straighten me out?
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Re: Vacuum Advance Tube Support
Duane,
Usually one side of the distributor band is tinted red, the other is natural.
The red side may be toward the inside, but is most often toward the oustide and visible. The judge(s) "should" have looked to see if there was red present on either surface.
I do not see the clip noted on any of the cars pictured in Dobbins' book.
As you have learned, just because a judge makes a deduction does not mean that they were correct.
PatrickVice-Chairman (West), Michigan Chapter NCRS
71 "deer modified" coupe
72 5-Star Bowtie / Duntov coupe. https://www.flickr.com/photos/124695...57649252735124
2008 coupe
Available stickers: Engine suffix code, exhaust tips & mufflers, shocks, AIR diverter valve broadcast code. -
Re: Vacuum Advance Tube Support
Duane, I don't know the particulars for your 70 (My 71 350/270 has the clip for the vacuum tube) but for the distributor tag, I also show the aluminum side exposed (red on opposite side) for the original tag on mine.
I hope others with the same situation will chime in because we are led to believe this is incorrect. MikeComment
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Re: Vacuum Advance Tube Support
Michael,
Both my '71's have the natural aluminum side exposed on the distributor band, as well.Comment
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Re: Vacuum Advance Tube Support
Thanks Warren, and Duane you are correct. They could have either side exposed. The TIM&JG does state that but goes on to state " On 70-72 Corvettes, the overwhelming majority of bands have the red side out".
MikeComment
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Re: Vacuum Advance Tube Support
I was sent this photo from a VERY reliable NCRS source as original 70 L-46, to aid in my research to have the tube duplicated. As you can see no support. In the dozen or so examples I have never seen a support/clip. Could you PM or email contact info for the judge
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Re: Vacuum Advance Tube Support
Dennis,
That photo you included of the 70 L-46 motor, it shows a vac nipple with a black cap, right under the choke mechanism. My L-46 7040207 carb does not have that nipple, nor have i seen it on others.Last edited by Robert M.; November 26, 2009, 01:46 AM.Comment
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Re: Vacuum Advance Tube Support
Mine is configured like Dennis' picture with no clip, but I have seen later production in 1970 which had a clip. Here's a pic from the Del Val meet that shows the clip - hard to see behind the wire. This car had the later closed air cleaner and was completely restored.
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Re: Vacuum Advance Tube Support
Nor does mine. I had first thought that was a 70 calif. version carb(507), but came to find out there were 207's supplied with that tube. Some archive on this.
As far as Greg's photo,(good pic), I suspect the later L-46(closed A/C) also had a different advance tube, as the bends in the photo would indicate. Could be 71 setup for late 70's? That setup I am not familiar with.
Someone did mention to me that the closed air cleaner's tube needed to exit and bend down sooner for clearance. I put some faith in that since I always notice the small rubber hose, (exiting the carb to the tube), a bit bent down from the open A/C base pressing on it.Comment
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Vice-Chairman (West), Michigan Chapter NCRS
71 "deer modified" coupe
72 5-Star Bowtie / Duntov coupe. https://www.flickr.com/photos/124695...57649252735124
2008 coupe
Available stickers: Engine suffix code, exhaust tips & mufflers, shocks, AIR diverter valve broadcast code.Comment
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Re: Vacuum Advance Tube Support
Patrick... I had to take a double look myself. What you see as foam on the TCS soleniod in Greg's photo is actually tha short rubber hose that in my photo has a white stripe.
All 3 ports(nipples), on the 70 solenoid are used, so none would have a foam filter as the 71 piece I noticed in your great collection of photo's .Comment
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Re: Vacuum Advance Tube Support
Wow, what a good discussion. I plan to leave my 70 L46 without the support clip. I noticed that the Dr. Rebuild catalog, which shows many vacuum tube configurations for 1970-1972 engine options, doesn't show a support clip for the 350/350 engine. He does show a clip for the 1971 270 HP engine; however the TCS valve is in a different location on the 1971. Happy Thanksgiving everyone.Comment
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Re: Vacuum Advance Tube Support
Don't have the doc's catalog handy,but you'll notice there also isn't a tube listed for the 70 L-46.(Or any other catalog for that matter). Like a lot of other parts, some venders will sell you a one size for all, or a bend it yourself version. At least the doc's catalog used to ask for a sample of it to fab.. Kuddo's for knowing there's a different.
Let's face it, unless some nut like me is just obsessed about it, there ain't a whole lot of money to be had for a vender with this one .
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Re: Vacuum Advance Tube Support
For reference, the 70 AIM does not show the clip. The 71 AIM does show it for the base engine.Comment
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Re: Vacuum Advance Tube Support
According to an NCRS judge, my vacuum advance tube is original for my 350/350. I ought to send pictures and dimensions to the 70 Corvette Registry.Comment
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