Mechanical Tach Cable Issues - '73 Vega V8

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Mechanical Tach Cable Issues - '73 Vega V8

Postby ol55 » Wed Dec 30, 2015 11:05 pm

Installed the mechanical tach cable to the chinese HEI with the tach boss. I had bought a 90 degree cable adapter but was better off without it. Problems so far:

1) when I put the distributor back, It was a tooth off. The only way it would run (rough) was with the timing marks off (see picture). Have been told that one way to solve this is to move the #1 back to the #2 position and so on. At this point the tach cable is against the oil pressure gauge pipe, so I think this would give me more room to adjust the timing also. Never have done this so are ther any disadvantages?
2) Can I get it back a tooth (to old position) just by moving the rotor counterclockwise?
Image

3) The Tach cable coming from the tach will not reach the dash tach and has a female end on it. There was an extension from that cable that was too long and was not working. Need a male to male extension of maybe 6". Any sources?

Thanks,
Larry
'73 Vega GT Hatchback hot rod.
'76 Cosworth
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Re: Mechanical Tach Cable Issues - '73 Vega V8

Postby spencerforhire » Thu Dec 31, 2015 8:24 am

You can move the plug wires around if necessary to get the timing where you need it. The standard arrangement with #1 pointing roughly at the #1 cylinder is only for convenience and neatness. That way, only two wires( #3 on the right bank and #2 on the left) have to cross over. As long as they're in the right order and you use a timing light to verify, #1 can go in any of the 8 possible positions.
Other possible fixes for interference could be to put a right angle fitting on the oil pressure line or even move it down to the other spot above the filter boss(not always tapped, sometimes it has a soft plug in the hole).
I've never seen an HEI distributor with a tach drive; does it have an OEM application?
The "fleet"-
77 Vega Estate wagon- project(someday)will have TPI305/T-5, S-10 spindles/axles
72 Vega HB Drag Car -383/'Glide/9"(9.35@146.19)(5.94@117.28 1/8th)
76 Vega GT- 400/4spd/9" retired from active duty(rusty)
03 Silverado 2WD ex.cab (work truck/parts hauler)
04 Silverado 2WD ex.cab (retired)
06 Haulin' 20ft enclosed car transporter
93 Suburban- 350/4L60(retired)
00 Saturn SW2- wife's car
01 Saturn SC2- younger son's project
00 Saturn SL2- daughter's car
98 Saturn SW2- spare
and 3 more Saturn "parts cars"
Note- the very act of listing all of these has made me realize I have some kind of problem.....

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Re: Mechanical Tach Cable Issues - '73 Vega V8

Postby Smiley » Thu Dec 31, 2015 5:37 pm

you can loosen the dist clamp and slide it back, pull the dist up just enough to clear the cam gear and turn the rotor clock wise as you let it down into the next notch in the cam gear then rotate the crankshaft clockwise with a ratchet by hand while jiggling the dist till it drops all the way down.

If I had an HEI I would try a GM HEI Corrected Distributor Cap ACCEL # 8141R
no more crossed wires
Image
http://www.ebay.com/itm/Distributor-Cap-GM-HEI-Corrected-ACCEL-8141R-/121668563479?hash=item1c5402f217:g:7ooAAOSw8-tWVtRJ&vxp=mtr
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Re: Mechanical Tach Cable Issues - '73 Vega V8

Postby spencerforhire » Fri Jan 01, 2016 10:07 am

Those corrected caps sure do make for tidy plug wires, but someone on here (73astregt I think) had a mystery misire with one.
The "fleet"-
77 Vega Estate wagon- project(someday)will have TPI305/T-5, S-10 spindles/axles
72 Vega HB Drag Car -383/'Glide/9"(9.35@146.19)(5.94@117.28 1/8th)
76 Vega GT- 400/4spd/9" retired from active duty(rusty)
03 Silverado 2WD ex.cab (work truck/parts hauler)
04 Silverado 2WD ex.cab (retired)
06 Haulin' 20ft enclosed car transporter
93 Suburban- 350/4L60(retired)
00 Saturn SW2- wife's car
01 Saturn SC2- younger son's project
00 Saturn SL2- daughter's car
98 Saturn SW2- spare
and 3 more Saturn "parts cars"
Note- the very act of listing all of these has made me realize I have some kind of problem.....

Visit http://www.spencerforhire.ca
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Re: Mechanical Tach Cable Issues - '73 Vega V8

Postby 73astregt » Fri Jan 01, 2016 10:35 am

spencer is right it was me that had the problem with the corrected cap, was fine for about a week then the engine started popping back thru the carb really threw me for a loop figuring out what was wrong! from what ive found online the msd6al ignition box makes too much spark for the cap to handle and it started cross firing between #3 and #6 cylinders only way I figured it out was after going thru resetting all the valve lashes in the motor my last resort was remove the corrected cap and install the old one that came off, end of problem! pissed me off as now I have a set of accell cermic boot plug wires that I made up to fit the corrected cap that now will not fit the standard cap doggone wires were not cheap! :bang:
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Re: Mechanical Tach Cable Issues - '73 Vega V8

Postby Monza Harry » Fri Jan 01, 2016 12:42 pm

That does make a whole bunch of neat in a hurry! But that cap isn't exactly cheap either the eBay link from Smiley was over $60! I am surprised at Accel as they too make a "CDI" ignition, and has been a reputable company for years. I am willing to bet that is now made in a "Global Facility" read as China. Fred those sound like nice wires, how many will be too short if you re-shuffle them, many custom DIY sets have the option to buy the wire/boots, and connectors separately, maybe an avenue for you to pursue. Larry you never posted where you found that HEI Tach Drive distributor. That would be a nice piece for some builds. Harry
I'm not a hoarder I'm a preservationist 78 Monza Spyder (Soon To Be 2+2 with Spoilers)
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Re: Mechanical Tach Cable Issues - '73 Vega V8

Postby ol55 » Fri Jan 01, 2016 5:33 pm

Harry, The distributor is an for a '74 Corvette with Mechanical Tach Drive. I assume Chinese. There are several that look the same. Don't want to link to the one I think I have -ONE star rating with a "piece of ----" comment! The old points dizzy also had a Tach drive and was out of a (72?) Corvette.

Does anyone know the length of the cable for a mechanical tach drive? Is it the same cable as speedo cable?

This piece is on the other end of the Tach drive cable. It spins. If I put the extension on it does not spin. Why??
Image

Those wires look unlike my yellow spaghetti mess...someday.

Thanks,
Larry
'73 Vega GT Hatchback hot rod.
'76 Cosworth
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Re: Mechanical Tach Cable Issues - '73 Vega V8

Postby monzabug350 » Fri Jan 08, 2016 1:54 pm

Try MOROSO, I have a mech tac and I pulled up Moroso and used the tach p/n and got a load of info from it. In the cable drive section they list cables by leingth (?) and the type of the ends for a given tach p/n and prices. I think MSD lists a tach drive small cap dist also, have to look in the dist section. If you want to impress people they also list a HEI dist that looks like a magneto but no mech tac hook up.
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