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Join Date: Dec 2002
Location: Malabar, Fl
Posts: 22
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911T tune up
I just acquired a 1970 911T. The car has a bad backfiring problem. Can anybody help me with tune up specs. Need to know ignition timing, dwell angle, points gap, plug gap and idle rpm. I want to do a tune up to see where I am. Any info/tips would be appreciated
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12-14-2002, 03:01 PM
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here are the specs from a chilton book from the early '70's:
'70 911T: spark plugs: W250P21 gap: .024 inches point dwell: 38 +/-3 (bosch) ; 40 +/-3 (marelli) point gap: .016 inches timing: 0 degrees, 35 BTDC @ 3,500 RPM idle speed: 850 - 950 RPM |
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12-14-2002, 04:30 PM
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Join Date: Mar 2001
Location: Marysville Wa.
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the plug heat ranges in the old manuals can't cope with today's fuels on carbed and MFI cars. they run too black and foul easily. NGK BP6ES works well these days. see how they look after a 1000 miles and go hotter if needed. NGK numbers go down for hotter, as opposed to bosch which goes up. BP5ES would be hotter.
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12-14-2002, 05:09 PM
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Location: Massachusetts
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Quote:
you need 35 degrees at 6000RPM, not 3500. Mark S. '70 914-6 |
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12-14-2002, 06:37 PM
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I think you're right about the high end timing (6000 rpm). What is the timing at idle?
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12-14-2002, 06:50 PM
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Location: Marysville Wa.
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when you set the timing at full advance, which is the rpm where the timing quits advancing anymore, whatever it idles at, timing wise, is what it idles at. in other words, it doesn't matter. yours may well get to the full advance point well before 6000rpm. try it and see. use the last mark on the pulley (farthest to the right) if you don't have an adjustable advance timing light. raise the rpm until you don't see any more timing advance as you shine the light on the pulley. the idea is to get the full advance mark to line up with the fan housing mark at that point. turn the distributor to accomplish that. the idle speed may have to be turned down a bit when you're done.
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12-14-2002, 07:03 PM
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Join Date: Jul 2000
Location: So. Calif.
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On a 69T, the timing at idle should be 5º ATDC, but make sure it meets spec on the top end (35º BTDC) and let it be whatever it is at idle.
Sherwood Lee http://members.rennlist.org/911pcars PS: The timing at idle could also be 0º (TDC) depending on whether you have a "smogged" engine or not. Last edited by 911pcars; 12-14-2002 at 11:10 PM.. |
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12-14-2002, 07:33 PM
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my mistake on the high RPM timing.........
it should read 35 degrees BTDC at 6,000 RPM. |
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12-14-2002, 08:56 PM
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Join Date: Feb 2000
Location: Lacey, WA. USA
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Follow John's advice.
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Man of Carbon Fiber (stronger than steel) Mocha 1978 911SC. "Coco" |
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12-14-2002, 10:38 PM
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Join Date: Nov 2002
Location: gatlinburg tn
Posts: 752
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backfire out the tail pipe is an overrich condition or exhaust leak.
check your float levels/seats and exhaust durring your tune up. john , did you see the van in this month vw trends? pretty sharp.
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72 911t grey/black mine 74 914 2.0 black/ tan hers 02 g500 black/black womanproof 01 f250 psd dirty the mule 60 correct craft starflite cool 69 correct craft torino hauls butt 72 correct craft ski nautique fun 66 vw 1500s will finish someday |
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12-15-2002, 08:06 AM
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