Timing Marks on 1972 350 Pick up - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Momboy007 · 05-17-2008, 12:55 AM

Hello All,
Well you finally have me straightened out on my HEI conversion, now I only have one question remaining and it is concerning the timing marks, On my marks, it looks like on the counter clockwise most part of the marks there is an "A" then a bunch of hash marks, then on the furtherst clockwise, there appears to be a "B or 8" Cannot really make it out and then one in the middle of the 2 that I would assume is TDC, which mark should I try to align the timing light to to get 8 to 10 degrees BTDC?
Thanks so much everyone for you help previously and now
Rick

Sinister · 05-17-2008, 01:48 AM

The B is is BTDC the A is ATDC. The one in the middle is TDC. Get the mark to line up with B.

Momboy007 · 05-17-2008, 07:48 AM

Hello All,
So the A is not for advance? That is how it was originally timed.
What I mean is just counter clockwise of the TDC mark is an A, that would be retarded, is that what you are saying, and I want to be 8 degrees, on the B, Correct?
thanks all,
Rick

Sinister · 05-17-2008, 05:00 PM

Quote:

Originally Posted by Momboy007

Hello All,
So the A is not for advance? That is how it was originally timed.
What I mean is just counter clockwise of the TDC mark is an A, that would be retarded, is that what you are saying, and I want to be 8 degrees, on the B, Correct?
thanks all,
Rick

You know I may be wrong on this. This is how I have mine timed. But now that I think about it it doesn't seem right. Here's a link to a timing tab at Summit. http://store.summitracing.com/partde...2&autoview=sku
Click on the picture. It looks like advanced is to the left. Maybe someone who knows for sure will chime in.

Sinister · 05-17-2008, 07:12 PM

**truckdude239** · 05-17-2008, 01:34 PM

yes good luck mine wont runa t 8 btdc dont know why

**WorkinLonghorn** · 05-17-2008, 10:09 PM

Yeah,that's right.Advance is to the left ON THE TAB. If you are running timing TAPE on the balancer then it will look the other way relative to "0" on the tab.

LONGHAIR · 05-17-2008, 10:34 PM

The balancer is rotating clockwise, so if the engine was stopped with the balancer mark aligned with the "0" (TDC) anything to the left (counter clockwise) would be "before" (advanced).

Quote:

So the A is for advanced, anybody know what the B stands for?

The A is not advanced.
B= before (advanced) Before Top Dead Center
A= after (retarded) After Top Dead Center

There shouldn't be much marking on the ATDC side (2 degrees usually) It was only in the begining of the emissions regulations of the late 70s-early 80s that they did that.

Sinister · 05-17-2008, 10:29 PM

So the A is for advanced, anybody know what the B stands for?

Sinister · 05-17-2008, 10:38 PM

Well, I just went out and checked my timing and it was right on the money. Must of had a brain fart. On my timing tab though, the A is to the left of TDC, and the B is to the right, which seems counterintuitive. My apologies to the original poster for the miscommunication...

Momboy007 · 05-18-2008, 12:30 AM

Hello All,
So, correct me if I am wrong, 8 Degrees BTDC is to the left, or counterclockwise of the zero mark, or TDC on the tab?
Thanks all

P.S. Did we figure out what the a and B stand for on the tab?

Rick

Sinister · 05-18-2008, 12:38 AM

Quote:

Originally Posted by Momboy007

Hello All,
So, correct me if I am wrong, 8 Degrees BTDC is to the left, or counterclockwise of the zero mark, or TDC on the tab?
Thanks all

P.S. Did we figure out what the a and B stand for on the tab?

Rick

Yes.
I think the jury is still out on what A and B mean.

Momboy007 · 05-18-2008, 12:48 AM

Thank You Sinister and workinlonghorn, now it all makes sense!
That helps a whole bunch
Rick

LONGHAIR · 05-18-2008, 03:00 AM

????????????????????????????????????????????????

**WorkinLonghorn** · 05-18-2008, 12:48 AM

Clean it off with a rag. That "B" is actually an "R" which stands for "Retard".(Which is what I feel like 'cause I had to actually go out and look,after all these years)

**WorkinLonghorn** · 05-18-2008, 03:40 AM

On mine,and lots of others I've worked on it's A=Advance and R=Retard.

05-17-2008, 12:55 AM	#1
Momboy007 Registered User Join Date: Mar 2008 Location: Southern California Posts: 82	Timing Marks on 1972 350 Pick up Hello All, Well you finally have me straightened out on my HEI conversion, now I only have one question remaining and it is concerning the timing marks, On my marks, it looks like on the counter clockwise most part of the marks there is an "A" then a bunch of hash marks, then on the furtherst clockwise, there appears to be a "B or 8" Cannot really make it out and then one in the middle of the 2 that I would assume is TDC, which mark should I try to align the timing light to to get 8 to 10 degrees BTDC? Thanks so much everyone for you help previously and now Rick

05-17-2008, 01:48 AM	#2
Sinister Between Trucks... Join Date: Mar 2002 Location: Los Angeles, CA. Posts: 3,830	Re: Timing Marks on 1972 350 Pick up The B is is BTDC the A is ATDC. The one in the middle is TDC. Get the mark to line up with B. __________________ Beat it to fit, Paint it to match...

05-17-2008, 07:48 AM	#3
Momboy007 Registered User Join Date: Mar 2008 Location: Southern California Posts: 82	Re: Timing Marks on 1972 350 Pick up Hello All, So the A is not for advance? That is how it was originally timed. What I mean is just counter clockwise of the TDC mark is an A, that would be retarded, is that what you are saying, and I want to be 8 degrees, on the B, Correct? thanks all, Rick

05-17-2008, 07:12 PM	#5
Sinister Between Trucks... Join Date: Mar 2002 Location: Los Angeles, CA. Posts: 3,830	Re: Timing Marks on 1972 350 Pick up __________________ Beat it to fit, Paint it to match...

05-17-2008, 01:34 PM	#6
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,237	Re: Timing Marks on 1972 350 Pick up yes good luck mine wont runa t 8 btdc dont know why __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

05-17-2008, 10:09 PM	#7
WorkinLonghorn Senior Member Join Date: Dec 2006 Location: Studio City, Calif. Posts: 2,883	Re: Timing Marks on 1972 350 Pick up Yeah,that's right.Advance is to the left ON THE TAB. If you are running timing TAPE on the balancer then it will look the other way relative to "0" on the tab. __________________ '69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme.

05-17-2008, 10:29 PM	#9
Sinister Between Trucks... Join Date: Mar 2002 Location: Los Angeles, CA. Posts: 3,830	Re: Timing Marks on 1972 350 Pick up So the A is for advanced, anybody know what the B stands for? __________________ Beat it to fit, Paint it to match...

05-17-2008, 10:38 PM	#10
Sinister Between Trucks... Join Date: Mar 2002 Location: Los Angeles, CA. Posts: 3,830	Re: Timing Marks on 1972 350 Pick up Well, I just went out and checked my timing and it was right on the money. Must of had a brain fart. On my timing tab though, the A is to the left of TDC, and the B is to the right, which seems counterintuitive. My apologies to the original poster for the miscommunication... __________________ Beat it to fit, Paint it to match... Last edited by Sinister; 05-17-2008 at 10:40 PM.

05-18-2008, 12:30 AM	#11
Momboy007 Registered User Join Date: Mar 2008 Location: Southern California Posts: 82	Re: Timing Marks on 1972 350 Pick up Hello All, So, correct me if I am wrong, 8 Degrees BTDC is to the left, or counterclockwise of the zero mark, or TDC on the tab? Thanks all P.S. Did we figure out what the a and B stand for on the tab? Rick

05-18-2008, 12:48 AM	#13
Momboy007 Registered User Join Date: Mar 2008 Location: Southern California Posts: 82	Re: Timing Marks on 1972 350 Pick up Thank You Sinister and workinlonghorn, now it all makes sense! That helps a whole bunch Rick Last edited by Momboy007; 05-18-2008 at 01:04 AM.

05-18-2008, 03:00 AM	#14
LONGHAIR just can't cover up my redneck Join Date: May 2004 Location: Columbus OH Posts: 11,414	Re: Timing Marks on 1972 350 Pick up ???????????????????????????????????????????????? Last edited by LONGHAIR; 05-18-2008 at 03:01 AM.

05-18-2008, 03:40 AM	#16
WorkinLonghorn Senior Member Join Date: Dec 2006 Location: Studio City, Calif. Posts: 2,883	Re: Timing Marks on 1972 350 Pick up On mine,and lots of others I've worked on it's A=Advance and R=Retard. __________________ '69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme.



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.