After hours of searching on timing light accuracy, msd box scatter, dial back light issues, timing light brands etc....I decided to test out a couple today.



The baseline:



1)My car is running locked out timing(no vacuum or centrifugal advance) so its really simple to check.



2)The timing light I have always used is a Sunpro(Actron #7519) dial back style. I have had this thing 15yrs and its always worked well, but the reason I was questioning this is now my car has a MSD 6AL and everyone says the dial back lights are not accurate, especially on a MSD ignitions. I really had no idea where I was at. On the dyno, we set the timing at 31* with a Snap On digital light. Upon installation in the car after stabbing the distributor, I set the timing at 32* with my Sunpro light and thats where I have been running it.




So today I go to Sears to buy a Craftsman non advance light, only to find out they are not selling them anymore...All they had was a Craftsman dial back style and the Craftsman Professional series (digital) with the tach and other stuff. Well since I already have a regular dial back, I decided to roll the dice on the digital model.




My balancer is already degreed so I figured the standard style light would be easy to test against the dial back method but....since I couldnt find the non dial back light, I will just have to hope the dial back method is accurate.



I came home tested both at idle, 1500 rpms and at 3000 rpms(since MSDs are supposed to only fire single sparks after 3000).



Both lights read IDENTICAL at all engine speeds and degrees.....Both light lights had about the same about of reading fluctionation at idle(I attribute this to the MSD multiple sparks but this was minimal) at 1500 rpms, both lights were reading the same smoothness at "0"(using the dial back set at 33*) and at 3000rpms, the line was rock steady at "0".



So for me, I consider two timing lights that are reading IDENTICAL to be pretty accurate, eventhough neither one I am supposed to be using due to their dial back feature and the MSD interference. I will say the digital light is pretty bad ***, the strobe is much brighter then the old Sunpro light and the digital action makes it idiot proof to add a degree or two with great accuracy. Lastly the tach feature is nice when you are laying over the fan revving the **** out of the motor thinking your are "up there pretty good" only to find out you are at 2k or less....LOL



I will keep both and continue to benchmark them against each other but, I guess this is close enough for me. As long as they are consistant, the absolute numbers shouldn't normally matter TOO much, but my motor is on the edge of detonation so I need to keep the timing in check at all times.



Sorry for the long post, just thought I would throw my experience out there.

 

I also used my dial back as to compare to my dyno reading & found no difference either, at all rpms. I then tested my old non-dial back & again got the same readings as the dyno & the dial back. Also running a MSD 6AL. Go figure???? I called MSD & spoke with a tech and he said, it only matters in some cases.

 

Thanks for the write up. I was in the market and looking at those Craftsman. Glad to see they are up to par.

 

guys that lock the dist. often run the under dash MSD timing control#8680. up to 15* adjustment on the fly. my friend got it and the cruise mpg was so high i didn't believe him!

 

Yeah the #8680 may be on my to do list... Mainly so I can easily switch from my race gas tune(33-34*) to my pump gas tune(31*).. Thats about 30-40hp difference on mine.. Not sure I trust the accuracy of the 8680s adjustments yet....Need to do some more research...I don't have a lot of room for error...38* lunched a head gasket on my motor in the first 100 miles on pumpg a....

 

That's good testing. I've heard it for years, but never seen it to be a problem. I'm still using my snap-on analog dial back light from back around 1980 or so.

Was the head gasket on the current motor???


JIM

 

Was it you that had the balancer fall off you crate motor in the garage. If so you have come a long way

 

I'm intrigued, does anyone know where this myth that adjustable timing lights are inaccurate came from?

It's certainly never made it across the Atlantic

 

My MSD manual states that some dial back timing lights won't work well with the MSD 6AL (and other) set up. The reason is that the multiple spark coming from the box for 20 deg of crank rotation causes the light to fire radically. It's not really inaccurate it's just that it looks like a blur of timing mark over a large area making it difficult to find the actual location of the mark when it fires.

Most timing inaccuracies are caused by the tab being mislocated or the harmonic balancer slipping. Periodically one should use a piston stop tool or dial indicator to set the number one cylinder on TDC and check to be sure the marks are lined up correctly.

 

NO...that def. was not me...LOL

 

Did you lose a head gasket on this motor?
I've been reading your posts about the big block swap on a few different forums, and havent seen you mention that.

 

I have seen problems with the Snap on lights and performance engines as they seem to show about 6 dgrees more timing then the lights I use and we use the one wire lites from Flaming River.

We had a circle track customer burn up a piston because his Snap On light was not accurate beleive it or not he did this twice!!!

Here are some good links to look over on lites.

http://www.dragracingonline.com/tech...-lights-1.html

http://www.chevytalk.org/fusionbb/sh...hp?tid/173877/

 

I'm confused by this as I don't know the MSD system, is some kind of wasted spark system?

 

Looks like these systems are available in Europe. I have the MSD 6AL with a Blaster 2 coil, MSD 8.5 spiral wound spark plug wires (solid wires won't work), platenum spark plugs, MSD Pro Billet Corvette distributor with mechanical tach drive and vacuum advance.

Here is the Eurolink

http://www.msdignition.de/

 

I think wasted spark is an accurate description.

 

Looked at the instruction, I didn't realise the 6AL was a multispark capacitor discharge system, this explains the potential timing light inaccuracy

 

I was just looking at the Sears digi light just last night and almost brought it home with me. This post couldn't have had better timing.
Equus has had a digi light on the market for many years now but i worried how it would work with my MSD box. Ya know, i just trust the craftsman name more than the Equus brand that has had all the bells and whistles on the market for a long time. Sears sells them both but now its good to know the craftsman is accurate while it has all the bells and whistles too. One nice item the Equus has is it displays both rpm and advance at the same time where it looks like the craftsman requires u to toggle back and forth by switch. An accurate tach is a must have for me.

Thx for posting,
cardo0

 

My sears dial back with the tach (digital) absolutely does not work with my Digital 6 MSD.

Bill