I'm looking at the Innova 3568 Digital Timing Light. $70 on Ebay new.
Need recommendation for a Carb for better MPG!
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Looks like the one I have. Nice light.
Swinger 340
Well-Known Member
My two cents. I had a 69 340 in my 72 van and used all the 72 attached items to make the motor look stock. You could not see the timing marks because they were hidden under the later year items. I always timed by ear and it ran great for 40 years. When ever I had to remove the disturber, I would place a notch at the base of it and also mark the block, so I was close to where I had to be, then use my ears for final adjustment. I have seen many old-style (Craftsman's) timing lights at garage sales for 5-10 dollars.
Very interesting, I will add this info to my project, THANK YOU!!
OttawaCharger
Member
you definitely want want with the ability to advance on the tool. As Toolman pointed out, our LA's timing marks only give you 10 degrees and if you want to check total timing in the future, you'll need much more than that. The digital ones are nice as they usually have a built in tach too.
Also, I'll leave it to the 340 experts on the board but you'll probably need more initial timing than what the factory manual calls for due to modern gas blends. My 360 for instance is happiest at around 12 BTDC which is 7 degrees more than what the FSM calls for.
Also, I'll leave it to the 340 experts on the board but you'll probably need more initial timing than what the factory manual calls for due to modern gas blends. My 360 for instance is happiest at around 12 BTDC which is 7 degrees more than what the FSM calls for.
This is the kind of priceless info that I really respect because I would not have your experience. THANK YOU! One thing, could you elaborate more about when you say "you definitely want one with the ability to advance on the tool" what that means? Sorry but I'm trying to learn. If I understand this correctly, are you saying that you can get a digital timing light that will allow you to advance the timing? If so, do you know if the Innova 3568 will do that?
Over the years carburetor wise the biggest difference in mileage i ever saw was when I stupidly wanted to try a Holley 1850. Because my brothers ramcharger had one and it seemed to run good. Both his and mine (Holley carbs) wound up in the scrap pile in short order, because we couldn't pass a gas station. At the time I had a 318 powered Cordoba. Went from those to TQs that I randomly picked at the junkyard and both ran just as good as those Holley's did but mileage on each dang near doubled vs what they were getting with the Holley 1850s....
In my brothers case he lived a couple of towns over and had to go for smog test. Couldn't get his ramcharger to pass to save my life. Went to that TQ and passed with flying colors.
So that's what made me go find another TQ for my car. (And I've never had to succumb to or bow down to a smog test, on any vehicles I have ever owned with where I live. I've since moved 30 miles further south of where I was at in those days)
In my brothers case he lived a couple of towns over and had to go for smog test. Couldn't get his ramcharger to pass to save my life. Went to that TQ and passed with flying colors.
So that's what made me go find another TQ for my car. (And I've never had to succumb to or bow down to a smog test, on any vehicles I have ever owned with where I live. I've since moved 30 miles further south of where I was at in those days)
You are at least the 2nd person to suggest a TQ, thank you! Do you know if they still make them new or look for good used on Ebay? This could be a relatively cheap improvement
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OttawaCharger
Member
Sorry, I worded that poorly. When you set your timing, you're pointing the tool towards the balancer and the light strobes when #1 cylinder fires. in front and just beside the balancer is the timing tab that has marks for every degree of timing from -10 to 0 to +10. With a traditional timing light, when the light flashes, you'll see that the timing mark on the balancer is aligned with a degree mark on the timing tab indicating where your timing is set to. With the timing light that has adjustment, the tool can strobe the light earlier or later by XX degrees you dial in on the tool. This allows you to watch for the strobe to light up the 0 degrees on the engine mark and your engine is actually set to the degree of timing indicated on the tool. Since the tool allows for more than 10 degrees, you've got more to work with.
Great explanation, thank you, makes sense!!
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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IMHO,
you, for straight fuel economy;
you need to get the cruise rpm down to something like 65=1800, then re-engineer the advance for whatever she needs, then tune the carb; any carb.
But, to run 1800, with a factory 340 cam and headers is counter-productive for two reasons;
1) with the very late Ica, the lower rpm that you run it, the more time becomes available for the pistons to push, just-inducted A/F charge, back up into the intake, and
2) with 44* of overlap, the headers are gonna "suck", some of that just-inducted charge, right across the chamber and out into the pipes
3) both of these actions are counter-productive to fuel economy
So
if your 340 still has a factory spec cam, then get rid of it.
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>If she also has headers and you want to keep them, then you will need a cam with less overlap, a longer power-stroke, and if you need more pressure then an earlier closing intake. To get some power back, your cam needs to have a higher intensity. That is to say, faster opening and closing rates.
> While the 318 cam is a good candidate, in terms of durations and lack of overlap, I feel that there are many better options.
>But if you are running log-manifolds, which kill overlap, then you can run a lil more overlap, as may be necessary, to satisfy the other requirements.
>After the engine has been set up for a higher efficiency, THEN, you can consider a lower cruise gear. How low will depend on the installed cam.
For selecting the minimum cruise rpm, here's what I do;
Put a vacuum gauge on the intake. Warm up your engine. In Neutral, rev her up slowly, bit by bit for as long as the vacuum increases. Once you get to about 1700 rpm hold it there for a few seconds until the gauge stabilizes. I put it up on the Fast-idle cam, or wedge a shim in the curb-idle screw.
Next, without regard to the actual numbers, pull some timing in, bit by bit, until more timing does NOT produce any more rpm. Write the vacuum number down, together with the advance number. Then increase to 1800rpm and repeat. Then 1900, then 2000.
At 2000, fine tune the rpm by playing with the mixture screws, to achieve the highest rpm. Continue until the vacuum no longer increases, or say 2800 with a really big cam..
At whatever rpm produces the highest vacuum, this is the lowest rpm that your engine first becomes efficient. If yur going for fuel economy, then there is NO POINT in trying to cruise at any lower rpm. Higher rpm is ok but, economy may suffer and usually does.
Sometime after 1800 rpm, depending on the cam, your vacuum will plateau for a few hundred rpm. You can cruise anywhere on that plateau and expect similar fuel economy. declining a hair with increasing rpm. Eventually, the vacuum will decrease, and you wanna stay away from that.
BTW
you can do this experiment, with your current engine, exactly as it is. For me, it has worked with every cam that I have tuned, up to the biggest which was the Mopar 292/108. My current cam, 276/286/110 (230/237@050) cam cruises best economy at over 2200, so mine is set up for 65=2240. But it's still lousy, cuz of the late closing Ica, which, IIRC is around 66*. It is what it is.
BTW-2
The 340 cam already has a modest 44* of overlap, which with log-manifolds, one would think it would be a candidate for good fuel economy. And the cylinder pressure of the early ones was great. But, the late-closing intake valve (~66*, just like mine), killed it.
As I remember it, the 340 cars that I have had, ALL of which had 4-speeds and usually 3.55s, all used to get best economy at over the speed limit, which in those days was 70mph.
>Except the one that I installed a 318 cam into ........ and sold the 340 top end off, in favor of the 318 top end. Hyup, that was a torque monster! With a 5-speed, I could see such a combo as killer, for a guy not wanting to wring it out every day. That 318 cam, or one like it, in a 340, will pull ANY starter-gear/any cruise-gear, cuz it already makes near to max vacuum at idle, and has as good as NO overlap, and an extremely early Ica.
That was 1974 or thereabouts.
I would do it again, but, with a 5-speed, I would like a lil more top-end rush than what that 318 cam can provide. Which is very doable because the 318 cam is about the smallest cam you can ever find for an SBM. Ima thinking, a 360 2bbl cam, or one like it, would be a good compromise, if the cylinder pressure didn't get out of hand.
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Your info = Gold, THANK YOU!!!
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