Yes, definitely keep your vacuum advance - a car driven on the street needs vacuum advance to handle high vacuum, light throttle driving.
My new stock stroke 400 build
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I talked to my engine builder yesterday, and he said the same thing that was in the FBO article. The timing mark on that plug indicates too much timing, but then again I am running vacuum advance. I will clean up the plug and disconnect the vacuum advance for my trip to Pumpkinfest this weekend and read it again. I will continue running vacuum advance, but at this point I am working on getting the jetting and timing worked out before I pull the car apart for the winter and get the rad recored. I also bought a quick change secondary spring kit, so I can play with the secondary opening which currently seems very slow. I'm not thrilled about having to chase my overheating problem, but I love analyzing and resolving issues.
71Beeper
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Dave, it was great meeting you at the Ruthven show.
Try switching your vacuum advance hose to a manifold vacuum port - just to compare.
You can always switch it back if you don't like it.
Try switching your vacuum advance hose to a manifold vacuum port - just to compare.
You can always switch it back if you don't like it.
I brought the car into town today to have my engine builder listen to it and see what he thought. He liked the way it ran, and when we put the timing light on it, it was about 16 degrees initial and 38 total. Once we hooked up the vacuum advance it jumped to 34 initial and 56 total, which he felt was way too much. I promised to try it without the vacuum advance for a bit and see how it acts and whether it has any effect on my overheating issue. He said too much advance can be as bad as not enough as far as overheating is concerned. If I find a difference, I might take the distributor out and recurve it over the winter and possibly try to limit the total vacuum advance, so I can still use it.
Your timing mark is dead on zero?
Personally I would try backing it off 3-4 degrees and drive it a bit.
Those numbers sound pretty good to me.
Especially if you had fuel injection
Yes, the balancer is new and the timing marks were verified Don. No fuel injection, still messing around with the Holley.
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In my humble opinion, therein lies your problem!. A Holley? But you may be excused due to the fact it’s not stock. Certain you will get things sorted out.
Usually if we saw 4 barrel carb fire when I started driving, it was on a Ford product or something with a Holley. Never saw a Rochester or Carter on fire.
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PRHeads
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Fwiw, When utilizing vac advance, my preference is to set it up so the max it can reach is about 45*.
This generally requires either a pretty slow mechanical curve and a fairly normal vac can(basically like a stock distributor with low initial timing), and/or a vac can with a pretty short travel.
I’m sure plenty of people run them at 50+ , but I’m going to pass on that.
This generally requires either a pretty slow mechanical curve and a fairly normal vac can(basically like a stock distributor with low initial timing), and/or a vac can with a pretty short travel.
I’m sure plenty of people run them at 50+ , but I’m going to pass on that.
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I try to set ignition timing at 34 degrees at around 3,000 rpm., with vacuum advance plugged. Initial timing just lands where it does. At cruise, under little load, the engine can take more timing, to maximize fuel economy. As load is applied, by pressing on the gas pedal, the vacuum goes away, and timing returns to mechanical values. At steady cruise, your engine can tell you that it has too much timing, by the feeling of "fluttering" or "hiccup". I have been able to reduce this by sticking a small Allen key through the vacuum port of the advance canister, and turning the screw inside. This controls the amount of vacuum advance travel available. Make sure your advance tube is hooked to "ported" vacuum at your carb.
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I was always taught that Chrysler distributors were engineered to work with ported vacuum, while GM and Ford used straight (unported) manifold vacuum. I read through the discourse, and at the end, found that the subject car was a '72 T/A (GM). As I understand it, ported vacuum gives little or no vacuum to the advance canister at idle, and then gradually increases it, as the carb blades open, uncovering the vacuum ports under them.
Thanks for all the responses. There has been a minor change of plans. I went to a swap meet this morning and picked up a brand new MP distributor. It says it has a performance mechanical curve. I am not sure how much vacuum advance it has. I am going to put it in and see what kind of timing it has. I did find an article about how to limit the vacuum advance .
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Only ran 50 degrees on two engines....neither were stock but both had really low compression and ran like crap with less timing. I actually used 3 different timing lights the first time I ran into that to make sure my lights weren't lying to me.
Wonder if that's the newer one with the adjustable mechanical advance
It says it has 22 degrees of mechanical advance on their website. Also appears to have some light springs. I tried to tighten the vacuum advance adjustment a bit before I put it in. We'll see if it works. I am just waiting to borrow my buddy's timing light tomorrow, since mine bit the dust.
While I was out in the garage I installed a quick change vacuum secondary kit on the Holley. Yes I like Holleys, and I don't have much use for Carters. It had the stiffest spring in it so I swapped in a lighter one and we'll see how it works.
So it looked like a regular mechanical advance mechanism?
I usually go straight to the light yellow spring and work back.
Yep, it looked like a stock advance plate. I found it really difficult to see the colours on the secondary springs. I believe I have the plain one in now, which is two steps lighter.
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