so last time i just did a quick education on vacuum advance and got alot of feedback wanting more info. also some nay sayers so here is a video on just one of my cars on how its tuned for vacuum advance and how to do it
Botton line, what Chris is saying is true. Automakers and the EPA have known this for YEARS. The reason the EPA forced automakers to use ported vacuum for vacuum advance is the fact that engines produce lower emissions at idle with a lower amount of advance.
@lollipop84858 I also like being free from the Gestapo. Everything we do now is under some form of control. And if we don't, we are fined and / or imprisoned. Mostly under a democrat regime.
I’ve been experimenting with these same things. I hooked my mightyvac up to the vacuum canister to find out how much vacuum the engine actually wanted. Then I looked at how many degrees of advance that gave me. Then I adjusted the canister to give me that same amount of vacuum advance. Let me tell you the engine on my old truck ran so smoothly I literally thought it had died at the intersection - no joke. This took my 12-13 mpg 1969 F250 to 19-20 mpgs.
DUDE! I have been swinging and missing at my tune on this SBC of mine for well over a year now. Fouled plugs, swapping jets, power valves, timing, fuel octane. All along the way I have left he vacuum advance alone. I watched the video yesterday and today I hooked that advance up to full time vacuum on the carb base (650 double pumper holly) and I'll be dipped. I had a blast driving this ole Rickshaw wagon around today. Runs much much better now. This video here just confirms my actions today. Thanks for the tip to the direction I needed with this tune.
Once you follow the correct procedure to select the correct power valve there should be no reason to change the size! If you don't have a good book on Holley carbs, you should buy one.
A good friend of mine thought that his 1986 Dodge Ramcharger was just completely gutless despite being "cammed" as the previous owner had told him. I spent 3 days fixing vacuum leaks, cleaning and rebuilding the Edelbrock carb. to go back on the Edelbrock intake, set the initial ignition timing to slightly advanced instead of slightly retarded and made sure the carb. got the correct fuel pressure. He was stunned to see that with just a few quick revolutions the truck fired right up. I hooked checked over as much as I could and hooked the vacuum advance back up. After the cleaning, fixing and tuning the truck went from fighting to start, fighting to go, fighting to get to 50 MPH on flat ground.....Suddenly that 318 and 4 speed manual 4x4 was doing 70 MPH on the interstate and he could cleanly take off in 2nd instead of relying on the super low 1st. Even managed to improve his fuel economy by a noticeable amount too. That said, not his daily now so we can swap out the worn out 318 with something more correct for his plans.
OK, so update. I had a few days to tinker and put this video to use. I could never get my secondaries to open when I takeoff, when I stuck an Allen wrench in the vacuum pod I was able to do 4 complete turns to the right. I only had six points of vacuum. Now when I plug my vacuum hose back in Wham!! It went from 16 up to 32! I can’t believe how responsive it is already. Yes I’m listening for ping, no ping. Thanks for the video.
Thanks Chris for letting the cat out of the bag, I used the same timing and vacuum advance technique on my 73 Plymouth Satellite with a 318 , stock 2 barrel and it ran strong back in the day. Only mod was headers and 3.91 gears. Everyone could not believe it was a 318!
When these cars were new they only got 8 to 10 MPG around town, and around 12 to 14 on the highway. Believe me, I was there. That is for the small block versions, big blocks got much less than that. You are spot on right about using vacuum advance and dialing the AFR's and maxing out the timing. My 505 in the 73 Charger, a very heavy car, can get up to 15MPG on the highway. Most people do not understand how to dial in a powerful engine for max power, which goes hand in hand with max efficiency.
Fuel mileage has a lot to do with how it's maintained and driven. I can get 13.5 out of my brothers c20 truck, and he gets 10. He's owned it for 40 years
nice video Chris! I can say it again get one of those Progression Ignition Distrubators. They have a vac sensor so u dont need that much vac for advance. And you can do litterly every timing on every rpm/load. Its nuts!
Excellent videos Chris! I've been mirroring your experiences while tuning on my Ford 289 over the last several driving seasons. Everything you reference applies to all makes and models; and fuel injected ECU level performance can be achieved once you understand how the vacuum advance works in light load; lean conditions. Tuning vac advance in harmony with the centrifugal advance curve for your specific engine build yields a cool running highly efficient engine that is snappy on throttle and coasts down the freeways. Many hot rodders are running large radiators, and a marginal tune in consequence to not utilizing the information you've detailed so well here. One tip I will add in context of this video: As you optimize the centrifugal timing curve and vacuum; you may need to adjust the idle circuit, the accelerator pump nozzle size, main metering circuit and/or secondary jets to fully realize a unified optimal tune... Each step you take may require a trim on the vac advance adjustment of centrifugal curve; such that you'll achieve optimal AFR from idle to WOT. Some might reply; that's what Fuel Injection is for... but it is an extremely rewarding experience when you put in the effort; and makes driving these classics anywhere, and in any conditions; a true dream.
Great video Chris. Long time fan of your channel, but first time commenting. Glad that you stressed that every engine is different. That's definitely the key. The more you stray from the factory build of the engine, the more the fuel and spark requirements change. Especially when there's more valve overlap from a bigger cam, causing reversion in the intake, pulling exhaust gases back into the cylinder, diluting the intake charge, which is why the engine wants more ignition advance. Same with light throttle, low load conditions. You need much more ignition timing to create ideal cylinder pressure for the engine to run efficiently. Give the engine what it wants, not what you think it needs.
It makes sense once you think it through. Back in the day everyone tuned their cars by feel/ear and actual driving results. All this said, I don't run carbs any longer so this may not have as much of an impact although I will have to try some of this out on my 416 stroker in my 73 Cuda.
My advance has adjustable vac pod. Had no idea that was possible. Thanks. Also Blue Print suggested a cold plug which works at the track. But only figured that out after fouling plugs. Hotter plug, no problem for cruising. Great info Chris
Great demo. I agree, vacuum advance is the way to go. I notices some hesitation on acceleration, that's caused by all that timing dropping out abruptly. had the same problem. I installed an adjustable metering valve in the vacuum line to delay or slow down that vacuum drop rate. No stumble or flat spot, acceleration is snappy and smooth. also help with stumble off idle. adjust to suit. i used a metering valve off a fish tank bubbler.
Chris really does have a good way of explaining things, and he’s totally correct. People could definitely really improve the performance of their engines by listening to him. I didn’t know who he was until people quoted him on my site. Anyway good shout out to chris.
Chrysler vacuum pods are often marked for the amount of advance they will give. In the video I posted yesterday, I showed an example labeled 8.5. Depending on the year and model, there was a wide range that can be found and it's easier to tune when you know what you are starting with. You never showed how you are limiting your mechanical advance. I also give one example of how to limit mechanical advance in yesterday's video. Timing is a complex process that involves a depth of understanding that is far ahead of most hobby builders. Thanks for sharing your insights and how they relate to one specific build. Nice car!
Interesting. I have mild 318 in my 69 Satellite. I got 19mpg last summer, but I think there is more. I'll have to check vacuum timing next summer, yeah we already have snow here...
I think part of the confusion people run into on the ported vs manifold vacuum debate, is the manifold vacuum nay sayers are already not running enough initial timing. If you're going by off the cuff recommendations of 12-16 deg initial and a slower advance curve ( heavier springs ), the mechanical advance is too slow off idle to provide good driveability. The key Chris touches on here is treating each engine on it's own merits and tuning to best idle vacuum with the vacuum advance hooked up, granted a properly tuned carb. Ported vacuum WAS introduced in the late 60's to reduce off idle emissions passenger cars and light trucks, particularly because it was seen as an effective way to help counteract emissions industry wide when common circumstances were that your average driver would skimp on maintenance ( just like today ) , often waiting until they developed a driveability problem on their vehicle before they would perform recommended maintenance.
Best video I have seen. Old timer taught me exactly what you were saying. Set base timing with maximum vacuum at idle, retard 2°. Advance hooked up to manifold vacuum. Run hard under load, retard further if pinging. Very impressed with your video. Learned a few new things, and explained things I barely understood
Great video and I totally agree with connecting the vacuum advance to full manifold vacuum. However, too much timing can cause engine surging which is most noticeable when you let off the gas and coast at highway speeds; so you may need to tune the vacuum canister for slightly less advance.
I’ve been waiting for someone to explain this to me in a way I understand, great video. I’ve watched other good channels but they skip some of the basics. 👍.
I keep forgetting the younger folks have never seem a distributor vacuum advance or ported vacuum takeoffs on a carb and all that pre fuel injection stuff…yes I’m feeling old.
What's your opinion? I daily a carbed rig and I use ported. My problem is the hei distributor has a large timing curve, so I can't set my base as high as I want or it'll ping when I'm towing. The ported helps a lot in town driving but I have to unplug it to drive in the mountains, towing, because of pinging. On my old Chevy that had points, the distributor curve had less total advance, and I ran a lot of initial and hooked the distributor to ported vacuum and it seemed to work great. Not so thrilled with the hei distributor. I liked my points but I have had really bad luck with new manufacture points. The old ones I found in the junkyard last much better.
Some people claim that different weights limit the amount of advance on a GM HEI distributor, but the sure fire way to shorten the amount of advance is to take the distributor apart by knocking out the roll pin that secures the drive gear and pulling the shaft out to access the limiting slot and pin under the mechanical advance mechanism. You will need to get or make a bushing to fit over the pin to shorten the amount of advance travel. You may have to open the sides of the oval slot with a dremel or such for bushing travel clearance. The plate is hard steel, too, so takes a bit of effort to grind the clearance. A less complicated effort for your application might be to use heavy advance springs and even lighten the weights if necessary so that the mechanical advance will never reach it's fully extended limit at the rpm that you turn the motor to. You could probably get your initial timing where you want it that way.
When I would time my engine with a vacuum gauge I would connect the gauge to a manifold source, and then advance the timing to maximum vacuum. Then back the timing off one inch vacuum from max vacuum because if I left it at max vacuum my car would start pinging. Since the classic vehicle I own now is a TBI engine I time it according to the way the factory requires.
Great video!! I don't understand why almost nobody talks about initial timing. Everyone one talks about total or vacuum. Most of your time is spent on initial and vacuum.
Awesome video Chris. That Tall John Science sounds like it works. I think I remember home saying he got 18mph in his 440 ton grille. When I heard that I said, “WTF?”
Can you do more videos on tuning like this. Timing and carb please. This is where I have the biggest problem. Is stock different? There’s so many videos but yours is pretty in dept. For example, I didn’t know how to figure out what to set my timing to. In your video you said “advance until you hear pinging then back it off and take it for a drive. If you hear pinging, timing is too high”. That’s exactly what I needed. I really appreciate you making these videos!
My buddy had a '66 Chrysler convertible that had a manifold vacuum gauge on the center console (automatic trans). He would race against my '64 Galaxie XL (390 auto trans 1st car). Both would just hunker down when the kickdown engaged and we flew through the blacktop.
My 67 Coronet has a wimp 383. Low compression, Low vacuum signal. I run 20 inital and use a FBO lockout plate locked out at 14 degrees. 34 total. I hook up the vacuum can and it detonates it brains out! The last owner had a MP Distributor that made tons of timing. To drive it at 65 mph you had to set base at 6 degrees. I chucked the distributor and bought a reman mom mopar unit. Used FBO plate set to 14 and cranked up intial to 20 , 22 ish. Plug in the can and it`s a train wreck!
Years ago I bought a '68 Polara 500 with a 383 two barrel. The motor was SO carboned up that it pinged and rattled terribly. After blowing all that carbon out I drove that car for many years. I later added a Mopar electronic ignition conversion, Edelbrock intake, Holley carb, & dual exhaust. It was strong and was never finicky for high octane after cleaning the carbon out. Did you try Seafoam or something similar?
Maybe your carburetor is too lean at part throttle operation(?) Coolant system not full(?)... Make sure to use a coolant RECOVERY bottle to keep system FULL.
Also, if using a stock or very mild cam I would use the ported vacuum source with the 20° initial timing and I would expect it to need more than 34° of total.
I feel ya. I had to take my non daily driver out because the daily was in the shop( repairs beyond i wanted to do) found myself leaving it out of sport setting . Lol.
@@junkerup Understandable. I was there and seen with my own eyes and couldn't believe it. lol. Not to mention pulling over hills and I couldn't keep up. Truly was amazing. Could be a pretty cool video to prove it.
Thank you very much for the info there Chris that is a a good thing to do to get it more efficient and excellent explanation of how it works and why and you'll turn a lot of people on to that advantage but like you said it takes the right vacuum advance in that is kind of an issue if you use the OEM Chrysler it doesn't work real well but get an aftermarket one and hopefully they still make them that's the problem that old stuff it's tough to find it
Chris your performance camshaft (with a lot of overlap) bleeds off compression at low engine rpm and obviously more at cranking speeds. So at cranking speed and below peak power (at higher rpm) the compression ratio isn't 11:1 as its being bleed off by the large overlap. On a high torque low rpm camshaft 11:1 would definitely kick back on the starter motor if the static timing was kept at 22° BTDC. With a performance cam though, yes, it makes sense and is viable. I gather that you're using manifold vacuum for the vacuum can and not ported vacuum.
After watching this video and the last one from yesterday I’m going to do this to all my ford trucks bc I don’t have any mopars and I wana see if can get more fuel mileage on my big block 79
Wait, there's a screw adjustment in the vacuum pod?! I had to actually go check my Road Runner to see if it wasn't April 1st. Never touched it in my life, but I think that's about to change. Thanks for the video!
Always been using old school Accel full mechanical advance distributors,, much more Accurate control and best performance, as your passing your competitor... At 19 city miles per gallon with o.e. tri-power, 13.8 to 1 compression, FE big block Ford, it's set at only 30° full mechanical advance on 93 octane, no detanation and full maximum power when you want it...
I've often argued that non-emissions engines should run manifold vacuum. That way you're getting ignition advance at both idle AND cruise speeds. Why not have both? What's wrong with having lots of advance at idle? You can thin out the mixture too and have a nice lean, clean idle.
The point of vacuüm avance is that you're spark stay's at bpm by more rpm-'s What you must check is vacuüm hose doesn't colapse at high rpm normaly the use a plastic hardline with the silicone at both ends 🤙
PLEASE READ: Hey Chris, thanks for your detailed explanation. Can you address this question please ... What's your thoughts about detonation and cylinder temp? Advancing the timing will fire the fuel mixture before TDC earlier (as you have it set up once the motor is running). So, as the efficiency of the burn increases you use less fuel (leaner mixture) to produce the same power level, which means a (less fuel usage, more efficiency & better MPG). Does not the leaner fuel and advanced timing increase the cylinder temp which could lead to melting a piston? Since higher compression requires more octane is that not the perfect storm? I mean: high compression + higher octane + lean mixture + advanced timing = higher cylinder temp? which may cause melted piston. Am I all wet here? The reason I say this is I melted a piston doing exactly that. Since then, I usually run my engine a bit fat on the fuel mixture to keep the cylinder a bit cooler. I would appreciate your comments. **** An interesting test would be to use an Infrared Thermometer Temperature gun on header right at where it exits the head and measure the exhaust temp with STOCK settings and then with YOUR settings to see if the burn is higher or lower temp.
Thanks for all the info. I have 351c 4v. My engine pings when I have my vacuum connected at high load acceleration. But if I disconnect the vacuum it won’t ping. What can be causing that. Thanks.
Goldmine of forgotten tuning information. Thanks for sharing and making this video, Chris. I do have a question about that pistol grip shifter handle- as in what’s going on with it in the Charger since the car is an automatic? Is it for a parking brake or overdrive unit? What gives? Thanks in advance.👍🏻
More better info. I have a 72 cuda that has a bored and stroked,mild cam 340 It starts up very good. But its a dog. It has a gm style msd ,no vac advance. Looks like I may be looking for a new dist(lightening maker).I also have a msd box
I have a bone stock '70s slant six with a carter 1bbl. I've had the vac adv plugged into the carbs ported port. The port on my intake manifold had a bolt in it. I found a vac line insert for the manifold and am now running the vac adv there. My question is what do I plug into the ported vac on carb? Right now I just have it capped off.
You're dead right about efficiency as the measurement of power includes a very indicative thing called volumetric efficiency which means higher VE vs. Lower VE means one makes more power per drop of fuel than the other
Great video, question, should you not plug up your vacuum line when unplugging it from the vacuum advance canister when setting base timing? I may be wrong, but are you not creating a vacuum leak which causes a rough idle while you are setting base timing. When I disconnect my manifold vacuum advance when doing base timing, I always close off that pipe with a plug or screw to keep a smoother idle for accurate base timing. Then once set, I add the manifold vacuum back onto the canister which adds advance and smooths out idle and slightly increase rpm.
What about the "allen headed bolt" inside the vacuum advance for adjustment's. And the different degree mark's on arm and small block & big block difference, I made them there mistake's
It's nice to see another car guy who can curve a distributor and setup a vacuum advance, on the street, your just not that bright if you lock out your advance curve.
Most don't associate power and efficiency with economy..362cid small block chevrolet, david vizard camshaft, 10.8:1 cr full manifold vacuum advance and 26-28 mpg.. no b.s.😊
How do you tune an engine that a very long connecting rod like a 351m Ford? Would you add more total timing or advance initial? I'm running a HEI distributor on this engine and I have put a curve kit in it with the middle weight springs. Should I go ligh 23:03 ter on the springs? Also this engine is cammed and 4 barrel carb, 750 edelbrock. Stock heads that have been worked over. .020 head gasket and zero deck flat top forged pistons
REF 20:21, How does one get total mech advance of 34 degrees, at 1040 rpm, unless the mech advance has been locked out at 34? I thought he sets Max mech advance at 1800 rpm?
