Carburetor choice

[rumblefish360]

Well if it starts easy and runs well ……

Your guy could have just gave it a race like advance and said set max timing at 34-36 & your GTG! How fast the advance comes in is a mystery though.

In my younger days…. (OH Boy!)

We would disconnect the vacuum advance, loose a advance, put a timing light on it and rev it until the advance stopped. It was a very quick advance and we just twisted the distributor up a lot.

It worked for us then.

 

[rumblefish360]

I didn't say it wasn't heavy; I said;
(Your car is not that heavy.)
lol

I guess it is all in the way you say it… lol ext can be hard sometimes. Remember that joke?

A&E, time well spent (Not wasted time)

Or

A&E, time, well, spent. (Wasted time)

 

[texas360]

Well if it starts easy and runs well ……

Your guy could have just gave it a race like advance and said set max timing at 34-36 & your GTG! How fast the advance comes in is a mystery though.

In my younger days…. (OH Boy!)

We would disconnect the vacuum advance, loose a advance, put a timing light on it and rev it until the advance stopped. It was a very quick advance and we just twisted the distributor up a lot.

It worked for us then.

I really need to learn ignition a little more in depth

 

[rumblefish360]

It’s not that hard really.

 

[318willrun]

I really need to learn ignition a little more in depth

Some have a locked distributor, so it starts, idles, and runs at total timing. If your distributor isn't locked, then you are using initial timing, but that won't change anything when you are up in the rpm's and racing it. It will matter at low RPM's and leaving a stop sign.

 

[texas360]

I don’t believe it locked. I jut think springs have been lightened and vaccuun advance had been disabled.

 

[Super-Cuda]

I really need to learn ignition a little more in depth

… And AJ/FormS commentary is a great place to start! He has given you an in-depth, educated viewpoint from which to start.
He wrote a response to you of about 3/4 of a page on how to properly tune your car . I think it's fantastic that someone takes the time to do that! His response is very well thought out and comes from years of experience. There is a wealth of experience on here and most are only too willing to share it . I've learned a ton on here and my car runs way better because of the advice I've received. Stick with it, try the suggestions given, if you Fu#k up, just start again. You said in a previous comment you wanted to learn, well you've come to the right place for an education!!

Cheers!!

 

[thesiren74]

My 360 liked 18° initial timing and 35° total timing you need to limi timing in the distributer either welding the slots or easier buy the plate.

 

[AJ/FormS]

For street;
if you do not run the V-can, you are just cheating yourself out of a tremendous amount of free torque, and the potential to make fantastic fuel-mileage.

The curve you build inside the D with the advance weights and springs will NEVER be correct, for anything but running at WOT, and mostly only correct after about 3500rpm; no matter how perfect you make it.........
At all other throttle settings and at almost all rpms below 3500 or so, the curve is dead, dead, DEAD wrong. And is is ALWAYS retarded!
It is the job of the Vacuum Advance mechanism, to try, try, TRY, to get closer to ideal, for more of the time.

Most engines make BEST power, with the Timing adjusted to cause the peak cylinder pressure to be imparted to the crank at a very specific point of the crank's rotation. This is usually about 25 to 28 degrees AFTER TDC. All the timing controls are designed to achieve that, by starting the fire early enough. Under certain conditions, your engine might like over 60 degrees of lead. other times, maybe just 10*. If your D has no vacuum-advance, this is impossible.
For a race engine this is no big deal, because it has just two modes of operation, namely WOT and idle.
But for a streeter, this is not true.

For example, cruising at 65mph-2400 rpm, your engine might be wanting high forties to mid fifties, or more, for Cruise-timing. It wants it, to keep cool, not burn your headers up, and so you can lean it out, and thus get some decent mpgs.

Around town; accelerating normally, the engine might like timing variously between 55 and 35, to make the torque that you are looking for. But if the D is only supplying 25/30, your performance will be sluggish, and she will suck gas, because your right foot is always deep into the carb to find the power to make you happy, AND, you will probably always be in one gear lower from where you should be.

Why is this?
This is because the Peak Cylinder Pressure, is never achieved (until after 3500 at WOT) and what is being made, is always late and chasing after the piston.
How much power is being lost, at these Part-Throttle settings?
IDK, but I'll guess your 360 will feel like a well-tuned 318 down there.
If you have a manual trans;
this is doubly important because there is no Torque-Multiplication of the TC, nor slip, so the engine is married to the tires, at whatever speed they are going.
At 35mph with 3.55s, in 1.40/ third gear, My 367 is sitting at 2200rpm . So cruising around, MY engine is getting 45 degrees and loving it. She's purring right along all sneaky-like being smooth and quiet. But as I lay on the throttle, bit by bit, 22 of those will drop out, to prevent detonation. Finally, at WOT and still 2200, the timing is 23*, nice and safe. A split second later, the tires may slip and if they do, all hell will break loose, lol.
What's yours getting?

 

[j par]

Sir, everyone uses initial timing. The initial timing is where the distributor is set when the engine fires and at very low RPM. After a certain RPM, centrifugal force moves on the springs and the counterweights inside the distributor to produce additional timing. You don't have a vacuum advance, so that will not play a part in your timing. The initial timing plus the various timing increases due to centrifugal force will equal the total timing you mentioned of 34-36. There is a lot of performance tuning available through the distributor, so that is another avenue for you to optimize your vehicle.

Everyone?...

 

[mopardude318]

For street;
if you do not run the V-can, you are just cheating yourself out of a tremendous amount of free torque, and the potential to make fantastic fuel-mileage.

The curve you build inside the D with the advance weights and springs will NEVER be correct, for anything but running at WOT, and mostly only correct after about 3500rpm; no matter how perfect you make it.........
At all other throttle settings and at almost all rpms below 3500 or so, the curve is dead, dead, DEAD wrong. And is is ALWAYS retarded!
It is the job of the Vacuum Advance mechanism, to try, try, TRY, to get closer to ideal, for more of the time.

Most engines make BEST power, with the Timing adjusted to cause the peak cylinder pressure to be imparted to the crank at a very specific point of the crank's rotation. This is usually about 25 to 28 degrees AFTER TDC. All the timing controls are designed to achieve that, by starting the fire early enough. Under certain conditions, your engine might like over 60 degrees of lead. other times, maybe just 10*. If your D has no vacuum-advance, this is impossible.
For a race engine this is no big deal, because it has just two modes of operation, namely WOT and idle.
But for a streeter, this is not true.

For example, cruising at 65mph-2400 rpm, your engine might be wanting high forties to mid fifties, or more, for Cruise-timing. It wants it, to keep cool, not burn your headers up, and so you can lean it out, and thus get some decent mpgs.

Around town; accelerating normally, the engine might like timing variously between 55 and 35, to make the torque that you are looking for. But if the D is only supplying 25/30, your performance will be sluggish, and she will suck gas, because your right foot is always deep into the carb to find the power to make you happy, AND, you will probably always be in one gear lower from where you should be.

Why is this?
This is because the Peak Cylinder Pressure, is never achieved (until after 3500 at WOT) and what is being made, is always late and chasing after the piston.
How much power is being lost, at these Part-Throttle settings?
IDK, but I'll guess your 360 will feel like a well-tuned 318 down there.
If you have a manual trans;
this is doubly important because there is no Torque-Multiplication of the TC, nor slip, so the engine is married to the tires, at whatever speed they are going.
At 35mph with 3.55s, in 1.40/ third gear, My 367 is sitting at 2200rpm . So cruising around, MY engine is getting 45 degrees and loving it. She's purring right along all sneaky-like being smooth and quiet. But as I lay on the throttle, bit by bit, 22 of those will drop out, to prevent detonation. Finally, at WOT and still 2200, the timing is 23*, nice and safe. A split second later, the tires may slip and if they do, all hell will break loose, lol.
What's yours getting?

What, in your opinion would be the best vacuum advance distributor available? Cost not a factor. I currently have an MSD pro billet mechanical, with digital 6 plus box. I’m thinking a VA distributor would be better for my street driven small blower equipped small block.

 

[AJ/FormS]

What, in your opinion would be the best vacuum advance distributor available?

Sorry man, I have never bought an aftermarket D so I cannot say.Nor have I ever tuned a blower-equipped engine.
Honestly, the possibilities are mind-boggling, and I have zero experience for this combo.

But I can see that the VA equipped D could be a benefit to your street combo, if you are now limiting your maximum Power-Timing, to some sub-optimum number, as compared to a Normally-Aspirated engine..

Like; if your boost does not begin until 3000, but your stall is 2200, then yeah, the VA could bring up the low-rpm torque, and especially it could help with fuel-economy.
But if your stall is 3000 or more, I can't see it being of much/if any, help, except again with fuel economy.
But if your boost begins both at low-rpm, AND at light throttle, then I'd say forget the VA............

And if you have iron heads, I suppose you'd have to be real careful to avoid detonation at Part Throttle.

 

[318willrun]

For street;
if you do not run the V-can, you are just cheating yourself out of a tremendous amount of free torque, and the potential to make fantastic fuel-mileage.

The curve you build inside the D with the advance weights and springs will NEVER be correct, for anything but running at WOT, and mostly only correct after about 3500rpm; no matter how perfect you make it.........
At all other throttle settings and at almost all rpms below 3500 or so, the curve is dead, dead, DEAD wrong. And is is ALWAYS retarded!
It is the job of the Vacuum Advance mechanism, to try, try, TRY, to get closer to ideal, for more of the time.

Most engines make BEST power, with the Timing adjusted to cause the peak cylinder pressure to be imparted to the crank at a very specific point of the crank's rotation. This is usually about 25 to 28 degrees AFTER TDC. All the timing controls are designed to achieve that, by starting the fire early enough. Under certain conditions, your engine might like over 60 degrees of lead. other times, maybe just 10*. If your D has no vacuum-advance, this is impossible.
For a race engine this is no big deal, because it has just two modes of operation, namely WOT and idle.
But for a streeter, this is not true.

For example, cruising at 65mph-2400 rpm, your engine might be wanting high forties to mid fifties, or more, for Cruise-timing. It wants it, to keep cool, not burn your headers up, and so you can lean it out, and thus get some decent mpgs.

Around town; accelerating normally, the engine might like timing variously between 55 and 35, to make the torque that you are looking for. But if the D is only supplying 25/30, your performance will be sluggish, and she will suck gas, because your right foot is always deep into the carb to find the power to make you happy, AND, you will probably always be in one gear lower from where you should be.

Why is this?
This is because the Peak Cylinder Pressure, is never achieved (until after 3500 at WOT) and what is being made, is always late and chasing after the piston.
How much power is being lost, at these Part-Throttle settings?
IDK, but I'll guess your 360 will feel like a well-tuned 318 down there.
If you have a manual trans;
this is doubly important because there is no Torque-Multiplication of the TC, nor slip, so the engine is married to the tires, at whatever speed they are going.
At 35mph with 3.55s, in 1.40/ third gear, My 367 is sitting at 2200rpm . So cruising around, MY engine is getting 45 degrees and loving it. She's purring right along all sneaky-like being smooth and quiet. But as I lay on the throttle, bit by bit, 22 of those will drop out, to prevent detonation. Finally, at WOT and still 2200, the timing is 23*, nice and safe. A split second later, the tires may slip and if they do, all hell will break loose, lol.
What's yours getting?

I have never found "tremendous torque" in a Vacuum advance. In fact, I've really never found any more power by feel and all my cars are street cars. Regardless if stock or a built small block, I've not found it. Some claim 1 mpg on fuel, but I've not sought fuel mileage so badly on my classics to hunt for that last mpg. I'm sure it helps because the factory spent the $$ to put them on the cars. Tremendous amount of torque would be like, 40 ft lbs or 60 ft lbs of torque difference ???

 

[j par]

I have never found "tremendous torque" in a Vacuum advance. In fact, I've really never found any more power by feel and all my cars are street cars. Regardless if stock or a built small block, I've not found it. Some claim 1 mpg on fuel, but I've not sought fuel mileage so badly on my classics to hunt for that last mpg. I'm sure it helps because the factory spent the $$ to put them on the cars. Tremendous amount of torque would be like, 40 ft lbs or 60 ft lbs of torque difference ???

I'm shocked there's still people who read his ramblings LOL... A tremendous amount of hot wind LOL...

 

[448Scamp]

Everyone?...

Everyone except anyone who locks the timing curve out uses initial.

 

[AJ/FormS]

Did you do any tuning?
Did you get it up to 60 degrees or more?

In my manual-trans car, which is geared at 65mph =2240rpm; every 3 degrees added at 60 mph, will produce a 1 to maybe 2 mph speed difference, beginning at about 50 degrees, and going to 63* the highest I have tried. With the more speed from the first 3* to less speed on the last.
What this means, of course is that to maintain my speed, I get to close the throttle. And with the more closed throttle, I get to take fuel out, and thus decrease my fuel consumption.
Now, per the math, this is 13* additional timing, or 4 increases of 3*, and so a speed increase of perhaps 6/8mph; that's about 10/12%. I would and do, call that tremendous.
Your results may vary.
After all, I run an 11/1, 367 with a Commando/GVod manual trans, and a 230/236/110 cam, and my cranking cylinder pressure is already 177psi or more.

But if you are cruising with 3.55s then your rpm is likely to be about 2900 with 27s and at zero-slip ; say 3020 at 4% slip. At this rpm, with a good working VA, you might already be up to near 50* of timing. The efficiency of the engine at this rpm is very significantly better than at 2240 , and it may not want much more than 50 to 56. And so it will be very difficult, if not impossible, to see any difference, unless you can change the timing on the fly.

As for Torque at Part Throttle, the only time the VA is working; You have to be able to adjust the timing while driving, to experience the difference. Otherwise you are just driving deeper into the throttle. AND, you may not see a difference on a vacuum gauge; the divisions are just too gross.

The goal of all timing devices is to put the peak cylinder pressure at or near 25 to 28 degrees after TDC. My Vcan has been modified to bring in 22*. If at 2240rpm this takes 56 degrees, and my V-can is at 22*, then the rest, 34* has to come from the Power-Timing. Since at 2240 rpm, my mechanical is only 24, I'm 10* short. But, I have a dash-mounted, dial-back, timing box with a 15* range............. so I'm good to go.
So unless you have played with numbers this high, on the fly, I'm not surprised by your results.

Here in Manitoba,
our 87E10 gas is up to 1.39C, per liter yesterday.
=5.06 per USg in Canadian Dollars
My Barracuda with a 223/230/110 cam made over 50% better freeway mpgs than city mpgs and on one certain test-trip made nearly double. Now granted,not nearly all of that was due to the VA; never-the-less, I am talking 10 mpgs or more difference. With a 66 liter tank (~14gallons Imp), that comes to 140 additional miles per tank, at the very least; that cost me only time in the tuning, to get. How much of that is ONLY in the VA I cannot say, butum; I'm still calling it; "tremendous".....

 

[rumblefish360]

You’re delusional when it comes to the “tremendous” amount of torque.
However, if your mileage hunting, it n a nutshell, what your trying to say without the long blowing post is;

“The most advance with the smallest amount of throttle opening.” (That the octane can handle.)

 

[Super-Cuda]

I'm shocked there's still people who read his ramblings LOL... A tremendous amount of hot wind LOL...

Well J-Par,

I don't know if these are ramblings... 318will run has the time slips to prove how well his combinations work! I think its very impressive what he does with an engine a lot of people think can't be made to perform!

 

[j par]

Well J-Par,

I don't know if these are ramblings... 318will run has the time slips to prove how well his combinations work! I think its very impressive what he does with an engine a lot of people think can't be made to perform!

Well AAndrews,

He was quoting AJ and that was who I was talking about...
Gotta love the internet the misunderstandings fly like the wind...

 

[rumblefish360]

So like misunderstandings, so do Assumptions.

@texas360 This below quote & ….

My 360 liked 18° initial timing and 35° total timing you need to limi timing in the distributer either welding the slots or easier buy the plate.

That’s normally a good area. Give or take….
It’s worth playing around with it to try & find a little something. Mileage settings and power settings for the track can only be combined so much.
It is possible to strike a good balance.

A local guy I know asked me how to get more power out of his 318 Duster. (Sporting a ‘78-318) I asked what he did for timing. It was @ stock settings. I’ll just fast forward to the end area where I cautioned him on using a race advance curve. He went there anyway. The engine started to knock. The move was made from 87 to 89 & the knock went away. So I asked him a few questions.
Does it feel faster, stronger? A resounding YES!
What did it do for mileage? I’m waiting on an answer….
I do not know how total with the vacuum hooked up.

 

[Super-Cuda]

Well AAndrews,

He was quoting AJ and that was who I was talking about...

Well AAndrews,

He was quoting AJ and that was who I was talking about...
Gotta love the internet the misunderstandings fly like the wind...

No problem !

But... First thing I'm doing tonight is hooking up my Vac advance and following some of AJ's suggestions. Although my car is performing well, it eats gas! At the price we pay here in NFLD , Canada, $1.70 per litre, that's $6.43 a US Gallon!!

I'll be the Guinea pig ! I've got nothing to lose, it doesn't cost me anything but some time and I may very well pick up some significant fuel savings. I've been following discussions about Vac Advance for a while now and even read in this months Mopar Action Mag, an article by Richard Ehrenberg about why every street car should have vac advance hooked up. So, I'm going to proceed and I'll post the results. Presently have a Magnum 360, airgap intake ,Eddy aluminum heads, 10.1 compression, holly 770 Street Avenger carb, 7500 Hi-Rev electronic distributer and ECM, TTI 2.5 Exhaust, 3.91" Sure griop 4-speed 2.66 1st gear, Scorpion roller rocker setup, 1.6 . I'll post cam specs later.

I very open to suggestions, comments, Etc. so fire away!!

Cheers!!

 

[AJ/FormS]

Without a working advance, your Part Throttle timing Is
guaranteed
to be seriously retarded.
Firstly, it is retarded by the fact that your advance curve has a beginning point set up to achieve an ending point, that is intimately chained to the Power-Timing.
Secondly, it is retarded by the fact that you had to limit it to what your engine can handle at WOT.
Thirdly, it is retarded because it is impossible to build a timing curve to satisfy the Part Throttle requirement.

At 2400 rpm and at Part throttle, your engine may be asking for 48 to 56 degrees, (or more with open chambers and low-compression).
But your curve can probably only supply 20 to 28 degrees. So, the timing is already about 28 to 36 degrees retarded, for Part Throttle operation. EVEN WITH A MODIFIED CAN, she will still be retarded!
The peak pressure for optimum performance needs to be at or near 25/28* ATDC. But as shown, your peak may not occur until 56* ATDC. The pressure will NEVER reach it's maximum potential, because the burn started 28/31* late and is finishing at 28/31* late, chasing after the piston which the crank is
already YANKING down the hole, costing you power and fuel right there.
Now; in the past, I told you guys how I was able to get 32 mpgUSG out of my 10.7 Scr 367/3+1 A833/ and GVod/ with 3.55s.
And some to most of you, laughed at the claim.
And now, you poo-poo my use of the word "tremendous".
It is obvious to me, that you poo-pooers have no understanding of ignition timing past the determination of your Power-Timing. And even that, most of you are guessing at.
Some of you are thinking that the V-can is there strictly for fuel-economy purposes. But that is only part of it. I challenge you to Tee a vacuum gauge on your spark port, and map out what the can is doing exactly, then drive around for a few hours.
I'm guessing that my engine spends well over 80% and closer to 95% of it's time with a lot of vacuum showing on that signal line.
With my maps I can tell you what timing my chambers are seeing, at every rpm and load setting. And that knowledge, friends, is power, lol. But hey, I'm guessing that not everyone of you needs that power, or economy.
Now,, just suppose
that your car requires 20 hp to cruise at 35 mph. With 3.23s, and in 1.45 Second gear, that will be about 2150 rpm. So the torque requirement is 49 ftlbs. And you adjust your gas pedal to get it. Your sparkport should be pulling enough vacuum to max out your Vcan. Suppose that while holding the throttle right there, you dump the Vcan, all 22/24 degrees of it. Suppose that action dumps 4 or 5 ftlbs. and your car slows down, so you have to gas it back up, to continue cruising at 35 mph.
Now; that loss of say 5 ftpounds while not sounding like much, is in fact; 5/49= 10%, so ......... If you can't see that as being "tremendous", IDK, maybe I used the wrong word for you.
But remember; your timing at 2150 by the distributor is ALREADY retarded for this rpm and load setting, as explained above; so no wonder you suffer with the lousy fuel economy.
Add to that a possible very low cylinder pressure, the product of a late closing intake valve, and a low Scr, well, some of you call that doggy, lazy, or one guy used an Aussy phrase that I cannot recall.

Second challenge; install a scanner on your modern EFI grocery-getter car, to display timing and load. Then go drive it at Part Throttle and cruising, just to see what the factories are doing with computer-controlled timing..........
Com'on you naysayers, I'm rooting for you.
Contrary to most guys experience, it is possible ha achieve some degree of BOTH power and economy, and I suggest this carries up to and a lil past 1hp per cube; so with a 360, that would be to 360 hp. With a 273, perhaps 273hp; and so on.
After that number, the engine is biased more towards performance, and by the time you get to say 235/240 degrees of intake duration, your engine is spending less and less time at high enough vacuums and low enough throttle settings, to properly use the sparkport. I found that the 230/237/110* cam in my combo, is pushing the envelope.
Good luck, y'all.

 

[AJ/FormS]

For those that may have missed it; I know I almost did:
AAndrews said;

But... First thing I'm doing tonight is hooking up my Vac advance and following some of AJ's suggestions. Although my car is performing well, it eats gas! At the price we pay here in NFLD , Canada, $1.70 per litre, that's $6.43 a US Gallon!!

I'll be the Guinea pig ! I've got nothing to lose, it doesn't cost me anything but some time and I may very well pick up some significant fuel savings. I've been following discussions about Vac Advance for a while now and even read in this months Mopar Action Mag, an article by Richard Ehrenberg about why every street car should have vac advance hooked up. So, I'm going to proceed and I'll post the results. Presently have a Magnum 360, airgap intake ,Eddy aluminum heads, 10.1 compression, holly 770 Street Avenger carb, 7500 Hi-Rev electronic distributer and ECM, TTI 2.5 Exhaust, 3.91" Sure grip 4-speed 2.66 1st gear, Scorpion roller rocker setup, 1.6 . I'll post cam specs later.

I very open to suggestions, comments, Etc. so fire away!!

Cheers!!

My combo is, so far, practically identical to yours.

 

[thesiren74]

So what carb is everyone recommending again?

 

[AJ/FormS]

The one you already have I think was the consensus.

But as for me, it's hard to beat a 750DP for ultimate power and ease of tuning the basics. But it is as good as impossible for me to achieve any fuel-economy with them. or any Holley really; they seem to all be quite rich on the low-speed circuits. Well ,maybe just the old ones that I am used to seeing.

If you need the cruising-economy, a metering rod carb is hard to beat, but they don't work all that well on a big-cammed engine.

The ideal carb set-up is probably a 6-pac, but consider the expense!

For you; a spreadbore is probably as close to ideal as it can get. Consider the Goggle-valved Demon, but ideally you would install it on a matching intake.