uh oh, stumbling, sounds like a diesel

[HotRodPC]

Yes, Ported is what Driver and I are suggesting. Rich is saying manifold vacuum.

I never knock anyone on their opinion on the matter. Both can be right, depending on how you want your vehicle to run. And if more would jump in on the topic, you'd see it's about a 50/50 ordeal. You'll get 100 to say Manifold, you'll maybe get 101 to say Ported. I just say if you're going to jump into the conversation and voice your vote, then be prepared to explain why you think the way you do as Rich, Driver and I did.

 

[Driver4r]

That makes sense to me, if you add timing on newer engines at cruise you can really help mpg.

So to do that you would have it plugged into a ported source?

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off of idle has to be timed. And any engine you can add more advance to get more VE. So long as you dont over-advance it. Theres a fine line. And when setting your timing, let it warm up, and make sure you can still start it. So much advance will cause the engine to kick against the starter when cranking over. If this happens, back off the distributor untill it will spin without to much hassle.

Now if we start talking aftermarket ignition, then we can start dicussing timing controllers, they will retard it to start then advance it back to where it was. You can also set them to keep advancing more with more throttle.

 

[350runner]

Go ported! Just cause it sounds better at idle lol

Sent from the dust in front of you!

 

[HotRodPC]

Going ported also helps in not having an engine dieseling or run on problem when you shut it off if you shut it off at idle speed as most people do.

 

[rich weyand]

From a retired GM ignition systems engineer:

"Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it."

Read the whole article here. Or not. You probably don't need any more performance anyway.

http://chevellestuff.net/tech/articles/vacuum/port_or_manifold.htm

 

[Driver4r]

The Q-jet showed up in the later 60's(1966), so since then, things have been vacume controlled. Emissions didnt really hit untill 71. Then in the later 70's the "cat" was equiped to vehicles, then the 80's is when it really got bad.

But from a performance point of veiw, timed is better. it doesnt mess with your initial timing.

IMO, the ls6 was one of the greatest engines to be installed in production vehicles, and it just barely made the cut-off date. It was rated @450hp, but underrated cause of inssurance, and in reality it made more like 550-600@5600.

 

[rich weyand]

I know all about 1960s cars. That's what I learned to drive on. The performance went south on January 1, 1968. My dad bought a 1968 Ford Country Squire with a 390 quad in late 1967, and specified that it be built prior to the changeover on January 1 to the new rules or he wouldn't take it. The new rules: ported vacuum and AIR pump. He took delivery 2 days before Christmas in 1967.

"Things" have been vacuum controlled since Studebaker brought out the vacuum advance in 1930.

But don't bother to try it. You don't need the performance. You really don't.

 

[Driver4r]

I know all about 1960s cars. That's what I learned to drive on. The performance went south on January 1, 1968. My dad bought a 1968 Ford Country Squire with a 390 quad in late 1967, and specified that it be built prior to the changeover on January 1 to the new rules or he wouldn't take it. The new rules: ported vacuum and AIR pump. He took delivery 2 days before Christmas in 1967.

"Things" have been vacuum controlled since Studebaker brought out the vacuum advance in 1930.

But don't bother to try it. You don't need the performance. You really don't.

Im sorry ford bent over the barrel so early. Hope they atleast got a jar of lube befor the government raped their ass.

But GM didnt really start limiting performance untill 71. Untill then they were still building FOR performance.

 

[rich weyand]

GM put AIR pumps and ported vacuum on beginning in 1968 as well. Ford and GM both built for performance through 1970, Chrysler through 1971, before they reduced compression ratios for unleaded gas. But AIR pumps and ported vacuum began on all Big Three cars by law on January 1, 1968, and a lot of guys buying those monster cars, like the 70 Chevelle SS454 and the Buick GS Stage 1, the Mopar Hemi and 440 6-pack, and the Ford 429 Super Cobra Jet and 427 side oiler, all ripped that **** off and retimed the vehicles properly. I know. I was there. We used to disassemble the AIR pumps, machine the vanes off the impeller, and put them back on to pass visual inspection.

Other guys left the cars stock and would brake torque the car to get it off timed vacuum and onto manifold vacuum to get a decent launch. Before timed vacuum, you didn't have to: just push the go button and hold on. No off-idle stumble to worry about.

Trucks didn't get all that stuff until later. When my dad next bought a new vehicle in 1975, he bought a truck to get around all that. An F-250 with a 460 Lincoln engine, but that's another story. (That's why I'm a Chevy man: my dad owned Fords.)

Anyway, I just recommend to anyone reading this thread to not listen to any of us. Go ahead and try it both ways. For each, time it up with as much advance as it will take without pinging under load. Drive it and see which you like better. That's what I did, and my reaction was, huh, forty-five years and nothing's changed, and I put it back on manifold vacuum.

 

[rich weyand]

i think I will start a new thread for my vacuum line questions......

i might also try manifold vacuum. not sure where it is hooked up now, but at idle if i disconnect the port it has no effect, so must be ported, or nothing at all. who knows on this truck!

still unsure of where to start with the timing, 8 btdc, 4btdc?

On a 305? Start with 12 or 14 BTDC, and then keep dialing it up until it pings. SBCs LOVE advance. Keep advancing it until it pings under load (like pushing up a hill at low speed with your foot in it), then back off two degrees. You'll probably end up with 16-20 degrees of advance. Together with the centrifugal advance (20 degrees on the stock disti), that will make 36-40 degrees total timing.

 

[350runner]

Im sorry ford bent over the barrel so early. Hope they atleast got a jar of lube befor the government raped their ass.

But GM didnt really start limiting performance untill 71. Untill then they were still building FOR performance.

LAMO! DAM. LOL

Sent from the dust in front of you!

 

[350runner]

GM put AIR pumps and ported vacuum on beginning in 1968 as well. Ford and GM both built for performance through 1970, Chrysler through 1971, before they reduced compression ratios for unleaded gas. But AIR pumps and ported vacuum began on all Big Three cars by law on January 1, 1968, and a lot of guys buying those monster cars, like the 70 Chevelle SS454 and the Buick GS Stage 1, the Mopar Hemi and 440 6-pack, and the Ford 429 Super Cobra Jet and 427 side oiler, all ripped that **** off and retimed the vehicles properly. I know. I was there. We used to disassemble the AIR pumps, machine the vanes off the impeller, and put them back on to pass visual inspection.

Other guys left the cars stock and would brake torque the car to get it off timed vacuum and onto manifold vacuum to get a decent launch. Before timed vacuum, you didn't have to: just push the go button and hold on. No off-idle stumble to worry about.

Trucks didn't get all that stuff until later. When my dad next bought a new vehicle in 1975, he bought a truck to get around all that. An F-250 with a 460 Lincoln engine, but that's another story. (That's why I'm a Chevy man: my dad owned Fords.)

Anyway, I just recommend to anyone reading this thread to not listen to any of us. Go ahead and try it both ways. For each, time it up with as much advance as it will take without pinging under load. Drive it and see which you like better. That's what I did, and my reaction was, huh, forty-five years and nothing's changed, and I put it back on manifold vacuum.

At what point did dad get tired of returning home on foot?

Sent from the dust in front of you!

 

[HotRodPC]

Yeah, I'd have to agree, all the auto makers took hits in the late 60's. Even GM, if they didn't yet have the plumbing drilled and tapped for the AIR in the heads, they at least had the meat there to do it anticipating it was right around the corner. This is why you can actually gain alot from some heads just by grinding out the smog bumps that are there and not used. Olds big block for certain that I'm aware of. There's alot of that goes into auto history that we don't know about. Point is, Olds BBs didn't have the AIR YET, but they were still reduced by it because it was built into the head ports and we didn't see it, but it was there the whole time. Also, emissions devices did come on cars in CA as early as 66. And the ones that didn't get it, it was required to be retrofitted in the early 70's as far back as 66. So in 72 or 73, maybe even later than that, you had to take your car to a shop and pay to have a TVS (Temp Vac Switch) put into your upper radiator hose, like a splice, and what it did, was kept timing from being able to be advanced by vacuum until the motor had reached at least 160 degrees. Of course once certified and got your windshiled sticker, just bypass the vac hose and close the hood.

 

[rich weyand]

He switched back to Chevies after the F-250. Lessee. He had a 1936 LaSalle. Coupla Kaisers. 55 Chevy B210 (2-door wagon, not Nomad). 63 Ford wagon with a 289. 68 Ford wagon with a 390. 75 F-250. Then he went to Impalas, I think. I was out of the house in 1971, so I don't recall much of the later cars.

The 68 wagon was a pretty nice car. Never stranded us that I remember, though the 63 did. Twice. The 68 looked really cool, and the 390 was a hot rod before pollution controls kicked in. Lessee. Yep, here's a pic of one in the same ubiquitous late-60s green. He didn't have the carrier, though. Cleaner lines without it. Was a whale at the helm though: there was a half-second delay before she would heel over, and the body roll was silly. He let me take it to prom in '71.

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[rich weyand]

Yeah, I'd have to agree, all the auto makers took hits in the late 60's. Even GM, if they didn't yet have the plumbing drilled and tapped for the AIR in the heads, they at least had the meat there to do it anticipating it was right around the corner. This is why you can actually gain alot from some heads just by grinding out the smog bumps that are there and not used. Olds big block for certain that I'm aware of. There's alot of that goes into auto history that we don't know about. Point is, Olds BBs didn't have the AIR YET, but they were still reduced by it because it was built into the head ports and we didn't see it, but it was there the whole time. Also, emissions devices did come on cars in CA as early as 66. And the ones that didn't get it, it was required to be retrofitted in the early 70's as far back as 66. So in 72 or 73, maybe even later than that, you had to take your car to a shop and pay to have a TVS (Temp Vac Switch) put into your upper radiator hose, like a splice, and what it did, was kept timing from being able to be advanced by vacuum until the motor had reached at least 160 degrees. Of course once certified and got your windshiled sticker, just bypass the vac hose and close the hood.

Back in the day, we got expert at ripping all that stuff off, or defeating it while maintaining appearances for visual inspection, and reversing the engines to 1967 setup. It was all silly anyway. PVC valve gives you 90% of the pollution benefit. Throw in vent lines on the fuel tanks and you have cleaned things up a lot. TBI and the better gas mileage later on helped some more. Most of the other stuff was nonsense that trashed performance for little benefit.

Unleaded gas is a different story. Releasing 7 million tons of a neurotoxin into the atmosphere was probably not a good idea.