Search results for query: *

So you admit that Chevy didn't do what you claim all GM did but you continue to beleive it. Wait! You don't beleive anything I've posted but you want me to tell you why your car is setup differently than the Chevy? :rofl: Keep repeating it, but that won't make it true. Post 100. Lots of...

re. post 85 "GM, who used MVA, could not meet the stricter HC emissions standards coming into effect in the late 60s & had to switch to PVA." So its been claimed. But evidence shows that Chevy had used a timed port before needing to meet 1968 emissions requirements...

re: post #85 Go and look at actual examples and documents to determine the facts just like the other gentleman did. The change in initial timing to reduce CO and HC to meet California and then Federal targets was not accomplished by changing the vacuum advance source. That's a myth.

Thanks for checking. Its always better to see for ourselves anyway.

Basically yes. The initial timing of a pre-emisions or non-CAP engine provides good power, and idles smooth and strong. The same engine with a CAP package used much less initial advance. The mechanical advance in the distributor makes up for that above idle rpm. Pick an engine in the mid-60s...

Not if the distributor's advance curve is set up right. Get a strong idle at 500 rpm with the non-CAP set up as mentioned earlier.

yea. That's the best. People can scroll down to the examples from the 1940s if in a rush, but really worth going back and reading Shrinker in depth.

Which is a good example of why technical decisions should not be based on opinon polls. :thumbsup:

If that's working out, then go with it. One issue that I've run into is particulalry noticible with an automatic transmission and a hot cam. Manifold vacuum is fairly low, idle combustion is on the cold and diluted side, and the idle mix is somewhat leaner. When the transmission is placed in...

Exactly. I said it was BIG Myth. Case in point. It's an easy conclusion to come to when just experimenting with switching to the the manifold source using a distributor designed for a retarded initial timing - as many of us have. Its actually a better method than just advancing the initial...

Not sure how you got to equating complete combustion in that context (you can go look at the booklets) is only for emissions reduction. Yes it is from a 1969 MTSC, but it says nothing different than 1959.

You can often use manifold vacuum to offset the the retarded initial timing on CAP/CAS set up. Its a lot simpler for many people than correcting the advance curve. However, since this thread is about myths, its a myth that ported vacuum has anything to do with emissions. This is a big myth...

That is not unique to Chrysler. It is a provision to address the occassions when the retarded initial timing used for emissions reduction does its job a little too well. Retarding the initial timing puts more heat into the cylinder walls and helps insure a hotter and more complete burn of the...

Idle is surprisingly high load, and before emissions concerns, fairly rich. The engine is producing very little torque at 500 or even 600 rpm. A percentage of that goes to overcoming friction. So best to think of it as a high load, somewhat rich and dense situation. As far as what a factory...

Pressure, Load, and Temperature in the chamber all effect the combustion development. Changing rpm changes the time available for the pressure to develop before its largely wasted (in the form of heat into the cylinder walls and out the exhaust). from Chrysler Master Technicians Conference...

You're describing general benefits of using vacuum advance. 1. Mileage Yes 2. Throttle response It might. Wouldn't guarentee it. 3. Cooler running Yes. Whether it will always be a noticible difference is another story. 4. Idle quality Depends on the distributor setup. If the advance...

In general, bad. However if you are going to buy his stuff, then in general you should follow his setup advice. However the info posted there was snipped and put together from a variety of pretty reconizeable sources. That's a big hint isn't it. This is one of those cases where you will...

:rofl:

Now your purposely taking that out of context. Yes. Absolutely many manufacturers used manifold vacuum as a way to overide the retarded initial timing that was being used for emissions control. The purpose of the late timing was to put more heat into the cylinder walls. The CTO overide was...

Fuel distribution at idle is due to the change in air pressure, which is quite high. However the velocity is low. AFR at idle should be relatively dense. Ironicly, it was the need to clean up the HC at idle that resulted in the somewhat leaner idle mixtures which too many hot rodders believe is...

For example, from 1959 (Session 136) of the Chrysler MTSC. In fact, its interesting to note that on some early Clean Air Packages (CAP) Chrysler did use a manifold vacuum connection to the vacuum advance. This was to insure the leaner closed throttle mixtures were given enough advance to burn...

The evidence doesn't support those claims. All you have to do is look at various pre-emissions shop manuals and cars, especially Chrysler products. You could also take a look at the published research and testing in fairly well known books (well known by people who made engines for cars...

Some are not adjustable, some use washers, most use an allen key. See first part, section b How To Limit and Adjust Chrysler Vacuum Advance Cans

Should have mentioned that one of the 'secrets' of part throttle power is the fuel mixtures get leaner. They only need to go richer again when approaching full throttle. That's the power valve opening point (or rod step up in Carter)

Correct. The tricky part is the part throttle loads. Too much vacuum advance under light load can feel like 'trailer hitching' but that's rare. Don't know if you went to the linked thread but this is an example of how turning the adjuster counter clockwise shifted the vacuum advance...

Yes, agreed. The manufacturer does not claim or mark it DOT. But it meets ECE. It does seem stupid. Especially because the way it was first told to us, by very enthusiastic promotors of the Cibie's and other top quality E-code lamps was that the ece standards were better. But now we know a...

Great cutaway view. Link added from the "How to adjust" article

What you're saying is basically right. You may be OK with Vixen. Here's how it works. When the car was made the manufacturers used parts that met standards set out in federal regs and industry standards. Fed regs for safety are Federal Motor Vehicle Safe Standards (FMVSS) which often also...

JWSpeaker and Trucklight's LED lamps are the only ones I've read about that seem to keep all the light in the acceptable zone. Within the lit area, there are visble patterns. "Hilldweller" did a bunch of semi-scientific comparisons with photos and light meter. Jeepforum Headlight Shootout -...

The FBO plates require a lot of fiddling or the curve is too much at low rpm and then gets cut off too early. With a distributor machine and knowledge its easier to do that (use the plates and then change or adjust springs to get it right ). Easier for most people looking for more performance...