I've been wanting to add a vacuum gauge inside my car for this same reason...to watch what happens with the vacuum readings as I drive. As handy of a diagnostics tool as it is under the hood, I can't see what's going on in real world applications (highway driving, accelerating, etc.) without one inside the car. Looks like I need to pick up some tubing and route mine inside. I can always disconnect the gauge and plug the hole when working under the hood. badddad/simple man/groberts.....I appreciate ALL the input, even if there are fundamental differences...it gives me options to try! I'll do some testing over lunch and let you all know how it goes.
Ok, things improved some when I backed off initial timing some. I still don't think it's "there" but I think I'm getting closer. Some of what I'm feeling at this point (all RPMs but still slightly stronger at 1500-2000rpm and smoothes out nice after 3000rpm) may be from old motor mounts along with a crappy single exhaust that has some drone to it.
You're going backwards here bud. Backing off the initial timing while simultaniously running ported/timed vacuum will only make for less NOx.. make it richer at idle than it already is.. and ruin your light throttle economy even moreso. I edited my previous post(#29) to provide more clearly defined/linked info for you to study up on in hopes that it may help you get further along here. Good luck with it all.
EGR? If EGR is incorrectly hooked up and open at idle it will require 4 to 5 turns to stay running. Unplug it.
Thanks for that awesome link and the info for timing numbers I can use. Mine doesn't have a ton of low-end power or any surging at this point (small carb), but it does run waaay better (when cruising or highway driving) after around 2500 where it smooths out and feels pretty peppy for a small carb. Mine never sees north of 4000 RPM. One problem I have when trying to measure total (initial+mechanical+vacuum) timing is that my balancer stops at 30°. I've made my own marks on the balancer based on the distances between marks using a flexible clothing measuring tape. I drove all day yesterday with ported vacuum hooked up to see how that felt and I noted all my settings so I can always go back to this as a re-starting point if needed. Cold starting was ok, warm starting less ok, low-end power was ok, 2500+rpm power was good. Today I'm going to be trying the manifold vacuum to see what results I get with the same amount of driving, cold and hot starts, power, etc.
I tried getting my car to run better running off of manifold vacuum but I couldn't get it to act any better or smooth things out any more than I had with ported vacuum. I retract what I said about getting closer....results from all these changes keep coming back to this same vibration. I know I'm not doing something right and it's KILLING me to not get this worked out on my own. I sure wish I could get a different carb on there to see if that would make a difference and clear things up so at least I would know if it was carb related. I know there's something I'm not doing right but sometimes you can't see the forrest because of all the trees.
Just me, but get you a Holley 2 bbl,(either a 500 or 350 cfm) bolt it on, set and tune it, then don't look back. You can pick these up secondhand, in nearly new condition for less than $100. Replace the powervalve and accellerator pump diaphram and 99% o fthe time, they good to go.
I've been looking at some of these along with some Autolite 2100's (1.21/1.23, both close to 350cfm) but can't find any at that price that look worth buying. Seen any lately?
Look on ebay. Every Holley I've bought in the past ten years, I bought only those that looked nearly new (including my 3x2 setup) There are lots of these around, bought by those who fail to learn to tune a Holley, or fail to run a fuel filter, or mistake an ignition problem for a carb problem. They get disgusted with them and sell em cheap. I pick em up for $100-150 and run em after changing the powervalve and acceellerator pump diaphram. These are the only two parts that will degrade over time if allowed to sit dry after running them (thin rubber diaphrams). Once you set a Holley, it stays set. And I'm talking for YEARS. Lots of guys love Autolites and swear by them, I just never had any luck with them. It may stem from the fact that they have not been manufactured for twenty+ years and most of them are far older than that. Old Holleys are trouble too, I learned long ago not to bother with them either.
HEY!!! I resemble that remark! Well, maybe...we'll see. Either way, I'm feeling a little lost at the moment. Maybe once I get my motor mounts in I'll feel better and get the other stuff figured out.
if you use a vacuum guage in conjunction with your timing light while tuning?.. you'll probably make much better progress here. The highest vac readings(at idle and cruise) will tell you when you're getting closer to right.
That's exactly what I do....and still this vibration will not go away! I even set my throttle to around 1700 where the vibration is at its worst and slowly adjusted my timing to see if it would make a difference....nope! Another thing I noticed is how much the vibration that is somewhat present at all RPMs smooths out when putting the car into gear. You can still feel it, and still it's pretty strong between 1500-2000rpm, but it isn't as "sharp" feeling. Not sure how to describe it.
I just talked with a guy named Bill who runs Ironhorse Classics which is nearby and he said: "Based on your comment of “stock” I am assuming that you are running hydraulic lifters. Has the adjustment on the valves been checked? If it is setup too tight the problem you are describing will occur. Additionally if they have been run for any length of time too tight the cam will wear quickly and you will see the symptoms you are describing." Sound right? Is there an easy way to check this?
Yea pull the valve covers and recheck the rocker adjustments. Might also want to verify that the balancer's outer ring hasn't slipped, throwing the engine's balance out of whack. Get #1 on TDC as close to at it's peak as you can, then look to see where the timing pointer is at in relation to the balancer's marks.
