Posts by michaelj
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668 Posts
Amen!
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668 Posts
I've heard you saying this repeatedly. I can't help but think that if your engine isn't playing "by the book" than there is something else going on. My guess would be that you should look for a vacuum leak, as that can really screw up idle and economy.
Just a random thought. I hope you find the reason. When you do, please post it for all.
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No apologies necessary. In fact it is refreshing to talk to someone that really wants to understand. I, too, want to understand more than I do, which is why this thread is of interest to me. I am by no means and expert. I learn by trying and talking to others more knowledgable and by reading.
If I were you, I would first do some diagnosing. Have you hooked up a vacuum gauge to your idling engine? I can tell you a lot. Read these:
gregsengine.com/using-a-vacuum-gauge
And From an ASE Study Guide
There was one really amazing page that I'm still looking for...
A simple vacuum test could reveal a wealth of info that you had no idea about. I'm assuming of course that you have a vacuum gauge. You may be able to rent or borrow one from a big box auto parts store for little to no $$$. Worth a try and it could definitively reveal issues for you.
After this initial test to see where you're at, the next thing I would do is to reset everything on your engine to factory specs (or if modified, recommended manufacturers' settings.) That means timing set back to factory, then idle, then idle mixture, then idle again. Recheck timing and test drive. If all feels good, then switch to your new manifold vac setup and do it all over again. At the very least, you're learning to live with/work on your engine. My Chevelle and El Camino are basically stock, so a baseline reset is easy for me to reproduce. I'm not sure what happens with "other" carbs/cams/distributors are introduced to the mix.
I hope this helps you at least get started. I'm sorry I'm not a more authoritative knowledge base for you. I would love to know how you do.
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As I'm coming to understand, THAT is the manufacturer's difference. I purchased a Moroso unit that the "adjustment' was entirely "how much" related. Everything always happened at the same vac level. If other units change the "when" vacuum... I don't know.
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I can tell you that I've learned this, based on my HEI rebuild thread: Different vac advance can pull at different vacuum levels. I put the Moroso unit on my 229 V6 and saw a HUGE drop in performance. While bench testing, I discovered that my OEM can operated a relatively low vacuum like 7" Hg. The Moroso adjustable unit operates at 16" Hg! When I was running the Moroso my economy was utter crap because I was never seeing full vac advance. Not even close.
I would suggest that you test your can to see at what vac level it is fully actuated at. I simply used a MityVac hand pump to pull until the actuating rod stopped moving. You can do it while installed on the engine. This will tell if you're at least in the ballpark of matching what the vac the engine makes to the vac the can needs.
Not sure how much help I've really been. :dontknow:
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