I was able to increase the idle vacuum enough to get the power brakes working very well by connecting the vacuum advance to manifold vacuum. That also made the idle a lot smoother.

 

Yeah, I'm at 850 in park. I gave thought to bumping it up a tad (and still may) but I doubt even 950 in park would give a substantial gain. Granted, I have been wrong plenty enough..what's one more? Haha

 

I think you are misunderstanding. Keep the idle RPM where it is. Connecting the vacuum advance to manifold vacuum increases the ignition timing, which will increase the idle RPM, so adjust the curb idle speed back down to 850.

 

I've tried manifold and ported source, no change. It's currently hooked up to manifold.

 

That should be plenty of timing. Have you put an advance light on it to see what the actual timing is at idle?

 

If you're meaning the dial back light, then yes. I dial it to 18 & line the balancer up to the zero on the tab. (The "new" zero, which has been verified multiple times).

When gathering total, I set the dial to that number (meant to look last night but I'm pretty sure it was 32°-I've got it written down in the garage) and ran the engine up until the mark stopped moving, and turned the dist to align the mark at 0. That verified my 18°.

14° mechanical advance seems low..but I don't know enough about it. Plus, the more mechanical that gets dialed in, the lower the initial 》》the lower the vacuum.

 

Yeah, 32 is pretty low. Did you do a compression test? If cranking compression isn't high, add another 4 degrees of base timing. Honestly, with a carb, I run around 1000 rpm in park. Doing those two things might boost vacuum a good few inches.

 

I have not done a compression test since putting everything back together.. but when I last did one everything was between 145-160 IIRC. Not quite where I'd like it with a new engine, but nothing was drastically off compared to the others.

32 total is low? What should I be shooting for? I'm afraid to add more initial timing to it, and not sure how to add mechanical timing (even then that wouldn't fix the vacuum being low). I meant to bump the rpm to 950 this weekend, but forgot.

 

Well, I had the car out a fair bit this weekend as the weather was amazing. Brakes do feel marginally better though it may be a mental thing as it's pretty much the same vacuum it always had been. It didn't have it yesterday, but today the more it drove, the more I noticed the off-idle stumble is back. Also, the final test was to be able to shut it down/ fire it up a couple times without issue.. and unfortunately it didn't pass that either. It did act a bit better, but still not 100%.

First guess, it's too rich whether that be due to mix or due to low vacuum.. but yet the off idle could be a part throttle lean situation. At the end of the day though, now that the cam timing has been verified/ corrected, I feel confident taking it to a dyno to have it tuned properly. I've never had a struggle like this, but at the same time I've done more in the name of troubleshooting than I've ever messed with.

 

How does it run compared to before?

 

Overall, I'd say a tad better.

 

I saw it asked before but did not see it aswered. How much vacuum advance does the distributor have?
Is it possible that your vacuum advance canister is leaking? I agree that 32* total Is low. What RPM is the mechanical advance in by?
Put timing into it until it pings or is hard to start to see if that makes a difference. Of course back the timming down from that point.

 

BAD IDEA!!!!!!!!!!!
This guy never heard one bit of pinging. Yet this was the end result. And you’re an idiot for suggesting that.

 

[QUOTE=cutlassefi;1558988]BAD IDEA!!!!!!!!!!!
This guy never heard one bit of pinging. Yet this was the end result. And you’re an idiot for suggesting that.

Well thanks for that.
But please in the future do not false quote me. Quote the full sentence or paragraph.
Good luck to the OP.

 

It does have a tendency when warm to be hard to start already, so I'm very hesitant to add timing. I'd thought about even knocking it back down to 16° initial just to be safe, but that'd put me at 30 total..which seems low for total timing..lol.

I had it out Monday to check leaks and see how it acted after a couple carb adjustments (didn't bother with the vac gauge) and it ran pretty well. From a stop, it'll light the tires up (note-not power braking) pretty easily considering the 3.23 gear..so I think the vacuum is just going to be what it is.

I'll keep chugging along on getting things closer until I can get the dyno time..but knowing the cam timing is correct is a big box that's been checked.

 

[QUOTE=Alank;1559057]Ok, back the (timming) down to what? Doesn’t matter, it’s typically too late then anyway.
I’ve taken apart even low compression engines with the same results as pictured. That’s NOT the way to do it.
Thank you.

 

Forgot to update the most recent outings.

I noticed it was still hard to start when warm a couple weeks ago, so I went ahead and bumped initial down to 16°. Out of curiosity, I checked vacuum and it was up to 9".

I drove it to work yesterday, and after sitting in the parking lot all day, I hop in and try to fire it up and it kicks back as if it's still too advanced. I think I'll keep backing it down 2° and trying it.. though if my numbers are still accurate, I'm at 30° total now and it still acts too advanced (ignition)

 

Recurve the distributor for more mechanical advance to keep the total at 32-36.

 

Yeah, I was afraid of that. When it was restored, it also received a "performance recurve" based on the engine specs, but maybe he went too far? Here's the dist. card

Not gonna lie though, I've not fully understood this no matter how many times I'd looked at it.. lol

 

Agreed. Does the vacuum advance even work and how much does it change the timing when you hook it up???

 

As is is typical, Ken didn’t do it right. A “performance curve” should be quicker than that for sure.

 

Totally agree with this. Even the Factory Performance Information is greater then this. If it were me I would look into the timing of a W-30 cam as a STARTING POINT and go from there.

 

Check those numbers with a dial back timing light. Honestly, it might be time for fully adjustable distributor like a MSD. More initial with the same full throttle total should increase idle vacuum. Something is off, maybe sticking advance weights?

 

Oof, a lot to unpack (and thankfully so)

I looked through notes when I got home. I do not recall, nor have notes regarding checking the vacuum advance.

I had timed previously by unhooking and capping the vacuum advance, and running the engine up to where the timing mark stopped moving on the balancer, then zeroing the distributor using the dial back light. That put me at 18° initial. It runs well there, but struggles on restarts.

When I initially fired the car after engine install, I believe I had the ignition around 12° per the CSM, but between lackluster performance, the spark plug issue, and chasing vacuum, I went with the total timing route and had stuck there ever since.

Now, after the change in cam timing, I have made sure to keep better notes of how things are acting since I no longer have that as a variable.

I can drop initial down to address the warm start issue, and adjust the mechanical timing within the distributor/verify vacuum advance is where it should be..but my brain says the more I back off initial timing, the worse my vacuum will be. I'm currently up to 9" but know the carb still needs some tweaking as well.

 

Some folks with high compression / advanced timing struggles install a coil kill switch. Open the switch, turn the key to starting to crank the engine, then when it’s turning over, close the switch so it fires up.

 

I thought I'd responded to this, but I guess not.

I don't think I'm at 10:1 as expected, but even still-if the curve in the dist. isn't where it should be, I'll start there first.

 

So, should I be looking for more mechanical advance, and for it to come in sooner (smaller bushing/lighter springs)?

Currently, I've got 12-14 mechanical advance (can't remember the exact right now being at work) so when I build to 32 degrees total, it puts the initial stupid high. Even with the initial at 16 degrees where it is currently, it still acts hard to start as if it's got too much advance in it already.

 

Did you put a different stop bushing in it? Because your distributor specs sheet that you posted above says you have 22° of mechanical advance.

 

I have not, and that's part of what I don't understand about the spec sheet. In finding total, I'd rev the engine up until the line on the balancer stopped advancing. Then I'd rotate the distributor until the zero and the line matched up, while showing 32 on the dial..that put me at 18 initial (32 total - 18 initial = 14 mechanical)

So yeah, I didn't understand how it showed 22° on the spec sheet.

I have not run the test since getting a timing light that also shows RPM (which has verified the tach is wrong) but I also didn't pay attention to the tach the previous time..I only watched the line on the balancer.

 

Ken@Everyday did it right? If so that explains it.
The last dist of his I had on my dyno had multiple problems. Biggest one was the dwell would change 5* instantly upon revving it, with no vacuum advance hose connected. He’s a hack.

 

Correct.

 

Do a search of Lars Grimsrud he has written many articles on recurving points and HEI distributors.

 

Wow. Great write up.
http://corvette-restoration.com/wp-c...ine_Timing.pdf

 

agreed, that was a good read.

I had it out to lunch yesterday, and noticed it is acting like its loading up while driving around town. I didnt have time to mess with it too much, but I did back the ATP back 1/4 turn (previous was 1/2 turn to richen up, so I'm backing off of that halfway]

I did notice a couple weird things, but I'm not going to really have time for trial/error at least until next weekend (weather permitting). In the meantime, I'm going to do a bit more reading/researching and come up with a bit of a game plan.

 

brotherhood,

Here is some Factory Information that you can use as a reference STARTING POINT, this information comesfrom spring of 1970. It should be easier to work with today Dial Back timing lights.




I cannot stress the point of use this information as a beginning only as the quality of gasoline today. Hopefully this information will help you better to dial in your timing. Where in Ohio are you located, I'm about 1/2 hrs West of Toledo?

 

Much appreciated, I'm hoping to have an opportunity to work on it this weekend now that its back from the exhaust shop. I'm in Urbana (north of Dayton, west of Columbus)

 

Mark wrote:
Ken@Everyday did it right? If so that explains it.
The last dist of his I had on my dyno had multiple problems. Biggest one was the dwell would change 5* instantly upon revving it, with no vacuum advance hose connected. He’s a hack.

Bernhard wrote:
I know were I would be starting.
I would go through the distributor and ensure that it is functioning correctly and bringing in the timing were I wanted it.
Just backing off the timing until you feel it runs better is not the idea approach. Tuning and trouble shooting are all about collecting accurate information so that you can proceed in a methodical manner.

 

Now that I have a better understanding, I agree. Thats on my to-do list next. Something that those car continues to show..is the amount of things I paid people to do to keep my inexperience out and hopefully eliminate problems..well, that didn't save a blasted thing. Lol.

No better way to learn, then to do..but Id rather practice on something not worth so much..haha