Poor life choices - C4 content

Harvey wrote: All of this seems just as arcane to me as getting EFI working at this point.

This is a problem with the gen 1 SBC. Proper port fuel injection requires either a relatively rare and crappy factory manifold, hacking up an LT1 manifold, a $$$ aftermarket manifold, or machining a carb manifold for injector bungs and fuel rails. There's no good cheap and easy solution, hence the carburetor and distributor, which aren't really that bad once you get over the learning curve.

Andrew Nelson and Aussie Steve seem to have carbs and SBCs figured out....just sayin'

Forgive my peanut gallery opinions, but...

It seems to me that the ignition has not yet been sorted out, based on the reported timing readings and various questions about vacuum ports. So the FI vs Carb debate is secondary (rimshot!)

Take another look at Broken Yugo's posts, and work at getting the timing right. Double check the firing order. Look at the timing without the vacuum connected (ports plugged) and give a report about what is going on. Then let us know what it is with the vacuum connected to the correct port. Best of luck!

Pete, please forgive me, I just don't Know what to say about all the trouble your Having. Peace Brother.

As I have said before this is an almost 3 Handed Chore, Try to get one of your bud's over to at least watch One thing while you do the other 3 or 4 things. Some thing just came to me....that is a very late model 350, over the years 3 different timing marks have been used, what or where are you using for a mark, the FI engines use a mark that is nearly Straight up, look up this info and determine which you have, we may be missing the real TDC, the timing tab on an early model 350 is to the right of an FI and an early engine '60's' is even farther to the right than that

In reply to GTXVette:

Good point, it's not hard to get a mismatch of parts (or have the balancer ring slip if it's an old one) and have your zero mark be nowhere near zero. It might not be a bad idea to start from the beginning and confirm TDC, reset timing, double check the mech advance mechanism is moving freely, etc.

The way I've been told to do it without a proper piston stop is to pull all the spark plugs out, put the biggest* zip tie you have in the #1 hole, head first, until it touches the cylinder wall (so it's under the flat part of the head), then roll the engine over manually until the piston hits the zip tie, mark this point on the balancer (put some masking tape on it) under the zero point on the timing tab, then pull the tie out, roll it past TDC, reinsert the tie and bring the piston to a stop from the other way, mark that point of contact. True TDC is exactly between those two points.

Also, I probably don't say this enough, a lot of ignition problems can look like fuel problems.

In the Land Before Zip Tie's; we used a #2 pencil, Preferibly THE TEACHERS.

I know Pete only used the one from this engine,so it isn't an Issue. I have to mark my stuff, Like I have One 454 that is Internal Balanced, Almost blew it(mentaly) trying to figure out where that OTHER Balancer Came from.

In reply to BrokenYugo & GTXVette:

The balancer is new, but the timing cover is stock. I did confirm the piston was at TDC(at least as well as I could) with the balancer aligned with the zero mark on the timing tab.

I did do some testing tonight to try and determine what the existing advance curve looks like.

Since I still don' have any working gauges, I picked up this multimeter with tachometer from Harbor Freight after work. It has settings for the number of cylinders, with a mark by the range labeled "x10". So I was surprised at idle to see it fluctuating between 6 and 7 on the display. My best guess is they're expecting it to be clamped to a coil lead? Anyway, for these measurements I took the display reading x80, and the results seemed plausible.

-My base idle RPM, with the vacuum advance disconnected, was calculated as about 600rpm. My base timing was steady at 8-degrees BTDC.

-With the vacuum advance reconnected(ported, not manifold), the idle speed jumped to 850rpm, and the total timing was 17-degrees BTDC.

-At 1000rpm I had 24-degrees BTDC total.

-At 1500rpm I had 45-degrees BTDC total.

-At 2000rpm I had 50-degrees BTDC total.

-At 2500rpm and above I had 54-degrees BTDC total.

That seems like way too much total advance, correct? Should I try it without any vacuum advance, or should I start swapping springs and/or weights again?

For some reason in the recesses of my addled mind I thought on a mild SBC total advance above 3000 rpm was around 34-36° max

I'm surprised it will even run above 3k. Gonna go out on a limb here but sounds to me you've got the carb working pretty good and your problem is ignition timing

But don't get me to lying.

In reply to Pete Gossett:

Do the same test with vac advance disconnected and the port capped off.

In reply to Ovid_and_Flem:

That's the max total advance range I'm seeing suggested too.

In reply to AngryCorvair:

I'll do that tomorrow evening and report back!

I also discovered I'm losing brake fluid on the rear circuit, so I'll have to get it in the air and see where it's going.

AngryCorvair wrote: In reply to Pete Gossett: Do the same test with vac advance disconnected and the port capped off.

Yes. Initial should probably get happy at somewhere between 12-16btdc with no vacuum at idle. Dont confuse yourself with the vacuum advance right now. Its purpose is to add lots of timing under low load conditions for mileage, emmissions, and drivability.

Don't even worry much about what the base timing is. Just set full mechanical advance to 36° by 3000rpm, then tell us what the base ends up being.

Rev it higher too, to see that the advance doesn't continue to advance after 3000. I added limiters to my distributor as it was still advancing.

Those numbers are normal with the vacuum advance connected, when running nice and lean at part throttle/light load it likes that much advance. You want to do all of this with the vacuum can disconnected and the vacuum leak capped off (shove a golf tee or similar in the distributor end of the hose), we're only concerned about the mechanical (full/heavy load) advance here. As I understand it adjustment (which you can't do with the stock can) of the vacuum advance often isn't necessary on a mild motor and that's more of a thing you have tune on the street with an otherwise sorted car anyhow.

In reply to SkinnyG:

It ran out of advance right at 2500rpm.

You guys really have me questioning whether my harmonic balancer matches my timing cover, and I'm starting to think it doesn't. If that's true it would be causing 20-degrees of retard from indicated...which would mean my timing is much more reasonable.

I've not heard any knock either. Shouldn't I hear some if it's truly 20-degrees above suggested max advance?

Not with vacuum advance connected and free revving. Under load, yes. But, under load the vacuum advance goes away at heavier throttle.

Again, disconnect the vacuum advance. Retest and post numbers. Then we can start with what really is.

In reply to Pete Gossett:

Given enough vacuum to fully activate it (which you'll probably have free revving at 2500 RPM) the vacuum can should add something like 20 degrees. Again, it's normal, it drops out when the engine is heavily loaded (vacuum is inversely proportional to engine load).

Here you'll see the stock HEI units range from 7 to 15 distributor degrees so 14 to 30 degrees of advance at the crank since the distributor is running at half speed. http://outintheshop.com/faq/Vac%20Adv%20Spec.pdf

What you measured sounds about right, should also measure without the vac advance, to get the whole picture. Under load (or acceleration) the vac advance will drop, it increases advance under no load. For racing to have better control of the timing, typically the vac advance isn't used. It can improve gas mileage since most of the time normal driving there is little load.

Ok, thanks everyone. I'll plug the vacuum advance and report back tonight.

Pete take the Original Balancer and look at the Key way, hold it in front of the new one...are the timing marks in the same place? you will Never ever need more than 35-6 deg. adv.. a Stock dist. can't even produce that much without a kit and AND weights that are sloted more to attain extra adv. I am going to call when I get back from the DR.. Noonish

I spoke to GTXVette a couple times today & he gave me some good tips. First I checked the original balancer and was surprised to find the timing mark was actually about 7-degrees before the crank keyway. I tried to check the new balancer, but I couldn't see anything with the crank bolt in, nor could I loosen it without the engine turning, so I didn't pursue it any further tonight.

I did check timing throughout the RPM range with the vacuum advance capped, and found:

-8/9 degrees at idle ~720rpm -10 degrees at 1000rpm -23 degrees at 1500rpm -25 degrees at 2000rpm -29 degrees at 2500rpm

The only problems are I don't think the timing mark on this balancer is actually correct, and I'm not sure I'm reading/calculating RPM correctly on this multimeter. Because if I were, and the 54 degree total I read last night was correct/possible, I'd probably have major spark knock.

So I simplified...

Knowing that I'd not yet had any knock, I advanced the distributor a couple degrees, went for a short acceleration run, then tried again. I did that 5 or 6 times until I got a slight bit of ping, then backed it off a couple degrees. I pulled out the timing light & and checked my base idle + vacuum advance... 42-degrees. Ok, obviously thats not accurate, ergo my timing mark must be incorrect.

I will say it had much better acceleration, and slightly less hesitation. GTXVette and I also discussed swapping in a heavy advance spring, so I'll try that next time.

One other thing that points towards the timing mark being wrong: all the instructions I've read mention the vacuum advance can should be pointed generally toward the front of the car, but initially mine was pointing over the valve cover. This made it difficult to adjust the lock bolt, as I only had a bit of room between the canister and the carb to insert & try to turn the wrench. With the distributor advanced further I can fit the wrench between the canister & firewall, where there's much more room.

So overall I think it might have been a tiny bit of progress.

The added advance from the vacuum might not cause any ping. Since any load or acceleration will reduce the vacuum advance. Of course to really measure, need to ensure you really have the correct zero mark.

Typical HEI will sit with the square wiring peg off the cap pointing pretty much horizontal. This puts the vacuum can kinda in-between the #8 intake runner and the valve cover, beautifully hiding the hold-down bolt.

When you get a chance, do the zip-tie thing and find out for sure where your timing mark is. The new balancer I got for my 350 was only 1° retarded.

I am in agreement of swapping in a heavy spring. What are you running now for springs? I think I'm running one light and one medium (though every setup is different). Also currently running 23° base (it just worked out that way), and a vacuum can that allegedly gives me 18° (though my engine idles in gear at 8inHg, so I may never see that advance).

In reply to SkinnyG:

I have 1 light & 1 medium springs now.

Sometime I'll pull the #1 plug and positively determine TDC, then try to get some accurate timing measurements.

Check out the September issue of Hot Rod Magazine, Their Hot Rod to the rescue might help out it is mainly about Carb and timing issues on a lightly modded 350 chevy with HEI and a holley

I've ran a similar vintage small block Chevy at around 50 degrees of timing without pinging, so you might be surprised there.

I would definitely verify your timing mark as best you can, SBC's will run pretty decent upside down and backwards in my experience.