dartfreak75
Restore it, Dont part it!
Here is what I get when run the numbers. Im not sure how much that gasket compressed but I know what it was when it was new so im gonna go with .050 is 150 psi low for this scr?
Too much timing?
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dartfreak75
Restore it, Dont part it!
I completely misunderstood this comment yesterday I thought you ment cranking pressure like on the starter lol. Thats why I asked how do I do that. Now that I reread it today I know what you ment lol
Extreme to you or the engine? There are 2 ways to time it. One is where you (or others) want it and the other is where the engine wants it. As of right now, you haven’t really driven it enough to know what the engine wants. Make yourself or others happy and there is a chance your engine will not be.
dartfreak75
Restore it, Dont part it!
Yea I haven't driven it enough to really know what it needs I'm just going off what the vacuum gauge says and the affects to the idle.
1. Late timing will build heat much faster.I understand there is more than one way Rusty.
What I'm saying is that you don't have to pump so much timing into a car just to stick your chest out and say look at me, I have 20 initial. Maybe for a quarter mile blast. Backing it down a couple clicks will give you an all around much better running motor, that will also last much longer. No hiccups with the starter, no pinging, no knocking, no burnt pistons, and an overall cooler running engine. I also can run 87 in my cars, Have you seen gas prices in California ?
I'm sure Kevin will get it sorted out.
Thanks for the nice comments.
2. If your vacuum increases then your combustion is more efficient.
3. Late timing sends unburnt fuel out of the tailpipe.
mopowers
Well-Known Member
I understand there is more than one way Rusty.
What I'm saying is that you don't have to pump so much timing into a car just to stick your chest out and say look at me, I have 20 initial. Maybe for a quarter mile blast. Backing it down a couple clicks will give you an all around much better running motor, that will also last much longer. No hiccups with the starter, no pinging, no knocking, no burnt pistons, and an overall cooler running engine. I also can run 87 in my cars, Have you seen gas prices in California ?
I'm sure Kevin will get it sorted out.
Thanks for the nice comments.
Have you never seen an engine that 'likes' more than 20* initial timing? I run my 340 at 26* initial because it wants it. If I run it at 16*, it drops vacuum significantly, has a larger rpm drop in gear from P or N, takes forever to start, has drastically reduced throttle response, and runs noticeably rougher at idle. Those are all signs - to me anyway - that it wants the timing. Of course, total is limited to 34*.
If the OP's engine has it's highest vacuum, is quick starting, has good throttle response, and doesn't buck the starter or spark knock at 24*, why the hell not give it what it wants. It's not about running on the ragged edge - it's about tuning the engine and giving it what it wants. Plus, it'll apparently give him something to brag about? It's a win-win.
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factory 68 383 magnum is 155 psi at 3000 feet
I understand there is more than one way Rusty.
What I'm saying is that you don't have to pump so much timing into a car just to stick your chest out and say look at me, I have 20 initial. Maybe for a quarter mile blast. Backing it down a couple clicks will give you an all around much better running motor, that will also last much longer. No hiccups with the starter, no pinging, no knocking, no burnt pistons, and an overall cooler running engine. I also can run 87 in my cars, Have you seen gas prices in California ?
I'm sure Kevin will get it sorted out.
Thanks for the nice comments.
Now that's the last think this is about. Some combos won't have a decent vacuum signal or have good idle quality (good as they can given the camshaft) until timing is up that high......so trust me, it ain't about stickin titties out....although I like seein the right ones stickin out.
It's not what I consider "low", it's kinda in the middle. If your engine can stand the extra timing with no starter kickback and no detonation, there's no down side....as long as you limit total. It looks like it probably will.
That will be down around the high .030s to maybe ,like .042. I'd use .039 for figuring compression.
All HAIL to the one who got it right, ESPECIALLY with number THREE!
That ONE reason alone right there could be called the only reason the factories specced timing so low. Because it DOES send unburned fuel through the exhaust to run retarded timing. GUESS WHAT? Even to this very day, vehicle inspections STILL don't test the correct way to measure an engine's true efficiency. They measure for hydrocarbons. Hydrocarbons are only emitted when fuel burns. The more hydrocarbons, the more fuel has been burned, so an engine that emits a lot of hydrocarbons is putting more fuel to USE!
This is why backin off the timing will cheat your way out of that test, because it tests the WRONG way. Sure, pollutants aren't good, but what about RAW FUEL coming out of the tailpipe. That's both BAD and a WASTE of energy. Pulling the timing up makes more use of available fuel while making more power. There is no down side.
Johnny Dart
Well-Known Member
Which is why I mentioned "mild" small blocks. Do you read anything I write ?
I still stand by my statements.
You talk a good game Rusty, but I will compare cars with you anytime, anyplace. Lol
Say hello to my tail lights buddy.
Which is why I mentioned "mild" small blocks. Do you read anything I write ?
I still stand by my statements.
You talk a good game Rusty, but I will compare cars with you anytime, anyplace. Lol
Say hello to my tail lights buddy.
I agree with mild assesments. That said, a stock 340 can benefit from elevated timing. How much, I don't know until I play with one, but I can tell you from first hand experience MY stock 73 340 loved around 20 initial.
Just what is "mild"? A comp XE268H likes anywhere from 16-20 initial timing in almost every car I've ever tuned. And to me that is a VERY mild camshaft. Stock 318, 340's and 360's like 12-14. Start putting larger cams in them and that number goes up.
Initial timing doesn't kill anything... total timing is where you get hurt. And getting the complete system (initial, total, curve) correct takes a little work.
Engines will tell you what they want for initial timing. Give them what they want within the mechanical limits of the total system and be done with it. Dialing back on timing is a crutch and was done by the factory for one purpose, to meet emissions guidelines. That's why later cars were timed at such crappy initial settings. 68-69 cars barely had sufficient initial timing by the book.
Well spoken. You basically stated everything I stated in my videos.
I agree but too much can hurt power at idle.
People often judge how much initial based on how the engine runs in neutral. (Was plenty guilty of that myself) How well it takes the load when slipped into gear reveals how strong the timing and F/A combo is.
I know you know that but for guys like DartFreak just wanted to put that out there.
Exactly. Initial brought down 5 degrees or more compared to the same engines without CAP, and the AFR leaned out to 14.2. Idle rpms increased to help compensate for the loss of power.
Unfortunately a lot people, including hot rodders seem to be facinated with lean burning idle mixes.
I agree that a little more initial is often better than a little less. Some guys get carried away though...
Well that my
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@Mattax
Yep, you have to tune for what you have. If there is significant RPM drop in gear, you have an issue somewhere. If a stockisk 318-340-360 engine won't idle in N/P at 700 rpm, something is up. Even slightly cammed engines should idle below 750 without issue. It's all in the tune and finding the right mix.
If an auto trans in in play, do the same exact thing that you would in N/P, except in gear. Find where the engine wants timing. It's not rocket surgery! It does take some time, a little math and some elbow grease to get it right. The benefits are huge.
And a lean mixture smells just as bad out the pipes as a rich one, sometimes WORSE.
Yep, you have to tune for what you have. If there is significant RPM drop in gear, you have an issue somewhere. If a stockisk 318-340-360 engine won't idle in N/P at 700 rpm, something is up. Even slightly cammed engines should idle below 750 without issue. It's all in the tune and finding the right mix.
If an auto trans in in play, do the same exact thing that you would in N/P, except in gear. Find where the engine wants timing. It's not rocket surgery! It does take some time, a little math and some elbow grease to get it right. The benefits are huge.
And a lean mixture smells just as bad out the pipes as a rich one, sometimes WORSE.
Johnny Dart
Well-Known Member
Late timing as in what ?
The factory recommended timing setting ?
Say a 1970 340 at 5B TDC ?
Never did I recommend to run initial timing at the stock setting. I recommend between 12-14 as a baseline.
So what's your point in quoting me dana ?
No point. You win.
With the OP's lunati cam might need a little more.
I'd actually work the opposite way at this juncture. it's at what 20* and something rpm. right?
So now work it back down toward 14*. See where it makes the most power at idle with this carb.
Actually the first thing I'd do is find out where the idle throttle position is.
Use the initial timing to get the position in the operating range for that carb. ,020 to .040 transistion slots on an older Holley New ones maybe tighter to .020 .035 range.
Make sure the idle mix screws are providing a decent level of control.
Then start tuning by testing for best performance when slipping into gear (or place in D for an automagic)
Both early and late timing reduce maximum power an engine can make under given conditions.
Whats the max power of an engine at 550 or even 700 rpm?
Think about it (or go look it up).
It's not much.
When even a small load is placed on the engine at idle, that small load can be close to the max the engine is capable of at idle.
When an engine is engaged with an automatic transmission's pump and struggles to turn it, you know how little power that engine is making.
If you've ever had a vehicle where it could be put into first gear (manual) while it idled at like 500 rpm - that's an engine making power at idle. Not saying you're going to do that with a hot rod like this, just offering an experience for a sense of the difference.
Bottom line is idle in neutral is not a way to judge power.
I'd actually work the opposite way at this juncture. it's at what 20* and something rpm. right?
So now work it back down toward 14*. See where it makes the most power at idle with this carb.
Actually the first thing I'd do is find out where the idle throttle position is.
Use the initial timing to get the position in the operating range for that carb. ,020 to .040 transistion slots on an older Holley New ones maybe tighter to .020 .035 range.
Make sure the idle mix screws are providing a decent level of control.
Then start tuning by testing for best performance when slipping into gear (or place in D for an automagic)
Both early and late timing reduce maximum power an engine can make under given conditions.
Whats the max power of an engine at 550 or even 700 rpm?
Think about it (or go look it up).
It's not much.
When even a small load is placed on the engine at idle, that small load can be close to the max the engine is capable of at idle.
When an engine is engaged with an automatic transmission's pump and struggles to turn it, you know how little power that engine is making.
If you've ever had a vehicle where it could be put into first gear (manual) while it idled at like 500 rpm - that's an engine making power at idle. Not saying you're going to do that with a hot rod like this, just offering an experience for a sense of the difference.
Bottom line is idle in neutral is not a way to judge power.
All this is really interesting. I have learned a lot from this discussion.
The other side of the picture is too early means colder combustion conditions, incomplete burns, and lower pressure through the angles of highest leverage on the crank.
reposting this
reposting this
Incomplete burns.
Part of the reason for left over HC is 'heavy' components of gasoline take more heat to vaporize.
For example, this 8% eth fuel began to vaporze just over 100 degrees F, same as the non-eth. But it required over 300 degrees to vaporize the last 20% of the fuel.
It needed over 400 degrees to completely vaporize all of the fuel.
Race fuels are different. Most finish vaporizing at lower temperatures, even oxygenated ones.
Part of the reason for left over HC is 'heavy' components of gasoline take more heat to vaporize.
For example, this 8% eth fuel began to vaporze just over 100 degrees F, same as the non-eth. But it required over 300 degrees to vaporize the last 20% of the fuel.
It needed over 400 degrees to completely vaporize all of the fuel.
Race fuels are different. Most finish vaporizing at lower temperatures, even oxygenated ones.
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