This is a little how-to for setting the initial ignition timing on a small block Chevy before its ever been run. This is simply done by removing the spark plug from cylinder one and putting a finger over the hole. Then slowly turning over the engine with a long wrench or breaker bar on the harmonic damper bolt and feeling for when air stops blowing out of the plug hole.
When it stops, you should be near TDC. Generally, we try to aim the rotor so its pointing in the direction of where cylinder one is physically on the engine.
It just makes more sense this way rather than using one of the posts at the back. You may remove your distributor completely from the engine to align the rotor by hand if its degrees away from the post you will be using for cylinder 1. You will also need an oil pump priming tool to rotate the gear on the oil pump so that the rotor can align properly. Once the distributor is re-installed and the rotor is pointing in the direction of cylinder one, you need to be sure that the rotor and the post are closely aligned as possible.
That is, the rotor should be aimed directly at the post for cylinder one under the cap. To help with this, use a marker and put a mark on the cap to note which post is the one for cylinder one.
Make sure this mark is aligned perfectly with the post. Now, when you slip the cap over the distributor, you can kind of see where the post is aiming. There is quite a bit of margin of error here.
Congratulations, the engine is now timed to ZERO degrees, or at least close enough. But you probably wont be able to start the engine with this little timing; to start it, you will have to rotate the distributor by hand counter-clockwise to advance the timing until it fires. Its always nice to have a friend help you with this because they can crank the car while you advance the distributor. Of course, use a timing light to properly set the timing once the engine is running.
This method can be used to start an engine that has some sort of after market digital fuel injection system as well. It is recommended to set a 10 degree advance offset for the Chevy HEI 8-pin system.
Your ECU should have a location where to set this offset, and once this is set, this location will become the new zero. Just make sure your ignition table in the ECU is matching what the timing light is saying after things get going. You can follow all the replies to this entry through the comments feed. Guess it is a refresher for people who do know. I assumed that the reader already understood how to time an engine, just not how to on a fresh engine….
My motor has no distributor installed it was on 1 the line on harmonic balancer lined up. The oil pump gear was needing to be turned. Anyhow the gear lined up at the motor seamed to be degree off so I tried it the other way.Chevrolet's small-block V-8 engine timing specifications depend on the cubic-inch displacement and whether a manual or automatic transmission matches the engine. Small-blocks have cubic-inch displacements of, and The cubic-inch V-8 has the plug gap set at.
The point gap is. The dwell angle is The engine idle is rpm for standard transmission and rpm for automatics. The V-8 features spark plugs with a. The ignition timing is 2 degrees BTDC. The hot idle is rpm with a manual and with an automatic. The V-8 specifications are nearly identical to theexcept for the ignition timing.
With the manual transmission, the idles at rpm with an automatic it idles at rpm. The 's timing specifications are almost identical to the other small blocks. However, the ignition timing for the horsepower version with manual transmission is at Top Dead Center and 4 degrees BTDC with automatics. This article was written by the It Still Runs team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information.
Timing Specs for a Chevy Small-Block
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All times are GMT Pacific. Current time is AM Top. Attach Photos to Posts. Contact Us. My Cookies. Frequently Asked Questions. Forum Rules. Floyd B. Engine at normal operating temp. Idle adjusted correctly. Remove and plug vacuum hose to distributor. Hook up timing light to 1 spark plug wire.
Loosen distributor hold down bolt. Not too loose, just enough so you can turn the distributor. Start engine, turn distributor until the timing is where you want it, probably about 4 degrees BTDC. Tighten the hold down bolt.
Reattach the vacuum hose. Remove the timing light. You are done. That makes for inaccurate initial timing. That could explain alot of timing problems that i have 87K10 sb R4 gears.
More info! What is the timing? Then idle it down while checking the timing to make sure the is no mechanical advance in play. Once you get to the initial timing ONLY write it down and start bringing up the rpms until the timing stops advancing.
Take that total number minus the initial timing and that will give you the mechanical advance. To check initial only is like building a house with a measuring tape that the first 6 inches is marked off. Remember it is supposed to be fun!!
Lived long enough to where I now beat my kid's car on the weekend. Have you checked that your vacuum advance system is actually working? If you have a faulty vacuum can on your distributor then your timing will be too retarded for part throttle cruising such as at rpms. To check the vacuum advance is working watch the timing light reading as you connect the vacuum advance to full manifold vacuum whilst the engine is idling.
Just as you connect the line to full manifold vacuum you should see the timing jump up advance by degrees, and as you disconnect the vacuum advance from full manifold vacuum it should drop down by the same degrees.
My advice is for you to run your vacuum advance connected to full manifold vacuum at all times, but remember to disconnect and plug it whilst setting your initial timing. I hope this helps.I have a small-block Chevy in my Nova and just swapped on a set of used aluminum heads.
I was told the heads have cc intake runners, 64cc chambers, 65cc exhaust ports, and 2. I also put a new cfm Holley vacuum-secondary carb on it.
Prior to my changes, it had iron 76cc heads; an Erson cam with 0. With the old setup, I would pull 14 to 15 in-hg of vacuum at idle. It ran pretty well with 12 degrees base timing and no vacuum advance. The vacuum advance had caused a stumble off idle, which sounded weird to me until somebody suggested taking the vacuum advance hose off and plugging it, then it ran like a top.
But after I swapped the heads and carb on the thing, it now doesn't want to run anywhere under 30 degrees base timing. I actually found that out because I got frustrated with it sputtering and running like crap at 15 and 20 degrees base timing, so I turned the distributor as far as it would go, and it runs well. With mechanical advance, that would be about 55 to 58 degrees total at 3, rpm. I don't have any weird symptoms or overheating issues or anything.
It runs at to degrees Fahrenheit at the cylinder head and doesn't have any major driveability problems, other than I need to tune the carb, but I felt this was more important first.
Any ideas on this? Am I crazy, or is there a serious problem? Matt Vendouern Via email. No, this certainly is not normal. Running that much timing will usually detonate your motor into oblivion. Depending on your cylinder heads, compression ratio, camshaft, and centrifugal advance curve in the distributor, "normal" base timing for a street high-perf small-block Chevy is somewhere in the to degree before top dead center BTDC range, with total timing at full centrifugal advance about 34 to 36 degrees BTDC, as read at the crank.
But before you do anything I know this sounds lameit can't hurt to get a second opinion—try a different timing light and see if the results agree. All right, so it's not the timing light. If the cam and rocker ratio are the same as before, idle vacuum should remain about the same at the same base timing, or—due to a higher static compression ratio generated by the new heads' smaller combustion chambers—be even slightly higher. This assumes the valves and the carb's idle mixture and idle speed are properly adjusted.
Therefore, you need to get these items squared away at the normal base timing range. A vacuum leak leans out the engine, which can cause detonation and also burn valves. At the most basic level, if you put your hand or a rag over the carb at idle and the car keeps running, you have a vacuum leak somewhere for sure.
Use a vacuum gauge for more granular diagnostics. The most likely place for vacuum leaks are at the intake manifold gaskets or under the carb baseplate. Sometimes you'll have an intake manifold gasket that leaks out the bottom into the engine valley—that's really hard to spot with these quick tests. Usually, you can only find such a leak by pulling the intake and looking for blow-by signs on the intake gasket itself.
Are all the unused carburetor and intake vacuum ports on your new carb plugged off? Don't overlook the large PCV hose nipple present on many "universal" Holley carbs at the rear of the baseplate under the secondary float bowl. Are there any vacuum leaks in the automatic trans vacuum modulator or the power-brake vacuum booster check valve circuits either the devices themselves or the hoses feeding them? Temporarily plug the ports to those and any other external vacuum consumers including the PCV valve and see if vacuum improves.
SinisterCustomJun 7, How can total timing be set with a vaccum pump That's for figuring out how much vacuum advance you get, which isn't really too important, as long as it still runs smooth when cruising.
Pit Stop: Chevy Won’t Run Without 30-Degrees Base Timing
The info I gave is for how to figure out how much mechanical advance you're getting. FuelRoadsterJun 7, SBC's normally run degrees total Mechanical advance. Should be "all-in" by about 2, RPM's. Disconnect and plug the vac.Timing the ignition on a 350 sbc!
Check to see what your total timing is when it's fully advanced. Adjust to the aforementioned degrees. Also record the RPM's at which it stopped advancing. If it's way higher than the 2, start trying lighter advance springs to get it down in that range.
You will probably end up with degrees at idle, but the important is not the idle timing FossilJun 7, I know theres a X2 factor for the vaccume advance.Discussion in ' Engine Topic ' started byJun 25, Jun 25, 1.
Messages: 28 Likes Received: 0. Jun 25, 2. Messages: 1, Likes Received: 0. Hey, Man We all started this way!!!! If it starts good, then run it. Lower compression motors like lots of ignition timing. Jun 25, 3.
Jun 25, 4. Messages: Likes Received: 0. Sounds like a little gremlin in your engine going wild with a hammer when your in the gas. Keep an eye on the temp also. Good idea when on shakedown runs is to carry a wrench and screwy driver to pull the advance back a bit by the side of the road or parking lot it its detonating. Jun 25, 5. Messages: 1, Likes Received: 3. Jun 25, 6. You will. Sounds like a diesel to me. The engine will always run smoother with lots of initial. However you'll always be in a trade off with your initial and you're centrifigul.
If you're running 25 initial, then 18 mechanical, thats 43, way to much. Set it back so you're max is between Whatever you're initial is, thats what you'll have to work with. If you're running vacuum advance which you should behook it up to manifold vacuum. This way, if you only have 14 initial, the vacuum usually 10 or more degrees will be added in, giving you close to you're ideal 25 at idle.
It will go away under load, so you won't have to worry about detontation. Jun 25, 7.
built 350 wants 25 initial timing?
Jun 25, 8. Jun 25, 9. Did you dis-connect and plug the vacuum advance before setting the base timing and hook it up after? It sounds like you don't have the vacuum hooked up. Jun 25, You must log in or sign up to reply here.
Show Ignored Content. Share This Page Tweet. Your name or email address: Do you already have an account?There are instances where OEM design is so good that it lends itself to a broad range of applications within the high-performance aftermarket.
The GM one-wire HEI distributor is the world's simplest, most integral design ever introduced, and thanks to a clear distributor cap from Performance Distributors it's also the easiest to set initial timing. For those unfamiliar with the term, initial timing is what needs to be done to an engine's ignition system before the engine can be started for the first time.
On those gearhead TV shows it's always a big anticipatory moment whether the engine will fire up or not, but in the real world there's never a question if the job has been done right.
Some like to depend on removing the number 1 spark plug, and using a finger to feel for compression as the engine comes up to TDC, and then there's the method I believe is more absolute.
I prefer to remove the valve cover on the bank with the number 1 cylinder and establish the compression stroke by seeing if the exhaust and intake valves are closed at TDC. Naturally the location for number 1 on a Ford and Chevrolet engine are different, so the message here is no matter which make of engine is in question always verify the location of number 1. The basics discussed in this article apply to every internal combustion engine ever made. There are several brands with GM-style HEI one-wire distributors on the market, and with varying degrees of quality and pricing.
I've tried the really inexpensive HEI distributors and think they're great for installing into something one plans on selling the next day. My experience was the distributor cap and rotor disintegrated immediately, and when diagnosed they were the source of a bad miss.
There's no economy to be found in an unreliable part that will ultimately fail. I verified a horsepower increase for my C10 on the dyno, and made noticeable gains in fuel mileage. The most recent installation was last year into my Ford Track T with a It's the custom-build approach that sets Performance Distributors ahead of the pack.
With the cam specs handy I called and specified I wanted the DUI calibrated with an advance curve for octane regular unleaded gas. The engine fired right up the first time, and has run crisp without pinging ever since. In addition to being able to see the rotor contact the number 1 plug at TDC the clear cap DUI cap enables one to verify if the vacuum advance works. Performance Distributors clear cap comes complete with clear rotor, clear coil cap, and all hardware including the coil insulator and dielectric grease used on the coil insulator.
The existing distributor wasn't initially timed. It was removed by completely removing the distributor pinch clamp and lifting the distributor out.
How to Time a Chevy Small Block Motor
The timing degree marks on the harmonic balancer were made more visible by sanding with grit sandpaper. The TDC top dead center mark indicated by a zero was made more visible and identified with a Sharpie marking. A bright paint color works even better. Only the left bank valve cover needs to removed to gain sight of the valvetrain.