The best way to check total timing if you don’t have a dial-back timing light is to use these simple timing tapes from MSD. This is because the air/fuel mixture is being ignited in the cylinder too late in the compression cycle for maximum power. Small block Chevys (and most other GM performance V8 engines) perform best when the total timing (full centrifugal advance plus the initial timing setting with vacuum advance disconnected) is all in by 2,500 Œ 2,800 rpm and is set to 36 Œ 38 degrees. I've never had timing that high before, and I don't know if it's OK/normal or not. Since we know already that the HEI has 20 built into the stock mechanism the first thing we need to do is set the initial advance correctly- that means you need an initial advance between 12 and 18 degrees (you might want to retard it 2-4 degrees for daily street use just to build in a little safety margin). In most cases, these projects require only basic tools, and […] I could lock it out and give it a go - I timed it based upon Lars methods. 255 Posts . No I don't mean harder plugs, competition coils, lumenition etc., that only affect the efficiency of the spark, but the actual ignition advance supplied by the distributor. with Jeff Smith: Solving SBC Ignition Timing Problems Posted by Jeff Smith on July 1, 2020 at 5:17 pm A melonized distributor gear at … I think the timing needs to be more like 32 degrees. Determine your desired total timing. The size of the engine impacts the total timing requirements. As an example, a generic tune might be 14 degrees BTDC initial with another 6 degrees of mechanical advance for a total of 20 BTDC at 2,000 rpm. 88. the distributor, combined with initial static timing, is "total timing" (i.e., the 34-36 degrees at high rpm that most SBC's like). If your initial timing is 10 degrees, and we visually verified that mechanical advance allows 24 degrees, your total timing, theoretically, is then initial plus mechanical (10 + 24+34). have a sbc that the more initial timing you run the faster it gets @ the track but it gets to the point that it blows gaskets like oil seals valve cover on 6 deg runs 8.40 1/8 on 12 deg btdc runs 7.30 on 16 deg btdc it runs 7.20 cant go up past … ), Rev the engine past the point where your mechanical advance is fully engaged. Note* this post assumes that you already know how to … At 60 mph in high gear, a typical small-block Chevy needs between 45 and 55 degrees of advance. He writes both technical information and market commentary as a private consultant and has researched and authored business plans. I should also point out that the best way to REALLY check your total timing is to buy an $8 "timing tape" that basically wraps around your harmonic balancer and puts 60 degrees worth of degree marks ON THE BALANCER where you can easily see them. If fuel octane is not sufficient, detonation (pinging) will occur. advance line, hook up a timing light and read the timing while you or a friend opens the throttle a little. Engines with aftermarket camshafts change valve timing events (not to be confused with ignition timing), and this increases the amount of initial timing that is required. I am helping a guy with a sbc 406 with 18 degree eldebrock victor jr cylinder heads. Should be "all-in" by about 2,500-3,000 RPM's. The proper amount of total timing is critical. Check to see what your total timing is when it's fully advanced. The purpose of the vacuum advance mechanism is to offer more timing--typically 10 to 14 additional degrees--when full mechanical advance is not completely introduced. Chevrolet has manufactured the SBC in displacements from 265 to 400 cubic inches for a variety of applications. 350's Similar Specs (Usually, 3,000 - 3,500 rpm will do it.) Disconnect and plug the vac. In most cases starting out … Copyright 2021 Leaf Group Ltd. / Leaf Group Media, All Rights Reserved. Set your Timing Light to your desired total timing. The timing can vary between 2 and 12 degrees BTDC, the recommended spark plugs are different and even the plug gaps vary. With the manual transmission, the 327 idles at 475 rpm (with an automatic it idles at 450 rpm). Set your total at where you want it 34-38 and let the initial be what it is. This timing … Ignition Timing for Modified Engines An often neglected but important area when tuning an engine is the ignition system. First – When you […] Every engine will run a little bit differently. $7.99. Discussion Starter • #1 • Sep 13, 2006. i was thinking somewhere in the 32 to 34? I have just completed a 400 SBC build and am looking for advice about what I should set for total (base plus mechanical advance) ignition timing. To do this, measure the circumference of the balancer with a flexible, cloth or paper tape, measurer or install permanent degree tape to the balancer. For instance, if an engine has 10° of initial combined with 21° of mechanical, the total timing is 31° BTDC. I think that what is confusing you here is how the total mechanical advance is read by using a timing tape and timing marks on the damper instead of the timing marks on the timing tab on the engine. Rev the engine past the point where your mechanical advance is fully engaged. No I don't mean harder plugs, competition coils, lumenition etc., that only affect the efficiency of the spark, but the actual ignition advance supplied by the distributor. Do the same and set the total timing to 34 degs. Disconnect and plug the vac. The highest timing I got was 16 degrees advance giving me a total of 24 degrees advance right at 3,300rpms. Hagerty’s DIY series is your handy-dandy, easy-to-use video guide to tackling small projects any classic car or truck owner might encounter during the course of ownership. I think that what is confusing you here is how the total mechanical advance is read by using a timing tape and timing marks on the damper instead of the timing marks on the timing tab on the engine. I've been doing some tuning on my 400 SBC with the new AFR 195's (65cc chambers), and the things seems to like about 40 degrees of total timing. Make small movements when turning. Ignition delay occurs during the time that it takes to fully ignite the mixture with a spark plug. i would set the initial timing at least 12. more importantly you should set the total timing which should be about 32-36 degrees. In this Hagerty DIY, Kyle Smith walks you through the process of adjusting timing on a Chevy small-block engine. I think the timing needs to be more like 32 degrees. Discussion Starter • #1 • Oct 30 ... My 406 runs 16* initial and a total of 36* and I use ported vacumm which is a whole other issue with many opinions. This is done with a combination of initial advance, plus centrifugal or electronic controlled advance for engine speed, plus vacuum or electronic advance for engine loading and throttle effect. Tuned and modified engines have different Watch the timing mark on the harmonic balancer using the timing light. To find out what your mechanical advance is, remove the vacuum line from the distributor, plug it, rev the engine, and get a reading off the timing marks on the harmonic damper with the timing … I have seen SBC that will ping on 10* initial and 32* max timing on premium gas and I have built 9.5 compression SBC that like 22* initial and 38* max on low octane gas. Setting initial timing on a small block Chevy (SBC) John Milmont on October 20, 2012 — 8 Comments This is a little how-to for setting the initial ignition timing on a small block Chevy before its ever been run. The small-block Chevy engines vary in the amount of total timing based on a number of factors, but most SBC engines require between 32 to 36 degrees of total timing, with some older, less efficient engines needing as much as 38 degrees or more. (seems like a lot to me). If we shine a timing light on the damper (with vacuum hose disconnected and plugged), at idle, we would see 10 degrees. The early release of energy means that the rising piston has to fight against the increased cylinder pressure. Im trying to set my timing on my 388. Once started, a high engine vacuum signal connected to a dashpot on the distributor rotates the internal advance mechanism forward to introduce more timing for good off-idle and part-throttle engine response. (you won't see too many sbc strokers that like more than 34 degs total.) At high RPMs with full throttle application (no/low vacuum), the total timing may be: 12 degrees initial, 0 degrees vacuum, and 22 degrees mechanical advance, for a total timing of 34 degrees. For example, part-throttle total timing would look something like this: 10 degrees initial + 10 degrees vacuum + 20 degrees mechanical = 40 degrees of total timing. 2,940 147 2. (Usually, 3,000 - 3,500 rpm will do it.). Under full throttle loads, there is reduced vacuum available to the vacuum advance mechanism, and its advance is eliminated to avoid too much timing. You can also measure the diameter of the balancer and multiply by "pi" (3.14). Most Small Block Chevys like about 32-38 degrees total advance at WOT. As engine speeds increase above 3000 to 3500 RPM, the centrifugal force of the distributor mechanical advance weights overcomes the springs holding the advance mechanism in the retarded position and mechanical advance is fully introduced. Optimum Timing. Your browser either does not have JavaScript enabled or does not appear to support enough features of JavaScript to be used well on this site. This is a little how-to for setting the initial ignition timing on a small block Chevy before its ever been run. Additionally, the fuel burn is not as complete which increases emissions. Most naturally aspirated engines like a total timing of 34 to 36 degrees BTDC, (Before Top Dead Center) AKA "Advance". Vacuum advance has absolutely nothing to do with total timing or performance, as when the throttle is opened, manifold vacuum drops essentially to zero, and the vacuum advance drops out entirely; it However, you will need to test and tune to determine the best setting for you. All, this video was designed to help others. Once started, a high engine vacuum signal connected to a dashpot on the distributor rotates the internal advance mechanism forward to introduce more timing for good off-idle and part-throttle engine response. SBC total timing E85 vs. race gas SBC total timing E85 vs. race gas. Jump to Latest Follow ... well back to the timing issue. Rotate the distributor clockwise to retard the spark slightly, lightly tighten the nut, and check where the timing is with the timing light. 1 cylinder, with the engine at a predetermined rpm. The initial timing has nothing to do with it when racing because you are always above that and should be at your total. Post Aug 13, 2014 #1 2014-08-13T01:37. In my new distributor I put the "18 degree approximately" total advance stop bushing in the distributor. Too little timing can cause the engine to be sluggish and unresponsive. Start the engine. So if you set total timing to for example 36 deg and the dist had 25 deg mech adv 36 total minus 25 deg mech adv = 11 deg base timing. For performance applications, some modifications will be required to the advance "curve.". The engine has 36 degrees total timing now. Ignition Timing (Total Timing Method) This issue's subject is about setting ignition timing using the total timing method. The way we do it is to set the timing at 30 degrees total advanced on the No. I am wanting to know if there needs to be a difference in total timing when using E85 fuel vs. race gas on the same sbc engine. 10 degrees initial is definatly too low and that is why your engine is running rough. I find that usually 12* initial and 36* total plus vacuum advance of about 15* is a good base to start with. way for most people to set the timing, and is not a good procedure for optimum performance. Engines with aftermarket camshafts change valve timing events (not to be confused with ignition timing), and this increases the amount of initial timing that is required. $140.25. Watch the timing mark on the harmonic balancer using the timing light. Build details include: Bored 0.030 oversize New pistons (7cc valve relief) and rods 5.7" Original cast iron heads - … (you won't see too many sbc strokers that like more than 34 … The engine has not be on any kind of dyno. Setting initial timing on a small block Chevy (SBC) John Milmont on October 20, 2012 — 8 Comments. Chevrolet has manufactured the SBC in displacements from 265 to 400 cubic inches for a variety of applications. This is a potentially destructive condition and can burn pistons, valves or spark plugs and can cause damage to the upper connecting rod-bearing inserts, as well. That is typically 15-35 degrees before TDC (top dead center) of the power stroke depending on the engine speed. Total timing is the term given to the highest amount of advance. One Genuine Ford 2004 2007 5.4L 3V … Rotate the distributor until the timing mark lines up at zero with the light. I find that usually 12* initial and 36* total plus vacuum advance of about 15* is a good base to start with. However when I checked the total advance at 2500 It was well over 40+ degrees and hence I didn’t try running it with that amount of advance. If you're above 36 degrees, go back and reset your inital timing back a few degrees.. if it's below 32, bump it up a hair and try it again. Set the timing with the vacuum advance hooked up so you can do vacuum and mechanical advances at the same time. If you have an … The 1966 versions have an ignition time of 2 degrees After Top Center (ATC). At 2500 to 3000 rpm 36 degrees total (initial + mechanical) is fine. I have a weird thing happening with my small-block Chevy crate engine that has me scratching my head. At 2,500 rpms it was only at 12 degrees btdc. 636 Posts . I have not done any testing at the track yet with timing. Rev the engine to about 3000 rpm and watch the timing light to see where the total is. The cool thing about ignition timing is you can usually get a considerable performance increase for little or no money. I am helping a guy with a sbc 406 with 18 degree eldebrock victor jr cylinder heads. In a spark ignition internal combustion engine, the purpose of advancing the timing of the engine spark is to get past ignition delay. 88. How to set total timing on 79 350 SBC. This is intended for application with pre-emmission engines (generally pre-1975). Chevrolet has manufactured the SBC in displacements from 265 to 400 cubic inches for a variety of applications. I have seen some people claim that their Small block "needs" 40-45 degrees to "run right", these engines have some serious problems with combustion chamber design, low compression problems, or other very serious tuning and design issues. Check to see what your total timing is when it's fully advanced. The term "Total Timing" refers to the maximum amount of Ignition Timing applied to the engine. Adjust the timing light to find the total timing. Note that Total timing never includes vacuum advance. 3. At idle, like 600 to 1000 rpm, 38* timing is normally excessive unless there is something wrong. But, some time and effort will be required.AdvertisementClick Here to Read MoreAdvertisement Let’s start with a simple explanation of why we need spark advance and how much of it we want. Where should I set my ignition timing for the first start-up? … Aisin TKT-005 Engine Timing Belt Kit with Water Pump for 4Runner/Tacoma/Tundra. In addition to this, induction system, cylinder head design and camshaft timing play a great role in timing needs, as well. In addition to this, induction system, cylinder head design and camshaft timing play a great role in timing needs, as well. Everything you need for anything you drive. The engine is a 290-horsepower Chevy crate engine with a set of headers, a Holley dual plane intake, a 750 Holley 0-3310C Holley carburetor, and …
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