Timing Chain and Gear Sets; Chevy SBC 350 BBC 454 65K Coil HEI Electronic Distributor - Red Cap. should be idling around 30. Its no different than a Chevy, don't worry about initial timing at first, get a dial back timing light and set advance to 36 degrees at 2800 RPMs then see where the idle timing is but if you want to just set the timing mark to the top of the tab and drive to check for pinging and starting issues then move down the tab 2 degrees until it don't ping and it starts when hot. Edelbrock is the most respected name in performance. Danchuk # 2106 will work on amy 1955-1956 classic Chevy with a V8 engine. A small block chevy will take 20 or so degrees of initial advance without pinging,especially on low compression motors. The better plan is to start with a decent initial timing of roughly 10 to 14 degrees. I cranked in a lot of advance on the 350 sbc which resulted in great throttle response. How do I install my distributor and set my timing on my chevy 305? (vacuum advance in your left hand at about the 9 o,clock position and the rotor at the 3:30 o. 7L V-8 and an automatic. When I reconncet the vacuum advance I get even more advance when I rev the enginve. hei! so would i set my regular timing to the 16. Engine Vacuum Test. Shouldn't a 350 Chevy have it's timing set. As soon as the engine starts and a vacuum is produced, the vacuum advance mechanism advances the spark to about 18 degrees BTDC. The solenoid controls distributor vacuum advance and performs no throttle positioning function. Automatic Advance Automatic Choke Bearings Breaker Gap Cam Angle Carburetor Coil Compression Pressure Condenser Engine Engine Number fast Idle Firing Order Float Level Fuel gauge Gasoline Gauge Idle Speed Ignition Timing Manifold heat Control Serial Number Tappet Clearance Thermostat Tune-up Vacuum Advance Water Pump: Page #0337. It is quite common to run at up to as much as 14 or 16 degrees BTDC static timing, as long as you limit TOTAL timing, with all mechanical advance in, to 36 or 38 degrees. hei! so would i set my regular timing to the 16. com/?v= Learn how to set the ignition timing on your engine with help from MDS and Advance Auto Parts Products Featured in t. My car is now true dual exhaust with headers and Magnaflow through flow mufflers. Re-connect the vacuum hose and road test. In some cases, throttle body vacuum connections will be of ‘ported vacuum’, which changes in an odd way as the throttle is opened. This seems like a good place to add my vacuum advance questions. ESC Vacuum Switch On LE9 engine equipped vehicles with automatic transmission a "tip in" vacuum switch is used. Adjustable vacuum advance modules are sold by several aftermarket sources and provide the best way of fixing this. There is a vacuum port 2nd picture right under the airfliter. This is because vacuum advance is a load-based timing device. At WOT it is out of the picture so total timing in the initial and mechanical are all that are there. If the engine fails to start, rotate the distributor in small increments clockwise or counterclockwise until the engine starts. For better performance and gas mileage, advance timing about 3 degrees faster than factory setting. With the vacuum advance disconnected and idle around 700 set the base timing at 4-5 degrees before tdc. learn something here today. If I unhook the tem. Hedman Hedders & Trans-Dapt Performance Products are two of the hot rod industries original manufacturers, dating way back to 1954. The 1973-74 TCS system differs from the 1972 system in three ways. This is a reprint from another board author unknown but wanted to share this with the group as there has been some recent discussions on this. With that said ck your firing order 18436572 is chey firing order. Let the engine idle and write down zero in. Turning the adjustment in the counter clockwise direction until it stops will lock out the vacuum advance entirely. How to Set the Timing on a Chevy 350 Motor - Initial distributor timing on the Chevrolet 350ci engine is easily set by do-it-yourself car maintenance enthusiasts using just a few tools and an inductive timing light and should take only a few minutes. Vacuum advance should be limited to 10-15deg max. All I have to do is make a pointer so that it marks where TDC is. Make sure the advance is on full manifold vacuum. First, with emissions removed, the vacuum advance can on the distributor may allow to much advance. The car will not idle at less than 1000 RPM in gear. 8* advanced and she was running fine. hei! so would i set my regular timing to the 16. Its got a 350 with aluminum heads, a Comp 4x4 cam, lifters, springs pushrods, longtubes, carb, and I'm sure some other things that I'm missing. By design, vacuum advances are spring offset to give zero advance. Find CHEVROLET 5. I had a similar problem a while back. Only when a strong enough vacuum signal is present will it advance the ignition timing. Trouble timing 87 chevy 350 reman crate engine? The vacuum advance needs to be disconnected and plugged and the mark will be closer to the TDC mark on the timing. Idle Problems With Performance Camshaft I have read almost every article and threads on the Internet about this problem, but haven't found a working solution for my setup. Back in the day vacuum was provided to the vacuum advance via a formed hard line with fittings on either end that would screw into the carburetor and the vacuum advance unit. It is in my mud truck. I have a 1970 350 4b high compression. vacuum advance. We have over lots of customer reviews on Chevy Vacuum Advance to help you find exactly what you need. Make sure vacuum advance is plugged into right port on carb too. To graph the vacuum advance, use a vacuum source with a guage such as a Mity-Vac. It would most likely perform better with a different distributor and carburetor package,. Does this mean both are used to advance the spark and I should plug in at the base of the carb. Chevy SBC 350 BBC 454 Pro Billet Distributor 6AL CDI Ignition & Coil Kit This combination yields stable timing and spark delivery at any RPM. The ECM uses other electronic devices to help control the spark timing under various conditions (such as under load, deceleration, etc). When you are satisfied with the mechanical advance under different conditions, re-connect the vacuum advance and tune the can to pull in as much as the engine will stand under part throttle conditions. I had a similar problem a while back. Set timimg with vacuum advance hose off and plugged so no vacuum escapes. The diagram above is typical of the early HEI using 4 pin ignition module and vacuum advance, non EST 1974-1980. setting timing without timing light, use vacuum gauge? Chit Chat Area, Anything on your mind goes here. I have a 1987 350 small block chevy TBI. The vacuum increases slightly upwards until you approach 35 degrees advance. While watching the vacuum gauge, slowly turn the distributor clockwise (advance timing) and look for a maximum reading on the gauge. Higher initial (base) timing will give you great power off the line but starting can be affected if set too high. hei! so would i set my regular timing to the 16. Too much! With the stock vacuum advance is when you start getting the "3 rocks in a coffee can" kinda detonation. Under 8" it does not give any advance. The Chevy 350 firing order is 1-8-4-3-6-5-7-2. Vacuum Advance Lock Plate $7. The most important concept to understand is that lean mixtures, such as at idle and steady highway cruise, take longer to burn than rich mixtures; idle in particular, as. The vacuum advance canister, located on the side of the distributor, provides additional timing only when the engine is pulling vacuum. When setting timing on a Chevy 350 engine with a vacuum gauge are you suppose 2 disconnect the vacuum advance? Before anybody gets started on using a timing light let me go ahead and say this. The question is about using a vacuum gauge to set timing and NOT A TIMING LIGHT. ), burns faster, doesn't need the additional spark advance, and when the throttle plates open, manifold vacuum drops, and the vacuum advance can returns to zero, retarding the spark timing back to what is provided by the initial static timing. The right way to check total is with a dial back timing light. The TVS-GM#3016754 is used on all 1968 V8’s and on 1969 V8’s with automatic transmissions. By stock I mean stockish cam. At idle, a spark ported vacuum system provides zero vacuum advance where the older manifold vacuum advance system might have provided as much as 10-12 degrees additional timing. It will only confuse things. All of the moving parts are hand fitted to assure the smoothest advance curve possible. With 30-34* timing + your vacuum advance, you'll be at 38-44* which should be optimal. It has headers with about 2 ft of exhaust pipe. Setting the timing on your engine is one of the most misunderstood adjustments, the information on these pages will help you understand and answer all of your questions about ignition timing. If it does not hold vacuum, replace. If this happens set timing to 15 degrees, allow the engine to fully warm up, then disconnect the set timing connector to set the base timing to the correct specification. Buy online, pick up in-store in 30 minutes. Known primarily for exhaust headers, engine mounts, carburetor spacers and adapters, and chrome and aluminum customizing accessories, these two pioneering companies have 1000's of components to help your GM, Ford or MOPAR car or truck run stronger and look cooler. Q: Which way do you turn the distributor on a small block Chevy to advance the timing? We're having a family debate—I say one way, and my boys say the opposite! Also, I believe advancing the timing on a carbureted engine (without a choke) will help it start easier on cold mornings. of advanced timing be on a 350 chev. Any difference in timing, that might be necessary due to grade of fuel being used, can be established by adjusting the vacuum brake. Then tighten the clamp down and reconnect the vacuum line. The CEC valve is not used. The correct adjustment of a vacuum advance unit is critical to ensure that an automobile engine runs at its peak performance. Test the vacuum advance setting by load testing the engine. I put in a generic small block chevy distributor with vaccum advance and a supercoil from ACCEL. Prior to setting the ignition timing, remove the vacuum line from the vacuum advance canister located on the distributor and plug end of the vacuum line. You will need to hook up a timing light to number one (1) cylinder. Save on MSD Ignition Distributor, Chevy HEI, Street Fire 8362 at Advance Auto Parts. For better performance and gas mileage, advance timing about 3 degrees faster than factory setting. The (ported) timed spark port is only for emissions/EGR engines. The amount of ignition advance will depend on the engine version and model of auto, but is. As engine load or throttle position increases, the vacuum decreases, and so does vacuum advance timing. Delco 4-cylinder Distributors with Vacuum-Advance. The total timing is your INITIAL timing + your MECHANICAL timing. 7L that was Thunderbolt IV. While the engine is running, slowly advance the timing until you get the highest vacuum reading then back off the timing 1in of vacuum on the gage. The question is about using a vacuum gauge to set timing and NOT A TIMING LIGHT. Total is timing at idle, + mech advance. My car is now set at 14 degrees BTDC initial timing @ 900 and 36 degrees BTDC total including full mechanical advance @ 2500, both with the vacuum advance disconnected. Many people who tune engines disconnect the vacuum advance mechanism, and indeed on some distributors it is very hit and miss in operation and can cause anomalies in the timing. You have initial timing which is the timing at idle. Most V8 will happily cruise in high gear on level ground at 50° to 55° BTDC ignition timing. Keep in mind you're done with the distributor timing, don't try to compensate for a vacuum advance issue by retarding the mechanical advance. New edelbrock it's close to in tune, timing in the video is at about 20 degrees advance, I know that's wrong but I was playing with it at the time. com/?v= Learn how to set the ignition timing on your engine with help from MDS and Advance Auto Parts Products Featured in t. The CEC valve is not used. Distributor is a GM points. ” Most racing and street performance ignitions do not have vacuum advance and the stock type distributors that are sent to a shop to be recurved should have the vacuum advance removed and locked out. 7L 350 merc (chev/GM) This is in a 1986 Cruisers Inc, 25' weighs 7000 lbs. Vacuum Advance & Bracket With Timing Mark, 90 To Vacuum Chamber Item # 1909343A 39^51 This is the vacuum advance with the bracket and timing mark that is 90 degrees to the vacuum chamber. I am running my stock Ramjet 350 with EZ-EFI 2. Re: 89 Chevy 350 Truck Vacuum Advance Its a single wire tan with a black stripe, usually under the plastic cover on the firewall on the pass side and has a connector you can unplug. Raise the vacuum setting a few degrees, and again write down the vacuum value and timing in degrees. So I thought I should check the timing. Changing ignition timing can be a very basic tuning tool. There are some great kits for the purpose for sale online. 3 in time or find the timing marks on injection pump. http://video. This means timing the engine's total advance at about 3000-3500RPM (usually 32-38 degrees). Timing Vacuum Distributors ~~~ Both idle timing and static timing of 7. I am running my stock Ramjet 350 with EZ-EFI 2. The only time the vacuum advance adds timing is at part throttle, low load conditions when there is manifold vacuum. The 289 HP featured a high nodularity cast iron crankshaft that was Brinell hardness tested to ensure quality. LMC Truck offers 1973-86 Chevy Blazer 1973-86 GMC Jimmy Pre-Bent Fuel Lines and Vacuum Advance Line. Trouble timing 87 chevy 350 reman crate engine? The vacuum advance needs to be disconnected and plugged and the mark will be closer to the TDC mark on the timing. need all the info i can get please. Keep in mind when adjusting the timing, you have to turn the distributor clockwise to advance and counter-clockwise to retard. Use ported vacuum in this case; you don't want or need any more advance at idle. I Dont Know whats wrong with my 350 Chevy Engine? Unhook the vacuum advance from the distributor. Example: 10° Initial + 25° centrifugal = 35° Total Timing. Replace the vacuum advance hose. I set my timing wedge at 4:30pm to offset the lobe separation on the top end. We just got through a rebuild of my son's 350 and replaced everything. Save chevy small block vacuum advance to get e-mail alerts and updates on Pro Billet Distributor Red Small Big Block Chevy SBC BBC 350 454 Vacuum Advance. The final type is vacuum advance, determined by the vacuum canister attached to the distributor. The vacuum advance control unit on the distributor is intended to advance the ignition timing above and beyond the limits of the mechanical advance (mechanical advance consists of the initial timing plus the centrifugal advance that the distributor adds as rpm comes up) under light to medium throttle settings. This is a clever device that ties manifold pressure to a mechanical advance mechanism. I Dont Know whats wrong with my 350 Chevy Engine? Well this is interesting. It's a good read about mechanical advance vs. I run sunoco 94 and it runs great. So get out your timing light, clip it to the #1 plug wire, smear a white crayon on that thin line on the harmonic balancer, disconnect and plug (a golf tee works well) the vacuum advance hose between the carb and distributor, and fire it up. When the diaphragm in the vacuum advance fails, it will allow a small amount of vacuum to be lost. try 15 degrees advance at idle, then plug in the vacuum advance to the manifold vacuum for another 15. On my old 1985 GM 350 4WD truck the dist was installed so as the vacuum advance cylinder was on the passenger side of the dist & engine. Sought after for its durability, quiet operation and performance, the 350 has also earned a reputation for reliability and usability in a variety of applications, including boats. The timing connector for the Chevy Silverado breaks out of the engine wiring harness conduit adjacent to the distributor. Vacuum advance is a good method of controlling spark timing for a daily driver. recurve kits are available aftermarket. This is handled by the vacuum advance system. my chev 307 does that whenever the vacuum advance unit goes bad. My car is now true dual exhaust with headers and Magnaflow through flow mufflers. New SBC BBC Chevy 327 350 396 454 Pro Billet Vacuum Advance Red CDI Ignition Kit. The next best way we have found to check the vacuum and mechanical advance curves with the distributor in the engine is by using an OTC/SPX hand vacuum pump and an OTC/SPX advance reading timing light. But, with the attachment, you can check the MAP itself. Whatever the setup, advance increases with engine RPM and decreases as the engine goes under a load. Idle Problems With Performance Camshaft I have read almost every article and threads on the Internet about this problem, but haven't found a working solution for my setup. 5 whp at peak, and a consistent 21-22ft/lbs of torque from peak to 2300rpm and a consistent increase all across the board. If 36 max mechanical WOT timing proves more than what creates max power reduce it a bit. The additional advance to get. 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. The timing figures are to be applied to the engine when it is turning fast enough to have allowed the distributor to go to full advance condition. or run out of gas, but has gas. Keep the vacuum advanced un-hooked (plug the hose with a golf tee). This faithful reproduction makes sure that your engine will look 100 point perfect. My car is now set at 14 degrees BTDC initial timing @ 900 and 36 degrees BTDC total including full mechanical advance @ 2500, both with the vacuum advance disconnected. i've changed the plugs, wires and egr valve i also change the fuel filter but it was last summer. A-Team Performance HEI Distributor 65K Coil 7500 RPM Compatible with Chevrolet Chevy GM GMC Small Block SBC Big Block BBC 262 265 267 283 302 305 307 327 350 383 400 396 427 454 Red Cap. When setting timing on a Chevy 350 engine with a vacuum gauge are you suppose 2 disconnect the vacuum advance? Before anybody gets started on using a timing light let me go ahead and say this. As soon as the engine starts and a vacuum is produced, the vacuum advance mechanism advances the spark to about 18 degrees BTDC. with everything but people, a heavy beast. I have not adjusted the following because I do not really understand what they do. Trans-dapt 4960 Timing Tab Chrome Chevy 283-350 6. The best way to set vacuum advance is by feel, under real driving conditions. Record the value in crankshaft degrees. You can also find other images like wiring diagram, parts diagram, replacement parts, electrical diagram, repair manuals, engine diagram, engine scheme, wiring harness, fuse box, vacuum diagram, timing belt, timing chain, brakes diagram. Your big cam is the problem with your combination perhaps being "fiddly" - not your distributor. is provided as a simple way for most people to set the timing, and is not a good procedure for optimum performance. If you were to put a timing light on a car going down the highway with the vacuum advance properly connected, you would be extremely surprised to see somewhere around 40-50 degrees of ignition. If it does not hold vacuum, replace. Engine Vacuum Test. The final type is vacuum advance, determined by the vacuum canister attached to the distributor. You can tune the vacuum advance later as you have time and inclination - I think the instructions that came with mine recommended setting it for the slowest possible advance until everything else is sorted out. Heres and idea for you to try. There is a simple rule that you should always keep in mind when adjusting engine timing. In most cases. vacuum advance. Set the timing at about 16-18 degrees advance at idle. The vacuum increases slightly upwards until you approach 35 degrees advance. Timing too advanced will cause pinging (a rattling noise usually heard on acceleration), overheating cylinder heads and other problems too scary to contemplate. You should be able to check centrifugal and vacuum advance with the timing light and the engine running. try 15 degrees advance at idle, then plug in the vacuum advance to the manifold vacuum for another 15. When using the timing light to set timing ALWAYS disconnect the vacuum advance (non-computer controlled distributor) or deactivate the computer-supplied advance as described in your shop manual (if. Edelbrock is the most respected name in performance. So get out your timing light, clip it to the #1 plug wire, smear a white crayon on that thin line on the harmonic balancer, disconnect and plug (a golf tee works well) the vacuum advance hose between the carb and distributor, and fire it up. Level Sensor for BRC. Too much! With the stock vacuum advance is when you start getting the "3 rocks in a coffee can" kinda detonation. So unless you race at half throttle a vacuum advance will have no effect on performance. As soon as the engine starts and a vacuum is produced, the vacuum advance mechanism advances the spark to about 18 degrees BTDC. Scroll down and go to the section on Timing and Vacuum Advance, you'll see their articles on mapping your distributor advance and total timing. Where should I set the timing on my performance engine? There really is no specific initial timing specs for any performance engine. I have a 1970 350 4b high compression. With this setup, vacuum is lowest at idle and it increases as the throttle is opened (completely opposite to manifold vacuum). shut it off. Disconnect the distributor vacuum advance and plug the line. it is having issues when accelerating or going up hill it bogs down like air cut off. I have a 94 Cadillac Fleetwood with the LT1 with RPO V4P (aka, 7000# tow package). Example: 10° Initial + 25° centrifugal = 35° Total Timing. Higher initial (base) timing will give you great power off the line but starting can be affected if set too high. Adjust the idle to 800 or 900 rpm and set the idle mixtures screws for best/highest idle (highest vacuum). On an automatic transmission, a vacuum modulator leak will cause the engine to pull the transmission fluid into the combustion chamber, creating an abundance of smoke—along with transmission shifting problems. I Dont Know whats wrong with my 350 Chevy Engine? Well this is interesting. Setting the timing on your engine is one of the most misunderstood adjustments, the information on these pages will help you understand and answer all of your questions about ignition timing. when i re-checked the timing it had moved to 8 deg. Tip: Periodically checking your engine vacuum will help you learn how your engine is doing and allow you to spot behavior out of the norm. The starter labors to crank the engine. The question is about using a vacuum gauge to set timing and NOT A TIMING LIGHT. Establishing static or initial timing is the foundation. , SVDA) on aircooled VW engines (vacuum hose disconnected and plugged on the single-vacuum distributor). Set with timing light wire on no. 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. Since then the service light has come on for a few days at a time then goes off. Restrict the mechanical advance, give it enough timing at idle to compensate for your cam, and make sure your total is somewhere between 36 to the lower 40s if you do NOT use the vacuum advance. Vacuum Advance Lock Plate $7. Toggle navigation Community Chevy Automotive Sales Inc. What is the ignition timing on a 383 Chevy Stroker engine? I just tuned a 383 this past weekend and it runs beautifully. If it does, check the vacuum advance unit diaphragm with a vacuum pump. With 30-34* timing + your vacuum advance, you'll be at 38-44* which should be optimal. In this Hagerty DIY, Kyle Smith walks you through the process of adjusting timing on a Chevy small-block engine. The 289 HP featured a high nodularity cast iron crankshaft that was Brinell hardness tested to ensure quality. setting timing without timing light, use vacuum gauge? Chit Chat Area, Anything on your mind goes here. How much centrifugal advance ("total timing") is in effect at cruise rpm?. If the vacuum advance control unit is not fully pulled in at idle, it will be somewhere in its mid-range, and it will fluctuate and vary the timing. I set my timing wedge at 4:30pm to offset the lobe separation on the top end. EVERY one used a vacuum advance to pull a better idle vacuum, even the heavy hitters in the 10s. Hey guys, chevy 350, mild cam, hei dizzy I am having an issue getting my timing dialed in. Back in the day vacuum was provided to the vacuum advance via a formed hard line with fittings on either end that would screw into the carburetor and the vacuum advance unit. This will cause a gradual degrading of performance and many times will go unnoticed for a long period of time. This will indicate any adjustments required on advance curves, weights, etc needed to obtain the correct total timing while retaining a LIVEABLE initial timing. The best way to check and set the advance curve is on a distributor test stand, then confirm the results with an advance timing light such as the type we use from the Black Light series of timing lights supplied by OTC/SPX Tool Company. So get out your timing light, clip it to the #1 plug wire, smear a white crayon on that thin line on the harmonic balancer, disconnect and plug (a golf tee works well) the vacuum advance hose between the carb and distributor, and fire it up. The best way to set vacuum advance is by feel, under real driving conditions. The diameter will correspond to the timing indicator or timing cover being used, you can't mix them - the 7" will be too far away from the 8" marker and the 7" marker will run into the 8" balancer. That should be a 350 cubic inch engine with a carburator, HEI ignition with a vacuum advance. - I have been working on a 74 chevy g20 van with a 250 inline 6 motor and it has a rochester monojet carb on it, I have put the timing mark at 0 degrees and the mark jumps back and forth a little bit, the other day I had it perfect and now i cant figure. If you trying to total the engine at 36* you would simply set the idle timing at 18* and this bushing will allow it to advance another 18* to bring your total to 36*. Vacuum Advance With Roots Style B&M 144 Supercharger Hi, I know this is mainly a blow-through board,as we own a couple,but I have a question about the Vacuum Advance with a "roots stlye" B&M supercharger on a 350 sbc. This can be checked with the engine running at idle with a timing light. Adjustable vacuum advance modules are sold by several aftermarket sources and provide the best way of fixing this. I Dont Know whats wrong with my 350 Chevy Engine? Unhook the vacuum advance from the distributor. Takes tools to maintain a car, a timing light and vacuum gauge are probably two of the more priority items you'll need to keep things tuned up. We have over lots of customer reviews on Chevy Vacuum Advance to help you find exactly what you need. It is capped with a black cover, loooks like it is on the metering block. vacuum hose and set timing 2 degrees advanced from factory specification adjustments. Its function is to provide a momentary contact closure (signal) to the ESC controller during a throttle "tip in" condition which then briefly retards spark timing to minimize knock. It is quite common to run at up to as much as 14 or 16 degrees BTDC static timing, as long as you limit TOTAL timing, with all mechanical advance in, to 36 or 38 degrees. CAUTION: You must recheck your piston to valve clearance after advancing or retarding you camshaft timing. Initial advance is set to 12* and total mechanical is at 32. so i installed a 1987 truck 350 engine. selecting a vacuum advance spec: How much engine vacuum is produced at cruise? If max vacuum at cruise, on a car with a radical cam, is only 15 inches Hg, a vacuum advance control unit that needs 18 inches to peg out would be a poor selection. I'm not sure what rpm it fully comes it at, but I would say around 3000. Then depending on the amount of timing advance in the distributor, you go from there, but in any even, you do not want more than 38 degrees total timing at 3000 = rpm. We have over lots of customer reviews on Chevy Vacuum Advance to help you find exactly what you need. If it pings with vacuum advance you have to limit the the advance or get a can that drops out at a lower vacuum. Connect vacuum gauge to full unported vacuum at base of carburetor, now shut motor off and turn both idle mixture screws all the way in but be sure that you only use light pressure as. 88 chevy 350 w/ tbi problems. Many people who tune engines disconnect the vacuum advance mechanism, and indeed on some distributors it is very hit and miss in operation and can cause anomalies in the timing. With this setup, vacuum is lowest at idle and it increases as the throttle is opened (completely opposite to manifold vacuum). To graph the vacuum advance, use a vacuum source with a guage such as a Mity-Vac. High vacuum signals are indicative of low engine loads at a closed or nearly closed throttle position. Mechanical timing is related to RPM only and has no idea of the load you are pulling. Keep the vacuum advanced un-hooked (plug the hose with a golf tee). hei! so would i set my regular timing to the 16. As engine load or throttle position increases, the vacuum decreases, and so does vacuum advance timing. I’ve been seeing a lot of discussion and questions regarding distributor vacuum advance control units; what do they do, which ones are best, what was used on what, etc. Generally, most Chevy V8's, both small and big block, operate most efficiently with timing curves of 36 to 40 degrees advance total timing (mech plus initial), with initial advance (set with a timing light with vacuum advance disconnected) in the 10-14 degrees for a street use engine. To graph the vacuum advance, use a vacuum source with a guage such as a Mity-Vac. One source for vacuum advance is a small opening located in the wall of the throttle body or carburetor adjacent to but slightly upstream of the edge of the throttle plate. Just order a balancer for a late-70s era 350 Camaro engine and it'll have the mark in the right postion to work with a 1:30 position timing tab. The best-known small block V8 in GM's stable, the Chevy 350 engine is considered one of the 20th century's best engines. In my '86 C25 crew cab with a 350 small block and automatic transmission, I run 10 degrees advance (measured w/the vacuum line. 94 chev silverado. Make sure vacuum advance is plugged into right port on carb too. Difference in polarity but it makes no difference in how an engine runs. The timing needs to be without a vacuum signal, that way you are getting just the centrifugal timing with no hint of advance. top speed 40mph at 4800 rpm, cruise 30mph at 3500 rpm. Heres and idea for you to try. Since then the service light has come on for a few days at a time then goes off. you might be gong to full advance to early causing ping. I have a 1987 350 small block chevy TBI. i've changed the plugs, wires and egr valve i also change the fuel filter but it was last summer. Keep in mind you're done with the distributor timing, don't try to compensate for a vacuum advance issue by retarding the mechanical advance. Unplug the vacuum advance and put a little nail in the line so it doesn't suck air does it Miss after you do that? If so that is the sign of a timing chain that has stretched. Engine Vacuum Test. Adjust the vacuum advance in the clockwise direction until a spark knock is noticed while driving the car in highway and city conditions. recently had a power issue with the engine that was in my boat. is provided as a simple way for most people to set the timing, and is not a good procedure for optimum performance. This is handled by the vacuum advance system. The total timing is your INITIAL timing + your MECHANICAL timing. Impressions. Most Chevy V8's perform best with total timing set between 36-40 degrees (depending on engine, drivetrain and vehicle). 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 has no part in the "total timing" equation. The HEI distributor supplied with the 350 HO engine has mechanical centrifugal and vacuum spark advance with the following curves: Mechanical Advance: Vacuum Advance: RPM Advance Vacuum (in. Get Yours Today! We know our parts and products. Mechanical timing is related to RPM only and has no idea of the load you are pulling. up the the counter and says I need a valve cover gasket for a "350 CHEVY". A small block chevy will take 20 or so degrees of initial advance without pinging,especially on low compression motors. See what that does for you. This relay is normally closed to block vacuum and opens when energized to allow vacuum advance. I'd be more concerned about timing under load and would modify the vacuum advance to retard under boost, but that's me. I have really bad detonation now when under load. Remember vacuum advance is load dependent, so you cannot check it with a timing light with the car in neutral. Ignition Systems Cheat Sheet for the Chevy Small Block For our budget-oriented purposes we find that conceptually at least, GM's HEI distributor is a near ideal choice in terms of practicality. That should be a 350 cubic inch engine with a carburator, HEI ignition with a vacuum advance. timing is done with the hose to the vacuum unit disconnected and plugged. VACUUM ADVANCE: The vacuum advance system consists of a vacuum diaphragm mounted on the distributor body. Trouble timing 87 chevy 350 reman crate engine? The vacuum advance needs to be disconnected and plugged and the mark will be closer to the TDC mark on the timing. Easy to use parts catalog. 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. This faithful reproduction makes sure that your engine will look 100 point perfect. It is in my mud truck. If vacuum is unplugged from the unit, I get a clean rev to 6000+. The correct adjustment of a vacuum advance unit is critical to ensure that an automobile engine runs at its peak performance. RockAuto ships auto parts and body parts from over 300 manufacturers to customers' doors worldwide, all at warehouse prices. Our '83 class-C Chevy motorhome has a (CA emissions) 350 4BBL HD (heavy-duty service), no cat converter or ECM, basic HEI ignition. If you know your Year Make Model, put it in the selector so that we can guide you to a product that fits your vehicle. done my best to line up the #1 terminal to the rotor. Adjust the idle to 800 or 900 rpm and set the idle mixtures screws for best/highest idle (highest vacuum). Keep the vacuum advanced un-hooked (plug the hose with a golf tee). Suggest pulling the distributor and inspecting the.