TaylorM Posted July 30, 2019 Report Posted July 30, 2019 Hi guys I know some of this info is in past topics but I have had trouble pin pointing an exact solution. What I have 1959 plymouth 230 flathead 6 *stock* Just upgraded to a Tom Langdon HEI My issue (which might not be an issue) - I set my distributor to 10 degrees advance without vac (tom reccomend 10-15) as soon as I include vac, advance will jump to 35 at idle and increase rpm from 800 to 950ish. This tells me I'm on a manifold vac since its pulling at idle? This was the original hook up for the distributor on the carb. Also if I try to idle down on the carb mix screw it will run rough at around 60rpm. I have ordered a carb rebuild kit also Before we did anything we set the motor to tdc with a micrometer, verified point on balancer, set the distributor in at 0 and adjusted from their. Motor was great compression and oil pressure. Only 24k original miles, verified all valves are free and motor idles at 800 and revs smooth. My questions - What is a good idle rpm -What should my advance be at idle with vac -should I trash the timing light and just drive it till she pings and back off the advance - is there a ported vac option on a carter bbs, or should I keep it full vac like original Quote
greg g Posted July 30, 2019 Report Posted July 30, 2019 Have you called Tom? Normally the dist takes a ported vacuum from the carb. Manifold vacuum is basically the opposite signal. 450 to 500 is the idle rpm. What happens when you disconnect and plug both vacuum sources? Most carbs have a vacuum port not familiar with the area bbs but if it is a stock carb mounted on a stock single carb intake it should have a vacuum port. There have been quit a few discussions here about the proper vacuum source for Langdons items but I don't recall the solution. Quote
Lloyd Posted July 30, 2019 Report Posted July 30, 2019 The vacuum advance is usually ported below the throttle plates. I think later models moved them above for emissions but the BB carb is below. At idle you have high vacuum but a lean mixture which takes longer to burn so the spark needs to be advanced to insure a complete combustion. I know that later model cars tried moving the vacuum port from below the throttle plates to above the throttle plates. This was for emission reasons. What they were trying to do was get the exhaust temp up so it would burn the combustibles from the exhaust gases better. What it did was increase the exhaust temp and the vacuum advance no longer worked at an idle which meant hotter exhaust train components and a worse idle. Quote
TaylorM Posted July 30, 2019 Author Report Posted July 30, 2019 46 minutes ago, Lloyd said: The vacuum advance is usually ported below the throttle plates. I think later models moved them above for emissions but the BB carb is below. At idle you have high vacuum but a lean mixture which takes longer to burn so the spark needs to be advanced to insure a complete combustion. I know that later model cars tried moving the vacuum port from below the throttle plates to above the throttle plates. This was for emission reasons. What they were trying to do was get the exhaust temp up so it would burn the combustibles from the exhaust gases better. What it did was increase the exhaust temp and the vacuum advance no longer worked at an idle which meant hotter exhaust train components and a worse idle. This is exactly what I had thought and why I was having problems deciding what to do. I did not see any option for ported vac on this carb. At the same time it seems to idle good and rev through the rpm but idles a little high around 740 but I can lower it around 640. Quote
Sharps40 Posted July 30, 2019 Report Posted July 30, 2019 Stock cam, I'd use ported vacuum and 15 degrees initial advance may be way too much anyway.... Set #1 at TDC Drop in the dizzy, rotor pointed at what ever tower you want for #1. Align the nipples on the rotor with the nipples on the ring. Install cap/wires. Ensure power is full voltage (12V) from an ignition on only source, heavy gauge wire, 10 or 12g. Start car. Warm Up. Adjust idle. Check timing, should be close to 0 (TDC). Loosen clamp and turn dizzy to 10 or less degrees advance. Adjust idle. Check advance at 3000 or so RPM....shooting for 32 degrees all in. Go drive. If no ping, done. If ping, try an advance closer to factory of TDC to 4 Degrees advance. Final note, you probably have a soft can bringing in about 10 degrees on vacuum. Figure about 18 to 25 degrees mechanical built in to the dizzy weights. As such, 0 to 4 degrees initial timing will likely get you all in for 32ish degrees at 3000 rpm. (If you have to, measure and mark your timing wheel in 2 or 4 degree increments so that you can see the new 32 degree mark aligned with the pointer on the timing cover. Its like using a tape but just sharpie marks carefully placed on the balancer.) Quote
TaylorM Posted July 30, 2019 Author Report Posted July 30, 2019 45 minutes ago, Sharps40 said: Stock cam, I'd use ported vacuum and 15 degrees initial advance may be way too much anyway.... Set #1 at TDC Drop in the dizzy, rotor pointed at what ever tower you want for #1. Align the nipples on the rotor with the nipples on the ring. Install cap/wires. Ensure power is full voltage (12V) from an ignition on only source, heavy gauge wire, 10 or 12g. Start car. Warm Up. Adjust idle. Check timing, should be close to 0 (TDC). Loosen clamp and turn dizzy to 10 or less degrees advance. Adjust idle. Check advance at 3000 or so RPM....shooting for 32 degrees all in. Go drive. If no ping, done. If ping, try an advance closer to factory of TDC to 4 Degrees advance. Final note, you probably have a soft can bringing in about 10 degrees on vacuum. Figure about 18 to 25 degrees mechanical built in to the dizzy weights. As such, 0 to 4 degrees initial timing will likely get you all in for 32ish degrees at 3000 rpm. (If you have to, measure and mark your timing wheel in 2 or 4 degree increments so that you can see the new 32 degree mark aligned with the pointer on the timing cover. Its like using a tape but just sharpie marks carefully placed on the balancer.) I have done this procedure but my only concern was the advance. I do not have an option for ported vac on this carb and from my understanding it is better to run it like original with manifold vac. Tonight I'll check and see what my advance is at 3k and set her back to 5deg without vac hooked up first Quote
Andydodge Posted July 30, 2019 Report Posted July 30, 2019 (edited) About 10 yrs ago when I installed the Langdons HEI on the stock 41 Plymouth 201 it was the best thing I had done to the car, admittedly the engine had an Oz only Holden 6 issued Stromberg single barrel carby which is a bolt on job and used extensively here in Oz as they are much more prevalent here then the Carter carbys now.........the vacuum line was connected straight onto the carby vacuum port as it had been with the stock dissy, tho' to be fair the car when I got it was an older restoration by persons unknown and was 12 volts, for what thats worth............apart from increasing the spark plug gap to 45thou the install required nothing else, and resulted in vastly improved instantaneous starting, smoother running and a "seat of the pants" quicker varoom........the timing was adjusted to I think 10degrees BTDC....may have been a little bit more now I think about it, maybe 12 degrees........and that was it.........I sold the car 5 yrs ago like a dope so can't give any more info, a decision I still regret........lol.............andyd Edited July 30, 2019 by Andydodge Quote
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