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need advice resurrecting a muscle car |
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CAL(KS)
Orange Level Joined: 18 Sep 2009 Location: Chapman, KS Points: 3786 |
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Posted: 03 Apr 2024 at 8:28am |
hey folks. I've owned a 69 plymouth roadrunner since 1995 when i started high school. This was my only car for several years and was driven off and on until about 2007 when i bought a home and started having a family.
Jumping back to 1999-2002 i had spare money in college and installed a hot comp cam, hooker headers, oversized stainless valves, roller rockers, mopar performance single plane intake, mopar performance distributor and ignition box, a speed demon 750 with mechanical secondaries as well as a limited slip 3.55 diff. It sat until 2012 when I wanted to get it back on the road. I discovered then that the fuel tank was full of rust, and the fuel sender was rusted off in the tank as well as needing some cleanup in the engine compartment due to a hacked up engine harness. I purchased a MSD igniton box but never got around to getting it installed. The car has always been stored inside but suffered some light damage due to building collapse in Dec. 21 from that bad wind storm that blasted through the central plains. A few small dings and a crushed grill but fared very lucky as the hood was up and suffered no damage. Fast forward to a month ago and my 17 year old son wants to take it to prom. I purchased new fuel tank, sender/suction tube, mechanical pump, filter, hoses, clamps, carb rebuild kit and other misc. Got all the new parts installed as well as the msd box and fixed the wiring. Removed all the spark plugs, cranked engine to get fuel to carb and build oil pressure. Nearly pissed myself several times pulling wires and checking spark. YOW! Put all the plugs back in started it up. ran but rough and went through some adjusting of the carb. got it warm enough to change oil and drain antifreeze. I will add that i only had access to 87 octane gas but did add octane booster before putting in car. Long story short, i have been through the carb 3 times, still cant get it to run well at all rpms. Changed pickup in distributor thinking it was faulty as ohmed low but didnt change anything. idles well but backfires and shakes at ~2000 rpm. change timing, doesnt backfire but sounds like detonation when accelerating on test drive. cant get the shakes out of engine at any timeing above idle. firing order is correct per book, and was not changed. all plugs firing per rpm of engine when wire pulled. Other than vacume advance not functioning im out of ideas. I will borrow a test light to check as mine burned up in garage fire...... Edit... when accelerating seems ok but definitely not right. when holding steady rpm shakes on and off when driving or parked moving throttle by hand Edited by CAL(KS) - 03 Apr 2024 at 8:39am |
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Me -C,U,UC,WC,WD45,190XT,TL-12,145T,HD6G,HD16,HD20
Dad- WD, D17D, D19D, RT100A, 7020, 7080,7580, 2-8550's, 2-S77, HD15 |
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iowallis
Silver Level Joined: 04 Jun 2017 Location: North Iowa Points: 338 |
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Vacuum leak somewhere would be my guess. Check valve on the brake power booster (if it has power brakes) is a leak that isn’t very obvious.
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PaulB
Orange Level Joined: 12 Sep 2009 Location: Rocky Ridge Md Points: 4706 |
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As mentioned vacuum leaks will cause endless problems, also be aware that ALL gasoline available today even the ethanol free gas is EPA mandated to be oxygenated in some manner (it burns leaner) than gas did 50 years ago. That requires the jetting to be richer. You can either check with an Air/Fuel monitor or an EGT gauge.
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If it was fun to pull in LOW gear, I could have a John Deere.
Real pullers don't have speed limits. If you can't make it GO... make it SHINY |
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DanWi
Orange Level Access Joined: 18 Sep 2009 Location: wttn Points: 1774 |
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Sitting that long is it possible you have a valve sticking?
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CAL(KS)
Orange Level Joined: 18 Sep 2009 Location: Chapman, KS Points: 3786 |
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this car doesn't have power steering or brakes. only vacuum lines are to pcv valve and distributor advance. other line on carb is capped with new plug. I also removed valve covers to check for stuck lifter/and or valve. did not find anything unusual but was at cranking speed.
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Me -C,U,UC,WC,WD45,190XT,TL-12,145T,HD6G,HD16,HD20
Dad- WD, D17D, D19D, RT100A, 7020, 7080,7580, 2-8550's, 2-S77, HD15 |
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CAL(KS)
Orange Level Joined: 18 Sep 2009 Location: Chapman, KS Points: 3786 |
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Is it possible the octane booster is past shelf life? i hadnt thought of this, but i doubt many are using it anymore Edited by CAL(KS) - 03 Apr 2024 at 9:56am |
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Me -C,U,UC,WC,WD45,190XT,TL-12,145T,HD6G,HD16,HD20
Dad- WD, D17D, D19D, RT100A, 7020, 7080,7580, 2-8550's, 2-S77, HD15 |
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CAL(KS)
Orange Level Joined: 18 Sep 2009 Location: Chapman, KS Points: 3786 |
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I did some electronic searching and found detailed tuning information (with pictures) that is not included with the carb or kit. something caught my attention. I need to verify i dont have the constant vacume port hooked to the distributor instead of the transfer vacume port. this would confirm my thoughts on timing issues but if so im a dummy for getting them mixed up. frustration clouds the mind... cant verify till off work though.
Edited by CAL(KS) - 03 Apr 2024 at 10:59am |
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Me -C,U,UC,WC,WD45,190XT,TL-12,145T,HD6G,HD16,HD20
Dad- WD, D17D, D19D, RT100A, 7020, 7080,7580, 2-8550's, 2-S77, HD15 |
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PaulB
Orange Level Joined: 12 Sep 2009 Location: Rocky Ridge Md Points: 4706 |
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Vacuum line to distributer needs to be connected to a "ported" connection. this would be a port that does not receive vacuum when at dead idle. Not knowing what your carburetor is I can't advise where that connection is. A "Motors or Chilton" manual for you car would help here,
YES, EPA continually is changing the formulation of gasolines seasonally as well as regionally. the only real way to get the A/R ratio near what's needed is with an A/R monitor or an EGT gauge. You can guess and maybe get close. Are burnt valves or worse worth guessing? With the other changes that were made to the cam, intake and other things OEM setting are out the window.
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If it was fun to pull in LOW gear, I could have a John Deere.
Real pullers don't have speed limits. If you can't make it GO... make it SHINY |
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CAL(KS)
Orange Level Joined: 18 Sep 2009 Location: Chapman, KS Points: 3786 |
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Me -C,U,UC,WC,WD45,190XT,TL-12,145T,HD6G,HD16,HD20
Dad- WD, D17D, D19D, RT100A, 7020, 7080,7580, 2-8550's, 2-S77, HD15 |
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DMiller
Orange Level Access Joined: 14 Sep 2009 Location: Hermann, Mo Points: 30971 |
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Need to take a spray bottle of water and spray around all Intake Ports while running, gaskets pull and shrink over time especially on a sitting engine. Any Capped off Intake vac Ports will need be looked at as well, rust does not limit to fuel tanks or bodies. Can also see a Hanging Valve, engine not rolled in forever, carbon build up, varnish from old oil and moisture, put a Vacuum gauge on it and report the response at idle and mid range rpms.
Edited by DMiller - 03 Apr 2024 at 1:50pm |
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Thad in AR.
Orange Level Access Joined: 12 Sep 2009 Location: Arkansas Points: 9438 |
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Compression check and vacuum test needed.
Spray carb cleaner/wd around the intake to head around the base of the carb and every vacuum connection. To see if it picks up a little while idling |
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GSTROM99
Silver Level Joined: 12 Dec 2020 Location: Greene, IA Points: 244 |
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Compression check results?. Pull off individual plug wires to narrow down if ONE particular cyl is the culprit. Digital temp reader on each header, will tell you the same. Is the ignition advance working? I don't know Demon carbs - replace with Holley? The "Ready to Run" MSD distributors are nice and easy, to eliminate the electronics.
Edited by GSTROM99 - 03 Apr 2024 at 5:13pm |
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Ed (Ont)
Orange Level Joined: 08 Nov 2009 Location: New Lowell, Ont Points: 1273 |
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Unhook vacuum line to distributor for now. Plug at carb of course. Start and run to check if any different. What is your initial timing? Maybe set to a few degrees of advance (4-6). Start and run. What does the dist cap look like or is it new? Just start trying one thing at a time. Anything. To me it almost sounds like a firing order issue but you have double checked it???
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Ed (Ont)
Orange Level Joined: 08 Nov 2009 Location: New Lowell, Ont Points: 1273 |
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What motor do you have there? With what you have told us about your engine build you probably do not need any vacuum to distributor. Hot rod motor does not need it. Most of the mopar engines run well around 34 degrees of total timing measured at 2500-3000 rpm. Initial does not matter except for starting - if hard to turn over get a better starter. Most of the chevy small blocks like 36 degrees on the dyno. Take the front and rear bowls off that demon and check for dirt as well.
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Ed (Ont)
Orange Level Joined: 08 Nov 2009 Location: New Lowell, Ont Points: 1273 |
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Also on your vacuum. Anything above the throttle plate is ported vacuum. Anything below is manifold vacuum. As I said for now try no vacuum to distributor. Should run good without. It is only for fuel mileage going down the road easy.
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DaveKamp
Orange Level Access Joined: 12 Apr 2010 Location: LeClaire, Ia Points: 5744 |
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If the distributor has no mechanical advance, he WILL need vacuum advance, as it will either start and run at full retard, and not accellerate at all, or if manually advanced, self-destruct trying to crank at full advance. Proper troubleshooting requires measuring here. Measure timing, and observe advance and retard. Shoot temps of each exhaust port and look for a cold port. Lift a plug wire slightly when there's a miss and see if it clears (increasing a gap will clear carbon fouling of the plug). If the distributor is suffering from stray spark, the ignition trigger coil may be getting false triggering. More measurement of basic functions is necessary... get the facts FIRST.
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Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.
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KMAG
Orange Level Access Joined: 26 May 2020 Location: Elizabethtown, Points: 669 |
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I'd double check all the ignition wires go to the correct spark plugs or bad plug. It would explain your results.
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Codger
Orange Level Joined: 23 Dec 2020 Location: Illinois Points: 2032 |
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B, or RB engine? I'd lose the electronic ignition for testing and go back to breaker points myself unless you have a known good replacement. Seen a lot of MSD and like competitors capacitive discharge ignition systems fail from both age, and/or lack of use. The capacitors break down over time and can yield many of the results you are experiencing. This can be exacerbated if the distributor shaft, or bushings are not in good condition. Another problem with the 383 engine, (B series) and 440 engine, (RB series) if you have planed the heads and not addressed the intake manifold mounting flanges for angle correction is they will not hold intake gaskets long term. This is more pronounced on the 440 than 383. A high performance camshaft utilizing a lot of valve overlap makes a vacuum gauge a guestimate as they won't carry a steady 17" - 21" of vacuum at idle speed. 1-8-4-3-6-5-7-2 is the standard firing order for the engines of the time and was very standard with exception of Ford who had to be different. I would be leaning on the ignition system for faults/failure from the writings.
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A career built on repairing and improving engineering design deficiencies, shortcomings, and failures over 50 years now.
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CAL(KS)
Orange Level Joined: 18 Sep 2009 Location: Chapman, KS Points: 3786 |
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wow thanks for all the tips guys. I cant believe i didnt post, but this is a matching numbers 383 4 spd car. the distributor is a genuine mopar bought as a kit with the orange electronic box. it has a mechanical and vacume advance. i changed the magnetic pickup to verify it wasnt the problem. $20 insurance. I would say this car has less than 5k miles on it since all the upgrades in 2000 so wear is very unlikely and original points distributor is long gone.
I had a few minutes last night after moving some hay bales the neighbor bought and needed to get to. I did in fact have the vacume advance hooked to the constant vac port instead of the correct one and switched it. I adjust the timing by feel as i dont have a timing light yet. took a short 1/2 mile jaunt and back. power and acceleration have definitely improved, but still getting vibration off and on at constant engine speed while cruising and occasional popping from the exhaust. I will absolutely look into all the suggestions, but its feeling like a timing light and further carb adjustment will correct the issues. definitely need to give some attention to the brakes before any longer test drives are taken. thanks
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Me -C,U,UC,WC,WD45,190XT,TL-12,145T,HD6G,HD16,HD20
Dad- WD, D17D, D19D, RT100A, 7020, 7080,7580, 2-8550's, 2-S77, HD15 |
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Lars(wi)
Orange Level Access Joined: 14 Sep 2009 Location: Permian Basin Points: 7155 |
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Fresh, non-ethanol fuel?
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I tried to follow the science, but it was not there. I then followed the money, and that’s where I found the science.
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AC7060IL
Orange Level Joined: 19 Aug 2012 Location: central IL Points: 3335 |
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Cal(Ks), congratulations on owning an Iconic Mopar machine. Is it a 383 magnum, 4speed/Automatic, front bench seat, & Hi-C orange paint?
What everyone else mentioned, Plus, get your distributor vac hooked up to a carb port. Also check your fuel pressure at carb inlet to verify that all your new fuel parts are operating satisfactory. Does your 750 demon, when disassembled for repair, contain a small black fuel hose(s) that feeds its nozzles from its accelerator pump? If so, check that it’s ends are tight & not leaking.. Ethanol has a nasty way of deforming/swell it. Here’s a video on a 625 demon. https://m.youtube.com/watch?v=tEUNN0S5Qe4&pp=ygUTNzUwIGRlbW9uIGNhcmIgcnVzdA%3D%3D Hope you get it running right. |
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CAL(KS)
Orange Level Joined: 18 Sep 2009 Location: Chapman, KS Points: 3786 |
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Me -C,U,UC,WC,WD45,190XT,TL-12,145T,HD6G,HD16,HD20
Dad- WD, D17D, D19D, RT100A, 7020, 7080,7580, 2-8550's, 2-S77, HD15 |
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CAL(KS)
Orange Level Joined: 18 Sep 2009 Location: Chapman, KS Points: 3786 |
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Me -C,U,UC,WC,WD45,190XT,TL-12,145T,HD6G,HD16,HD20
Dad- WD, D17D, D19D, RT100A, 7020, 7080,7580, 2-8550's, 2-S77, HD15 |
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Steve in NJ
Orange Level Access Joined: 12 Sep 2009 Location: Andover, NJ Points: 11776 |
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Easy way to know manifold vacuum from ported vacuum is any port above the throttle blades is Ported vacuum. (vacuum advance) Anything below the throttle blades is manifold vacuum. You could have a couple valves sticking from sitting. I'm not a snake oil guy, but a little Marvel Mystery oil added to the crankcase could help unstick a couple valves or lube up some lifters if that's what's causing the shake. A tight valve could cause the same issue. I installed a Demon Carb on the wifes 55' TBird a few years ago. That seems like a nice Carburetor. Adjusted up nicely as well. The main reason why I put that on is because of the the new style fuel bowl that runs 20 degrees cooler. The old T-Birds are like the old Corvettes. Tight engine boxes with not much air movement which builds under hood temps. The T-bird owners used to call the OEM Carb that was on them "tea pot" Carbs because they used to percolate all the time in the summer and then vapor lock. So far we haven't had that since we put the Demon Carb on.. Glad to see there's still a lot of folks that have the oldies but goodies still on the road today like myself. That's great that your son is interested in it. We need more of the younger generation into Antique Cars! Steve@B&B |
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39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife
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