CarburetorsCarb discussion and questions. Upgrading a Third Gen carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.
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Running a 350 in 87 Formula. Originally a 305 car. Original CCC q-jet (slightly modified), Accel bilitech distro (CC), headers, Edelbrock egr intake, all emission controls intact and functioning, Torker S/R heads, mild cam 204/214 @.050, 420/442 lift. Nothing outragous, just good low end grunt. Car ran flawless for two years, then started acting strange. At warm-up engine is fine, but as soon as NOT is reached the tach goes crazy, and the engine gets erratic. Seems like it's not getting enough fuel or timing is going in and out, backfires through carb AND exhaust. Initial timing is at 4 BTDC. Verified no vacuum leaks, fuel pressure is steady at 6 psi, (Carter mech.) Car also has the in-tank helper pump, verified working. Also swapped out the Hypertech Thermomaster Chip for stock chip, no change. Pinned out the cables to the ECU, all good. Swapped out ECU, no change, swapped old one back in. Anyone think of anything at all that I am over looking, and does anyone know if the tach going nuts is related to this, because the tach doesn't go nuts until NOT. Two thoughts I am having are the knock sensor, and/or ESC, haven't checked those yet. Thanks in advance for any and all suggestions.
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__________________ The earlybird may get the worm, but the second mouse gets the cheese.
Last edited by csmith3; 05-26-2009 at 09:21 PM.
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Tough one eh? Well, I'm rebuilding an 80's q-jet from a GMC van, and going to go with non-CC distro, and see what happens. Still wonder why the tach is tripping though. One more thought, I do have an MSD 6 on it. Something else, I swapped out didtros. No change. Hmmmmm.....(as I scratch my head) The best part is that she throws no codes at all. Hmmmmmm.......If the knock sensor or ESC were bad I would imagine there would be some codes. Also since I have laptop with Vista I can't seem to get any diag programs to work. Oh well it is a fun exercise in futility.
__________________ The earlybird may get the worm, but the second mouse gets the cheese.
Something might be shorting out, I had a simliar problem on my camaro, Cleaned all the wires and didnt do it for awhile. Could be a bad chip in the dizzy, make sure theres alot of silicone grease on that one.
I had the same problem with my tach and it turned out to be the plug wires. Installed Accel 300+ and tach problem went away and engine run's fine again.
Five7kid, yes I did use the same coil on both distributors. It is a relatively new accel unit. I did not think of that possibly being the culprit. Even new parts nowadays can't be ruled out. Thanks.
87_355ci_camaro, the dizzy is a pretty new accel bilitech unit, and, as I said, I swapped it out for the stock unit and nothing changed. Thanks.
Auggie, I'm running MSD 8.8's that are brand new, so I'm pretty sure they're good. Thanks.
I will try a coil swap and let you guys know what happens. Thanks for all of your input and ideas. They really do help.
__________________ The earlybird may get the worm, but the second mouse gets the cheese.
Soooo, I swapped out the accell 140011 coil for the old stock coil, now the tach reads normal, no more flipping all over the dial. But, after reaching NOT, there is still some issue with timing I think. It will just falter and stall. Fires right back up, and runs normal for a few minutes, but then starts to get a little eratic. I can feather the gas and keep it going, but if it's in gear it just dies. Not as bad as with the acell coil, but still seems to be sort of the same problem. This really affects drivability, can't get too far from the driveway.
__________________ The earlybird may get the worm, but the second mouse gets the cheese.
Alriiiiiiight! Like to start by saying I thought I knew a lot about these cars, but I have learned alot over the last couple months. I believe I found the issue. I know I'm a bit wordy, but bear with me please. I switched to a non CC Q-jet (late 80's GMC van carb) and accel distro yesterday. She fired up on the first try(!), I dialed timing in to 12 BTDC, but the tach was still going nuts and it sounded like timing was very retarded and when I hit the throttle she would rev a bit, the tach would flip out and she'd die. So, I bypassed the MSD-6 and she fired right up, and purred. I checked timing, still at 12 BTDC, and she runs like there was never anything out of whack. I rebuilt the Q-Jet myself, (I love those things and have built/modified several) and I either got lucky or maybe I am starting to understand them, because it runs very good, no hesitations, no bogging on first try. So to make a long story short, (and, forgive me, a little bragging) the MSD-6 failed after a short period of time, about three years. IMHO It should have lasted longer, the NHRA uses MSD stuff religously.
I want to thank everyone who contributed advice/knowledge, and I will be checking in on a regular basis to see what's up.
__________________ The earlybird may get the worm, but the second mouse gets the cheese.
