it is unlikely that #2 or #8 plug wires are running along side #1 wire for distance great enough to cause induction crossfire, it would be nice to see pics of the OP's setup.
Oh sorry when I searched Comp's website for '268H' that one came up first. It must be this one: http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=73&sb=2 Actually, they were stuck for a while. The timing read a constant 35 degrees. But after I freed them they started working. I'll get pics of the engine soon.
"choppy idle" 110 lobe seperation, dished pistons, 64 cc heads .... Go back and re-read my first post on this thread. Low compression and both valves open at the same time you need a lot of ignition lead to make any cylinder pressure. Kinda weak on the bottom end of the rpm range. On the flip side, it likely pulls pretty hard upstairs If you put the compression back up to 9.5 to 1 or more, you would be back where everyone else says you should be (and where you think the timing should be as well) Either put a little blower on it or run it "as is" with the timing cranked up.
Thanks Banana, I can't afford a blower so I'll be running it as is then! You're right, it pulls much harder once you get above 3000 rpm. And to porknbeaner, I can turn the idle down as low as 600 rpm, but that's what it ends up at when in gear, so I keep it up around 1000 in neutral.
Now all you need is the right torque converter and you won't need the idle so high in neutral. It will get up into the cam much faster as well with a little more converter stall.
That sounds about right. Too bad the guy who built my trans was quick to recommend a 2000RPM converter :/
OK. I've gone through this whole thread again, and nowhere did I see that you checked to see if the plug wires were installed in the cap correctly. Let me tell you a little story. About 25 years ago, I bought a '68 Corvette. It ran terrific. In my quest to get it to perform better, I did a basic tune-up. After I was done, I was going to time it. Much to my surprise, I had the same problem you have. I could get it to run great by timing it "by ear", but when I put the light on it, it would hardly run at the stock settings. I then checked to see if the wires were in the cap correctly. They were one off. I moved the wires to the correct positions, and tried again. This time, I could get it close by ear, but when I went to advance the distributor, the advance can hit the coil. After much hair-tearing, I went on the NCRS Technical Discussion Board (you know, the anal-retentive Corvette guys). From them I found out that the distributor drive gear should only go on one way, even though it is easy to istall it 180 degrees off. There is a "dimple" on the gear that indicates how to install it correctly. I pulled my distributor, and lo and behold, the gear was on wrong. I pulled the gear off, bought a new roll pin, and re-installed it correctly. After this, the distributor could be set to a postion where the car ran great with the wires in the stock positions, but it was still wrong by the timing light. I drove it this way for a few months, but it always bothered me. I finally came to the conclusion that it was a slipped ring on the harmonic balancer, so i pulled it off and checked it. Yep it had slipped. I sent the balancer out to a guy in Oregon who specializes in these things, who rebuilt it, and I finally got evrything together and working right. Bottom line, there were three different things wrong with the car, and I'll bet it took about two years to figure everything out. Someone probably rebuilt the distributor, installed the gear improperly, and when they couldn't get it timed right, they moved the wires on the cap. Don't assume there is only one thing wrong. Oh, and to the guy who didn't understand my "if it ain't broke, don't fix it" comment, I was not referring to that particular situation, but to people who advance it so easily. In the case that it may be broken, not fixing it can lead to a lot of problem. If it is broke, FIX IT.
as i posted previously, if the two wires going to the electronic distributor internals are switched, you get what you describe. i service porsche 911s and see it occasionally when a connector plug is replaced and someone swapped the ground and signal wires. worth a look.
I see this thread is very old but, I'll bet the farm this was the solution. After a day of trying to figure out the same problem on a ZZ4 350 it was the answer to my problem. THANK YOU MAD MIKE!!!
I wish the OP would chime in and tell us what he eventually found wrong, if he did find anything, that is......Hello? Are you still out there?
Old thread but.....If you installed a brand new harmonic balancer, and checked TDC, did you compare the old balancer to the new one first? Sounds like you replaced it, and the two balancers have different timing marks. If I checked TDC and it didn't match the mark on the new balancer I would have made a new mark at true TDC. If it was mine I'd recheck TDC and mark it permanently with paint, a filed notch, or timing tape.
The answer is on pages 4 and 5 of this thread. I am sure he is still running it with the timing set where he had it. Right from the very first post the OP said he had checked, double and triple checked to make sure the damper and timing mark was accurate at TDC yet every other post insisted that the damper and/or timing tab is the problem for 6 pages...
A google search led me to this thread. I've got a .040" over 350ci, roller cam block, four bolt mains, 1pc rear. 11:1 compression with .030" quench height. ZZ4 crank & rods, Speed Pro H345ncp40 pistons. Pro-Comp 210cc heads with 58cc chambers, angle plugs. Comp Cams XR276hr10 cam, Scorpion 1.7:1 rockers, cloyes geardrive. RPM Air-Gap, 1" tapered spacer, Mighty Demon 800cfm carb. Recently I've been wideband tuning the Demon for performance and to diagnose a rough idle/stalling when coming to a stop. The problem only happens while slowing down coming to a red light or stop sign, or parking it after a drive. When it happens I can see on the wideband it goes way lean, pegs the gauge at 22:1. I figured I didn't have enough initial timing to maintain stable enough vacuum to draw through the idle circuit. I had the timing set for 15 initial and 38 degrees mechanical max. Pulled the dist and made a bushing that will allow timing to go from 22 initial to 38 max. When I set the dist back in, I eyeballed the rotor and cap alignment and gave it a fair amount of advance so it would idle. It fired up in half a crank and idle never sounded so good, my the wideband gauge was reading in the low 12's whereas previously it was in the 14.6-15.3 range at idle. I set the idle speed via the carb, put it in gear and re-set the idle fuel screws. Sounded great, rev'ed quicker then it ever has before. I get out and put my timing light on it (Actron digital dial back), 35 degrees initial. I set the timing back to 22 and the idle began to get sloppy/rough sounding and the exhaust note was not nearly as "tuned" sounding. I do have a new digital MSD 6a, I've always suspected the dial back for accuracy with the MSD but the flash/mark doesn't fluctuate or scatter/jump around. Last month I had the heads off and I turned #1 cyl to exact TDC with a dial indicator. I set the sliding timing mark exactly where the dampner mark lined up. I'm thinking I may just go drive it, if it pings (May be tough to hear over a geardrive and dumped flowmasters) pull some timing out and try again. If it doesn't ping just keep adding until it does. I tried to get the timing marks as accurate as possible. It makes no sense to me, but if the engine wants more I'm going to give it. Anyone ever come up with the idea behind the phenomenon? I do live at 5400ft elevation and I know engines can tolerate a bit more timing in higher ground, but not anything like this.
That is not a lot of advance if it is 22 at idle.(as long as you have good fuel) I have as much as 42 full advance after about 4500 rpms. 22 to 1 is too lean. smaller primaries can help. That is why I have always like Quadrajets.
You have a completely different combination than the OP in this thread. The issue with the engine in this original thread was that he has a cam with a lot of overlap and not much static compression. Therefore, it does not have much "running compression" at low rpm. You state you have 11.0 static compression which is plenty even with the cam you have. I would try locking the timing and set it about 35-36 and see how it likes that then possibly work backwards. You may end up with a shorter curve maybe (initial at 28 or 30 and total at 35-36 maybe?). From my experience, each engine likes something different from a timing curve perspective.
Thank you for the reply Bad B, This engine is in my daily driver, wouldn't I want a traditional (yet radical) mechanical timing curve to build torque compared to a locked out timing? I'm more then willing to give a try, however I'd hope to not need to purchase a starter retard box. If I did lock out mechanical timing I'd intend to keep the vacuum advance for high manifold vacuum cruising. The trans is a 4L60E with a manual valve body and a non-lock up 2800-3200 10" converter with 4.10:1 rear gears. Perhaps it will be more forgiving on the lack of torque building timing. I'm going to see what the "vacuum gauge/ max initial timing" have to say.
So.. if you keep vacuum advance, what do you gain? When you step into the throttle, the vacuum drops and the timing retards with it. That usually makes it fall on it's face. I have never been able to make a modified SBC run "better" by using the vacuum advance. I never use it. Mechanical advance only. That is my opinion based on decades of fixing guys cars who spend a lot of time trying to make an engine have good power and drivability while insisting on using the vacuum advance. I plug the vacuum advance, set the total and they can't believe how good it runs. They never look back and enjoy their car. Posted using the Full Custom H.A.M.B. App!
Vacuum advance is not needed, especially on a hi performance engine, but it does improve mileage on a street only car, and especially on a heavier car. I don't have vacuum advances on either of my hotrods, but my daily driver truck still has it. I've tried running without it, and it works fine, but mileage went down the tube too.
Vacuum advance allows for slightly less fuel consumption while cruising. I am using the same pointer and balancer mark with the light. I just experimented in my garage...22 initial, 850rpm, 14.3-14.9 AFR. In 4th gear 8-10" vacuum. 30 initial, 860rpm, 14.4-15.1 AFR, in 4th gear. 10-12" vacuum. rev'd engine and loaded up against the flash stall of the converter. No missfires, no hesitations, stopped and started a dozen times with no starter lag. (Old large body, rebuilt starter). 45 degrees initial, idle rpm screws completely backed off the blades. Fuel idle screws not even an 1/8 turn from closed. 880rpm in 4th gear, 14.3-14.8 AFR. 10-12" vacuum. I returned the timing back to 30, adjusted the carb. Went for a drive. Astounding throttle response, no hesitations or stumbling. No missfires or pinging (that I could hear over a geardrive and dumped flowmaster super 40's) . It will throw you back in the seat harder then ever before. Idle AFR would still go lean coming to a stop but wouldn't stumble and a second later the AFR's would come back down and rest at 14.6. Once parked, stoped and started 3 times. Even waited for the coolant temp to climb once turned off for heat soak. No started lag. And a header pipe is even touching the starter for max heat transfer With the vacuum advance on a ported source, adding 15 degrees of timing. Cruise was steady and smooth. No surging as typical with too advanced of timing. So, I really do 't know what's going on with it. Unless my timing light is just extremely off. I'm considering wiring in a GM ign control module and using a standard induction light just for checking. I think that'ss what I'm going to chalk it up as, MSD vs inexpensive over the counter digital timing light.
Bad B I know what you mean about Vacumn Adv. I run a 327/300 hp Stock in my 50 Merc & did away with the Stock Dist, But I am using the GM Dist from my Race Car since I don't Race anymore, which is a Dual Point Tack Drive ( Needle Bearing ) Dist & if memory servis me right it Totaly Timing 36-38 and No Problem Pulling Power running a PowerGlide 18" Vacumn Just my 3.5 cents
At the recommendation of Bad Banana I locked the mechanical advance of the dist. Bolted the rotor plate & shaft to the trigger wheel, re-installed and set up for 38° by my timing light (which may not be accurate). The idle has never sounded so clean nor the throttle response so crisp. https://www.youtube.com/watch?v=w3z88rCe7UE
I have read this entire thread and not seen the a single post stating what I would believe the problem is. That is a substantial vacuum leak. Back in the 80s I was hanging with a guy that was running a 71 Mustang dirt circle track car. 351C engine. He thought it was pretty fast from test driving it. We got it to the track and he got his but kicked. Checked timing, 60* advanced, Traced the problem to a miss-matched 2b car gasket. Once corrected it ran fast and timing was where it should be. I have also seen this in leaking intake manifold to head gaskets.
That's bad news, I'll try to rule out those as a possibility or narrow them down as potential problems.
Had this happen on my bbc, msd ignition and dial back to 0 timing light.......would not give me accurate results. Hope this helps. Scott
"Vacuum Advance", the famous misnomer of ignition timing control. In many OEM applications it does indeed LOWER timing when the go pedal opens up in order to compensate for engine LOAD. Clearly race and hot rod engines like their lead times high, but to a point. In a stocker they wanted smooth running, good manners, decent mileage. I ran a solid shaft distributor in my racer at 36...ALL THE TIME. Well, except for the 22deg start-retard built into the MSD stuff. I'm not so sure a street car would have liked that too much, but for WFO only operation I can tell you it mighty ferocious. I can feel it now, foot to the floor, 2 step bangin away at 4500, let go of the trans brake and BANG up to 5500 and GONE! 7200, SHIFT!!, through the eyes at 7800 and all done about 10sec later. Sometimes I really miss that car...
I completely agree vacuum advance has no role in racing. But on the street it does. If you drive 30-100 miles a day with an 11:1 SBC, if it even yielded 1mpg better that could be $10-$50.00 difference a month going in the tank just for hooking up the vacuum advance.
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