Hey guys,
There must be something wrong with my 289 CI engine. My best idle, manifold vacuum, initial timing setting is at 30 degrees advanced.
If I lower it towards typical 8-10 deg it starts stumbling slightly, vaccuum, and idle.
Any ideas where to start looking for the reason? Everything online tells me this setting is way high.
It runs good this much advance, starts right up, strong running.
It does have a pulsing engine vibration when I rev it up over 1500 RPM, in all situations, with and with out vaccuum hooked up. It vibrates every 5 seconds for about 3 seconds long, over and over. At idle, it purrs like a kitten.
I’m wondering about the timing chain being off, or maybe the Pertonix II system is bad.
History:
Engine rebuilt in 2012 just before I bought it.
Had a C4 tranny and a standard intake and Ford 2BBL carb. Ran fine as far as I can remember.
Over the past three years I have put an Edelbrock Performer intake and Eddy carb.
New distributor from NAPA. New spark plug wire and plugs.
Exhaust is out a 351W manifold set into 2" dual exhaust.
Has Borgeson PS, PB, hi output alternator, thermal fan.
Just put a new harmonic balancer on it to try to fix this engine vibration problem. Didn’t change anything.
I’ve been working on this issue off and on for years.
Hope someone can give me some pointers.
Thanks!
My first thought would be you have the wrong damper. It’s not uncommon for a new damper to be off by quite a LOT. Get a TDC stop. Rotate your engine slowly by hand until you lightly hit the stop. Mark the balancer. Then rotate it counter clockwise until you touch the stop again. Mark your damper again, and measure the distance. the half way point is true top dead center. Have you checked for vacuum leaks? I’m running my initial at 12 degrees and have run small block timing as much as 14 degrees. As far as vibration goes, your flexplate could be the culprit for the vibration, as could your torque converter. I would start spraying carb cleaner around your carb base, and by your intake ports. I would then check for leaks at your vacuum hoses and fittings. What is your idle speed when you set your timing? Those are a few things to start with.
I did this once without a TDC stop, just visually looking at the top of the piston. I will do it again with a stop.
I was hoping the old damper had slipped a little, but the new one shows the same timing when using the timing light.
I’ll check TDC again, maybe it’s a little off.
If the TDC off, what is the possibility that both the old damper (Ford) and the new damper are off balance? Seems like it would be rare.
That’s kind of odd that both would be that far off, but not unheard of. I would still check tdc, look for vacuum leaks, and also look at flexplate/converter. I had the same type of vibration on my '95 pickup (300 I6, E4od), and when the converter finally starting shuddering when locking up, the same vibration got much worse (5 second intervals, 3 second vibration). Put a new torque converter in, and vibration went away. Imbalance could be at either end. You are basically looking at harmonics translating to the chassis from the engine.
Are you checking the timing with the vacuum advance connected?
If you are you probably will see close to 30 degrees depending on where initial timing is actually set.
My initial timing is 10-12 degrees BTDC with the vacuum advance disconnected, when it is reconnected it jumps to about 25 degrees BTDC.
If your initial timing was actually 30 degrees BTDC it would probably be very difficult(or impossible to start).
That’s an odd vibration to not be consistent. Sounds like two vibrations where they sometimes cancel each other and other times they emphasize each other. Try taking off the fan belts and revving it up…watch your temp gauge with no fan or water pump action. If the vibration were constant I’d say they could have put the wrong flexplate. Not sure if the 289 is neuTral balanced or not. Perhaps there is a 302 flexplate with a 28 oz weight, or a late 302 flex plate with a 50 oz weight? My 58 Monterey will run not so good and it’s usually some crud clogging up an air bleed in the boosters of the carb. They are pin holes and it doesn’t take much. Your 2100 is similar in design. 30 degrees at idle is way high. Like the others, I’d suspect something wrong with the balancer, or timing pointer. Are you reading on the #1 wire? If you were previously a Chevy guy, you’re on the wrong side. Is your firing order correct? Does the cam have a 302 or a 351 firing order? Is a rocker set too tight? Did you do a compression test?
Was the missing T the funny part? Let me correct it ----“Not sure if the 289 is neutral balanced or not”---- HA HA HA HA HA HA HA HAH A HA HAH A HAH H H A HA HA HA HA HAAAAAAAAAAaaaaaaaaaaaaaa…
Good advice given. Check it all out.Try another timing light. That worked for a guy on the torino-cobra site proving sometimes it’s the simple things that trip you up.
Hi Guys,
Thanks for all the info.
I finally had time to use the piston stop to check my TDC point on the HB. It’s spot on, the new HB.
So, I went ahead and put the setting at 10 BTC, and increased the idle back to where it was before (good steady 650 RPM or so).
I am checking the #1 Piston, FYI
I was going off of Mustang Projects timing setting using Vacuum and RPM to set it. Since the best Vacuum, (only about 1 In higher than at 10BTDC), and lowest idle set screw setting ended up being at 30 BTDC, I was concerned. Does high altitude have anything to do with this? I am at 7000 Ft.
So at 10 BTDC the vacuum reading is about 1 in lower, and the idle set screw had to be turned about 3/4 turn to bring the idle back up.
I am curious about the comment about the rocker arm tightness. Would that cause the pulsing vibration at higher rpms?
I do believe the Flex Plate is correct. I looked at the weight through the AOD inspection plate, and measured the length. I compared it to the weight on the old C4 flexplate, and its the same thickness and dimensions. So I figure that means its a 28 oz.
I’ve checked for vacuum leaks and the carb cleaner trick, and no effect. Everything is new and tight.
I set my initial with the car not running, then start it, let it warm up, and double check the idle speed, and timing at the lowest rpm possible with the advance hose plugged. Once I am satisfied with those three things, I hook my advance hose back up, check the idle speed with vacuum advance, and adjust that if necessary. I then hook up my vacuum gauge to a full vacuum source and use it to set my curb idle mixture for the highest vacuum reading.
That is my process, and it has served me well. You can set your initial timing with a vacuum gauge, and I have resorted to that when I found the marks on a damper to be off, but I usually use it as an aid, not the gospel to set my timing. I DO however use it for mixture settings. If you DO use the gauge, you should keep advancing the timing until the vacuum either stops climbing, or starts climbing at a slower pace, and back it off a few degrees. Usually until it starts to drop, and then back to it’s peak. I would suggest going 10-12 BTDC as a good starting point, and then look at your rate of mechanical advance, as well as your total advance. Then go to your fuel system. Also keep in mind that even similar engines in seemingly similar cars will differ somewhat. It’s what I call manufacturing tolerance. What works one one engine may be completely different for another, even if they are the same size and same build. All it takes is for something to differ by a couple of thousanths, ccs, etc.
And yes, altitude, barometric pressure, etc., ALL effect an engine and it’s tolerable parameters. Even my fuel injected cars all seem to pick up a few ponies on a cold dry day even though they are affected less than my older machines.