Hmmm, ok. I have my homework cut out for me. Later today I will first change the fuel filter as I have not done so since the last rebuild (3K). Start with that then will try all of the above watching the RPMs closer as well. I will also post some pics of the motor with the ram air pan off so you all can see exactly what I have going (or not going). I truly appreciate ALL of you offering up our ideas/thoughts.
I will post later on today with some additional info-
Definitely do any maintenance items first like the fuel filter - I should have mentioned that earlier! That's why in the old days the first thing was a "tune-up" - not any actual tuning going on, just replacing the plugs, cap and rotor, fuel and air filters, checking the plug wires - then seeing if the problem is still there.
Update: Changed the fuel filter, no change. Changed the timing just a bit no change. I am now begining to wonder if this could be electrical as now the car is not starting on it's own. Put cables on it and bang fires right up. Take the cables of, turn the headlights on and she stalls. Also, the other night when the bulk of all of this became worse, I noticed that my turnsignals were flashing very slowly. Ground issue? Bad altenator? Would an electrical problem cause my backfiring/breaking up problem or is all of this two seperate issues?
Ok boys and girl (just for you Vikki). As a result of this latest issue here is what I found. To start, problem is now solved. However, in trouble shooting this issue I found the following and have since fixed.
1) Plugs were toast, replaced with A/C 43 (are these correct)? 2) Alt. was toast (installed in 03 and was completely shot). This was a $35 Advanced Auto alt. and they replaced free of charge. 3) Battery was beat up from bad alt. also installed in 03 replaced with a new one. 4) Found a vacuum port on the very back of the carb that was wide open. Now installed a plug on it and car runs better. 5) Changed my timing a bit (rotated it clockwise) car runs much better. Going to buy a timing light tomorrow. 6) Still going to have the carb. set up correctly (SOON). 7) Once carb. is set up I will look into fuel pressure etc. because I still think (for some reason) the car is not getting enough fuel. 8) Still need to look into vacuum advance, make sure the vacuum switch is working properly etc.
Thank you all for your help/suggestions etc. Looks like this time around things are all set and back up and running!!
One thing on these old cars. It always amazes me how quickly you can work on these cars. I pulled both the battery and alt., took them to Advanced Auto and had them tested, got the two replacements, bought them home, installed them and went for a test drive all in between the above two posts.
In my new Dodge 1500 Ram, I'm not sure I could find the alt.!
Yeah for sure. I just really need to get the timing right, the carb. set up right and vacuum advance working properly. I think once those items are addressed I will be in good shape...
Oh one other thing that I found. When I replaced the fuel filter, the new one was twice as long as the one I replaced. The one I replaced was not even long enough to stick out past the housing that it goes into. which is correct? They both seemed to have worked but what gives with the difference in them?
Timing light, vacuum gauge, and volt/ohm/rpm/ meter are a must have if your tuning/trouble shooting yourself. There's no way around it unless you've tuned the same combo's for years. Even then, you'll find them the most valuble tools you have. And you wont be using the "wag' method.
Back firing under wot(wide open throttle) is "usually" timing and or secondaries opening to fast. Leans out fuel mixure, then "fuel dump" fires up inside intake. The secondary air flap can be adjusted to slow down/speed up air flow. Theres a tension spring and screw on one side. Tightening it will make "air flap" open slower/later. Usually what needs to be done.
The 4 lean/rich plugs...? Could be the open vacuum port. But more likely bad fuel distribution from carb. Do you have another to swap/test? I aways had a known good spare(same one) since 79 just for that purpose.
Hook up distributor to full manifold vacuum. But be sure to disconnect and plug it at intake/carb port when checking initial timing. As for setting...thats a tuff one. Depending on cam and degree install, could be anywhere from 8-18 initial, and 32-40 total. OH, and SET TIMING BEFORE final adjusting carb.
You need vacuum gauge and rpm meter when ajusting carb. Try for highest "steady" vacuum reading at lowest idle(within reason). EVERY engine is alittle diff.
The pattern of the rich/lean plugs doesn't match up to the distribution pattern of the dual plane intake (outside two on one side and inside two on other side) so it's not likely a carb problem.
Backfiring when transitioning to full throttle is affected by the secondary air valve adjustment. Full throttle mixture after transition is controlled by the secondary rods.
If you are up for it..I have 4 more weeks off of work and you are a 6 hour drive away. I'll come over, take a look at the engine and aside from any mechanical issues (wiped out cam) I'll have her running top notch in a few days.
Si Vis Pacem Parabellum
1967 Starlight black PMD Engineering 400 Auto 1968 Alpine Blue 400 4 speed 1968 Verdoro Green 400 HO 4 speed 2013 1LE 2SS/RS Inferno Orange Camaro.
Sounds like a carb problem dumping fuel and fouling out the plugs. It is either during WOT or idle circuit or possible a warped air horn causing air to leak in.
Want a quick solution? Take it to a carb shop and have it rebuilt, telling them exactly what you have stated about the plugs. I bet $200 will solve most of your issues. Then final tune.
I used to live in Cocoa Beach.. Will be in Miami on a layover the 23rd of Jan..
Si Vis Pacem Parabellum
1967 Starlight black PMD Engineering 400 Auto 1968 Alpine Blue 400 4 speed 1968 Verdoro Green 400 HO 4 speed 2013 1LE 2SS/RS Inferno Orange Camaro.
I am leaning towards a carb set up due to the fact that last spring when I bought my Q-jet from 69firebirdman, all I did was take it out of the shrink wrap, set it on the intake & hook everything up. I never touched a screw or anything as I have no clue what I am doing when it comes to carbs.
Could be a carb adjustment. But with it being new I doubt it's anything more than that. I suppose he could have got a bad one but not very likely.
I am going to find someone local who knows what they are doing with Q-jets and have them set it up. The car is running at about 98% now with all the things I have done over the last few days (thanks to all of your suggestions).
There is just a SLIGHT hint of a break up issue and that is ONLY at around 5k. As long as I stay lower than that with the RPMs the car runs awesome. None of the other issues now exists.
Little by little the kinks are getting worked out. For my next step I am pulling my front bumper and grills this w/e and installing the new ones my wife got me for Christmas.
A "valve train very slight adjustment" will not propagate to specific plugs and more random ,the number.
If the "very slight adjustment" fouled the plugs that bad and that fast, his push rods would have fallen out or bent. A slight adjustment would not foul the plugs and you would have definitely heard a noise where the valve lash would have needed attention.
The motor was professionally built correct?
Si Vis Pacem Parabellum
1967 Starlight black PMD Engineering 400 Auto 1968 Alpine Blue 400 4 speed 1968 Verdoro Green 400 HO 4 speed 2013 1LE 2SS/RS Inferno Orange Camaro.
There have been pages and pages of history over the last year on this engine. Lots of history to read. The plugs may be a separate issue from the high rpm breaking up. I wanted to put the carb 'in context' as being a(fairly)new carb. It can only help. It separates the carb issue as 'new carb' issues, rather than 'old carb' issues.
The stock intake (dual plane) has two plenums and each feeds the outside two plugs on one bank of the engine and the inside two on the other bank. If you can remember which ones were where like Vikki said or check the new ones for colour, you may be able to isolate which side of the carb may be dumping fuel like Tom said.
The left side of the carb feeds into the left H-shaped plenum and supplies cylinders #1 and #7 on the left bank and #4 and #6 on the right bank. The right side of the carb feeds cylinders #2 and #8 on the right bank and #3 and #5 on the left bank. Since #1, 7, 2 and 8 are the ones (corners only) that are black I'd be more inclined to suspect that oil is getting past the guides during "spirited" driving (sloshing to the front and rear in the valve cover) and fouling the plugs. They may have gotten the guides and/or seals wrong during the rebuild.
The carb could be dumping extra fuel and doing the same to the plugs but it sounds like the engine is running pretty good now. A check of the new plugs might be very handy to see what is happening now before going deeper.
Very possible for there to be builder error because there have been many build mistakes on this particular engine. Mostly top end stuff..... More than one builder involved, ect.
There is just a SLIGHT hint of a break up issue and that is ONLY at around 5k. As long as I stay lower than that with the RPMs the car runs awesome. None of the other issues now exists.
"Known" to be good now? I'll concede that there may still be tuning issues but until some new symptoms arise ...
I feel very confident in the most recent rebuild. This builder has several high profile Pontiac racers who use his services. My guess based on my limited mechanical knowledge and my interaction with this car for the last years is that my current issue is a fuel/carb./timing issue.
When you consider I have been monkeying with the timing without a gun, not sure if my vacuum advance is even working and the carb. has never been touched, I would think this is where my problem lies.
Keep in mind the car is now running excellent with the only exception being RPMs above 5k. New plugs, new alt., new battery, new plug wires (date coded stock type) have all made a huge difference over the last couple of days.
Amazingly, I've been tracking my milage last few days, I can not beleive it but if I drive the car around town I am getting 14mpg right now. I never dreamed I'd get that. Doing better than the brand new Dodge 1500 Ram (Hemi) that we recently bought...
Yea good call, don't need that. Everything was new this past build, crank, pistons, rods etc. Definately do not want to do any damage that's for sure. I'm going to pull the new plugs I just put in and take a quick look at them just for the heck of it. I haven't driven the car too much since all of this but I'd still like to look at the new plugs...
Thanks again, you guys have been great and very helpful!!!
Is there a way to upload a .wav file to this site? I have a good wav file of my engine running. I can't beleive how good it recorded. My 9 y/o recorded it on his Ipod. LOL
Update: Put a vacuum gauge on all the ports of the vacuum switch and found I have NO vacuum from any of the 5 ports. With that said I re-routed the dist. vacuum line to a port that actually had vacuum. Set the timing where it sould be, tested the mechanical and vacuum advance and everything is dead on.
Car now starts, idles and runs great. However, it does still break up at about 4800 rpm. One of the guys helping me said he is 100% sure that it is the Petronix as he has a 68 GTO (original owner), recently installed the Pertronix unit and had the exact same problem. Went back to points and car is fine. My next step is to intall a set of points and see if it eliminates the problem.
Also installed the new bumper and grills today from NPD. Excellent fit and look great. Very happy with them, I'll post some pics tomorrow as it got to dark and then we went to Old Town for the cruise night. We arrived and ten minutes later it poured like crazy. Oh well, it was a nice ride and a good chance to see how she ran with timing set right and vacuum advance etc.
Update: Pulled the Pertronix II out today and installed a set of points. The breaking up at high revs still exists. The mechanic friend that I have made here is an oldtime Pontiac guy who knows his stuff. After the points were installed he went and got his book and we looked up the carb numbers that I have on the car.
As it turns out, my Q-jet is for a 74 Pontiac. So, with that info he feels that it is not set up correctly due to the smog area and most likely has the wrong metering rods/jets etc. So, now the carb comes off and gets a rebuild with the correct parts to match my engine. Hoping this may very well be the issue...