O.k. Here's the deal. Newly rebuilt engine, all new internals. Stock Q-jet was hosed, so bouhgt a new reman Q-jet. Let me back up, the original Q-jet worked, but it had so many leaks it was impossible to tune, so I replaced it. The distributor was completely rebuilt as well. Now, I put the new carb on and after priming, the car starts right up. Ran great for a few minutes, throttled up nice and then it started to develop a "miss" and sputtered out. Now, it won't start at all. I have good spark, getting fuel, timing is perfect...it's driving me mad!!! It sounds like she wants to crank, it has that stumble a little bit like it wants to kick over, but it doesn't. The only other thing I am wondering is this. When the car ran, the GEN light was on. The cafr has a new alternator. I checked output at the ALT and it's charging. I check voltage at the battery and it's holding a charge. Two issues here, but not sure if the 2 could be related, i.e. weak battery = weak spark. I'm STUMPED!!!

 

If you try priming it again and the same thing happens, try checking the threaded port on the back side of the base plate. The backside being the side by the distributor. There should either be a plug in the port, or a hose coming from it, but not open. I had a q-jet in a 82 pickup do the exact same thing, and I had overlooked plugging that port.

 

Yeah, actually, that threaded port has a steel line in it that connects to a rubber line that goes to the brake booster. I've checked for vacuum leaks and have blocked off all the ports. Last night when I was cranking it so much, their was fuel actually loading up in the exhaust.. It really almost seems like an ignition problem. I am thinking though that when the other carb was on there and was nto tuned right, it could have been running way rich and fouled the plugs out. I am going to try and swap new plugs in today and see what happens. The plugs that are in there were new from the start, and are not carboned up, but are black..a good indication that it was running rich with the old carb on there. I'll swap them out today and see what happens.

 

double check the spark....sounds like an igniton problem to me especially if yu can verify that gas is going through the carb

 

Good point about the ignition. I swapped in a new distributor tonight and changed the plugs. The plugs were soaked with gas. The car will start right up now, but when I try to rev it up, I hear poppin and crackling coming from the primaries in the carb and the car will not rev up. It labors and pops and crackles and sometimes will burp up thru the carb. By those indications, you would think I had a timing issue, but I have it set at 10 BTDC with the vacuum advance plugged. When I have the timing light on it is sportic as well, which would indicate a miss. But, here is what I am thinking...I wonder if I have stray voltage somewhere? I'm not sure but it's driving me crazy!!! I should be cruising down the road right now happy as a lark and instead I'm about to slam my head in the door!

 

hei or points?

 

I would start with a static timing test.

 

HEI ignition. Static timing is dead on. It acts exactly like the time I accidently swapped 2 wires on a 454. It will run, but when you try and put a load on it or rev it out.. it pops and crackles thru the carb. I doubt it, but I did buy a new cam thru Summit and the cam card does not have the firing order listed but I would not think that it is anything different than stock. Trying to call summit tech line right now!!! AAAAARRRGGGGHHH!!!!

 

I had more or less the same problem with my demon 750. the carb idle mixture was too rich and fouled out the plugs. search this forum for 'backfiring, missing' and you'll see my story. Sounds like your carb id too rich.

 

Thanks EBBENR!! I have tried to adjust the idle mixture screws using a vacuum gauge to get the best possible setting. No joy. This is what I have found in the past few minutes. When I put the pickup of my timing light at the end of the wire closest to the cap, I get consistent flashing of the timing light. When I move it all the way down towards the spark plug, the flashing becomes inconsistent, even more so when I accelerate. I tried this on a few different wires and get the same effect. These are new wires, but I have gotten new caps before that were defective so..I am going to get new wires and try that this afternoon. I have friends who work in auto parts stores and they told me that sometimes someone will bring a defective part back and instead of going into the defective parts bin, they make it back to the shelf!! Yipes!!! Anyway, I'll post later today after the new wires are installed.

 

I'd also try changing the plugs again and putting on the old carb. While you have the new one off, make sure the idle mixture screws are out only 1 turn and that the carb isn't on the transition circuit.

 

I meant to say one thing at a time.

 

o.k. Old/new wires were bad. The "new" wires had too much resistance. The wire for cylinder 1 had 18K ohms over 4 feet of wire. I'd say that s a tad too much, and by tad I mean WAY too much. So, replaced witha set of MSD's which I should have used in the first place. Still having the same problem though, although it is better. Still spitting fuel out of the carb under throttle and popping and crackling thru the carb.

It still really seems like a timing issue. If it is popping and crackling and spitting fuel up thru the carb, means that an intake valve is not closing before it fires. It idles fine, starts fine, but as soon as you put it under load, it falls on it's face and pukes. Not sure if this matters but I have an aftermarket timing coverf on there with the timing pointer that bolts to the front. I am going to pull plug number 1 tomorrow and get the piston to the top and see where the notch is on the balancer as opposed to the timing mark. Other than that, I can't think of anything else it could be! I have also readjusted the valve lash. Backed off till I heard it clack, then tightened till it got quite and then gave it a quarter of a turn.

What else could I be missing? Other than my brain!?!?!

 

Your first post threw the first red flag for me. I have yet to see a reman quad that was correct out of the box. I'm a service manager at an independent shop so I've seen my share of rebuilt quads, and everytime they end up being a headach. The only way I end up correcting them is rebuilding the reman. Plug wires are actually ok up to 7k ohms per foot. Try going back through your qaud and double check everything is correct for your application, Jet's, Rods, float level, etc.


Pat Kunz

 

Valves too tight ... specially if hydraulics ... lifters pumped up & holding valves open. Common mistake in new motor w/ new cam.

 

Jackson, thank you for the reply. With the car running I backed off on each valve until it clacked and then tightened till it got quiet and then gave it a quarter turn more. You think I should back off the quarter turn until it has some miles on it? The symptoms definitely point to a valve not closing all the way. The heads were completely rebuilt and all the springs were checked. ll new valves were put in and treated to a 3 angle valve job.

 

First, I'd suggest a compression check ... loosen rocker arms & pump air in & see if it holds pressure. It is also possible the valves' stems have burrs/or guides are not reamed loose enough / or stem(s) had a burr & scarred the ID of guide (causing stem to stick) ... UNlikely (new) but maybe bent valve stem(s) ... either causing valve(s) to stick open.

 

O.k. I ran a compression test on all 8 cylinders and they are all 180 lbs. Rechecked the timing and even swapped in a different carb. Still have the same symptom. Still popping and crackling and spitting fuel up thru the carb. Won't rev up.. only revs to about 2G and then it won't go any further. I replaced the entire distributor, the plugs (again!), installed MSD wires...I'm stumped! If I can get it running again tomorrow I will reset the valve lash. Last time I set them, I did it with the car running, loosened till it clacked, then tightened till it got quiet then gave it a quarter of a turn. I will back off and tighten until it stops claking and leave it at that. The only other thing I can think of is that the cam is wiped out. Maybe not completely, and it is opening the intake valve a little bit but then slamming it closed too early. Does anyone have any other ideas?

 

It could be a timing issue. Why not check and see what your timing is doing when you are at that 2G RPM. I would think that if we are trying to set them at 36 degrees at 2500 to 3000 RPM, that at 2000 RPM you would have just a little less than the 36 degrees.

 

Cam Card has a different firing order? Is it a 4-7 swap cam? Did I read that right?

Post the summit part number

You should have a 18436572 order.