Quenton Member # 1274 posted January 31, 2004 01:14 PM ------ Dan -
What rear end gears are you running, and did you advance the cam at all?
Q
TOHCan Member # 3011 posted January 31, 2004 03:29 PM ------ And what were you running before the change, and exactly how does it differ/disappoint?
Q, I went with your suggestion on the rear end gears and put in an Auburn posi with 3.55 gears. I love the gearing. The highway is no problem (TH-400) and when the engine is running well (very finicky) I'm happy with everything. I'm not sure if the cam is advanced.
When I bought the car it had been rebuilt to have low compression to run 87 pump gas...it had zero power; had 6x-8 heads. The car came with the original intake and 62 heads.
I had the engine rebuilt, bored .040, crank needed to be turned .010, and everything mic'd to produce 9.5:1 compression so that I'd have no problems running 93 octane. I put in a 068 cam and changed the ignition over to electronic (Pertronix). I got a date correct Q-jet. I had the heads done by a shop that I hadn't used before and I'm not really sure what they did to the heads; I really wish I had researched more about head work before having them done.
So with everything rebuilt I did the recommended break-in, taking it easy for 250 miles and then gradually moving up from there.
This all happened in September; it was chilly sometimes. On a cold morning if I set the choke the car started right up and when warm would run alright...except with an extremly high idle.
When warm I had to give the car 1/4-down gas pedal to get the car to start...otherwise it would just turn over and over and over. When it started up there was tons of black smoke (fuel) and whenever I revved it up there would be black smoke. Mechanics finally pointed toward Q-jet. It was rebuilt twice and was marginally better. Finally found that the top plate (horn?) of carb was bent from over-tightening bolts at some time. Engine builder machined it flat and this made the greatest difference. With this change I had the timing reset and carb adjusted and now at least I got a good slow idle out of it. Still needed to hold pedal down to start it up. Around this time he did a compression and leakdown test: all cylinders have 150 lbs. and don't leak down less than a pound or two.
Over the last couple months there has been grey smoke coming out on startup in the morning and at the end of the day after work. It's not using a lot of oil but the best the I can figure is that the heads are leaking oil down through the valves. The engine builder said he had his machine shop check out the heads when they mic'd them and they looked alright. He said that there is a chance tranny fluid is being sucked in and being burned at startup???...this sounds weird. The problem has been getting progressively worse.
I really think it's the heads. Here are the line items on the head work receipt; I gave them the correct springs for the 068 cam: 16 valve seals - $1.92 5 freeze plugs - $2.50 16 valve locks - $8 Valve job - $75 resurface - $45 magnaflux - $18 clean rocker arms - $5 Total - $143
I took the car to a guy that is closer to my house and deals with classic cars often. He thinks the problem is the heads, particularly a valve guide or two.
I'm thinking to make it worthwhile to get the heads off and take a look at them I'll go ahead and have some porting done and get a multi-angle valve job along with the other work.
I'm confident in the bottom end of the motor. I'm less confident in the heads and carb.
The smoking is a problem. The power isn't what I expected. If the engine doesn't fall on it's face when I goose it (happens most of the time) then I can get about 1.5 rotations of the tires. I thought they'd spin a little more. Once the engine does get revved up it takes off pretty well and chirps the tires when it shifts to second (I don't have any kind of shift kit).
Next time you have the Q-jet apart, put some epoxy around the primary and secondary fuel-well plugs on the underside of the main carb body. File around the edges of the plugs to get clean metal for the epoxy to grip onto. These plugs frequently leak fuel into the intake, causing hard starting/flooding after sitting for a short time while hot. Also allows the fuel to drain out overnight and the engine needs a few cranks to get fuel back into the carb. If the engine does fire right away when cold, the problem could be a needle valve not seating and fuel overflowing into the intake, which matches your complaint of lots of black smoke. Seal the plugs anyway. This is likely the source of your grey smoke on startup, and should also take care of your hot start/ 1/4 throttle problem. Bad guides give a puff of blue on startup and at an idle, and it sounds like they were checked, and new seals should take care of that. A leaking vacuum modulator on the trans will allow tranny fluid to be sucked into the intake via the vacuum line (back of the intake manifold). Once you get the carb back on, you can go through the tuning list found at Quadrajet question. How well is your distributor set up? Regarding tuning the carb and distributor for power, a friend of mine was having trouble with his Buick 455 not feeling quite right. Swapped out his carb and dist. with mine, and went from about 5 feet of rubber to omigoodnesswheredthecargo? Doubt if your car is that badly out, but it should put down some serious black. Q's point about the cam timing is important. Most street cams benefit from being about 4 degrees advanced. I also don't trust the timing set to be accurate and check every one. If the cam is retarded, you'll be down a bit on the low end and may not make it up on the top end like most people think. The worst I've seen (other than having the timing out a tooth - oops!) is a cam that had the keyway out enough that it was halfway between teeth on the gear - had to build an adjustable gear for it (OHC furd)! To check your cam timing quickly, remove the left side valve cover, remove the #1 rockers and spark plug and get the #1 on TDC with the pushrods both moving (exhaust closing, intake opening). Reach into the cylinder with a narrow screwdriver and rotate the engine to TDC several times (rock back at least 20 degrees each time)to verify TDC on the timing tab (only count the normal direction of engine rotation when noting this). Be as accurate as you can. A long dial indicater is best. Bring the engine to TDC, rotating it in the proper direction for the final time. Put a straight edge across the tips of the pushrods. The intake should be even or slightly higher than the exhaust pushrod. .050" higher is about 4 degrees advanced. If the exhaust is higher (double-check), you may want to go back in and correct this. Like I said, this is a bit of a rough check but works.
i cant really help you except to say that the guy who told you the trans fluid thing is just blowing smoke, so to speak. it is something that happens, but only if the vacuum modulator on the transmission is bad. if it was, the vehicle would not shift up correctly, if at all. you would definitely recognize it as a transmission problem. but you can always check the vacuum line for signs of fluid.
This probally doesn't relate to your problem, but it's an interesting tid-bit behind some some of those gremlins that get 'cha.
In the mid 80's I had a problem with my quad loading up at idle, and if you you'd gun it a few times, it would clear up. When it wasn't loading up, the carb was right, able to dump full throttle from idle. Often, however, the **** thing would load up at idle.
When I'd remove the air breather, you could see that the feul bowl was flooding, and the gas poured down the venturi. I played with the float, setting way low. Even so, nothing helped.
One day when it was loading up, I pulled off the lid for the bezillionth time. When I touched the float, I noticed that the seat was binding, and the Jesus clip mad it bind, so I took the Jesus clip off, half the reason was to try it without it, and the other half of the reason was to get a new Jesus clip.
(The wire clip that goes from the float to the seat is called a Jesus clip because when you take it off, and it flies away, you say, "Jesus Christ! Where did that son of a ***** go?")
Anyway, that was about 15 to 17 years ago. I have never been into the carb since, and I have never had a problem since. I'd thought I throw this in so if you have a loading up problem, it's something to check.
One thing you might want to do is check out your timing. With 62 heads and the factory intake, your timing might be badly retarded to prevent detonation. Either have the distributor re-curved to match the set-up and the fuel (talk to Banshee about this - he's got a good place to send distributors) or run some octane boost or racing fuel so you can run full advance.
I once had to limp my 11:1 455 home on 91 octane pump gas. In order to keep from pinging, I had to retard the timing - a lot. (And mess with the mixture.) The car could not get out of it's own way, no matter how I tried. After filling up on a mixture of 91 and 101 octane fuel, I could feel the car still running like s*** as I left the filling station. Within about a block, I could literally feel the car surge as the fuel made it from the tank to the carbs and started to get dumped into the engine. Within a block I had to pull over and advance the timing up to 12* because the oil and water temps were in the red.
Q, everything is set up for 9.5:1 compression; I don't think I'm having problems with pinging or risk detonation. Would you think I'm at-risk?
What do you guys think about the chances of a leaking vacuum modulator? Scott thinks it would show up in a real shifting problem, do you guys feel the same?
Another question I have about this Q-jet, is the choke supposed to open on its own when the engine warms up? When I start it on a cold morning (like today) I push the throttle all the way to set the choke and then start it up. It turns over a few times and starts up with a very high rev idle (I don't have a stinking tach). The car will stay at that idle forever until I go out and pump the throttle (I guess releasing the choke) and then it idles like normal.
Take matters into your own hands and advance the timing until it does ping, then retard it a little at a time until it doesn't do it. Make sure you can hear it! Some exhause noise might hide it. Got any hils near you? A low RPM pull up a hill will expose detonation.
What you describe is the correct function of the choke on a 1969 Pontiac. Stinkin' tach or not.
The "fast idle cam" is what effects the RPM's when the choke is engaged (cold engine). It looks like a stepped arm on the passenger side of the carb. There is a screw that adjusts this setting. When I originally put on my quadrajet the fast idle arm was wedged way up so the car would "idle" at 3,000 RPM! Here is the description on how to set it ("borrowed" off a Corvette site):
FAST IDLE ADJUSTMENT
Close the primary throttles and position the cam follower above the high step of the fast-idle cam. Turn the fast-idle screw clockwise until it touches the lever then turn it down three full turns. Readjust the fast idle rpm with the engine cold and running (choke closed).
This page has a drawing showing where it's located:
The vacuum modulator diaphram can have a small hole in it and still function more or less correctly. If it has a large enough hole to not respond to engine vacuum, it would be sucking up the tranny fluid fairly quickly, enough to notice within a few days (in my experience). Take Sixstarved's advice and pull the vacuum line off at the tranny and check for fluid. This will either confirm it or eliminate this as a possible problem. The tranny will shift at a much higher rpm with the vacuum line disconnected (not as high as full throttle, but still high and hard) so make sure you have it back on correctly. As far as the timing goes, another check would be to wait until your tank is almost empty, then put in half a tank of the next lower grade fuel. If it doesn't start pinging after about an hour of driving, you may need more timing. At my altitude (3200') I can usually run 9.5-10:1 on mid-grade fuel. This tuning of carbs and distributors is one of my tasks at work, and I usually have to fix what the other "performance" shops have done, so I can walk you through the whole thing if you want (as can several others here). "Why suffer through long acceleration when you can lessen your misery....."
