FNG Old fart really needs help with 77 C30 350

[Rustywer]

So I've posted twice before with no response, and I have just about had it with this 77.

Long story short.....
350, blew the headgasket. Reworked 822 heads, reman distributor, new fuel pump, and it falls on it's face under load.

Have the distributor, I believe, 1 tooth retarded but used the old vacuum guage timing set and have it at max vac (20" at idle 650). Vac will drop if I retard or advance. Idle is fairly smooth with a slight pop from the exhaust, but the air injection is on ported vacuum and the valve was recently freed up with a little clean and lube. Cam looked good when i had it apart and the pistons are .030 over. This motor was worked about 60k miles ago and the bottom end looks ok. I have the valves at approximately 3/4 of a turn past zero lash. The quadrajet adjusted out ok, and unloaded (REVVING) the secondaries open and response is good.

The issue is that as soon as I put a heavy load on it (towing) it comes up ok in 2nd then goes flat when i shift to third and will not climb even a slight incline and heats up to just into the red on a stock temp guage. Even without a towing load, performance drops off as it heats up to 3/4 deflection on that same guage.

I won' say that there aren' t any vacuum leaks, but spraying carb cleaner at the base of the intake will only cause a very slight deflection in idle.

I'm really frustrated with this little project. Right now i have about $4500.00 invested in this thing, and a wife who loves to remind me that she said "Don't buy that truck" PRIDE GOETH BEFORE THE FALL I GUESS.......

Any help would be appreciated.

 

[MadOgre]

Sorry you got no response before.

If you get any difference in idle when spraying carb cleaner at the base you definitely need to fix that.

So it pulls good in gears 1 and 2 and then falls flat in 3rd? correct? Is this a standard or automatic ?

Is it the engine coolant temp that heats up or the tranny temp?

 

[Rustywer]

It's a Saginaw 465 (3 over a granny) and it is engine temp. I've tightened down the intake as far as I dare and the exhaust manifold temps aren't excessive. I'm thinking it may be the carb, but the popping has me concerned. The vac guage needle vibrates a bit at less than max vacuum , like it has an RV cam in it, but I don't really want to tear this thing apart again to prove it. A friend suggested backing the timing off to achieve about 18" of vacuum, but the more I retard the timing, the less power I get.

 

[MadOgre]

A timing light would be more reliable with possible vacuum leaks. There are quite a few variables with the fuel system like worn fuel pump, dirty fuel filter, crap in the tank, corroded fuel lines, fuel lines to close to heat, inlet seat and needle malfunction, improper float level etc,, etc,,,

Being off a tooth on the distributor simply means the cap will sit in different position when proper timing is achieved. Non issue.

I find it really strange that it would perform fine in lower gears and not in 3rd. Unless you have like 3.08 gears and 44 inch rubber ?

 

[Rustywer]

The timing doesn't start to achieve a decent performance at idle until it gets to at least 14 B T D C and i had to advance it further to get to the vacuum I have now. My light doesn't have a delay / advance function. Base timing has to to be running close to 22 - 25. I replaced the fuel line during the work with a steel braid shield, put the paper filter in the carb inlet, and added a glass tube filter in the fuel line. The line is well clear of the manifold, but lays against the heater hose ( bundled and zipped together about 12" off the carb) fuel flow is good, pump is new. Nothing changed in the driveline, stock rear, 16's, nothing
over the top.

I just read through the vacuum diagnosis post and at least at idle and unloaded everything looks normal as far as vacuum performance. I haven't done an engine like this in at least 25 years, and everything I'm trying makes me look like a rank amature.

 

[MrMarty51]

How is the radiator ? partially clogged ?
To Me, heating under loads could be radiator, timing or carbeuretion, being the fuel mix, in the high side may be too lean. A rev without a load on will not let You know about what is going on with fuel mixtures.
Might try a set larger on the mains.
Also, an intake leak of any kind can and will, cause a lean condition, creating excessive heat in the combustion chambers.
I would too, get that distributor set to the proper location, just to make things right.
Be My guess that the intake will need to be pulled, surfaces cleaned thoroughly and new gaskets installed, unless the carbs. base gaskets is messed up or, the carbs. flange is warped so when the carb. is tightened down, it still will leak under vacuum.

 

[Rustywer]

Marty,
Thanks for the reply. The radiator is clean, with at least a 35 to 40 degree drop top to bottom. I had the intake cleaned when it was off, then block sanded the faces with 120 grit. Had a can of copper coat spray, but didn't use it on the intake. I guess my real concern here is am I short on the valve adjustment, and do I really want to go through the carb. Again it's been more than a few years since I've had one of those scattered across a bench looking at the exploded diagram. I will tell you, we could have used the Internet back in the 80's. You tube videos can be helpful. Although I noticed the stars are mainly Good ol Boys, and I'm a born again redneck (Jersey Boy).

Not knowing if the cam is heavier than stock, and having the timing way advanced is kinda making me concerned. I will say, the guy who did the heads, did it right. New guides, seals, springs with what I think are inner and outer spring sets (there's an inner ?????)

BTW, my Granddaughter named this one, it's Charlie Brown. ...Go figure.

 

[MrMarty51]

Before tearing into the carb, be sure that the rear/secondaries are not opening too quick, that is a major problem with these carbs.

I have run the valve lash at 3/4s a turn many times, without any issues whatever. Some instructions, back in the day, even said to adjust 3/4s a turn.

What I found, when I tore down My last Q-Jet carb was, it all come back to Me when I got started.
Take some real nice pics. of the linkages, that is the only part of them carbs that is of a real concern.
The accelerator arm, roll pin, does`nt have to be completely removed, just shove it back with a screw driver then pull it out a ways with a diagonal cutters, the rest is easy.
Adjust the secondaries so they do`nt open so fast as to create a bog when the rears is opened all the ways.

 

[MrMarty51]

I just do`nt unnerstand it, How Your granddaughter could have came up wit a name likeum that. LOL

 

[Rustywer]

I ordered the carb kit this morning, might as well run through it just to be sure. A good friend can do those things in his sleep. I will keep you all posted.

 

[rich weyand]

Sounds like you have the vacuum advance connected to ported vacuum. Connect the vacuum advance to unported (manifold) vacuum, and set the base timing (with vac advance disconnected) to 16 BTDC, then hook the vac advance back up to unported vacuum and see what you get.

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[highdesertrange]

I am concerned about the popping out the exhaust. have you tried to disable the air injector pump to see if the popping goes away? highdesertranger

 

[rich weyand]

I had popping out the exhaust when I was running way retarded. The distributor had not been clamped down tight the last time they tuned it up, and it rotated retarded.

Here's an obvious question, but you said it had been a long time since you worked on old-school vehicles, so don't take offense BUT: You are disconnecting the vacuum advance when setting the timing, right? 14-16 degrees BTDC should be right with vac advance disconnected, but if it reads 14-16 BTDC with vac advance connected, that would be 4-6 degrees AFTER top dead center for base timing. That would result in poor performance and engine overheating, because the burning charge is being run out through the exhaust runners, heating the heads. You will also get missing, resulting in popping in the exhaust.

 

[Rustywer]

Maybe I left a few details out..... The vac advance is on non - ported and I'm pulling 20 " on that port. The air injection is on ported vacuum and i believe I need to have it on ported. Paying much more attention to what it's doing under load today, it will pull good in granny, 1st, and 2nd. I hear and feel the secondaries open but it will stumble occasionally, and feel like someone pulled the compression release. If I flutter the accelerator, it will come back and continue on fairly well. 3rd gear will not get out of its own way, little on no low end and when I try to get into the secondaries, it falls flat on it's face.

I get the same symptoms unloaded in the lower three gears with better throttle response, but it will not bogg down as much and feathering the accelerator will allow me to use the benefits of the secondaries. I have to climb a 1.25 mile 6% grade on the way home, and it will drop from 70 to 60 mph in that stretch in high gear and I'm in the secondaries but not at W O T. I did notice that after that run and the engine temp getting to 3/4 deflection It will cool off over the 2 miles on a 45 MPH drive to the house, which ends in low gear climb of 10% or better. As I park, the engine seems to be rougher in the idle and I almost want to say misfiring.

Again, I think it may be the old quadrajet, just needing a little more than a little attention.

 

[Rustywer]

Have to laugh Rich. But yes, advance is disconnected, at 14 to 16 B T D C base timing its a lazy old dog and about 15 to 17" of vacuum. Then I reconnect the advance vacuum and start advancing it and the quick 1" flutter continues as it climbs to 19" then the flutter fades as I reach 20". Max vacuum is about 20.5 then I back it off to a solid 20"