Rob delta

I have an 83 307 with the ccc q-jet. The tps is new and adjusted correctly as is the mixture solenoid. The timing is set a little over 20 degrees. I have a very slight hesitation when accelerating from idle (gradually accelerating, not wot). It may not happen all the time and is not all that noticiable. My main issue is when i go to WOT from idle at a stop. The engine really stumbles then recovers and takes off. Also, when at a cruising speed if I go to WOT the engine doesn't stumble but there is definitely a hesitation before it takes off. I've checked the secondaries and they do open fully when holding the throttle open. I assume there will always be some delay on the secondaries opening when going to wot. but is it possible that the primary vacuum break is bleeding off vacuum to slowly and therefore preventing the secondary air doors to open quicker?? But I am also aware there is a way to adjust the tension on the secondary air door but before touching that is there anything else that can be causing this? Is the mixture becoming extremely lean for an instant and then recovering when the engine picks up speed?
Thanks to all in advance for your help

CQR

Sounds like just the opposite is happening. I would say that, by your description that the secondaries are opening too fast. Check your pull-offs for proper operation, but I'm gonna guess that you need to tighten up the wind-up on the secondary air horn. Your hesitation off idle sounds like a weak accelerator pump or misadjusted pump rod.

oldcutlass

X2 on accelerator pump

Lady72nRob71

Yes, check secondary air door spring tention first. Also check you vac hoses and carb bolts - could have a vac leak. Does the EGR valve plunger move freely? Easy stuff first.

AZ455

That's what I'm thinking also. It's somewhat difficult to set correctly, or it has been on mine anyway. I have the same problem. I currently have the tension set where the manual suggests, which made an improvement, but I think I need to tighten it up even more.

Rickman48

Only times I've had WOT problems, I've changed the bronze filter in the carb, and/or the fuel pump.
Make sure the fuel system is up to par, first!

AZ455

Bronze filter? Are you just talking about the small fuel filter in the fuel inlet of the carb?

The fuel pump is a good idea, I suspect mine is likely due to be replaced. Going to test soon. They're cheap and easy at least.

Rickman48

Yes, the older ones are bronze - newer - paper.
Just be carefull - easy to F. U.

Rob delta

Thanks for the responses. Today while driving I was able to test things out a little. First: from a stop at idle going to wot. It didn't really seem to stumble as i used to remember it doing a while back. I think the hesitation i did experience is due to the gearing in the rear and the 307 trying to overcome the weight of a delta 88 at a dead stop. But once it begins moving it takes off pretty well.
Second: Cruising at around 30-35mph then going to WOT. Again it didn't really bog the engine down, however there is a slight lag time til the secondaries open. I think it might be because the vacuum break takes a second or two to bleed off vacuum which then releases the secondary air vent This may be normal but I am not sure. Ok so the secondaries finally open, engine revs up and car takes off. Problem is i leave a cloud of smoke behind, seems to fade away after like 3-4 seconds. Now this smoke only seems to happen when i'm already cruising along then go to WOT. Is this because of a momentarily rich mixture? why does it only seem to happen when i'm already at a cruising speed?

Rob delta

The exhaust cloud doesn't happen from idle to WOT (or only very little). It's when already in motion and then going WOT that I leave the smoke behind

Rickman48

My '86 GP 2+2 [CCC]used to wear out the primary throttle shafts about every 60k miles.
Grab the linkage and move it around - if it's loose, you might consider having it re-bushed for a permanent fix. At the time, I'd get one from a yard, as they were plentiful with low miles.
You might also consider advancing the timing a bit, to compensate for stretch in the timing chain.
My water pump went out @ 68k, and I did a Cloyes for longevity. Both were still in it when I sold it @ 230k.

Rob delta

There doesn't seem to be much play trying to move the linkage around. I believe the timing was at 22 degrees last time i checked. Any ideas what can be causing the rich condition i explained in my last post?

CQR

Again having the secondaries opening too fast will give you your bog and smoke.

Rickman48

Any play is a vacuum leak - how many miles, and did you check the carb base gasket????????

AZ455

I can see the secondaries opening too fast causing a bog from a momentary lean condition, why the smoke?

CQR

The lower plates open the uppers open slowly and at the same time raise the metering rods for the secondaries. If they just flop open then the metering is a sudden rich condition. the motor cant take such a huge flush from the big secondaries.

Rob delta

That makes a lot of sense. When the air vent flops open to quickly, the first thing to come to mind would be a lean condition but considering it also lifts the metering rods, i have a rich condition for a few seconds til the engine recovers. I will try increasing the tension slightly and test it out. Service manual calls for 1/2 turn past zero tension. I have no idea what the current setting is, but it does have some tension but i guess it's not enough. How do i know if i went too far with tightening, will it again bog down?
Thanks for the help

CQR

Yes. I would rec. 1/4 turn adjustments at a time