My New '68 Camaro Z/28 Butternut Yellow

[dannystarr]

I think I might have figured out my problem. The only thing I have not done is adjust the vales. Valves out of adjustment? Would that cause the 4.5 Vacuum reading instead of 12 or 14? Going to plug the vacuum line for the brake booster. Maybe it's leaking inside the cannister?.. Danny

[cook_dw]

Yes it can.

[bcmiller]

I don't know if the valves being off would cause that issue or not.  I am not saying it would or it wouldn't.  But I think they would have to be off quite a bit to cause that problem.

How did you check for vacuum leaks? 

The old school way to check for vacuum leaks it to use an unlit propane torch or carb cleaner.  But this can be dangerous.  I am not telling you to do this.  But if you want to know, here is how it is done.  Again, if you do this, be CAREFUL.
http://www.popularmechanics.com/cars/how-to/maintenance/how-to-find-a-vacuum-leak-2

I prefer the torch method, outside of course.

If all the vacuum hoses are original, it might be a good idea to just go ahead replace them.  Of course keep the originals.

[dannystarr]

Well the new carb came. I installed it and heated the engine up to operating temp. I think I may have had/have 2 issues. Cause after I set the Fuel/air mixture with the vacuum gauge the vacuum went up to 12 to 14. However it still wants to climb up by itself at an idle with very little throttle. You give it a little and it winds up by itself. Takes the vacuum gauge down to zero, then races up to 45. I pulled the booster hose and plugged the manifold port and it made no diff. So canister in booster is not leaking. I took it for a ride and it actually runs good, pulls like hell. But I have to leave it in gear and apply the brake to help bring down the idle. Once it is down at the stop sign, it is fine. And off ya go, come to another stop sign and it rides back up. Temp at top of radiator hose near thermostat neck read 164. Temp at bottom rad hose near water pump neck read 172. This is after a 5 mile drive. There is SO many things it could be. The throttle spring is pulling ALL the way back.
#1 - Valve overlap
#2 - Gases passing by the rings
#3 - Sticky Valve
#4 - Burned valve
#5 - Poorly seated valves
#6 - Valve guides worn
#7 - Weak valve spring

[dannystarr]

#8 - Late valve timing or manifold leak
#9 - Spark plug gap
#10 - Faulty points
#11 - Ignition retarded
#12 - Manifold leaking.. I sprayed carb cleaner all around it the best I could and I could not detect any rpm changes.
#13 - Partially clogged exhaust
It's endless... Danny

[BULLITT65]

start with the easy/cheap stuff like spark plug gap, points, condenser ( you want to probably put new ones of those anyways) and then go from there. I purchased an older car about a year ago and had similar issues with vacuum. (Did a Compression test, and it was fine). It was not one single issue, but every time I replaced a part, say points for instance it ran better. I replaced the plugs, better still. Carb gasket, a bit better. I was an eagle eye with that vacuum gauge, some small piece would bump up my vacuum, and/or make it run that much smoother. I think the car hadn't run in years. While it was frustrating not having the easy fix, it was a fun journey seeing it come alive more and more with each small fix. Good luck, and keep us posted..

[janobyte]

Outside a general tune up ,which is always a plus ,heed the advise from some previous posts and focus on your distributor. Sounds like it may be staying at full advance. Do you own a hand vacuum pump ? (Miti-Vac ?)


1. Disconnect your vacuum line ,plug source, and hook up pump to your distributor.
2. start engine, obtain initial timing.
3.Give a few pumps to full advance. 3 gr. on TAC ? Engine will speed up (good old timing tape on the harmonic balancer a plus here ! Mr Gasket--cheap)You can obtain a reading to see where you are at for full advance. A must to properly set up your curve. ***see weights/springs (previous post)
4. Release pressure on the pump ,does your engine idle back down ?

Something also to be said for adjustable timing lights here.

As far as checking for vacuum leaks: plain old spray bottle with water. I fight fires for a living.

Any issues with your distributor ,just send it out... labor was very fair ,goes through the tumbler ,set up on the good old SUN machine.

[ko-lek-tor]

If the cam is a wild grind and vacuum is low, try cracking secondary throttle plates open a little. This is done by removing carb, flipping over and a small screw on bottom by plate on pass side below Vac. diaphram. this allows a little more air flow and allows primary plates to be closed more. If primary plates are opened too far, it uncovers idle bleeds causing poor or no idle circuit to work.
I'd also go back to checking with timing light to see if advance weights are opening too soon as mentioned in earlier post (too lighty spring). If vacuum guage is steady, not ticking back and forth, this would rule out valve train IE sticking valve,burnt, spring broken etc...Exhaust clogged is checked by holding at, say 3000rpm with Vac guage and see if it starts to drop after a minute or two. My 2 cents.

[janobyte]

Ko-lek-tor is correct, check Holley Tech, actually a gap measurement posted. I do not know it off hand.  If he's got the old 30-30 in it ,it's choppy but not overly aggressive. Brakes were fine without an added vacuum reserve tank. Plus the tuning specs for that Z motor has long been in print

Not saying to go do it, but I ran a far more radical cam and had the best luck drilling a small hole in each of the primary throttle plates....per Holley. Never could adjust them open enough to not take out the idle circuit. World of difference. Experimented with accelerator pump cams. (duration) Ended up with a surprisingly crisp ,off idle set up. Must for the street. This was on a 850 double pump.


If I was a betting man, I'd say his problems are in the 46 yo. distributor ....certainly was not a mistake having that old carb gone through also.

Be patient Danny ,your not going to jump in a TEN year old car ,not knowing maintenance history, and honestly expect to have no issues. Also consider it presents as having little attention over the years. All in all ,relatively minor issues, as to be expected with theses old rides...half the fun of owning one.

[jdv69z]

Not the same thing, but years ago I had an erratic/idle vacuum issue with my 302 and spent a lot of time playing with the carburetor until I finally check out the engine's compression and spark plugs. What I really had was ring failure in one cylinder, and needed a rebuild. Might want to verify that your engine's compression is good? How do the plugs looks?

[bcmiller]

One thing that you may want to double check is that all of the intake bolts are tight.  Do not over tighten them or break them off - but make sure they are good and snug.  Can't tell you how many times that has been an issue on engines I have worked on.

[cook_dw]

First things first.  Lets not make this anymore complicated than it needs to be and get back to the basics.

Place your hand & or rag over the opening of the carb while it is idling.  Does it idle up or load up and die?

[dannystarr]

Well I will get to my latest news when I get a chance, and thanx to all for the help thus far, will need more help I am sure.
 Thought I would share a few more pictures. Smog hose clamps, Pump pulley.
 

     And these stampings on the front of each head. Anybody know what they mean? Looks like on the right is a "6", and on the left is a "0" ... Danny

[dannystarr]

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[dannystarr]

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