Mr D.

I have a 65 327 350hp w/ Factory AC and freshly restored 2818 Holley. Everything on this car has been restored over the past 2 years and now I’m tweaking the bugs out of it but seem to keep coming up short on getting this Holley setup correctly. Engine seems to idle fine at 700 RPM (will not idle with AC on) but feels like it is loading up around 1500 RPM when going slow in 1st or 2nd gear. I have been through the timing and everything checks out per specs with full timing advance coming in at 1500 RPM and temp gauge reads just under 180 degrees.

I have been reading other threads about the workings of the choke which I know was not working correctly. Last weekend I got my idle set using a vacuum gage to achieve the best vacuum than set my curb idle to 700 RPM which is where this engine seems to idle best. Today I started playing with my choke and did the following;

1. Set the choke coil housing at 1 mark Lean
2. With throttle in the open position and choke valve closed against unloader tang measurement is good using a 3/16 drill.
3. Started car and set fast idle to 1500 RPM and let engine reach operating temp.
4. Moved throttle and fast idle cam did not drop.

Couple of things that I discovered during all this is that the choke heat tube is only getting hot half way up the tube so I disconnected the heat air tube at the choke housing and checked for vacuum at that point and had nothing. So it would seem that my problem lies with no vacuum at the choke housing pulling heat into the choke coil.

Has anyone ran into this problem?

Thanks for any help.

Mr D.

ttt

BarryK

can't answer your carb questions but i'm wondering about your timing setting where you say your advance is all in by 1500rpm. That is VERY low rpm and a very fast advance. you aren't having detonation issues with it coming in that soon?? usually the recommended settings are to have the advance all in between 2500-3000rpm.

Mr D.

Barry, can't say for sure at this point about detonation issues because I have not really driven the car but so far (19 miles) no problems.

Pop Chevy

Try a higher number power valve. It may be opening too soon.
Pops

Matt Gruber

why use a choke in FL?
that's why i moved here

C Ray

While I doubt the problem is the power valve but isn't the number on them the inches of vaccuum it takes to keep them closed? Thus, if he did change it wouldn't he need to go to a lower number to keep it closed more?

JohnZ

Make sure the choke hot-air system tubes aren't blocked or restricted, and the system is drawing hot air through the exhaust manifold heater tube into the choke housing; if hot air isn't reaching the bimetallic coil in the choke housing, the fast idle cam won't drop.

Mr D.

I'm just **** and want everything to work.

I figured out the problem with some help from Joe over at NCRS, don't know how I missed it but I forgot to install the fresh air tube that runs from the bottom of the exhaust manifold to the air cleaner. Ordered one last night.

Mike Geary

That tube can be a real PITA to install. I think I had to drop the heat riser to get the tube end into the manifold tube. Then the solenoid head shield was in the way. Then the tube was slightly misformed, which made the attachment ear misaligned with the bolt hole, and so on!

Hope yours goes more smoothly!

rgs

That missing tube only provides a clean filter source. Without it, the choke should still work. Like running your engine with the air cleaner removed. The carb will simply pull un-filtered air from below the manifold. Now you may have pulled some debris into the choke housing that is blocking the vacuum passage.

Mr D.

So if I read this correctly your saying I should feel vacuum at the choke housing with the heat tube removed?

Coves4me

Mr. D, You are correct that you should feel vacuum at the carb inlet where the vacuum tube for the choke connects. It is also true that without the fresh air intake hose from the carb to the underside of the exhaust manifold, a vacuum from the carb will still be drawn by the carb at the inlet under the exhaust manifold. However, if the tube inside the exhaust manifold has corroded and/or deteriorated, it will allow carbon particles to be sucked into your carb and choke housing. This is very common. Your carb could have sucked in exhaust particles and clogged the orifice in the carb where the choke vacuum is supposed to be drawn. Because you are probably drawing no vacuum through your choke housing, your carb is running rich and that may be causing your "loading up" at part throttle. I, like Barry K, am confused when you say that your timing is all in at 1,500 RPM. Too soon. Perhaps you mean just the mechanical advance? Hope this helps.

Mr D.

I have zero vacuum at the choke housing and I'm guessing I never had any as the heat tube only gets hot half way up the tube. The car has 18 miles on it so I don't think it's a carbon particle problem. I will pull the housing off this weekend and do some more checking.

As for full timing coming in at 1500 RPM (vacuum + mechanical) I could be wrong but I don't think so. I will run back through all this also and post up the results.

rgs

No vacuum at the choke housing points to a blocked passage. Are you using a stock manifold and gasket? I'd pull the carburetor and trace the vacuum port through to manifold vacuum and ensure that the vacuum passage makes it through. Somewhere along the way, its blocked.

I'd also verify that the tube going through the manifold is in place and in good shape with no leaks into the exhaust passage.

JohnZ

The hot air is drawn by manifold vacuum into the choke housing, through the thermo coil chamber, past the slots in the choke piston, through the bottom of the housing, and exits the housing through a passage in the main body, into the intake manifold (see diagram below). That vacuum connection to the choke piston serves two purposes - it activates the choke pull-off as soon as the engine starts (like the pull-off diaphragm on later Holleys), and it also provides a continuous low-level vacuum source to keep pulling hot air through the thermo coil housing in order to keep the choke blade wide open once it warms up. If the carburetor is clean, the vacuum passage is open, and the choke piston and its bore aren't gummed-up, there should be a low level of vacuum at the choke housing air inlet at all times when the engine is running.