Sounds like once You get the carb "back to normal" & the timing set, it just needs a good break-in run...
SOLVED! 318 2500-3000 rpm idling issue. Don't think its a regular vacuum leak. Swapped 2 intakes, 2 carbs ,and 6 different gaskets still no luck.
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PlymouthPontiacEnthusiast
Active Member
Only thing that's probably gonna limit me for the moment is the car is not driveable, still need to build the clutch pedals and the body work rewire all the dash electrical yada yada. So I can't test it under load right this minute gonna be a few months. I figure reading plugs is a bit tough idling in the driveway you need to be under load to get a good read on them I assume?
PlymouthPontiacEnthusiast
Active Member
Yeah it ain't driveable yet so when I get the rest of the car in order I'll have to get it out there under load and see what it does
Make sure the discharge nozzles ALL show a clean, strong stream of fuel, I posted pics of one My buddy Scotty had purchased....I had to rebuild it for Him...it was full of dried powdery residue....almost entirely blocking the accel pump inlets in the bowls..
I know You've changed the PV, so You've seen what's 'visible' , ...but just be aware that the circuits may need checked....
Correct way to read plugs. Make a WOT run into high gear, back off the gas and switch the key off. Coast to the side of the road and read the plugs. Otherwise, you're reading pulling into the driveway almost at idle.
You should not have the secondaries open more at idle, leave them where the factory set them or risk opening up another can of worms.
Power valve shouldn't change the idle, likely a poorly set up carb at idle running on the wrong circuit.
10" of vacuum at 800 rpm, put more initial on it like 18* and see if you can get the idle to come around. That reading is probably a pretty decent size camshaft.
10" of vacuum at 800 rpm, put more initial on it like 18* and see if you can get the idle to come around. That reading is probably a pretty decent size camshaft.
gentlemen, i believe i have identified the problem
PlymouthPontiacEnthusiast
Active Member
So if I pull up the initial timing would I have to limit the distributor weight? How much timing would a stock distributor be adding? I'm probably gonna put some tape on the balancer and see what it's totaling at.
PlymouthPontiacEnthusiast
Active Member
Also I think it's not making enough vacuum to keep the factory PCV valve cover checkball from leaking. Do I need a specific pcv that will work to take care of the crank case fumes?
I'm no carb expert but I think that's what the idle air bleeds are for.
PlymouthPontiacEnthusiast
Active Member
Okay so I should try dropping the idle air bleeds down a size or two? There are eight, four are for under throttle and four are for idle is that correct?
I believe you go bigger to lean the idle but I would do some research and/or let somebody with experience weigh in.
Cuda416
Well-Known Member
Chiming in because I had a similar problem a couple of years ago.
First, this never seemed to be answered, might have missed it though.
I've heard of people doing this to open the secondaries when they didn't know about the secondary adjustment screw under the pass side of a holly. Is that what this is? A method to "add air"? Seems problematic.
Second, our problem stemmed from a slightly off angle of the port surface is the air gap clone we used due to a machining error, which created a vacuum leak "UNDER" the intake in the valley. Only when we removed it, added a bit of gaske-cinch did it seal properly. There was no other indication of a leak anywhere.
I quickly ran through the thread, but didn't see anything covering these issues other than the explaination of the secondary adjustment screw.
Anyway, good luck, problems like these are mind numbing sometimes.
First, this never seemed to be answered, might have missed it though.
I've heard of people doing this to open the secondaries when they didn't know about the secondary adjustment screw under the pass side of a holly. Is that what this is? A method to "add air"? Seems problematic.
Second, our problem stemmed from a slightly off angle of the port surface is the air gap clone we used due to a machining error, which created a vacuum leak "UNDER" the intake in the valley. Only when we removed it, added a bit of gaske-cinch did it seal properly. There was no other indication of a leak anywhere.
I quickly ran through the thread, but didn't see anything covering these issues other than the explaination of the secondary adjustment screw.
Anyway, good luck, problems like these are mind numbing sometimes.
PlymouthPontiacEnthusiast
Active Member
So I'm fairly certain the very first time I installed the intake, which was a JEGs airgap knockoff, I was having that problem. I think that's what sent me off on the "intake leak in the lifter valley" goose chase from there on out. It had to be cut to fit especially since the 318 ports are so much smaller than the 340-360 port size on the intake. The intake "rocked" side to side a bit when sitting in the V of the cylinder heads. Like the angle was off. But the vintage holly Street dominator intake sat far far snugger didn't budge left to right at all and the bolt holes lined up first shot. As well as allowing me to use steel shim intake gaskets with the right port size.
PlymouthPontiacEnthusiast
Active Member
Also hey since the core issue has been solved can I mark this post as solved? If now we're just discussing tuning it maybe I should make another thread when I get the car driving for actual load data.
Not a bad idea.
hillbilly timing tape.
How to - Hillbilly Timing Tape
Mark it with a sharpie if need be. All you need right now is a 15 btdc line
Yes you have to limit the advance in the distributor to keep total timing inside the box. Normal tuning stuff to get the engine what it wants, doing it right. If you fill in the slots, do the inside edge would be my suggestion.
Also.... ISOLATE the intake tract. Plug off EVERYTHING that is connected to it, PB booster, PCV, all of it and tune the carb at idle. Then add back items one at a time noting if the idle changes. If it does, look at why that item changed the profile.
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You don't limit the WEIGHT, you limit the total mechanical TRAVEL. You do that by using an FBO limiter plate or disassembling the distributor and welding and refiling the governor slots, which is the method I prefer.
What they're doing certainly isn't helping, that's for sure.
TT5.9mag
Two atmospheres are better than one
Find a new carburetor guy. Or learn how they work and tune it yourself.
Why are you trying to tune a carburetor on an engine, in a vehicle that can’t be driven? If it starts and runs, wait to tune it any further until you can warm it up, put it under load, and drive it. Leave the secondaries alone (lightly closed) for now. Get the initil timing sorted out as that’ll change your idle tune up.
Msmith3054
Well-Known Member
I am having a very similar proble m with my newly rebuilt 69 340. Shot carb cleaner all over the usual suspect areas, intake to heads, carb base gasket, every vacuum port I could find. No change at idle with butterfly’s closed. The only difference is I can adjust idle with the adjusting screw but idle changes on its own periodically.
Edelbrock Air Gap manifold, Edelbrock AVS2 650, manual brakes, original distributor with Pertronics module installed, stock exhaust manifolds, stock fuel pump running around 7 psi at idle.
I need to pull and inspect the plugs, I’ll probably change them for new as these are the original from 3 years ago from the full rebuild. I’ll do that and update this post.
Edelbrock Air Gap manifold, Edelbrock AVS2 650, manual brakes, original distributor with Pertronics module installed, stock exhaust manifolds, stock fuel pump running around 7 psi at idle.
I need to pull and inspect the plugs, I’ll probably change them for new as these are the original from 3 years ago from the full rebuild. I’ll do that and update this post.
Probably best to start a new thread.
First thing, make sure no fuel is dripping into carb venturis from the booster.
Good initial timing setting? Not the book.
BkrDude001
Active Member
Everybody has you on ignore. I've been following along waiting for the leak down test or someone to suggest head gaskets. But instead, I'm seeing the same things, that hasn't worked, over and over.
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