The Stovebolt Site Forums The Shop Area Engine Shop hard start continued

For those that have followed my thread on hard start for a month or so I'm still at it.Problem is, it will only start with partial choke even when hot. It also want's timing advanced so far I can't even see the ball. I'm setting everything with a vacuum guage. When running I get 22 in of vacuum and it's real smooth. When you crack the throttle the vacuum drops to almost zero and there is a huge flat spot.It gets a lot better if I leave the choke partially closed.I am doing this with only one of the 2 rottenchester carbs on it. Everyone assumed I had carb issues so I purchased a third carb.Different model I think 66 or later much bigger jet too. So after 3 carbs ( all rebuilt )The fact that it is doing exactly the same thing laeds me to believe that the issue is somewhere else. So the question is ;Is it possible to create to much manifold vacuum? It seems to draw so much air that the carb base is ice cold even with the motor up to temp with little water droplets on the base.I'm totaaly baffled by all this So I'm getting ready to pull the intake and look for what Idon't know. This is on a 2x1 offy manifold with fenton headers on a fresh rebuilt 235.

Wes,

Review a little more background (sorry): is the intake manifold heated?

The KISS technique of using one good carb should help to move this discussion along.

yes the manifold is heated.The carbs have all been rebuilt and floats set properly ,no leaks. Have sprayed starting fluid all around the carb and manifold when running.no change. Main jet on 2 of the carbs is 57 and the new one is a 71. But this is happening when it comes of the idle circuit when you crack the throttle ever so slightly. I just can't believe that all 3 carbs could have the exact same effect. I have a feeling that as I start to tear into this motor going backwards from the rebuild that I will find something stupid that I did that is causing these odd syptoms.

Have you tried using a blind gasket under one carb at a time, and tuning the engine to run right on a single carb? Once it's running well on that one, swap the gasket, and tune the other one for the best performance. If it still gives trouble after both carbs have been tuned for the best performance individually, and you go back to a properly synchronized pair, it should be obvious that you've got one too many carburetors.
Jerry

yes ,that is what I'm doing. I made a block off plate for one carb flange on the manifold and am working with a single carb.All 3 one at a time with the same results

Have you checked the camshaft timing? With the valve cover removed, turn the engine in the normal running direction (clockwise from the front) until the #6 exhaust valve begins to close. Just as the exhaust closes, and the intake begins to open, the #1 and #6 pistons should reach the top of their stroke, #1 on compression, and #6 on exhaust. One turn of the crankshaft later, the #1 cylinder valves will "rock" and #6 will be at TDC on the compression stroke. You can monitor piston position with a bright light shined into the spark plug hole, or by probing into the plug hole with a piece of soft wire. Don't insert a stiff tool such as a screwdriver into the hole, as a mistake while turning the crank could result in cylinder head or piston damage.

It's beginning to sound like the cam has been timed a tooth late on the timing gear. The engine will run that way, but it won't run right!
Jerry

thanks ,I've been wondering myself if that was the problem but I was very sure I had the marks lined up right when I assembled it. I will use your method to check that out in the next day or so. It will save me from pulling the balancer and timing cover etc.

Well I pulled everything apart and the cam timing was correct.Also pulled the intake and the lifters to check for any wiped out cam lobes.Everything was fine nothing unusual. I reassembled today and I'm back to square one.The timing wants to be all the way on the triangle to get a nice smooth idle. The motor only wants to start and run with some choke on even when up to temp. I've never seen a motor pull this kind of air. It almost freezes the base of the carbs from the volume it's pulling.I'm really baffled. Is it possible that this flywheel is not right for this motor? and I'm timing it and setting the valves off the ball. Seems to me it wouldn't matter.It's an 11" clutch setup that was off the old 53 hydraulic motor that came with the truck and ran ok. Also is it possible that this reconditioned 848 head could be the reason for the exceptional air flow thru the intake. It was just a standard valve job with a few new valves and all new springs and seals and shaved a little to true it up.Keeping in mind that this same intake, carb,dizzy and exhaust all worked decent on the old motor.sorry this is long but I'm really reaching for answers to this.Don't know what else to try

Tclerderman recommended I try the old original intake. So I resurected it from the junk pile and put it on.Same problem. Tried 2 different carbs. Both act the same.Has a really bad flat spot unless I leave the choke closed a little and doesn't like to restart after I shut it off. The really puzzling part is the timing Why does it only want to idle decent when I have it so far advanced that I'm up to the triangle on the flywheel with my timing light. When I try to get it on the ball the idle drops too slow on the verge of stalling? Anybody know how many degrees advanced I am if I'm on the triangle?

Just for grins, try taking the Pertronix ignition out of the equation. You've just about run out of fuel-related options, and the logical next step is to make absolutely sure the ignition is working right. I simply can't bring myself to trust an electronic ignition system that won't let me set the static timing accurately. It's a simple thing to swap back to points and condenser temporarily, and eliminate any doubt about ignition problems.
Jerry

that will be the next thing I try, maybe tomorrow. It's Miller and popcorn time now . thanks I'll let you know how that works out

I tried switching to the old dizzy with the points and got the same result so I'm back to the pertronix unit. I've learned what it takes to get it started with the right amount of choke and throttle etc. The timing still wants to be way advanced. I got a timing light with an advance dial on it and it looks like it runs pretty good at about 12 degrees advance. It idles better even at 18 degrees but it pops back thru the carb when you stab the throttle.So the best scenario is about 12 degrees. I still have a flat spot coming off idle to accelerate. Keep in mind none of this is being done under a load. I only have a motor and trans in a chassis for now.I will be going to a swap meet on Sun and hope to see some carter carbs that may work and get rid of the rootenchesters.Also I still see a puddle of gas in the bottom of the manifold (both the original and the Offy 2x1 )even after running a 1/2 hr when I pull the carb (s)