My banger has a twin downdraft Ansen manifold with 2- 94's down jetted to .043 and 4.5 power valve and a header, 2.5 fuel pressure. This engine was in a running car bought from a friend who drove it with a single late model downdraft carb and manifold--I didn't get that with the deal. Using a mallory dual point it would start instantly and rev no problem, but as soon as I try to drive, it will misfire like crazy. Retimed it a bunch and even went back to the stock dizzy--same problem. Whats wrong? Any help would be appreciated. Thanks --Greg
The .043 jets. Standard would be around .049, depending on what carb...model # is on left of bowl...what you have guarantees lean misfire. If you want to check...pull out the choke some to enrich and it will start to work.
I would check the intermediate shaft on the distributor. I experienced a similar problem and found it to be wear on the ends of the shaft. I would get it timed, then fire it up and it would idle decently. As soon as I would take it out for a test drive, it would run like ****. The ends of the shaft had worn to the point that they were sloppy. I put in a new stainless shaft and it cured 90% of my problems. -Mitch
when the engine is cold take a can of starting fluid and lightly spray around the intake at the base next to the block and around the base of the cars. See if you notice a difference in the way it runs. If so then you have an air leak. I don't really think .043's on a pair of 94's would be to lean but I could be wrong. If you'll describe the misfire a little better, it'll help us to help you. Does it misfire at idle, high RPM, on throttle, off throttle, engine under load, combination of those, or?
sounds like a leaky power valve on the front carby easy to change check their value also been a long time since I run twin 94s but 4.5 does not sound correct I think I used 3.5s when you do get them right you will love them
just to add there are 2 types of power valve the newer type has a small radius and will not seal you need the older style
Wow, our setups and indeed stories are virtually identical! Has it ever previously run on those carbs? The plug fouling and misfiring sounds like it could be overfueling. Indeed that's excatly what i experienced, along with manifold bolts backing off. My fix was the float level being too high on one carb. Fuel was virtually pouring in. Runs beautifully now and the plugs are perfect. Although I rebuilt the carbs I don't know the sizings on the jets or valves, sorry. My Ansen inlet and twin 94's had apparently been runing on a banger many years ago. After a freshen up and the problems outlined previously all is now great. Now just need a leakless waterpump and a think about the ignition - I see points getting consumed rapidly running 12v through them. Chris
^^^ I agree sounds like a carb issue. I had a similar problem on my 2x2 94 set up (on a v8 flatty)... Rebuilt the carbs multiple times. Nothing seemed to help. Finally purchased 2 new 97carbs. Bolted em on and motor runs like a top.
Air leaks...common and easy to get on inliner manifolds, but will generally kill idle and then become much less significant above idle as the leak becomes just a tiny part of flow. Bad seal at PV...very likely with unknowing use of many of the PV's coming in kits now, one of the few things that can enrich at all speeds...will foul plugs, will kill idle, will make everything above idle too rich...BUT an engine will generally pull through an overrich condition much better than it can a lean condition. You may have all or part of the above...but once past idle the car isn't going to be going anywhere with .043 jets. TEST THIS by running it through the beginning of the "misfire like crazy" zone repeatedly, pulling choke out progressively.
Did you buy or make spacers for the intake bolts and washers? Bolts need to be supported on both sides. Posted using the Full Custom H.A.M.B. App!
First off, made aluminum spacers the exact thicknees of the intake which bolts on a new 3/8 header flange I built. Used the good stainless lined gasket material for both intake and exhaust so no leaks. Yes the dizzy has a lot of play in the form of backlash in the intermediate shaft. you can move the crank and the dizzy will not move without a lot of rotation of the crank. Figured it will follow ok once put torque on the system. It does not pop thru the carbs, just misfires with no power. Number 123 black and sooty, number 4 brown. Even feathwering the gas cannot get it up to speed. Will idle down perfectly and responsive on all four idle screws. Will rev off idle no problem. Also the power valves were originals that I recalibrated with a vacuum pump down to about 4 inches, so yes they seal at the bowl properly not like the ones that aren't sized to the gasket. Thanks Greg
Unhook linkage on one carb and work throttle on the other carb and see if it revs better. I have the same type setup and could never get it jetted down enough to stop getting too rich and back firing through the pipe. I just drive mine on one carb with the other still hooked up minus the linkage to the 2nd carb. Not the ideal setup, but it might at least help in trouble shooting your problem.
Ok, gonna give it one last try today with all advice. Suppopsed to snow later so looks like i will be all done for the next few months.
How exactly did you "re calibrate" the power valves? Are you talking about the little br*** power valves inside the carbs or the holley 4 barrel looking "spark valve" that some 94's have on the base? If you're talking about the br*** type inside the carb, that right there sounds like the opportunity for a rich condition. Did you take them apart and tweak the springs? If they aren't sealing anymore that could do it. If it's the spark valve, I don't know what that would cause.
Sounds exactly the problem I had on my old "banger"..set your pionts to correct gap sounds like they are closed up.gap correctly and your problem should be cured,,, IT is NOT your carbs..
^^^^ fix the dizzy, the parts are not that expensive and if nothing else will elimate another soon to happen break down
Try it without Air filters some of the small air filters are very restrictive off idle this is twice as bad with 94s as it increases vacuum bring in the power valve early
You are never all done Greg. The snow just gave you an excuse to take things apart again and re-design the things Henry overlooked. The art work on your dash looks great. Here is a picture I took with my phone. We have to show you how to post pictures of your build. You have great ideas I think others would like to see.
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