the problem:
i have a bad miss when i hit cruising speed. the engine idles ok (not great) and accelerates great up thru the gears. once i hit cruising speed it starts missing and cutting out.

the specifics:
-brand new professional rebuild on a 75K mile slant out of a 75 duster installed in my 87 d150. the rebuild was done right with a 20 over rebore.
-brand new holly 2280 i bought from Dan a couple of years back. (BTW he is really missed around here)
-new comp cam 264s-10
-new remflex manifold gasket
-new distributor
-approx 15 lbs of vacuum with some needle movement
-the lean burn is long gone and replaced with the original chrysler orange box and ballast resistor (all new parts)
-suspecting a vacuum leak i sprayed all the suspected areas with starting fluid. the idle got worse only when i hit the carb at its two horizontal gaskets (not the manifold to carb connection but the two horizontal gaskets on the housing). i replaced the gaskets but the idle is still diminished when i hit it with ether
-i have blocked off the egr valve
-fuel pump is a little over a year old and worked perfectly on the original single barrel oil burner i just replaced.

this miss is driving me crazy. ive got a ton of money in this thing and want to do some more upgrades like a dutra dual someday when i can swing it. any help, ideas, or suggestions would be greatly appreciated

dean

Old or new p;ug wires, cap and rotor?

Richard

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Part of Tyrde-Browne Racing

What did you lash the valves to once the engine was hot? You should have a bunch more inches of mercury on the needle than 15.

What about the carb?
Something is wrong there.
Shouldn't have a change in idle if the gasket is working when you spray it down.

CJ

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Part of Tyrde-Browne Racing

new plugs, new wires, new rotor button, new cap

as for the valves i am not sure. they have been readjusted after the installation by a professional mechanic but i havent rechecked

thanks for helping me

dean

Ceej
as for the carb i am not sure either. perhaps i have a warped housing or something? it is brand new but maybe i need to try a diff carb and see if it helps??? now i just gotta find one.

dean

Take it apart first and make sure it's true.

You may be able to contact Dan via PM. Give that a try. One wouldn't expect a new carb to have warped mating surfaces. I've purchased carbs from Dan before, and they have always been as advertised. Perhaps there is something else going on there. I don't know the 2280's that well. Any shafts near the mating surface that may need a new seal/o-ring/gasket?

CJ

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Part of Tyrde-Browne Racing

On the valves, check them cold + .001" for the spec per the cam manufacturer. It will likely need to be slightly looser than factory spec. The mechanic may not have known that.

Perhaps a 264S owner will have the specs for you.

CJ

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Part of Tyrde-Browne Racing

thanks for the suggestions and i will start with the valve adjustment

looks like i have a lot of work to do to complete the diagnosis. sometimes i have a tendency to want to short cut the process by just throwing parts at it hoping something will magically cure my problem

just no time......

Dean