I recently built a 460 for my bronco. engine is as follows. C9 block bored .030, speed pro pistons 9.5:1. ported and polished D3VE heads, weiand stealth intake, Speed Demon 750 mechanical secondary carb, stock C6( switching to manual this spring) comp Xtreme Energy XE262H cam. the engine when in gear will not go past 2800 rpm. I thought at first maybe the distributor was coming to full advance and the engine wasn't liking it so I retarded the timing on it and it still would not rev and then the base timing was off so it did not run well. I then figured maybe it was the vac. secondary on the carb, I had been wanting a new carb for a while so I ordered up a new one , the engine idles better has better response and feels stronger but has the same brick wall at 2800. I tried again to retard the base timing and the engine just becomes unresponsive and hesitates again at 2800. I can make it go past by feathering the throttle but it doesn't feel quite right and I dont want to detonate. I do not hear pinging or any other tell tale noise but I do have fairly loud exhaust. I dont want to push my luck. any Ideas? this last run when I retarded the timing it seemed to have lost some vac. as well? the brakes were harder than normal. maybe I should disconnect the booster and see if its not leaking. the 400 that I pulled from this ran fine so I dont see why this is acting up. the distributor is from the 400 as well.

I know stupid question but,

Have you changed the plugs?

the engine has about 100 miles on it and has done it since the moment I rolled it out of the shop. the plugs were new when it was built. unless break in damaged them? I did just change the wires though lol.

yes if it was flooding, they could be fouled, I would pull some out and look at them, if the ceramic has black on em. change em!

This may sound dumb, but have you checked to see that you are getting wide open throttle butter flies with the accelerator on the floor? When you are mixing and matching some times the linkages have different travel distances or restrictions. Also, if you have one of those cold air flappers in your breather, it could be closing down and restricting your air flow. (rich condition).

Trees

The plugs looked kinda crappy when had them out to change header gaskets. I will try changing them out once. the holley 750 vs I had on it before did the same thing. the Demon acts better but still has the same 2800 rpm problem. It seems to hit on all cylinders and in park it will rev to 5000 no problem. with a double pumper I should be able to allow the engine to rev up before I let the secondaries open. it doesent seem to do that. I am also driving in slush, its not like theres that much load on the engine. the wheels are spinning and it still will not rev. I dont get it? I have an open element air cleaner.

Are you sure that the Distributor is advancing ? no splits in the vacuam line ?

airflow, spark, fuel, compression, exhaust flow, one of them is missing.

I dare say its the spark, either in the plugs or the spark is getting there at the wrong time.

make sure that your float level isn't to high and dumping fuel into the top of the motor.

there again make sure your fuel pressure is what it should be.

and again....stupid question....there is no choke correct and if there is it is OPEN correct? I know most of the demon carbs don't have a choke flap on em but I'v seen some of the 650 that did.

unhook the vac can and set your initial to 10* then have an assistant to rev the motor while you use the light and see if the centrifugal advance is working.

No matter whether or not your vac can is working it should rev over 2800 it might get there kinda slow but it will do it.

The demon at the moment does not have a choke, The holley did, manual and it was open. the float level is mid glass and there is no fuel coming out of the vents. the problem comes with the balancer, it appears to be solid but acts like it spun, the engine barely runs when the pointer aims at 10 deg btdc. the balancer is off from a 72 429 and is on a 75 460 crank, I dont think that has anything to do with it unless the key way moved between the two. My base timing feels really good and sounds good, starts hot and cold with no kickback or dieseling. I have 35" tires with 3:50 gears and it was spinning all 4 tires...well 3 of 4, locker in the rear and open front. it seems strange that in park it revs and in gear on slush while spinning the tires it still will not pass 2800. I think it has to be in the spark advance or vac. line to the dist. stupid question, what port is the distributor supposed to be on? ported or straight vac?? maybe i got them switched around.

ok theres your problem

almost all balancers are matched to the motor, which means the balancer may be the right size and fits but the keyway might be off.

your best bet is to pull the #1 plug and find your TDC

ok, once I find tdc then what?

OK one you find TDC put some timing tape on the balancer (be sure to measure it and get the correct size tape)

Then time the dizzy to 10* after tdc WITH THE VAC CAN UNHOOKED AND PLUGGED

have someone rev the motor while you watch the timing marks with the timing light, make sure the mechanical advance is in fact working and then hook your vac can back up and check to be sure that it is working.

To check the vac can I usually feel under the dizzy for the rod that hooks the vac can to the advance mechanism inside the dizzy. when the engine is reved the rod should be pulled out, or if the can is hooked to full manifold vacuum then when its hooked up at idle the rod should move.

what do you do if the cam doesnt like the 10deg? my last engine was more like 15 to make any power? on another note, this engine ran really poorly at other timing settings.( hard starting, dieseling, starter kickback, etc.) what vac port does the distributor go on ported or full?

well if the cam was installed correctly it should "run" fine at 10*

you might make more power adjusting your timing to compensate.

you say that the motor wont rev over 2800 RPM to me that saies

either the plugs are fouled

or the wires are crossed

or timeing is WAY off

not getting enough fuel at RPM

A wise man once said "air, fuel, spark - if it don't run something is missing"