i've completed a 302 injected to a 351w carbed swap, but the new engine misses. have tried new wires, plugs, cap and rotor and a new distributor, have pulled plug wires off one at a time, runs worse so that area seems ok, have noticed when idling motor seems to speed up and down as well but doesn't seem to do it all the time, any ideas, vacumn leak maybe? depending of which size of vac line i pull off the engine may run just the same or speed up, would like to set bauman transmission tcs but need truck running well to fine tune, any ideas, thanks

 

I would have said plugs and wires for the missing and a vacuum leak causes erratic idling. I would think if a vacuum leak it would be all the time.

 

thanks for the info, i just did a vac test, when idling the vac is from 12" to 13.5" with the needle very rapidly fluctuating, when the idle speed goes down the needle also goes down,( it still fluctuates,the idle slows and picks up on its own) when rpms are slowly advanced the needle stops fluctuating and steadily increases the inches of vac at higher speeds,( it remains steady above 15" vac)till it gets to about 18-19" at about 2000rpm, i also did a compression test all cylinders are 137 lbs.

 

you should have 15 to 20 inches at idle. that compression seems good but were they all at 137 psi.

 

yes all were at 137. i've double checked for any hoses off or cracked, the timing is set to 10 btc. not sure how i can check for small vac leak, someone said to use a hose and blow propane around all the fittings and intake manifold.

 

the 351 has a different firing order then the 302 does , also when your replaced the dizzy did you make sure that you were at tdc.

 

yes, correct firing order, and timed correctly, starts resonably well, runs smooth about 15" vac. will check on rpm at that vac reading, maybe i'll need to rip engine apart? again, how noisy should full roller rockers be?

 

noisy from what others have told me. you wouldnt think so but for some reason they are

 

You can check for a vacuum leak with starting fluid.

 

so i spray the ether around all vac fittings and intake manifold? anywhere else? the miss should disappear, or the engine will speed up? if i can't find the problem with this i guess its rip out time, one other thing concerns me, i installed full roller rockers in this engine, and its quite noisy, when i first started it up i wasn't sure how much noise was coming from the rockers and roller timing chain, i then went looking for other causes of noise, and found that the machine shop had installed the wrist pins in at least two pistons incorrectly, causing a gouged #4 cylinder, i had that sleeved, and reassembled the engine, still has in my opinion too much noise, nobody seems to be able to tell me how much noise is normal, may i'll install the stamped rockers from the old 302 in the 351 and try it before i rip it out again, any suggestions, it seems like a pity to take it out without trying this. any other causes for the noise, it sounds like noisy lifters, metallic clacking or tapping, new lifters, could they be bad, i've talked to more than one source and all the parts i have in this should work well together. any comments please!
the rockers are crane roller rockers 1.7's maybe too much lift, the rods are stock length.

 

i tried the starting fluid, that was suggested, thought it made a difference when applied to the passenger side between the head and intake manifold, so i flooded that area and the engine stalled, started it again and repeated the test, same result, so it would appear that i have a vacumn leak in that area, will install new gaskets tomorrow and start up on wednesday morning, will keep you informed, and thanks for all the suggestions. hope this does it.

by the way, is there any fool proof way to testing the lifters? someone suggested that i may have gotten some bad new lifters? when i set the rockers, i followed the manufacturers directions, and after a couple of min it seemed to follow the results they said were correct.

 

I would contact crane or compcam about your noisy lifter/rockers. Or go to one of the mustang forums, those guys use roller rockers and such all the time. sorry i couldnt be much more help.

late

 

hey thanks for all advise, greatly appreciated!

 

Another great way to test for vacuum leaks is to lightly spray the hoses/seals with WD-40. If any wd-40 is sucked in the motor, it doesn't do any harm but it does make the exhaust a nice white smoke. It also won't cause the engine to die, so it can be a little easier.

 

hey thanks for the wd 40 tip, will try this afternoon, i've replaced the intake manifold gaskets and carb to manifold gasket has helped somewhat, but using a vacumn gauge still has only 13.5" vac, and the needle stays fairly steady now, no more rapid fluctations, my car and my son's 95 f150 351w have 17.5" vac so it appears i still have a problem, slight miss still, very frustrating.