Blitzkrieg3002

Hello MustangForums Community... i come to you with a problem with rebuild that i've been constantly Tinkering with and can't seem to find a solution. Maybe someone out there has had a similar issue or can help guide me in the correct direction of a solution.

Okay so Firstly i will say my farther is a Mustang and *****'s enthusiest, owns his own self employeed body shop and has been working on these motors for quite some time... doing rebuilds/tune-ups/complete restoration of classic 65-68 mustangs as well as *****'s trucks and jeeps and is very very knowledgable on the rebuilding process of these 5.0's and early model 302 engines. I have a 1966 Mustang, that had a 68 302 motor that was getting old, burning oil basically and in need of a rebuild or new engine.

So, my dad had a (i believe 1986ish) 5.0 Roller motor rebuilt shortblock that he reworked up to that point himself where i stepped in and he helped me finish up the rest of the motor... we used a set of reworked 351 heads that had bigger valves put in and had been worked over, we cranked everything over did everything properly the heads turned out to have plenty of clearance to the pistons with the cam that we purchased. basically we got the motor all built and ready to go.

we pulled my motor and tranny (i had bought a new c-4 from summit that was a bit beefier along with a 2,000 rpm stall torque converter, and the correct 50oz flex plate for this setup) we got everything installed back in the car and fired it up.

the car runs and starts everytime but right as you pick it up off an idle there is a crazy vibration and the engine is NOT running correctly... so we started to troubleshoot and get the engine timed properly...

we attempted timing it to many different settings a bit advanced, dead on, and a bit retarded back. every time the vibration still occurs and the miss is still there... (we're not exactly 100% sure whats going if it is a miss/ Dead miss/ or even the engine at all as we replaced the torque converter and tranny and engine all in one shot so it's hard to say) so we decided to take it for a ride and go through the gears... the tranny seems to be operating properly and the stall converter the same... right *** you step on the gas from a stop to get the car moving you can just tell off the bat it's not running correctly the vibration is there and the engine doesn't have the power it should, (like it's running on 6 or 7 instead of all 8)

we pulled all the plugs, all are hot and not oily, all are slightly reddish brown to appear that they are firing... we tried the timing 180 as we thought maybe there was a possibility we were 180 off and that was not the case it would barely run and backfire like crazy so we set it back properly... we tried a different cap, rotor and plug wires along with plugs themselves and the issue still occurs. our next step is to pull the whole distributor and try another from another engine he has that's running properly in another vehicle actually and see what this does.

it seems strange because to me it seems as though when i have the car in park or neutral and fire it up it. at an idle it sounds extremely healthy and appears to be running properly... but as soon as we put it into drive or reverse and the engine actually has to (Make the car move, Put in some Effort) you instantly feel it's not running properly and the vibration)

i think the vibration is just from the engine not running on all 8 but not sure at this point... the gas is fresh and the carburator, (4 barrel edelbrock) we're using was on the old engine along with the same manifold and was running strong for many many years so were not sure that it could be this... any suggestions on what we should check would be greatly appreciated... thank you

projectresto83

How long have you let it run for at idle? What did it do then?

Blitzkrieg3002

@Projectresto83, not too long just let it run at various rpms nothing too high really i'd say a total of all the time it's ran altogether is around like an hour total now... but during the first start up probably 10 minutes or so enough to heat to a normal temp and run that way for a bit, maybe even about 15 - 20 actually now that i think of it... it seems to run healthy at an idle we did carburator vaccum adjustment and tried a lot of timing adjustment we were thinking next to try a new distributor and if nothing move under the valve covers to re adjust the valves

projectresto83

Did you get the firing order right? Sometimes a single swapped plug wire can see fine until the rpms are raised. It does sound like a timing issue. What is your base timing? Have you put a timing light on it when you rev it up?