Freshly Rebuilt 351W... firing problems

[z70what]

Ok.. here's what i'm running. i have a 351W freshly rebuilt and bored to .030. Edelbrock intake, Truck Avenger carb, DUI Distributor, Deka Intimidator battery, and Livewires plug wires (from DUI). Plugs are gapped at .055, and i have my plug wires on the distributor in CCW order for 1-3-7-2-6-5-4-8. I have fuel to the carb and spraying into the motor, i also have brite spark getting to the plugs. however, when i go to fire it up, i get nothing but backfires coming out of the carb. I traced the wires 3 or 4 times yesterday and set it to top dead center, and made sure the number 1 plug wire was traced to the number 1 cylinder, and the rotor on the dist was pointing to that wire. I can't figure out what's wrong? i don't want to keep cranking and turning over the motor on the fresh cam w/out firing.

Also, for the TA carb, it has an electric choke. Do i hook up the power wire to the hot side of the starter solenoid, or to the ignition post, or the start post?

Let me know what you guys think, i want to get this baby running.

Thanks

Luke

 

[z70what]

also, to power my DUI distributor i used the original wire that used to go to the coil. Since it is hot when the iginition is on, i figured this would work out fine.. is this ok?


Luke

 

[Hazegray]

The DUI needs a clean, constant 12V. The original wire you used could be the resister wire which does not provide the full 12V power needed for the DUI. To simplify your DUI installation, install a relay. Use the original coil wire (resister) to trigger the relay. See this link: http://classicbroncos.com/forums/showthread.php?t=77072&highlight=HEI+RELAY

But that doesn't explain the backfiring....

Are you sure your number #1 cylinder is on the compression stroke when you installed the DUI and timed it? Sounds typical of 180 degrees out on the timing...

 

[Scrapper_MV]

Who did the rebuild?

Can those DUI distributers be installed 180 degrees out of whack?

Are the timing marks on the balancer correct?

Did you put a new cam in it? There are two different firing orders for 351W engines, one for the early and one for the later models. Maybe they sold you a cam with the wrong firing order.

Did you degree in the cam?

The electric choke wire should be hot whenever the engine is running.

 

[z70what]

well, i'm going to go back tonight and get the motor on TDC (#1 cylinder in the compression stroke), and retrace my wires, and make sure my rotor on the dizzy is spinning CCW (b/c that's how i've set up my plug wires).

Then i'm going to just wire up a 12 gauge wire from the DUI dizzy directly to the "I" (ignition post) on the starter solenoid. Does the "I" post stay hot while cranking the motor as well? or does it cut off while the starter is running? IF so, where do i get this relay from (part # would be good) and how much does it cost?

Thanks

Luke

 

[Madgyver]

When it's backfiring, it could be one of 2 things or both, timing (cam or dizzy) or fuel..


Here you go, I pulled this from another post.... I didn't want to type it up again.....

This is what I always do.

• Make sure engine has new oil and oil filter in it.
• Prime engine oil using an oil priming tool or a gutted distributor and a drill. To use an old dizzy just remove the inners and the cam gear.
• Make sure there is oil pressure.
• Remove #1 spark plug.
• Using a starter switch on the solenoid, jog engine over while priming the oil pump a couple of times.
• Now place your finger close to the #1 spark plug hole and jog engine over. You will feel air pushing out the hole on every other stroke.This is the compression stroke and where you want to start as your baseline.
• Find the compression stroke and look at the timing marks. Use a breakerbar and socket on the crank bolt to line the marks up about 8-10 degrees BTDC on the compression stroke.
• Your distributor cap should be all wired up with your plug wires. If not, set it up where you want the #1 plug to start. Fit cap on the dizzy and mark position of the #1 plug on the dist. bottom half.
• Now drop that dizzy in while trying to land the rotor pointing in the area of the #1 mark you made. You may need to use the oil pump priming tool or gutted dizzy to turn the oil pump shaft for the new dizzy to drop in where you want it.
• Now you got the dizzy in. Line up #1 mark and rotor. Double check crank timing marks, it should be at 8-10 degree BTDC on the compression stroke. Reinstall #1 spark plug and wire, Lock down dizzy.
• Add fuel, make sure trans is in park, parking brake on, timing light ready, fire exstinguisher close by and charged. Wire up everything like you should and start engine. This baseline position with crank and dizzy will get motor started, if not, then you have other problems
• This is what I always do...........

Good Luck,
madgyver

 

[TJK74]

There are two different firing orders for 351W engines, one for the early and one for the later models. Maybe they sold you a cam with the wrong firing order.

I was going to suggest the same thing. The two different firing orders are the one for the 351w and the other being the standard 302 firing order. I went throught the same trouble back when I built my 351. My 69 351 runs the 302 firing order. Either call the builder and he should be able to give you the firing order for your cam or swap to the opposite order of what your running and give it a try

 

[70_Steve]

Then i'm going to just wire up a 12 gauge wire from the DUI dizzy directly to the "I" (ignition post) on the starter solenoid. Does the "I" post stay hot while cranking the motor as well? or does it cut off while the starter is running? IF so, where do i get this relay from (part # would be good) and how much does it cost?

The " I " post on the solenoid should only be hot while the starter is energized. This " I " post bypasses the resistor wire so that full 12 volts is applied to the coil when trying to start.

You could just temporarily run a jumper from the battery to the distributor, (good old "hot wire" techinque) just to check if the lower voltage at the distributor, caused by the resistor wire, is the cause of the backfires. Of course, if the engine starts you will need/want to be able to disconnect the wire somewhat easily. Aligator clips come in handy for this type troubleshooting.

FWIW, I'm betting the distributor is in 180 deg out...!

 

[z70what]

The " I " post on the solenoid should only be hot while the starter is energized. This " I " post bypasses the resistor wire so that full 12 volts is applied to the coil when trying to start.


FWIW, I'm betting the distributor is in 180 deg out...!

I think you are thinking of the "S" post. It is the starter post. the "I" post is energized whiled the ignition switch is in the on position. I am wondering if the "I" post is energized during starting and while the ignition is in the on position. B/c in most vehicles, things that are energized , such as the windows, they stop when trying to start the vehicle and all power goes to the starter. Anyone know the answer to this??

Obviously i have enough spark right now, b/c i'm getting backfires up into the carb. So, i know it's a timing issue. I was just curious about wiring up the distributor correctly, once i get it to fire up.

Luke

 

[daddyg]

Luke,

I am betting on the distributor being off 180. When I hooked up my pertronix I used my old ignition wire. The PO had removed the resistor already. I was wondering why my coil was getting so hot. I wish you were still a couple miles away I would come by and see if I could help.

Greg

 

[z70what]

thanks Greg, i wish i was still in town as well. Between my father (who rebuilds cars for a living now that he's retired) and you, i'm sure we could get this solved.. however, give me a few nights of tinkering after work this week, and i'll get it all figured out!

Luke

 

[jurob]

turn the motor over, as it aproaches zero on the balancer you should feel air coming from the #1 sparkplug hole. stop at zero and reinsert dist pointing at #1 cap post. if no air as approaching zero go around 1 more time.

 

[70_Steve]

I think you are thinking of the "S" post. It is the starter post. the "I" post is energized whiled the ignition switch is in the on position. I am wondering if the "I" post is energized during starting and while the ignition is in the on position. B/c in most vehicles, things that are energized , such as the windows, they stop when trying to start the vehicle and all power goes to the starter. Anyone know the answer to this??

OK, yeah, technically the I post has voltage when the key is ON, but only because it's being backfed from the resistor wire connection.

Wire 016, the pink wire under the dash, is the resistor wire, and it terminates at the firewall connector. On the engine bay side of the firewall connector, wire 262, from the I connection at the solenoid, is connected to wire 16 (continuation of 016), the wire that goes to the coil. With the key in the ON position, wire 262 and the I connection are getting power from the resistor wire 016. When the starter solenoid is energized, an auxiliary contact in the solenoid connect the I terminal to full 12 volts inside the solenoid, to provide a full 12 volts to the coil during starting.

Remove the wire from the I post and turn the key to ON. You'll see that the voltage is present on the wire 262, and not on the I post.

The only wire in the engine bay that will receive full 12 volts with the key ON and START is wire 904 (Green w/Red stripe) that goes to the voltage regulator.

http://www.wsu.edu:8080/~i6735189/68-71ign.gif

 

[Hazegray]

Just use this link for wiring the HEI (it's in my original post): http://classicbroncos.com/forums/attachment.php?attachmentid=38950&d=1138324813

Also, I put a kill switch in between the ignition (resistor) wire from post 86 It's easy to do since you can locate the resistor (pink) wire from the ignition switch under the dash, run through any type of on/off switch, then to post 86 on the relay. Turn the in-line kill switch off and no power to the relay.

 

[z70what]

Hazegray, where can i purchase this relay?


Luke

 

[z70what]

where is this voltage regulator you're talking about?? i will splice into the 904 wire if i can find it.. is it under the dash or under the hood??

 

[70_Steve]

where is this voltage regulator you're talking about?? i will splice into the 904 wire if i can find it.. is it under the dash or under the hood??

Under the hood. Voltage regulator should be located on the passenger side inner fender.

 

[Hazegray]

You can get a relay online (Bosch seems the best) or any autoparts store. I used one that had a rubber boot around it since I mounted it inside the engine bay on the firewall.

 

[76Broncofromhell]

Are you sure your cam is the 351W firing order?

 

[z70what]

WELL, i finally got her fired up this weekend!! It was a success. For some reason my 302 damper's TDC mark was not TDC. TDC on my 72 Gran Tourino 351W was actually on the "ADC" mark. Anyways, she purrs like you couldn't believe. Now i need some ear plugs, b/c i'm running open headers right now and it sounds like a Nascar firing up in my garage (the neighbors really love me after this weekend). Thanks for all your help. Now i need some driveshafts, rebuild my ps box, and get a new steering shaft! Then we'll be ready!

Luke