Datsun Small Block Chevy Swap Doesn't Want To Start

I am using a Proform HEI vacuum advance distributor base, Pertronix  Flamethrower  Coil, and Mr. Gasket clear cap and rotor. 

The motor came with an old Delco distributor but it was electronic for the 84 Vette it came out of so id didn't use it. I did take it apart to make sure i wired the new one correctly. 

Other than that i have a 12G fused wire that is switched running to the BAT terminal.

Ground at the distributor is only -.1V from the battery. 

I should also mention that I tried with the old cap, rotor, and coil.

Check that the distributor is assembled correctly.  Some can be assembled so that the mechanical advance actually retards with speed which produces symptoms like yours.

It was the jeezless battery after all.

My tests at home showed it was good but autozone told me it was bad in about 5 seconds.

I also took the distributor out and checked everything over and all was in order there. 

The only other difference is that I do not have my tac cable in right now.

So if that kills it when I plug it back in I will report differently.

Now just to overcome this periodic backfire out of the carb and I can break it in. 

Doesn't backfire when ether is applied. 

Backfire out the carb is TOO LEAN.  Fatten it up some wherever it is backfiring.  And first make sure you have no vacuum leaks.

Hmm so I tried retarding it a little and then some more advance to try and get it to idle on it's own and I went from carb backfires to exhaust backfires and now back to a carb backfire.

I have checked my timing over and over again so i don't think that can be it but here is a picture i took last week while troubleshooting.

I do not the the cam could have been installed wrong and I confirmed compression TDC when setting timing again.

Motor did idle low and choppy without miss or backfire for about 5 sceonds.

Watch the accidental 6/8 swap.  Doing so makes one spark during compression, and the other spark on exhaust.  Makes for rough running an backfires.

SkinnyG said:

Watch the accidental 6/8 swap.  Doing so makes one spark during compression, and the other spark on exhaust.  Makes for rough running an backfires.

I have no experience with the accidental 6/8 swap, but I can say the accidental 5/7 swap is similar.

I checked the plug wires again and they are in order.

I will try again in a little bit to see what it is. 

Okay so I got it to idle for about 5 seconds before it backfired again.

I am hesitant to keep going before i kill my new carb or burn the garage down. 

I raised the float level a bit and richend the idle mixture a 1/4 turn but the carb should be tuned as it was brand new out of the box on Friday. 

I ordered a piston stop that will be here Tuesday to make double sure the balancer TDC mark is accurate. 

If anyone here is in the Central Ohio area and likes free beer, pizza, or whatever else then stop on by!

Where's the timing when it is running?

In reply to Dr. Hess :

I wanted to check it but I don't have enough time to get a light on it. 

Edit: I started doing some more reading and it seems that maybe I am too far retarded. I started at 0 TDC.

Remote switch to the starter solenoid.  One hand on the timing light pointing at the indicator, with the other you push the button and start the car.  Or get a helper.  It should idle at TDC, kind roughly, but most motors want about 10 BTDC at least.

Do you have a grounding strap from the engine block to the frame? 

Yes the main battery negative cable has a 10 gage wire spliced to it that runs to the frame.

I will try some more tomorrow but it would only idle for about 5 seconds before a backfire would stop it.

In addition to the battery to the frame cable you should run a braided strap directly from the engine block to the frame.  

If you have inconsistent spark on an HEI with a good power wire hooked up to it, then the problem is in the HEI. Given that you tried the old cap/rotor/coil, the problem is probably in the pickup/module. Battery may have improved its behavior but definitely wouldn't fix it. A battery wouldn't affect the spark production (ie coil) by very much at all. The coil itself takes about as much energy to run as your dome lights. Engine would fail to crank (~4000w out of battery) long before it failed to spark (~40w) from a battery issue.

Engine doesn't have to run to check timing. You can pull every wire off the cap except #1, crank the engine, and see where timing is. Or leave the wires alone and just deny it fuel, whatever method you want to use to prevent it from actually starting or trying to. Now if you had something like a vacuum advance hooked up to full manifold vacuum then you might have correct base timing which turns into 20 degrees too much timing as soon as the engine starts. But, if your timing light works but won't flash consistently you probably have more of a spark failing to happen problem than spark happening at the wrong time problem.

Once you've verified that the timing itself is correct AND consistent, if it still misfires i would back off your rockers a little. You have lowish compression and backfires out both intake and exhaust. Valves not seating well due to overtight rockers can cause all 3 of those. 

SkinnyG said:

Sounds retarded.

HAHAHAHAA.

No, seriously.  I don't think you have it timed properly.  Try advancing the distributor a bit. I'm assuming HEI? You set the timing at about 10° and have the reluctor bits pointing at each other? Did you check to see if the harmonic balance is actually correct (the outer ring hasn't slipped/moved)?

 

Agreed.  Grab the dizzy and advance it a bit... or a bunch.  Worst that will happen is it will kickback or spit out the carb, then you know you went too far.  If that helps, check for TDC with the valve cover off and a flashlight/dowel in the plug hole.

Rockers go to zero lash plus 1/2 turn.  When checking zero lash, don't use the spin method, use the "masturbation" method.  The pushrods will still spin after zero lash so it's hard to tell.  Instead, give them a hand job up and down to find zero lash.  My first time I used the spin method on un-loaded lifters, and they still spun up to fully collapsed and I was confused why I had no compression.

Proper preload can be pretty much anywhere between 1/4 and 3/4 turn after zero lash.  One full turn can fully depress the plunger on some lifters.

Your compression doesn't sound bad, but it's possible you went a wee bit too far and it's holding the valve off the seat.

Okay when I am setting the distributor at 0BTDC where do i line the rotor blade up in relation to the cap post?

I was putting it right in the middle but adding more advance did not change the symptoms. 

I backed off the rockers a 1/4 turn and will hopefully get home tomorrow early enough to properly mess with it.

Neighbors have young kids so I try to call it quits with starting cars around 8PM.

Rotor should be pointing at post #1 on the cap.  Post #1 should be pointing at Cyl #1.

the tip of the rotor is about 10 degrees wide, if you look at it in terms of how long it's actually "in front of" any given terminal inside the cap.   so I usually ballpark the distributor position by verifying #1 is coming up on compression (with both valve covers off, confirm both valves on #1 are closed, #6 intake is opening, and #6 exhaust is closing), then set the balancer at 10* BTDC and rotate the distributor so the leading corner of the rotor tip is just arriving at #1 terminal.   that'll be pretty close.

Curtis said:

  If that helps, check for TDC with the valve cover off and a flashlight/dowel in the plug hole.

I've never been able to fit a dowel and a flashlight into a plug hole.

In reply to Curtis :

if you don't twist a little during self-service, you're really missing out.

I verified TDC on the balancer is correct using a piston stop tonight. I also watched the valves as the piston came to TDC (exhaust stroke) the exhaust snapped closed and the intake opened with a little overlap so It seems that my crank and cam are in time. I then set my distributor a full rotation of the crank after that (compression stroke) as Corvair described. It would start right up with some fluid, idle low and choppy for a few seconds and then die. I kept giving more advance and opening the throttle a bit to see if it would help and it really didn't seem to change much but I didn't get any backfires until i got it to a certain point it idles smooth but high for about 4 seconds and then shot a nice flame out again. I backed the rockers off last night so I am out really running out of ideas as to what I can do here.

AngryCorvair said:

In reply to Curtis :

if you don't twist a little during self-service, you're really missing out.

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