senator

Ok, ive searched and searched and messed with my 12a for weeks now and stll no better results. Heres the situation. Fresh streetport 12a, custom header, no muffler for now, custom intake, no trailing ignition for now, its a bare bones swap, no emissions/ electrical, except dizzy and alt. etc. I had a huge Edelbrock on it then went to a 350 cfm holley, same problems. Seems to take a few too many cranks to start, I can deal with that I suppose, but when it fires I cant get the idle any lower than about 1500 and it sounds like its ready to die. It is also very tempermental with any small changes to ignition timing. Another problem (theres a few) quickly opening the throttle is sounds and revs great, holding a raised rpm it sounds like its running on a rev limiter, then quickly open further and it does what its told. That is unless you quickly open full throttle from idle then it cuts out completely. Ive checked spark durring all this and it never drops out, but it still seems like part of the problem. I have the leading advance hooked to manifold vacuum because if its on ported, it retards timing as rpms go up. If I turn the dizzy counterclock wise, it advances timing. All of this seems backwards to me. Could the ignitor wires be crossed? Ive switched them before and it wouldnt start.

Ive checked for vacuum leaks, fixed the one, no real change. I dont wanna get rid of this project, and dont wanna tie up all my cash for another swap, like a TII. Thanks for any help

j9fd3s

iTrader: (3)

not sure what's going on really, but my P port won't idle without the trailing ignition.

if this were mine, i would go thru the ignition and make sure its 100% stock.

have you tried playing with the idle mixture on the carb? are these carbs on an RB manifold? any spacers?

senator

Ill try and get the trailing hooked up today just incase. As far as I know its all stock. Got all the parts for the build from a buddy that pulled them out of his running/ driving car a long time ago.

Ive adjusted the idle mixture with no noticable change. If there screwed in too far and it wants to die, then I unscrew about a half and leave it.

Also trying to drive it at low rpm it usually either dies or starts jearking. If I give it enough throttle and slip the clutch enough to get rolling then give it more throttle it cuts out unless the rpms are above 4k ish.

senator

Oh, not sure of the manifold maker, its steel though, four barrel. I have an adapter on it for the two barrel, maby an inch thick. I had a spacer on the edelbrock but it didnt help, maby because it was a 750??

Jeezus

iTrader: (4)

Idle circuit and accel pump. My carb is doing the same deal it seems.

jgrewe

iTrader: (1)

You vacuum advance has to go to venturi vacuum, not manifold. Try unhooking the vac hoses and plugging the manifold side. Now check the timing marks on the dizzy and the front pully, you may need to re-stab the dizzy, might be a tooth or two off.

Once you get it to start without any vac tubes then hook them up and work from there. It should rev fine to about 3K without any advance anyway.

senator

Ok, ive rechecked everything and the timing is deffinately going retarded with vacuum, so when its hooked to ported vacuum its at full adv only at idle. The timing was pretty retardede so I put it a tooth c-c-w and its about 10* btdc but it seems to run smoother with less adv. like 10* atdc.

Oh and I have to turn the dizzy cap c- c- w a bit for it to start, hardly runs where it should be, still a tooth off?

Thanks again for the replies!

senator

A tooth ccw,nothing, cw it runs but timing light shows like 45* atdc and i still have to move the cap from where it should be.

I hooked up the trailing plugs and it runs worse at idle, all other problems still there.

Could someone tell me where their dist rotor is pointing with balancer at tdc? And where the dizzy is set? That would be very helpful at this point.

jgrewe

iTrader: (1)

There is a notch on the bottom of the dizzy housing down by the gear. IIRC there is a dimple in the gear itself. Line these up for the stab with the engine at TDC. You should be able to see how the trigger wheel tooth is lined up on the pick up as it rotates a little on the gear pitch as you install it. The leading circuit is the one that should be pretty closed to lined up at this point.

Are you working with a stock pully or smaller dia(RB?) unit? TCD is the last one that comes around on the RB unit.

senator

Stock pulley as far as i know, regular alt belt fit just fine. Ive done that procedure before and same results, guess it wont hurt to make sure.

NCross

iTrader: (18)

Sure your dizzy is working right? Try swapping distributors. Try swapping coils if you have extras. Check your fuel pressure. Check your filters and plugs/wires.

senator

I was thinkin about gettn another dizzy. Tried another coil, same. New filter. New plugs, wires cap/ rotor. But that doesnt mean there good. Gonna look for another cap. I put a lab scop on the negative of the coil and it looks fine and doesnt drop out so i think the dizzys good, idk. With an inline spark tester it looks like its losing spark every once in a while at idle, raised rpm is just to rapid to tell.

Fuel pumps new but havent checked pressure

NCross

iTrader: (18)

Are you losing coolant? Could be sucking in coolant through a bad seal and bogging down.

jgrewe

iTrader: (1)

If you have the dizzy hooked to manifold vacuum you will get its whole vac advance at idle and it will drop(retard) as you open the throttle. There is no way for the vacuum pots to retard the timing if they are hooked up correctly.

There are also weights in the dizzy that will give you advance too. You could have these systems working against each other if you are using manifold vacuum to the dizzy. Just get the car started with no vacuum assist at all and find venturi vacuum to hook to the dizzy. manifold vacuum drops as you open the throttle, venturi vacuum goes up as more air goes through the carb itself.

senator

Ive hooked the vac. adv. to port vacuum, re-stabbed the dizzy started up, checked with light, timing mark appears about 30* on the right side of the pointer ( driver side) raising rpm the mark goes back towards the pointer.

I dont see how any of this could be correct. Seems advance should be on the left side, before the pointer. I still have to turn the cap about 20* ccw for it to start if its a bit warm.

Time for DLIDFIS? Not really sure what that means, but I get the idea.

Ive also tried a good Blaster 2 coil, same.

Coolant was a tiny bit low but I also have a small leak at the pump.

NCross

iTrader: (18)

What plugs are you using?

senator

br8eq NGK R. Theres 14 under the type.

Pressure tested cooling system, let it sit a while under pressure, lost a few pounds, guessing the small leak. Started it up, no smoke.

jgrewe

iTrader: (1)

Don't worry about any vacuum right now, totally unhook it. Get the car to start with no hoses to the dizzy and then we can tell what is going on. It sounds to me like you are getting manifold vacuum from where you think you have venturi vacuum.

senator

Ok, I had the dizzy hooked to a nipple on the manifold, manifold vacuum. Put the hose on a port on the carb that only has vacuum with open throttle, venturi/ port vacuum. So at the mani it advances under throttle (losing vacuum), on the carb it retards under throttle ( vacuum).

I have left the hose to the dizzy unhooked and capped the mani, and its basically the same situation, although with a timing light theres not much movement on the mark on the pulley with throttle changes. It seems my dizzy is vacuum retard?

Im not new to workin on cars, I do it for a living, but not a lot of rotary, carb and distributor stuff, but I deffinately know my way around them. This all just seems wrong. Thanks alot for the replies too.

jgrewe

iTrader: (1)

Weird. What side of the vacuum pots is the nipple? Dist cap side or away from it? Advance would be the side that is away from it. Do you have a hand vacuum pump, maybe look to see what is going on under the cap. You'll see one of the vac pots isn't adjustable, one is. The non adjustable is the leading, adjustable is trailing. That is how you set the timing split.

Does the car run better with no vacuum hooked up? Make sure the marks you're looking at mean what you think, I'm sure you can find an FSM to download here somewhere. There is some mechanical advance from weights, I don't know how much, but you should be able to rev it up smoothly until 3-4K rpm and have it come back to idle.

j9fd3s

iTrader: (3)

are you sure you have the advance retard direction right? mazda's timing number is a little tricky cause its not timing BEFORE tdc, its AFTER tdc.

so the stock marks on a stock pulley are TDC and 20AFTER TDC, or -20BTDC. so if you line the engine up on the left of the two marks, advancing is toward the right mark.

the other gotcha is that the coil in the front of the car is the Trailing coil.

just making sure we're all talking about the same thing =)

NCross

iTrader: (18)

Do you have ballast resisters on the coils? Are you using a 2nd gen coil with your setup? Are you using j-109 ignitors? Could be a bad ignitor. That could really throw things off.

senator

I lined everything up on the left mark, and hooked to port vacuum with a timing light the mark goes left, or back, while increasing rpm. So do I need to line everything on the first mark (right)? So at idle the mark should show just to the left of the pointer indicating ATDC, then increasing rpm it should move to the right, right?

No trailing ignition, one coil.

No ballast resistors, standard coil, tried a blaster 2, no change. I believe there j-109 ignitors, havent looked, ill check tomorrow. Cars at work. Could the ignitor be bad eventhough I get a good scope on the coil negative?

Im not sure I understand your first questions. I have looked at the pickup, the non adjustable one, as vacuum is applied with a pump and it rotates clockwise, which seems like it would be advanced given ccw rotor movement ( unless im totally wrong about info at top).

With no vacuum its mostly the same, until higher rpm. I think im lined up on the wrong mark....

Whisper

The pulley mark that's to the driver side (should be yellow) is leading, and it's at TDC. The mark that's to the passanger side (should be red) is trailing, and it's at 20 ATDC. If you don't have trailing, you should only be worried about the leading mark. Take the disty out, line up the leading mark to the pin on the engine, line up the reference marks on the disty shaft and housing, pop the disty in, make sure the rotor is pointing at the pickup cores and you should be close. Set your leading timing to the yellow mark at idle, by rotating the disty housing. If you apply vacuum to either trailing or leading nipples on the disty, they should both move the pickups clockwise, because that's the direction of advance. The pot that has screws on it is for the trailing, but since you don't have trailing, you can't really set that properly. Put in a trailing coil and hook everything up the way it should be, and then set your timing for both.

I think that should work...

That is assuming your pulley is on correctly to begin with. You should verify that your leading mark on the pulley actually represents the engine's TDC, and isn't off by 90* or 180*. There's a thread on finding TDC through the inspection plate, just do a search.

senator

Thanks for confirming what ive been doing. Took me a while to figure that all out. Ill have to check weather the pulley is on correct, I thought it only went on one way. Ive seen a procedure like this, forgot to check today though.

Remove rear plugs. With a mirror, turn crank until apex seal is visible in the center of trailing hole, mark pulley. Do the same for the leading hole. in between two marks is rotor 1 tdc.

With the pulley set to first mark, yellow, and the dizzy set as described, the sensor tooth is just before the pickup center. This looks right but when I start it the timing light shows maby 20* retarded ( on the right side of the pointer).