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Discussion Starter · #1 ·
Alright, I've been playing with this off and on for about 4 months now. I have an 87 roller 5.0, stock cam, stock heads, stock non-adjustable rocker arms. I'm trying to start the engine and it keeps backfiring through the carb, and then I get flame on top of the carb. It seems like I'm running too far advanced but I've played with the timing so much. I even removed a valve cover to make sure my rotor was hitting the dist cap at the right spot. Or, it also is like my valves aren't closing all the way. Is that possible with the stock pedestal mounted rockers? Since, I've replaced the spark plugs, dist condensor, made sure I wasn't 180 degrees off on timing, correct firing order 13726548. I checked the carb, accelorator pumps are fine, squirters fine, float levels fine, power valve fine. I even swapped carbs with a car I was driving today that ran fine, same backfire through the carb and flames. So I'm sure its not a fuel issue. I am almost sure it is ignition. Maybe its the dual points. Any ideas?
 

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Not sure what you meant by this:"I even removed a valve cover to make sure my rotor was hitting the dist cap at the right spot"??
 

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Sounds like he was double checking his TDC, but not in a very accurate way.


--Upgrading to a duraspark setup is something I would strongly recommend. Also did you make sure that you have the correct distributor gear to match the roller cam?

<font size=-1>[ This Message was edited by: gork1rogues on 7/30/06 10:06am ]</font>
 

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Id bet your distributor is 180 out. Or your firing order is suspect to the cam. Is it a stock style cam or the original cam that came in the 87 5.0? . If its original then Id check the firing order then ,turn that dizzy around.
Remember bring the #1 cylinder up on the Compression stroke. If the spark plug is out put your thumb over the hole and you'll feel a puff of air. Then line up the mark on the balancer on tdc , then check the #1 plug wire on the dist. The firing order goes CCW from there.
Good luck ,And let us know
 

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Did you just put the distributor in or was this a running engine as is?I'm trying to figure if this is a problem with assembly or just something that went wrong with an engine that was already together?
 

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Discussion Starter · #7 ·
On 2006-07-29 19:05, gork1rogues wrote:
Sounds like he was double checking his TDC, but not in a very accurate way.


--Upgrading to a duraspark setup is something I would strongly recommend. Also did you make sure that you have the correct distributor gear to match the roller cam?

<font size=-1>[ This Message was edited by: gork1rogues on 7/30/06 10:06am ]</font>
Yes, the distributor has a billet gear. I'm very tempted to go duraspark, thats what I'm running on the other car. I am thinking the problem is the ignition. I was sleeping awake last night and came up with this. I'm running points, no balast resistor, and a super coil. I think I keep frying the condensor on the dist.
 

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Discussion Starter · #8 ·
On 2006-07-29 19:14, 71hotrodpinto wrote:
Id bet your distributor is 180 out. Or your firing order is suspect to the cam. Is it a stock style cam or the original cam that came in the 87 5.0? . If its original then Id check the firing order then ,turn that dizzy around.
Remember bring the #1 cylinder up on the Compression stroke. If the spark plug is out put your thumb over the hole and you'll feel a puff of air. Then line up the mark on the balancer on tdc , then check the #1 plug wire on the dist. The firing order goes CCW from there.
Good luck ,And let us know
I am sure the dist. is not 180 out. I put the roller cam in the car, spider, dog bones, roler lifters, and correct push rods. It is a stock roller cam that came out of some random roller engine. Yes, it was a roller cam.
 

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Discussion Starter · #9 ·
On 2006-07-29 20:02, frdnut wrote:
Did you just put the distributor in or was this a running engine as is?I'm trying to figure if this is a problem with assembly or just something that went wrong with an engine that was already together?
Good question. It was a running non roller engine that I had previousely used. I swapped in all the roller stuff, something I've done before in the 351w. I think you're on to something with the distributor.
 

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[/quote]
I was making sure I wasn't 180 degrees out. I used a screwdriver into the spark plug hole and a 15/16 on the crankbolt to find TDC.
[/quote]

Ok you did the screwdriver thing, How can you be sure that its the compression stroke?
 

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The piston will be in the top most position twice per cycle in a 4 stroke engine. There is only one compression stroke.

All you have done with the screwdriver was to make sure that you had it at the top--could be the wrong part of the cycle.

The rotor in the distributor rotates 360 degrees once to EVERY TWO rotations of the crank. Removing the distributor cap to check rotor position did not necessarily verify that you were at TDC.

To determine TDC.

1. Pull #1 plug.
2. Ground #1 plug wire so you won't get shocked.
3. Place thumb over the outside off the spark plug hole, trying to fully cover it but not put your whole finger inside.
4. Have friend "tap" the starter lightly a few times until compression tries to blow your thumb away from the hole.
5. Check for location of the timing mark on the harmonic balancer. It should be fairly close to the pointer. Hand turn motor the slight amount needed to make the marks line up.
6. Remove distributor cap.
7. Check direction that rotor is pointing at. Should be #1 plug. If it is not pointing at #1, either move your distributor slightly or you will need to restab it 180 degrees out.
8. Repeat steps 3-7 until the rotor points at #1 cylinder.
9. Reinstall distributor cap, #1 plug, and the spark plug wire.
10. Start engine and time it with a light.

Another possibility is that you have flooded the the spark plugs with fuel. In that case, remove the plugs, clean them, and before reinstalling the plugs, turn the engine over a few revolutions without hitting the throttle. This will blow the excess fuel out of the cylinder. Reinstall plugs, recheck firing order, start engine an time.

Could the valves be adjusted too tight? Are you using the late model firing order for the roller cam?


_________________
Dennis

65' STANG, 3160 lbs

393W, 2.78 Toploader 4 Spd, 9" 3:70 Posi
Pro Comp Heads, Vic Jr. Intake, 750dp, 236/561 Solid Cam, 9.6CR, 1 3/4" Headers, Lakewood, Subframes, Caltracs



<font size=-1>[ This Message was edited by: dennis111 on 7/31/06 7:37am ]</font>
 

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Discussion Starter · #12 ·
On 2006-07-30 10:58, 71hotrodpinto wrote:
I was making sure I wasn't 180 degrees out. I used a screwdriver into the spark plug hole and a 15/16 on the crankbolt to find TDC.
[/quote]

Ok you did the screwdriver thing, How can you be sure that its the compression stroke?

[/quote]
I'm not trying to be a smart ass, please bear with me, I'm not trying to be pushy at all, I'm very grateful for all the resonses.

from my original post: "I even removed a valve cover to make sure my rotor was hitting the dist cap at the right spot." all that, at the same time using the screwdriver to follow the piston to TDC after the intake stroke. With the valve cover off I could watch the intake valve drop and rise as I turned the crank clockwise by hand.
 

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Discussion Starter · #13 ·
On 2006-07-30 13:14, dennis111 wrote:
The piston will be in the top most position twice per cycle in a 4 stroke engine. There is only one compression stroke.

All you have done with the screwdriver was to make sure that you had it at the top--could be the wrong part of the cycle.

The rotor in the distributor rotates 360 degrees once to EVERY TWO rotations of the crank. Removing the distributor cap to check rotor position did not necessarily verify that you were at TDC.

To determine TDC.

1. Pull #1 plug.
2. Ground #1 plug wire so you won't get shocked.
3. Place thumb over the outside off the spark plug hole, trying to fully cover it but not put your whole finger inside.
4. Have friend "tap" the starter lightly a few times until compression tries to blow your thumb away from the hole.
5. Check for location of the timing mark on the harmonic balancer. It should be fairly close to the pointer. Hand turn motor the slight amount needed to make the marks line up.
6. Remove distributor cap.
7. Check direction that rotor is pointing at. Should be #1 plug. If it is not pointing at #1, either move your distributor slightly or you will need to restab it 180 degrees out.
8. Repeat steps 3-7 until the rotor points at #1 cylinder.
9. Reinstall distributor cap, #1 plug, and the spark plug wire.
10. Start engine and time it with a light.

Another possibility is that you have flooded the the spark plugs with fuel. In that case, remove the plugs, clean them, and before reinstalling the plugs, turn the engine over a few revolutions without hitting the throttle. This will blow the excess fuel out of the cylinder. Reinstall plugs, recheck firing order, start engine an time.

Could the valves be adjusted too tight? Are you using the late model firing order for the roller cam?


_________________
Dennis

65' STANG, 3160 lbs

393W, 2.78 Toploader 4 Spd, 9" 3:70 Posi
Pro Comp Heads, Vic Jr. Intake, 750dp, 236/561 Solid Cam, 9.6CR, 1 3/4" Headers, Lakewood, Subframes, Caltracs



<font size=-1>[ This Message was edited by: dennis111 on 7/31/06 7:37am ]</font>
Thanks Dennis. I pretty much did all that, but I don't like the thumb method cause the engine can overshoot TDC and spin into the exhaust stroke without knowing it, that is why I was watchinf the intake valve and crank it over by hand and feeling with a screwdriver.

Can the valves to adjusted too tight you ask. I don't think so, I tightened them down at the base circle, 22 ft/lbs, on stock pedestal mount rocker arms. I think even if I was off on the base circle they'd be too loose. Late model firing order is the same as 351 firing order 13726548, yes to that.

If my dual points are gapped wrong could it cause this problem?

I really appreciate all the responses. I understand everyone wants to make sure I didn't miss something in assembly, and no one knows what I know and don't know. I just hope no one mistakes my responses as rude. I am listening to what everyone says. Eventually we'll figure it out. Thank again everyone.

 

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If you have a windsor type cam, in a 302 type block, you will have a different firing order then the standard 302 firing order. Only 4 of the 8 plugs will fire at the correct time ( not enough to keep the engine going). Giving the illusion of being 180 degrees out.

If you installed a new cam, check the cam card for the firing order. It may be a windsor firing order, because it is a better order then the old 302 order, not firing #7 and #8 one after the other.
 

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Discussion Starter · #18 ·
That is what it seems, but I'm using the stock non-adjustable pedestal mounted rocker arms. They are torqued to 22 ft lbs. I used the stock roller lifters and push rods for roller swap.
Someone mentioned something interesting to me recently. They said not all roller cams had the 13726548 firing order. Some non-ho roller cam equipped 5.0 engines had the 302 15426378 firing order. If this is the case then I'm not exactly 180 out, just 180 out on the middle two strokes of a revolution of the crank. And, if this is the case, then I have been wrong about he firing order being wrong, which many have been saying since the beginning of this thread. I will get back sometime this week and let everyone know if I'm a dumbass, or if I'm still having a backfire issue.

Thank you all for the great support. I try to do the same where I can.

Bart
 

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Discussion Starter · #20 ·
Hmm, don't have a tester at the moment. I was going to remove both the valve covers and watch all the intake valve as I crank the engine over by hand to get the firing order. The more I think about it the more it sounds like the answer. It does try to start but then it backfires through the carb. Probably my 3 7 and 5 4 firing at the wront moment. The thing that gets me is that I alway thought roller cams used the 351 firing orer. If this isn't it I'll do a leakdown test.
 
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