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-   -   351 Cleveland popping when accelerating (http://mustangforums.com/forum/classic-mustangs-tech/700111-351-cleveland-popping-when-accelerating.html)

Sparkiewalt 08-23-2013 03:26 PM

351 Cleveland popping when accelerating
 
I have a 1973 Mustang grande with a 351 cleveland 2v engine and automatic 3 speed tranny. It has headers, a 4 barrel vac secondary summit 750 carb and weiand alum intake. All this was on the car when i got it. It did not pop then. Both header gaskets were leaking and needed replacement, which I did.

I replaced plug wires with street fire spiral 8MM from oriellys. And a new set of plugs accel 0576S-4 with a 045 gap. It started the popping after I fixed the intake gasket which was blown out when I got the car. I am pretty sure I put the distributor back just like it was. The car has a GM HEI distributor. The weird thing is when I went to check the timing I have to connect my light to the number 5 cylinder to line up with the marks on the harmonic balancer. I am not sure how this happened.

Any way the engine cranks and runs great and it has good power, I can do a good burn out. but when I give it hard to mid range acceleration it starts a slight popping sound that is worse at first then almost goes away after I build up some speed. The pops have about a 1 sec interval. The distributor cap and rotor seem to be in fairly new condition.

The popping is not as bad since I changed the plug wires and plugs. timing set a 6 BTDC is better than 10 BTDC. 2 BTDC is about the same as 6.

67mustang302 08-23-2013 04:22 PM

You need to verify the timing marks on the balancer first. Sounds like the timing could be way out.

Sparkiewalt 08-23-2013 06:53 PM

If the timing was way out the engine would not run correct??

dawson1112 08-23-2013 07:07 PM

Those HEI distributors will run even if the plug wires are mixed up.

IF you have to have the timing light on the number 5 wire to light up on the mark then you likely have the dizzy out 180. I know its messed up but those hei dizzys will jump spark all over inside that cap.

Bring the number one cylinder up to TDC pull the cap and see where the roter is pointing I would bet you are way out. .
There is no way you should have to clip the number 5 wire to read timing.

Sparkiewalt 08-23-2013 08:50 PM

So you are saying that my engine will run and produce full horse power with the timing 180 degrees out???

67mustang302 08-23-2013 09:01 PM

If it's misfiring to other cylinders, it's possible. It would act like a DIS wasted spark system, fire to multiple cyl at once, and only 1 of them makes power.

HEI's seem to cause a lot of problems for a lot of people.

dawson1112 08-23-2013 09:03 PM

Quote:

Originally Posted by Sparkiewalt (Post 8270983)
So you are saying that my engine will run and produce full horse power with the timing 180 degrees out???


I don't know.. I know that my gmc pick up with a 350 ran when the wires were all mixed up . The HEI dizzy jumps spark all over . Are you getting full hp ? I don't know.

I do know that if you only able to see the timing mark using the number 5 wire something is way off.

The biggest clue is that you say you are pretty sure the dizzy was put back in the way it came out.

Verify this by bringing numer 1 up to tdc and see where the rotor is pointing. You either didn't get it stabbed right or the wires are all mixed up .

boogerschnot 08-24-2013 12:43 PM

Just pull the number one plug and rotate the engine by hand to verify. Either way, the things timing is definately off somewhere. You shouldnt be running at 2btdc. Does the popping sound like marbles in a tin can?

Sparkiewalt 08-24-2013 08:19 PM

The popping sounds like a small back fire. I took the timing chain off, it was pretty slack, I am going to replace it with a Zoom double roller set. But when I took off the valve covers I think I may have found some real problems, both the 6 and 8 had loose rockers. The previous owner "rebuilt" the heads so he said. I hope he did a better job on the valves than He did on the rockers.

Sparkiewalt 08-24-2013 09:18 PM

I will re-time the engine correctly and see what happens.

Sparkiewalt 09-15-2013 10:13 PM

I wanted to give an update. After replacing the plug wires, plugs and checking timing, I checked the rocker arms, several seemed loose, So I pulled the cam, sure enough I had wear extreme on 6 lobes, 2 were rounded off. Best thing I could figure is that the previous owner did not properly oil the new cam and lifters with a high zinc oil. I got it all back together and it is running great now. thanks for the help and I hope this thread may help someone in the future.

fastbackford351 09-16-2013 07:59 AM

I use to have an old 68 Firebird with a 400 and was running an HEI and had the distributor 180 out. It started and ran around the block but when I laid in to it it all went to hell. It coughed, popped and farted all over itself but I was able to nurse it back home.

I was under the hood and hadn't figured out what the problem was so I was frustrated and did the only logical thing I could think to do in my 20 year old mind and revved the piss out of it. It backfired hard enough so that it blew my mufflers apart and peppered my legs with dirt & gravel hard enough to draw blood.

Sparkiewalt 09-17-2013 07:48 AM

I have heard about the spark skipping around in these dizzy HEI distributors. But I have tried setting the distributor to the 0 TDC mark on the HB and then tried it 180 degrees and it will only back fire. I set it to the #5 with the HB on 0 TDC and it fires right up and runs great. Let me stress, my engine is running perfectly like this. I can smoke the tires down with my posi 9" rear end.

fastbackford351 09-17-2013 08:42 AM

Your distributor is a tooth off. Back it up and you'll be good to go.

Turn your engine until it is at TDC on the compression stroke and pull the cap. I'll bet you dimes to doughnuts that it is lined up under #5 on your cap. It needs to be under #1.

Lift the distributor up until it just clears the gears and rotate it back towards the #1 plug wire.

69mach1377 09-17-2013 09:27 AM

It must be revenge for using a brand x dizzy and timing to #5...why?

Sparkiewalt 09-18-2013 07:44 AM

I tried moving the distributor to the number 1, it will only back fire and pop, engine will not start. The only way I get it to start and run is by lining #5 up with TDC on the Harmonic balancer.

jimkaray 09-19-2013 01:07 AM

Quote:

Originally Posted by Sparkiewalt (Post 8282719)
I tried moving the distributor to the number 1, it will only back fire and pop, engine will not start. The only way I get it to start and run is by lining #5 up with TDC on the Harmonic balancer.

Did you just 'move' it over to #1 or did you reinstall it making sure you had #1 up at TDC on the compression stroke?

jimkaray 09-19-2013 01:14 AM

Quote:

Originally Posted by fastbackford351 (Post 8282267)
Your distributor is a tooth off. Back it up and you'll be good to go.

Turn your engine until it is at TDC on the compression stroke and pull the cap. I'll bet you dimes to doughnuts that it is lined up under #5 on your cap. It needs to be under #1.

Lift the distributor up until it just clears the gears and rotate it back towards the #1 plug wire.

Since he has it firing up on #5 by just dropping it back in on #1 won't have it timed up on 1's compression stroke. If it wasn't able to start then I'd say it was simply 180 off.

fastbackford351 09-19-2013 06:46 AM

But he is able to start, drive and lay rubber so he is close. Real close.

I went through this myself a couple months ago myself with very similar symptoms. There aren't that many components involved here so the fix is pretty straight forward.

1-5-4-2-6-3-7-8


Pull the #1 plug and put your thumb over the hole.

Rotate the engine with a remote starter until your thumb is absolutely blown off of the spark plug hole and that will be TDC or damn close to it.

Check your harmonic balancer and make sure you are indeed at TDC.

Pop the cap and make sure your rotor is pointing right at the #1 position. I'll bet it's not. I'll bet it's favoring toward #5 position.

Make sure that your wires are lined up accordingly. Most caps have a #1 molded in to them so double check to make sure they are squared away and wired correctly.

Sparkiewalt 09-19-2013 07:40 AM

the timing for my engine is. 1 3 7 2 6 5 4 8 ... so the #5 is no where near the #1 on the distributor cap. No one thinks this could be the wrong harmonic balancer??? I will check #1 for TDC but my money is that TDC on the HB will line up with TDC on the #5.


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