small block firing on every other cylinder in firing order - Page 2 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

cdowns · 11-18-2012, 02:22 PM

i would take all the spark plug cables off put them on a bench and WITH THE SERVICE MANUAL install them one at a time and see if there is any difference

biggestjohn · 11-18-2012, 03:04 PM

2 3 5 8 are feed by the left (drivers side) of the carb. If you are getting fuel, but no ignition, your plugs will be very wet. If they are dry, you are not getting fuel. I would suspect that the cylinders are running very rich, and gas fouled the plugs, but without seeing (hint) its hard to say.

Now all you have to figure out is why?

biggestjohn · 11-18-2012, 03:30 PM

After reading your posts thru again, I'm starting to suspect that there is a problem in your main fuel circuit.

It has been over 20 years since I had a 2 bbl apart, but if memory serves me correctly, when you remove the ventris, there are 2 check balls under there. Are they clean, and free to move? Are they there? Are the circuits clear?
You say that when you rev it up, it seems to run on all eight, so that would rule out the enrichment(power valve) You also say that when you move the throttles, you see fuel squirt out, so that rules out that circuit.

biggestjohn · 11-18-2012, 04:04 PM

Unfortunately, I don't have a 2bbl to tear apart, but looking at my Rochester carb book, I may be in error on the 2 check balls. Its hard to tell with the crappy schematics. Irregardless, when you take it apart, check every passage. Make sure that they are all flowing freely. Nothing in or behind the jets, idle passages clear. Bleed tube clear on ventris.........

I significantly doubt that this is a spark issue.

jd7 · 11-18-2012, 04:06 PM

I keep saying propane because you can control it better and it wont start a fire if your arcing somewhere. what do the plugs look like. It really sounds like fuel starvation. Have you checked the chain for play ? Pull the cap and rock the crank back and forth distributor should move with it.I am a mechanic by trade so i ask about basics they will lead you to the problem.I'm sorry if I sound abrupt

dlh760 · 11-18-2012, 06:48 PM

Problem has been fixed after I put my carb back together and back on it is running much better,really rich now but better. I am a mechanic by trade as well but had never come across anything like this before. I appreciate everybody's input and help. Dan
Posted via Mobile Device

Claus · 03-21-2017, 05:26 PM

I'm experiencing the same problem on my sbc 350,

I bought a project truck with a 350 and electronic ignition, had the heads checked, new plugs, 4 ported edelbrock carb.

the engine runs rough, with only little torque, pulled plugs and they are not wet or black.

it sounds like all cylinders are firing, but in the right sequence, have double checked firing order.

1 8 4 3 6 5 7 2, it seem odd that every other cylinder is misfiring

1 8 4 3 6 5 7 2

Have spark on all 8 plugs, by grounding individual leads one by one, while running, I narrowed it down to cylinder 2 8 3 5 can be grounded without the engine changing sound, which seem to me like a problem.

Hope someone can help.

Moose Monkey · 03-21-2017, 08:11 PM

#27 is the answer, I hope

Moose Monkey · 03-21-2017, 08:20 PM

Sorry, not much of answer. If those cylinder's are firing spark good, just might be fuel. Had
Elderbrock crack inside, sucking to much air.would not idle, very bad time starting

garyd1961 · 03-21-2017, 08:37 PM

Do you have a duel plane intake? Have you tried turning the motor over with the spark plugs out of the motor and grounded on the outside to see if they actually fire or not? If you have a duel plane intake I suspect one side of your carb is not working.

GASoline71 · 03-21-2017, 09:07 PM

Check your spark plug gap. With an HEI you need to open up the gap to at least .045

Gary

volksworld · 03-21-2017, 10:24 PM

not looking at a small block as we speak but does anything tap into one runner of the manifold like a brake booster hose? a small leak could kill that cylinder or a major one(blown booster diaphram?) might affect the whole manifold plane....if you got a 4 hole 1 inch spacer and put the carb on backwards you could see if the 4 dead cylinders suddenly became the live ones...then you'd know its a carb issue

Moose Monkey · 03-22-2017, 09:35 AM

Volksworld what a great idea

Claus · 03-22-2017, 01:54 PM

Hi Guys

it ended up being one side of the carburetor that was blocked, that became clear after your feedback and I took another look at the intake manifold, cylinder 2-8-3-5 is all in the same side of the carb.

I was able to clear out the block, now the engine runs like a champ.

Thanks for sharing your ideas,

11-18-2012, 02:22 PM	#26
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: small block firing on every other cylinder in firing order i would take all the spark plug cables off put them on a bench and WITH THE SERVICE MANUAL install them one at a time and see if there is any difference __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

11-18-2012, 03:30 PM	#28
biggestjohn Registered User Join Date: Apr 2010 Location: Russiaville Posts: 203	Re: small block firing on every other cylinder in firing order After reading your posts thru again, I'm starting to suspect that there is a problem in your main fuel circuit. It has been over 20 years since I had a 2 bbl apart, but if memory serves me correctly, when you remove the ventris, there are 2 check balls under there. Are they clean, and free to move? Are they there? Are the circuits clear? You say that when you rev it up, it seems to run on all eight, so that would rule out the enrichment(power valve) You also say that when you move the throttles, you see fuel squirt out, so that rules out that circuit. __________________ ......its not what your askin', its what your gettin'.... .......every time I screw up, I learn something. Needless to say, I'm learning all the time............

11-18-2012, 04:04 PM	#29
biggestjohn Registered User Join Date: Apr 2010 Location: Russiaville Posts: 203	Re: small block firing on every other cylinder in firing order Unfortunately, I don't have a 2bbl to tear apart, but looking at my Rochester carb book, I may be in error on the 2 check balls. Its hard to tell with the crappy schematics. Irregardless, when you take it apart, check every passage. Make sure that they are all flowing freely. Nothing in or behind the jets, idle passages clear. Bleed tube clear on ventris......... I significantly doubt that this is a spark issue. __________________ ......its not what your askin', its what your gettin'.... .......every time I screw up, I learn something. Needless to say, I'm learning all the time............

11-18-2012, 04:06 PM	#30
jd7 Registered User Join Date: Sep 2012 Location: canoga park, ca. Posts: 120	Re: small block firing on every other cylinder in firing order I keep saying propane because you can control it better and it wont start a fire if your arcing somewhere. what do the plugs look like. It really sounds like fuel starvation. Have you checked the chain for play ? Pull the cap and rock the crank back and forth distributor should move with it.I am a mechanic by trade so i ask about basics they will lead you to the problem.I'm sorry if I sound abrupt

11-18-2012, 06:48 PM	#31
dlh760 Registered User Join Date: Oct 2012 Location: valley center,ca Posts: 124	Re: small block firing on every other cylinder in firing order Problem has been fixed after I put my carb back together and back on it is running much better,really rich now but better. I am a mechanic by trade as well but had never come across anything like this before. I appreciate everybody's input and help. Dan Posted via Mobile Device __________________ 68 Chevy c10 longbed 307 with 305 H.O. heads,edelbrock performer intake,edelbrock performer plus cam,hei,Holley 650 double pumper and th400. Daily driver. It hauls butt,it hauls my butt where I need to go

11-18-2012, 03:04 PM	#27
biggestjohn Registered User Join Date: Apr 2010 Location: Russiaville Posts: 203	Re: small block firing on every other cylinder in firing order 2 3 5 8 are feed by the left (drivers side) of the carb. If you are getting fuel, but no ignition, your plugs will be very wet. If they are dry, you are not getting fuel. I would suspect that the cylinders are running very rich, and gas fouled the plugs, but without seeing (hint) its hard to say. Now all you have to figure out is why? __________________ ......its not what your askin', its what your gettin'.... .......every time I screw up, I learn something. Needless to say, I'm learning all the time............

03-21-2017, 05:26 PM	#32
Claus Registered User Join Date: Mar 2017 Location: Portland, OR Posts: 2	Re: small block firing on every other cylinder in firing order I'm experiencing the same problem on my sbc 350, I bought a project truck with a 350 and electronic ignition, had the heads checked, new plugs, 4 ported edelbrock carb. the engine runs rough, with only little torque, pulled plugs and they are not wet or black. it sounds like all cylinders are firing, but in the right sequence, have double checked firing order. 1 8 4 3 6 5 7 2, it seem odd that every other cylinder is misfiring 1 8 4 3 6 5 7 2 Have spark on all 8 plugs, by grounding individual leads one by one, while running, I narrowed it down to cylinder 2 8 3 5 can be grounded without the engine changing sound, which seem to me like a problem. Hope someone can help.

03-21-2017, 08:11 PM	#33
Moose Monkey Registered User Join Date: Sep 2016 Location: south jersey Posts: 118	Re: small block firing on every other cylinder in firing order #27 is the answer, I hope

03-21-2017, 08:20 PM	#34
Moose Monkey Registered User Join Date: Sep 2016 Location: south jersey Posts: 118	Re: small block firing on every other cylinder in firing order Sorry, not much of answer. If those cylinder's are firing spark good, just might be fuel. Had Elderbrock crack inside, sucking to much air.would not idle, very bad time starting

03-21-2017, 08:37 PM	#35
garyd1961 Registered User Join Date: May 2016 Location: Henderson NC Posts: 975	Re: small block firing on every other cylinder in firing order Do you have a duel plane intake? Have you tried turning the motor over with the spark plugs out of the motor and grounded on the outside to see if they actually fire or not? If you have a duel plane intake I suspect one side of your carb is not working.

03-21-2017, 10:24 PM	#37
volksworld Registered User Join Date: Apr 2011 Location: formerly NY currentlyNC Posts: 390	Re: small block firing on every other cylinder in firing order not looking at a small block as we speak but does anything tap into one runner of the manifold like a brake booster hose? a small leak could kill that cylinder or a major one(blown booster diaphram?) might affect the whole manifold plane....if you got a 4 hole 1 inch spacer and put the carb on backwards you could see if the 4 dead cylinders suddenly became the live ones...then you'd know its a carb issue __________________ 1970 short step c10 leaf spring 454

03-22-2017, 09:35 AM	#38
Moose Monkey Registered User Join Date: Sep 2016 Location: south jersey Posts: 118	Re: small block firing on every other cylinder in firing order Volksworld what a great idea

03-22-2017, 01:54 PM	#39
Claus Registered User Join Date: Mar 2017 Location: Portland, OR Posts: 2	Re: small block firing on every other cylinder in firing order Hi Guys it ended up being one side of the carburetor that was blocked, that became clear after your feedback and I took another look at the intake manifold, cylinder 2-8-3-5 is all in the same side of the carb. I was able to clear out the block, now the engine runs like a champ. Thanks for sharing your ideas,



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.