trying to start for first time. Backfiring... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Hogger54 · 03-21-2014, 09:13 PM

So it keeps backfiring when I try to start the engine. I haven't been able to get it to catch.
I have a 235 with an 848 head, an HEI dist. and dual Rochester 1bbl's(rebuilt). New plugs @.35 and new wires.
I am getting spark, and I have fuel getting to the carbs.
When I put new gasket in, and installed the new dist. I set cyl. 1 to TDC.
I have the plug wires going around the dist. in a clockwise direction firing cylinders 1, 5, 3, 6, 2, 4.
It seems like the second carb in the fuel line(closest to firewall) is the one backfiring.

Any ideas what my problem is(with the engine)?

OrrieG · 03-21-2014, 09:28 PM

Did you confirm that #1 was on the compression stroke?

Hogger54 · 03-21-2014, 09:49 PM

I'm 99% sure it was. I did it with a compression test gauge. And my borescope.

**mr48chev** · 03-21-2014, 09:51 PM

Quote:

Originally Posted by OrrieG

Did you confirm that #1 was on the compression stroke?

Yep, How did you determine that you had #1 up on the compression stroke?

By cranking the engine over with the starter and letting compression blow against your finger in the spark plug hole?
By checking the rockers to see that both valves are closed and the timing mark is showing in the hole?

By rotating the engine by hand before the head on and getting the #1 piston to tdc and dropping the distributor in?

If it is #3 there is that chance that you had it on tdc on the exhaust stroke rather than the compression stroke and have it 180 degrees out.

I'd pull #1 plug (the front one) and crank the engine over with my finger over the plug hole to make sure that the rotor is actually pointing to #1 when you get it up on TDC. If it is go to step 2 which would be figuring out why it backfires only on the back carb. If it isn't, correct that issue and see if it starts.

Hogger54 · 03-23-2014, 03:53 PM

Alright. I'm back to TDC by feeling the air blow out of the spark plug hole as I turn the engine over, then fine tuned with my borescope to get the piston right at the top.
Pulled the top off the distributor, and this is what it looks like. Where I drew the #1 is roughly where the contact for the #1 cyl. is.
I'm not certain, but it looks to be almost 180 degrees off. Am I not on the compression stroke.
Am I seeing that right, and what's the best way to get it in the right position?
Should I pull the dist. and spin it by hand, or can I just rotate the top piece by hand?

**mr48chev** · 03-23-2014, 04:44 PM

It appears that you have it set on the exhaust stroke rather than the compression stroke.

Old Truck Man · 03-23-2014, 05:06 PM

Ok you now have the engine number I cyl at TDC on the compression stroke. Simply place number one spark plug wire where the rotor is pointing and go from there. the engine wont care which position the distrubeter and rotor are located. It only want,s spark to ocuur when it has compressed fuel in the cyl with the valves closed. Ive simply moved the plug wites around on lots of engines. Ive probably made some other mechanic pull their hair out when changing the plug wires or dist cap

Tims37chevy · 03-23-2014, 05:10 PM

Yep pull it out just enough so you can spin the rotor 180

Highsider · 03-23-2014, 05:22 PM

I like Old Truck Man's method.

Hogger54 · 03-23-2014, 05:31 PM

Sweet. Thanks guys.

OrrieG · 03-23-2014, 06:46 PM

If you checked the timing marks and they are lined up then switch the wires so #1 is at the end of the rotor. If the marks are not there and you are not concerned about ever using a timing light, then switch the wires and set it using a vacuum gauge and your ear. Advance it until it starts to fall off a little, then pull it back a few degrees. Take it for a spin to see how it does under load and at 2K rpm. If it feels good, ok if not fiddle with it until it does. Every engine is a little different and has a sweet spot. I'd think about replacing that rotor in a while too looks like it might be arcing. I'm like Old Truck Man, follow your instincts.

55dude · 03-23-2014, 11:57 PM

get it fired back up yet?

Hogger54 · 03-24-2014, 04:30 PM

It's trying hard. It will hit on a couple cylinders then act like it seized up. I'll try again, but it only fires a couple times.
I did find a 5/8" hole in my intake manifold that I forgot to plug. So I'll put a bolt in there and see if I can find any other issues.

03-21-2014, 09:28 PM	#2
OrrieG Registered User Join Date: Jun 2006 Location: Idaho Posts: 8,800	Re: trying to start for first time. Backfiring... Did you confirm that #1 was on the compression stroke? __________________ 1959 Chevy Short Fleetside w/ 74 4WD drive train (current project) OrrieG Build Thread 1964 Chevelle Malibu w/ 355-350TH (daily driver) Helpful AD and TF Manual Site Old Car Manual Project

03-23-2014, 03:53 PM	#5
Hogger54 Registered User Join Date: Aug 2013 Location: Lumberton, TX Posts: 284	Re: trying to start for first time. Backfiring... Alright. I'm back to TDC by feeling the air blow out of the spark plug hole as I turn the engine over, then fine tuned with my borescope to get the piston right at the top. Pulled the top off the distributor, and this is what it looks like. Where I drew the #1 is roughly where the contact for the #1 cyl. is. I'm not certain, but it looks to be almost 180 degrees off. Am I not on the compression stroke. Am I seeing that right, and what's the best way to get it in the right position? Should I pull the dist. and spin it by hand, or can I just rotate the top piece by hand? __________________ My '54 3600 build. My '63 GMC build

03-23-2014, 04:44 PM	#6
mr48chev Registered User Join Date: Jul 2007 Location: Toppenish, WA Posts: 15,711	Re: trying to start for first time. Backfiring... It appears that you have it set on the exhaust stroke rather than the compression stroke. __________________ Founding member of the too many projects, too little time and money club. My ongoing truck projects: 48 Chev 3100 that will run a 292 Six. 71 GMC 2500 that is getting a Cad 500 transplant. 77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around.

03-23-2014, 05:06 PM	#7
Old Truck Man Registered User Join Date: Feb 2014 Location: Pocahontas Arkansas Posts: 684	Re: trying to start for first time. Backfiring... Ok you now have the engine number I cyl at TDC on the compression stroke. Simply place number one spark plug wire where the rotor is pointing and go from there. the engine wont care which position the distrubeter and rotor are located. It only want,s spark to ocuur when it has compressed fuel in the cyl with the valves closed. Ive simply moved the plug wites around on lots of engines. Ive probably made some other mechanic pull their hair out when changing the plug wires or dist cap

03-23-2014, 05:10 PM	#8
Tims37chevy Registered User Join Date: Jan 2011 Location: Champlin Mn. Posts: 54	Re: trying to start for first time. Backfiring... Yep pull it out just enough so you can spin the rotor 180

03-21-2014, 09:13 PM	#1
Hogger54 Registered User Join Date: Aug 2013 Location: Lumberton, TX Posts: 284	trying to start for first time. Backfiring... So it keeps backfiring when I try to start the engine. I haven't been able to get it to catch. I have a 235 with an 848 head, an HEI dist. and dual Rochester 1bbl's(rebuilt). New plugs @.35 and new wires. I am getting spark, and I have fuel getting to the carbs. When I put new gasket in, and installed the new dist. I set cyl. 1 to TDC. I have the plug wires going around the dist. in a clockwise direction firing cylinders 1, 5, 3, 6, 2, 4. It seems like the second carb in the fuel line(closest to firewall) is the one backfiring. Any ideas what my problem is(with the engine)? __________________ My '54 3600 build. My '63 GMC build Last edited by Hogger54; 03-21-2014 at 09:24 PM.

03-21-2014, 09:49 PM	#3
Hogger54 Registered User Join Date: Aug 2013 Location: Lumberton, TX Posts: 284	Re: trying to start for first time. Backfiring... I'm 99% sure it was. I did it with a compression test gauge. And my borescope. __________________ My '54 3600 build. My '63 GMC build

03-23-2014, 05:22 PM	#9
Highsider Registered User Join Date: Jun 2012 Location: Southern Iowa Posts: 944	Re: trying to start for first time. Backfiring... I like Old Truck Man's method. __________________ Jimi J from I-Oh-Way '57 Panel 3105 Met this deer... Roof Swap on my Panel Jim's Bread Truck

03-23-2014, 05:31 PM	#10
Hogger54 Registered User Join Date: Aug 2013 Location: Lumberton, TX Posts: 284	Re: trying to start for first time. Backfiring... Sweet. Thanks guys. __________________ My '54 3600 build. My '63 GMC build

03-23-2014, 06:46 PM	#11
OrrieG Registered User Join Date: Jun 2006 Location: Idaho Posts: 8,800	Re: trying to start for first time. Backfiring... If you checked the timing marks and they are lined up then switch the wires so #1 is at the end of the rotor. If the marks are not there and you are not concerned about ever using a timing light, then switch the wires and set it using a vacuum gauge and your ear. Advance it until it starts to fall off a little, then pull it back a few degrees. Take it for a spin to see how it does under load and at 2K rpm. If it feels good, ok if not fiddle with it until it does. Every engine is a little different and has a sweet spot. I'd think about replacing that rotor in a while too looks like it might be arcing. I'm like Old Truck Man, follow your instincts. __________________ 1959 Chevy Short Fleetside w/ 74 4WD drive train (current project) OrrieG Build Thread 1964 Chevelle Malibu w/ 355-350TH (daily driver) Helpful AD and TF Manual Site Old Car Manual Project

03-23-2014, 11:57 PM	#12
55dude Registered User Join Date: Jan 2007 Location: tacoma wa. Posts: 1,037	Re: trying to start for first time. Backfiring... get it fired back up yet?

03-24-2014, 04:30 PM	#13
Hogger54 Registered User Join Date: Aug 2013 Location: Lumberton, TX Posts: 284	Re: trying to start for first time. Backfiring... It's trying hard. It will hit on a couple cylinders then act like it seized up. I'll try again, but it only fires a couple times. I did find a 5/8" hole in my intake manifold that I forgot to plug. So I'll put a bolt in there and see if I can find any other issues. __________________ My '54 3600 build. My '63 GMC build



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