Need Help installing HEI/Timing - The 1947 - Present Chevrolet & GMC Truck Message Board Network

72MARIO · 07-12-2005, 11:47 PM

Oky they way I have doen it so far was cranked the motor over till it blew my fingfer off the 1 cyl. I droped the dizzy in with the rotor pointing to the 1 mark I scribed into the dizzy base. I eneded up 180 out. I fixed that. Now when I start it, It runs but back fires thru the carb. WHY ?

That's where I am stuck. Am I a tooth out ? Kinda new to this My dad usually helps me but he is away for the next 2 1/2 weeks so I am on my own.

Any help would be great.

aboyer · 07-13-2005, 12:31 AM

I would be willing to bet that if your carb is backfiring, that you have it 180 degrees out. Also, make sure you have the rotor pointed toward the number 1 cylinder (drive side, first cylinder)

If you are a tooth off on the distributor, the engine should fire, but misfire. Also, be sure to check your distributor cap numbering 1,8,4,3,6,5,7,2--numbering goes clockwise from #1.

Hope that helps

jhow66 · 07-13-2005, 12:40 AM

If it backfires when you give it gas the time is to low--turn dizzy counterclockwise to advance time--should be at least 10* BTDC with the cam you have.

72MARIO · 07-13-2005, 07:26 AM

Oky well I doubble checked the rotor is pointing at the 1 cyl and post on the cap withthe motor at TDC . So if I have the dizzy installed right is it still possible to see a back fire thru the carb if the timing is not right on ? It's kinda hard to get out of the truck and keep it running long enough to get the light in my hand and set the timing with out it dying.

Huck · 07-13-2005, 07:38 AM

Your timing has to be out quite a bit to get a backfire through the carb. Usually a few degrees one way or the other will not cause that. In most instances, I have found that I managed to get the plug wires out of sequence. Double and triple check that!
Then if it starts---and stalls, move the dizzy one way or the other a bit to see if it makes a difference. then start it and see what happens. IF you don't tighten the dizzy lockdown too much, you can adjust and tweek it a bit> often with interesting cam's, you have to kind of time them by ear and by performance verses a light as there is no reference guide. If this is a used dizzy, have you checked the vacuum advance on it? They can be shot and if you rev, you get all sorts of uguly things happening.

72MARIO · 07-13-2005, 07:54 AM

I better doubble check the firing order. If that will cause a backfire. Everything is brandnew. The cam is just a mild cam need between 10-12 initial.

72MARIO · 07-13-2005, 08:00 AM

Oky the wires are right. I pulled the cap off and made sure the rotor is pointing to 1 it is.
Could it be a tooth out still ?

jhow66 · 07-13-2005, 10:00 AM

Have you moved your time up yet?

Dual quad · 07-13-2005, 12:22 PM

Hey Mario, just a few thoughts here.

Although you checked for compression stroke on #1, did you confirm that you were at (or 10 degree advanced) of TDC at the balancer, prior to droping the dist in? Use the balancer as a reference here.

There is not really such a thing as being "off a tooth". It is just that the relative position of the distributor may be offset from normal. Generally, you should have adequate physical room to swing the dist body advanced or retarded without the vac can interfering with something.

It sounds like you droped the dist in to it's old position (which is correct), but the #1 piston was way advanced of TDC.

07-13-2005, 12:40 AM	#3
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	If it backfires when you give it gas the time is to low--turn dizzy counterclockwise to advance time--should be at least 10* BTDC with the cam you have. __________________ 56 Chevy Bel-Air 2dr. HT (purchased new) 71 Chevy Cheyenne SWB PU (502HO) 65 GMC short bed step--work in progress and my gofer

07-13-2005, 07:26 AM	#4
72MARIO Registered User Join Date: Nov 2000 Location: Huntsville Ontario Canada Posts: 4,051	Oky well I doubble checked the rotor is pointing at the 1 cyl and post on the cap withthe motor at TDC . So if I have the dizzy installed right is it still possible to see a back fire thru the carb if the timing is not right on ? It's kinda hard to get out of the truck and keep it running long enough to get the light in my hand and set the timing with out it dying. __________________ 1968 Suburban numbers matching all original truck now equipped with 6.0/4L80 on Accuair http://67-72chevytrucks.com/vboard/s...d.php?t=625017 1967 C/20 6.0/4L80 Roofing Truck 1990 V2500 Suburban "Plow Truck" 2005 TAHOE DD

07-13-2005, 07:54 AM	#6
72MARIO Registered User Join Date: Nov 2000 Location: Huntsville Ontario Canada Posts: 4,051	I better doubble check the firing order. If that will cause a backfire. Everything is brandnew. The cam is just a mild cam need between 10-12 initial. __________________ 1968 Suburban numbers matching all original truck now equipped with 6.0/4L80 on Accuair http://67-72chevytrucks.com/vboard/s...d.php?t=625017 1967 C/20 6.0/4L80 Roofing Truck 1990 V2500 Suburban "Plow Truck" 2005 TAHOE DD

07-13-2005, 08:00 AM	#7
72MARIO Registered User Join Date: Nov 2000 Location: Huntsville Ontario Canada Posts: 4,051	Oky the wires are right. I pulled the cap off and made sure the rotor is pointing to 1 it is. Could it be a tooth out still ? __________________ 1968 Suburban numbers matching all original truck now equipped with 6.0/4L80 on Accuair http://67-72chevytrucks.com/vboard/s...d.php?t=625017 1967 C/20 6.0/4L80 Roofing Truck 1990 V2500 Suburban "Plow Truck" 2005 TAHOE DD

07-13-2005, 10:00 AM	#8
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	Have you moved your time up yet? __________________ 56 Chevy Bel-Air 2dr. HT (purchased new) 71 Chevy Cheyenne SWB PU (502HO) 65 GMC short bed step--work in progress and my gofer

07-12-2005, 11:47 PM	#1
72MARIO Registered User Join Date: Nov 2000 Location: Huntsville Ontario Canada Posts: 4,051	Need Help installing HEI/Timing Oky they way I have doen it so far was cranked the motor over till it blew my fingfer off the 1 cyl. I droped the dizzy in with the rotor pointing to the 1 mark I scribed into the dizzy base. I eneded up 180 out. I fixed that. Now when I start it, It runs but back fires thru the carb. WHY ? That's where I am stuck. Am I a tooth out ? Kinda new to this My dad usually helps me but he is away for the next 2 1/2 weeks so I am on my own. Any help would be great. __________________ 1968 Suburban numbers matching all original truck now equipped with 6.0/4L80 on Accuair http://67-72chevytrucks.com/vboard/s...d.php?t=625017 1967 C/20 6.0/4L80 Roofing Truck 1990 V2500 Suburban "Plow Truck" 2005 TAHOE DD

07-13-2005, 12:31 AM	#2
aboyer Adam B Join Date: Jul 2005 Location: Westfield Posts: 151	I would be willing to bet that if your carb is backfiring, that you have it 180 degrees out. Also, make sure you have the rotor pointed toward the number 1 cylinder (drive side, first cylinder) If you are a tooth off on the distributor, the engine should fire, but misfire. Also, be sure to check your distributor cap numbering 1,8,4,3,6,5,7,2--numbering goes clockwise from #1. Hope that helps

07-13-2005, 07:38 AM	#5
Huck Senior Member Join Date: Jun 2001 Location: Shelbyville, KY Posts: 3,261	Your timing has to be out quite a bit to get a backfire through the carb. Usually a few degrees one way or the other will not cause that. In most instances, I have found that I managed to get the plug wires out of sequence. Double and triple check that! Then if it starts---and stalls, move the dizzy one way or the other a bit to see if it makes a difference. then start it and see what happens. IF you don't tighten the dizzy lockdown too much, you can adjust and tweek it a bit> often with interesting cam's, you have to kind of time them by ear and by performance verses a light as there is no reference guide. If this is a used dizzy, have you checked the vacuum advance on it? They can be shot and if you rev, you get all sorts of uguly things happening.

07-13-2005, 12:22 PM	#9
Dual quad Smell that burnin' rubber Join Date: Sep 2000 Location: Ontario Posts: 171	Hey Mario, just a few thoughts here. Although you checked for compression stroke on #1, did you confirm that you were at (or 10 degree advanced) of TDC at the balancer, prior to droping the dist in? Use the balancer as a reference here. There is not really such a thing as being "off a tooth". It is just that the relative position of the distributor may be offset from normal. Generally, you should have adequate physical room to swing the dist body advanced or retarded without the vac can interfering with something. It sounds like you droped the dist in to it's old position (which is correct), but the #1 piston was way advanced of TDC.



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