Backfire when starting

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Truedough
Posts: 3
Joined: April 24th, 2011, 7:36 pm
Stroker Displacement: 4.6
Vehicle Year: 1998
Vehicle Make: Jeep
Vehicle Model: TJ

Backfire when starting

Post by Truedough »

I bought a 4.6 stroker long block about 5 years ago and put it in my '98 TJ. From the day i installed it, when I start it, the engine kicks backward. Its hit and miss when it happens but it has always happened. Once running it runs great. There is no adjustment on the distributor for timing. I have talked to many of people and all are dumbfounded, Any thoughts???
AlexTJ
I made it to triple digits!
I made it to triple digits!
Posts: 126
Joined: July 9th, 2008, 11:07 am
Stroker Displacement: 4.7L
Vehicle Year: 1997
Vehicle Make: Jeep
Vehicle Model: Wrangler

Re: Backfire when starting

Post by AlexTJ »

How is the idle quality?

Also what are the specs of your stroker if you know them?
97 TJ - 4.7L - Lunati 63502 ftw
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unlimitedrubicon
I made it to triple digits!
I made it to triple digits!
Posts: 138
Joined: December 22nd, 2009, 5:50 am
Stroker Displacement: 4.6L
Vehicle Year: 2005
Vehicle Make: Jeep
Vehicle Model: Wrangler

Re: Backfire when starting

Post by unlimitedrubicon »

A backfire usually means either the cam timing is off, or the ignition timing. A backfire occurs when the fuel is ignited while the intake valve is open, so if you check both of those you should find one that is off. The third, but not as common reason could be due to needing a valve job so much that there is very little seal, but you would probably notice that in driveability.
AlexTJ
I made it to triple digits!
I made it to triple digits!
Posts: 126
Joined: July 9th, 2008, 11:07 am
Stroker Displacement: 4.7L
Vehicle Year: 1997
Vehicle Make: Jeep
Vehicle Model: Wrangler

Re: Backfire when starting

Post by AlexTJ »

unlimitedrubicon wrote:A backfire usually means either the cam timing is off, or the ignition timing. A backfire occurs when the fuel is ignited while the intake valve is open, so if you check both of those you should find one that is off. The third, but not as common reason could be due to needing a valve job so much that there is very little seal, but you would probably notice that in driveability.
Exactly, mine backfired through the intake and idled like crap until I cut the ears off the distributor and properly indexed it
97 TJ - 4.7L - Lunati 63502 ftw
Truedough
Posts: 3
Joined: April 24th, 2011, 7:36 pm
Stroker Displacement: 4.6
Vehicle Year: 1998
Vehicle Make: Jeep
Vehicle Model: TJ

Re: Backfire when starting

Post by Truedough »

Unfortunately i do not know any specs. I lost all the paperwork over the years. Once it starts, it idles and runs great. Its just starting it when it happens. I had it out about a year ago and checked the timing and it was correct. i am assuming the valves are good as it has done it from the day i bought it new. When i had it out I noticed the rocker arms really loose but i could not figure out how to adjust them.
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unlimitedrubicon
I made it to triple digits!
I made it to triple digits!
Posts: 138
Joined: December 22nd, 2009, 5:50 am
Stroker Displacement: 4.6L
Vehicle Year: 2005
Vehicle Make: Jeep
Vehicle Model: Wrangler

Re: Backfire when starting

Post by unlimitedrubicon »

If you have stamped rocker arms or non-adjustable rollers then the only way to adjust them is with longer pushrods. You will need an adjustable pushrod to measure the correct length to order.

How loose are they? If they are more than just a tiny bit from lifter bleed down it was either assembled incorrectly with the wrong length pushrods, or you have some serious wear on the valvestems or your cam.
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