1971 Ford Mustang Backfire

CAPTTHUNDARR

MEMBER
1971 FORD MUSTANG

Engine Performance problem
1971 Ford Mustang V8 Two Wheel Drive Automatic

Got a 71 mustang conv. That we put a create motor from jeg's in. The motor is a '87 thru '96 5.0 HO(it came with a 351 cam). Set the #1 piston to TDC on the compression stroke. I was told by the engine manufacture (Blueprint engineering) to besure to use the 351 firing order which I did. With the engine running and warmed up, any timing above 0 deg. BTDC the engine will backfire through the carb when the throttle is cracked quickly but revs smoothly when it is opened slowly. I don't get it.

3 Replies

MMPRINCE4000

MECHANIC
8,548 POSTS

I would check valve lash, wheather solid lifters or hydraulic. Sounds like a valve is hanging open.

Also call Jegs tech support, they have a pretty good tech. Section, if only to let them know you are having a problem before the warranty runs out.

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Tuesday, September 9th, 2008 AT 5:43 AM

CAPTTHUNDARR

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2 POSTS

What about the distributor beong "1 tooth out"?

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Tuesday, September 9th, 2008 AT 9:29 AM

MMPRINCE4000

MECHANIC
8,548 POSTS

If the engine is at #1 TDC and you install the dist. With rotor pointing at #1, you should be OK.

Check with Jegs and see if the timing chain was installed advanced.

Generally when you have too much advance the car will be hard to start, crank slowly, because the ign. Is firing the cylinder way too soon.

The fact that it is back firing, indicates an incorrect firing order or a valve hanging up, or a distributor problem.

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Wednesday, September 10th, 2008 AT 6:06 AM