When I said the Caprice was backfiring, I was wrong.

I never had a car backfire before, how am I supposed to know the difference.

What it does do is POP, ALOT, through the carb. The intake charge is igniting and firing out the carb.

I've narrowed it down to three possible causes.

Blown head gasket.
Really bad timing chain.
Stuck valve.


It only does this under load, uphill etc. And only when I give it more than barely any throttle.

Since it is a roller cam, I'm going to assume it's not a wiped out cam.

Which cause is it?

Doing it only under a load must be some kind of clue. It doesn't matter if I ease into the throttle or mash it.

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Shane McConnell[*]Webmaster of www.NEThirdgen.org[*]1991 RS 305 T5 15.6@88[*]1979 Z28[*]1987 Caprice

 

Probably a screwed up accelerator pup in the carb, it's not squirting liek it's supposed to. clogged nozzle or something.

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"American made baby. 100% American iron. The muscle among the masses. My hero. Yep, you can take your ergonomically designed, space age, computer controlled, 4 door, cup holding map lighted split double wishbone split fold down retractable cargo covered moon roof piece of transportation and keep it. For I have felt the thunder. And I know the difference!"
JSP Motorsports
ICON Motorsports

 

That's not the problem, the carb was rebuilt before I bought it, by PK.

 

i'll go with a burnt valve, do a compression check, or leak it down.

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ICON Motorsports

1st & 3rd
MM Black Diamond 538 F&AM

 

Any other guesses?

 

Somewhere a while back someone had something similar, I think it ended up being an EGR valve stuck open.

 

check for crossed wires, i had the same symptoms with one of my cars. it would run fine at light throttle and then under load it would act like a popcorn machine

 

oh and about the blown head gasket, TRUST ME YOU WILL KNOW WHEN THAT HAPPENS IT SUCKS!!!

 

I went through the same deal many years back. Ripped into the motor for nothing.....

Plugged cat was my cause.

 

my buddies caprice skipped timing when it chewed up the gears. Did the same thing. If it has been backfiring though the carb say good bye to the carb rebuild!!

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91 Z28 Camaro
305 TPI
Flowmaster 3" exhaust
700R4 with 2000 Stall and shift kit 3.42 rearend
One sweet sounding system

 

My car was backfiring or popping through the carb. turned out I had a spark plug wire burnt to hell.

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'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
FLOWMASTER
EDELBROCK 600CFM CARB.
KN AIRFILTER
UNDERDRIVE PULLEY
ACCEL HEI DISTRIBUTOR
2:73 GEARS

 

i had a similar problem years ago when i still had all the emissions equipment. my cat spit its guts out, the guts lodged in the muffler(the muffler looked like a marshmallow) causing a serious restriction in exhaust flow (obviously). i find it funny as hell now.

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85 IROC 350 11:1keith blacks,.555lift erson roller cam,1.5 crane roller rockers,edelbrock intake,holley 4150 750dbl pumper, nitrous oxide,full length heddman headers,true dual exhaust, 11"stall converter, 700R4, 3.73 locker

 

Well, monday and tuesday, I'm gonna gut the cat and pull the valve covers.

I was gonna gut the cat anyway, and the valve covers need repainted, so I'll check for a stuck valve or whatever.