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Topic: HUGE Misfire!

in Forum: C3 Engines


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HUGE Misfire! (1/10)
 7/12/24 8:17am
TwinTurbo WidebodyLifetime Member
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Ventura, CA - USA

Vette(s):
1974 Twin Turbo 1-off Widebody


Joined: 5/9/2024
Posts: 28

1-PM Tuesday Car running great

2-AM Wednesday feels like an erratic misfire. 

3-AM Wednesday about 1 minute later.  Car barely turns over!😡‍πŸ’«

4-PM Wednesday Full Scale Hot Rod & Customs ok’s car into shop.  (Really stepped up on expediting car in)

5-AM Thursday. Problem discovered!  Mount for MSD distributor had failed.  Distributor bouncing around like lottery number ballsπŸ€”

6-PM Thursday. Spark plug wires, Spark plugs replaced and OEM distributor mount replaced.

7-CRUISING HOMEπŸ˜ŽπŸ‘πŸπŸ‡ΊπŸ‡Έ

HUGE THANKS TO FULL SCALE, VENTURA CAπŸ‘πŸ‘πŸ‘



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Re: HUGE Misfire! (2/10)
 7/12/24 8:29am
F4GaryGold Member
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Grapevine, TX - USA

Vette(s):
1972 LT-1 convertible with factory air. 2017 Black Rose Grand Sport convertible.


Joined: 8/26/2006
Posts: 1463

#5...Do you mean the hold down clamp at the base came loose and the disty was rotating around randomly?



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Re: HUGE Misfire! (3/10)
 7/12/24 9:30am
TwinTurbo WidebodyLifetime Member
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Ventura, CA - USA

Vette(s):
1974 Twin Turbo 1-off Widebody


Joined: 5/9/2024
Posts: 28

Yep!  The MSD was installed 2019 and the mechanic used mount from original build in 1978-79.  Chromed POT (Piece Of Trash) METAL😡‍πŸ’«.  After 45 yrs, garaged for 42+ yrs, less than 1000 miles.

Oh how I love this carπŸ˜ŽπŸ‘πŸπŸ‡ΊπŸ‡Έ

Back on the road again



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Re: HUGE Misfire! (4/10)
 7/26/24 3:50pm
VNCRUISER
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North Hills, CA - USA

Vette(s):
1972 T-Top


Joined: 6/12/2003
Posts: 514

If the problem was the distributor, why were plugs and wires replaced too? I see repairs done like this all the time. Did they give you a reason for replacing plugs and wires? Or is that what was "recommended"?  I had a friend with a 66 El Camino that kept having a back fire. Took it to two different shops. One guy told him it was his carburetor and put  a Holley 2 barrel on it (it is a stock 283).  Still happened.

  Took it to another shop where they recommended installing an MSD box, plugs and wires... Still did it. He had now spent $1600.00 to fix the car and still had the same issue. He brought to my house and my brother and I looked it over. This car was original down to the smog pump. On the back of the smog pump is the "gulp valve". If the diaphram is torn in the valve, air mixture in the combustion chamber is change and causes the back fire.  We took the belt off to test and sure enough, with no air being pumped, no back fire. Removed the smog pump and plugged the holes on the exhaust manifold and sent him back to the two shops for his money back. No one would budge... The actual repair was about $12.00 in 3/8 pipe plugs. 

 

 Some of these shops really suck and don't know how to diagnose older cars.. 



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    Reid    '72 T-top

www.wildbunchcarclub.com

www.vannuyscruisingassociation.com


Re: HUGE Misfire! (5/10)
 7/26/24 4:31pm
TwinTurbo WidebodyLifetime Member
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Ventura, CA - USA

Vette(s):
1974 Twin Turbo 1-off Widebody


Joined: 5/9/2024
Posts: 28

Good questions and indeed plugs looked horribly arced,  wires were burned.  Over the past two years this shop has stood tall!  I truly appreciate the input 



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Re: HUGE Misfire! HEAT IS NO FRIEND! (6/10)
 11/2/24 11:00am
TwinTurbo WidebodyLifetime Member
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Ventura, CA - USA

Vette(s):
1974 Twin Turbo 1-off Widebody


Joined: 5/9/2024
Posts: 28

HEAT IS THE ENEMY!   After a 100 mile round trip from Ventura to LA Airport via Coast Route erratic engine action began.   You know, “that's not right” feeling?   Last time it was a distributor mount.   Went to shop and Chris at Full Scale Hot Rods & Customs had immediately discovered the plug boots had melted due to proximity to exhaust manifold.    Replaced all with a great David Freiburger idea!   Ceramic Boots on all plugs.   Noticed more pep immediately πŸ‘πŸ‘πŸ‘πŸ‘πŸπŸ‡ΊπŸ‡Έ AND now no fear of repeat. 

Now to compare FiTech Engine heat sensor with dash gauge reading.   No way the engine is running as hot as gauge reads.  With dash gauge connection immediately between exhaust manifold and rocker cover and very close to driver side turbo the dash gauge temp is surely reading higher than real.  Results to comeπŸ€”πŸ˜ŽπŸπŸ˜Ž



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Re: HUGE Misfire! (7/10)
 11/5/24 10:33am
TwinTurbo WidebodyLifetime Member
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Ventura, CA - USA

Vette(s):
1974 Twin Turbo 1-off Widebody


Joined: 5/9/2024
Posts: 28

Yep!  Aftermarket clamp crackedπŸ€”πŸ˜΅‍πŸ’«



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Re: HUGE Misfire! (8/10)
 11/17/24 11:10am
TwinTurbo WidebodyLifetime Member
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Ventura, CA - USA

Vette(s):
1974 Twin Turbo 1-off Widebody


Joined: 5/9/2024
Posts: 28

Drum RollπŸ₯πŸ₯πŸ₯

Results of dash engine temp gauge vs FiTech temp reading…Dash gauge shows about 210°! FiTech hand held controller shows 197°!!!!   That's comforting πŸ˜ŽπŸπŸ‡ΊπŸ‡Έ

 



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Re: HUGE Misfire! (9/10)
 11/19/24 8:42am
NorskyLifetime Member
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Burke, VT - USA

Vette(s):
SOLD - "The Toy" - '70 Convertible
SOLD - "The Beast" - '90 ZR-1 (#682)
SOLD - "Betty" - '28 Ford Model A Tudor
Still have - "BLKBRRD" - '78 Pontiac Trans Am


Joined: 1/23/2002
Posts: 7240

πŸ‘  Had a FITECH system in "BLKBRRD" for a spell (until the computer failed) and noticed the same thing.  COOLer is GOOD...!!!  πŸ˜Ž



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Jim Olson 

"The Toys"...!!!  Save the Wave!

Where I've been in a Corvette...!!!

Re: HUGE Misfire! (10/10)
 11/24/24 11:24am
TwinTurbo WidebodyLifetime Member
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Ventura, CA - USA

Vette(s):
1974 Twin Turbo 1-off Widebody


Joined: 5/9/2024
Posts: 28

Soooooo, after about a 2 hour drive there came an all familiar misfire.  I’ll describe it as engine has bronchitis.  Couldn’t get a regular gallop when acceleration applied.   Went to “go to shop” and turns out # 8 plug was fuel wetπŸ€”   All plugs swapped out for hottest in the market.  That was it. Compression is perfect!  I was told in 2019 when I bought the car “it's a project car”.   A really important element about the car is it was never driven prior to my purchase except about 2 miles to evaluate running gear, suspension, brakes etc.    So experimental project is the best moniker.  My changes to all things mechanical only added to the experiment.    Was it worth it?   ABSOLUTELY!   I expect more surprises and more appreciation at any moment.   πŸ˜ŽπŸπŸ‡ΊπŸ‡Έ



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