engine losing power when getting hot
#1614529
05/01/14 06:40 AM
05/01/14 06:40 AM
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Joined: Jan 2009
Posts: 106 Poland
willard
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OP
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Joined: Jan 2009
Posts: 106
Poland
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Hi, I have no car to compare but my 70 challenger, 383 with 220/226 @0.050 cam, 440 heads, KB400 pistons (domes), DP4B, HP manifolds, stock 727, stock clutch fan, holley SA 770, MP performance distributor and orange box, msd blaster coil (mounted in front of carb) + 0.25ohm ballast; has nice power and torque when engine is quite cold. During first 10 minutes after firing up runs like a raped ape, melting F70-14 in 2nd gear... but when engine is warm it runs noticeably weaker. No signs of any malfunctions but it is not as strong as during the first 10 minutes. When it is hot outside - 90 F and above it seems car loses 20% of power. Compression is 150-160 and even. I have no O2 sensor to check AFR but no hesitation, no stumble, no bogging while drive be it cruise, be it WOT. Timing is 20 initial and 36 total. Vac 17 in N @800, 15 in D @700rpm. I changed the jets to 71 front and 74 rear assuming the carb is too big but this made no difference.
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Re: engine losing power when getting hot
[Re: willard]
#1614531
05/01/14 12:00 PM
05/01/14 12:00 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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First I'd try & pin it down to either AF ratio or ign. I'd richen the pri jets significantly & see what happens. 4 or 5 numbers maybe . I ain't sure how far but make a very big jump & richen it way up for a day just for diagnosing
live every 24 hour block of time like it's your last day on earth
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Re: engine losing power when getting hot
[Re: Baxter61]
#1614536
05/01/14 02:50 PM
05/01/14 02:50 PM
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Joined: Jun 2006
Posts: 5,169 CT
GTX MATT
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master
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Posts: 5,169
CT
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You need to jet up, those carbs are lean out of the box. Put 75s in the primaries, 78s in the secondaries, and report back. That jetting worked well on my stockish 440.
Last edited by GTX MATT; 05/01/14 02:50 PM.
Now I need to pin those needles, got to feel that heat Hear my motor screamin while I'm tearin up the street
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Re: engine losing power when getting hot
[Re: GTX MATT]
#1614537
05/01/14 04:20 PM
05/01/14 04:20 PM
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Joined: Jan 2009
Posts: 106 Poland
willard
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OP
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Joined: Jan 2009
Posts: 106
Poland
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Ok, will enrichen the carb however this is almost stock 383 not a 440. Also the plugs show a rich mixture - but that can be misleading as I do almost only city miles. Distributor may be the culprit but I have no spare to swap. Engine has 2000 miles and I always measure compression when hot. I have a spare ignition box (stock blue one) can swap it to give it a try. Before resto that engine had 7.4:1 CR so I know how a lo comp 383 drives. Mine loses rather some torque than power.
PS It's not a vapor lock, I can spin it to 5 grand no issues, no fuel starvation.
Last edited by willard; 05/01/14 04:24 PM.
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Re: engine losing power when getting hot
[Re: willard]
#1614538
05/01/14 05:14 PM
05/01/14 05:14 PM
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Joined: Aug 2006
Posts: 2,540 God's Country Maryland
GODSCOUNTRY340
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master
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God's Country Maryland
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If not electrical it could be an internal clearance condition. Do you know what clearance the piston to cylinder wall is, and more importantly, what it is suppose to be? If the clearance was too tight when assembled, the piston expands when hot and gets tight in the bore, killing power.
I love the smell of Deer guts in the morning, it smells like... VICTORY!
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Re: engine losing power when getting hot
[Re: willard]
#1614540
05/01/14 09:36 PM
05/01/14 09:36 PM
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Joined: Jan 2012
Posts: 1,650 Harm City Md.
Dan Halen
top fuel
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top fuel
Joined: Jan 2012
Posts: 1,650
Harm City Md.
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Quote:
When it is hot outside - 90 F and above it seems car loses 20% of power.
That's normal, ask any drag racer.
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Re: engine losing power when getting hot
[Re: willard]
#1614541
05/02/14 12:26 PM
05/02/14 12:26 PM
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Joined: Jan 2003
Posts: 75,134 A Banana Republic near you.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,134
A Banana Republic near you.
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Quote:
Ok, will enrichen the carb however this is almost stock 383 not a 440. Also the plugs show a rich mixture - but that can be misleading as I do almost only city miles. Distributor may be the culprit but I have no spare to swap. Engine has 2000 miles and I always measure compression when hot. I have a spare ignition box (stock blue one) can swap it to give it a try. Before resto that engine had 7.4:1 CR so I know how a lo comp 383 drives. Mine loses rather some torque than power.
PS It's not a vapor lock, I can spin it to 5 grand no issues, no fuel starvation.
I was going to suggest trying to swap a distributor , but realize that you are in Poland so that is not so easy. You wouldn't happen to have a points distributor ?
Swap in the blue box , reset the timing , whenever you change those boxes the timing moves.
Which electronic distributor do you have , an old one that you had to weld the slots smaller or the new adjustable one ?
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Re: engine losing power when getting hot
[Re: JohnRR]
#1614542
05/02/14 03:50 PM
05/02/14 03:50 PM
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Joined: Jan 2009
Posts: 106 Poland
willard
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OP
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Joined: Jan 2009
Posts: 106
Poland
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I bought the distributor in 2009 and it's the new electronic unit (mallory?). Engine was assembled on the lose side so the piston to wall clearance shouldnt be an issue. Exhaust is 2.5in + super turbos, not most free flowing but the intake is close to stock too. Swapped the box but cant drive the car today - hail and storms here ;| If there's no change I'll change the jets. Good advice on timing - didnt know the box moves it
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