Carb issues LT1 1971
Thread Starter
2nd Gear
Joined: Mar 2021
Posts: 2
Likes: 0
From: Sweden
Carb issues LT1 1971
Hi, new member here!
I have a 71 LT1, and it runs great as long as you have like 2000revs and up. But when i´m getting rolling from start it will choke it selfs and somtime it misfires throu the carb.
I went out to the garage and noticed that i most likley have a carb from a 1970, could this be the problem or is it just tuning that i need?
Sorry for the broken english, i´, a swede :-)
I have a 71 LT1, and it runs great as long as you have like 2000revs and up. But when i´m getting rolling from start it will choke it selfs and somtime it misfires throu the carb.
I went out to the garage and noticed that i most likley have a carb from a 1970, could this be the problem or is it just tuning that i need?
Sorry for the broken english, i´, a swede :-)
Racer
Joined: Apr 2020
Posts: 264
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From: Sicklerville NJ
2022 C3 of the Year Finalist - Unmodified
It should run good with a 1970 carb . How did it run in the past ??? Check to make sure choke is fully opened , check timing , make sure firing order is correct , cap and rotor OK ( no cracks )
plug wires OK
plug wires OK
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
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From: New Braunfels Texas
Look down the choke horn and look at the squirter......whack the throttle a couple times.....is two nice streams squirting into the bores? If not.....you need an accelerator pump. Remove the front bowl and it is on the bottom. Google it up if you are not sure.......the pump diaphragm is very cheap and easy to change....be prepared to need a new float bowl gasket.
Jebby
Jebby
Safety Car
Joined: Sep 2005
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From: Orange County Ca
Also, a can of SeaFoam, etc. can sometimes preform miracles with a carb that has got a little gummed up.
Had a 1976 L-82, 4-sp
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From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
When was the last time you checked your timing? Too far advanced and it can back fire through the carb. Check your timing first before adjusting your carb.
Burning Brakes
Joined: Sep 2018
Posts: 1,002
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Rarely are the carbs set up correctly on a LT1.
Often the divorced choke is not correct - correct full choke has an idle of 2400 RPMs.
A long aluminum runner in the intake will cause fuel to fall out of solution and lean the mixture thus it needs more velocity until warm.
Often the divorced choke is not correct - correct full choke has an idle of 2400 RPMs.
A long aluminum runner in the intake will cause fuel to fall out of solution and lean the mixture thus it needs more velocity until warm.
Thread Starter
2nd Gear
Joined: Mar 2021
Posts: 2
Likes: 0
From: Sweden
Thank you all för good tips. I have done general adjustments on the carburator, and that works, no more misfire thru the carburator. It starts easy and idle quite high but as far I understand on all cylinders.But when I start to drive it starts weak and it obvisly don´t work on all cylinders. Next step for me is to use a vacuum meter och do some fintuning along with setting the timing. When the motor is warm it works fine except at low rpm. I hope i can fix it as sonn as possible, spring is comming!
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From: Im not allowed to tell you
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Lots of good info above. You could have a vacuum leak or your vacuum advance could be seized. During low RPM the carbs are operatig om the idle circuit until the transition over to the primary circuit. I would check your idle set screws and check the power valve and the accelerator pump. Your carb may need a general rebuild if its new to you, or just a good tuning. I would check your timing as was suggested.
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,050
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From: Marlton NJ
I always had an issue with the choke on my 70 LT-1 for 27 years. Depending on how I adjusted it it would:
1) start quickly, but then buck a little when the choke was still on, until warm, so it was difficult to drive until it completely warmed up, (or)
2) With a slightly different adjustment, it was guesswork to start ( two pumps or three?) and it usually quickly stalled requiring multiple starts. But then once started it ran terrific with a partial choke, for 2-3 minutes, and was actually driveable, until it warmed completely up.
I never found one adjustment that got it to do both issues well.
1) start quickly, but then buck a little when the choke was still on, until warm, so it was difficult to drive until it completely warmed up, (or)
2) With a slightly different adjustment, it was guesswork to start ( two pumps or three?) and it usually quickly stalled requiring multiple starts. But then once started it ran terrific with a partial choke, for 2-3 minutes, and was actually driveable, until it warmed completely up.
I never found one adjustment that got it to do both issues well.
Burning Brakes
Joined: Sep 2018
Posts: 1,002
Likes: 410
#1 is the way it should be set up, they were not designed to get in and go COLD, like you said, once it's at OPERATING temp it was fine.
I try to give mine 5 if not 10 minutes to warm up - at least down off the high idle to 1500 or so prior to taking off - it is much easier to drive -
* I have found if it is down right cold outside I almost have to warm it up before going anywhere or as soon as you give throttle it snorts and pops.
I try to give mine 5 if not 10 minutes to warm up - at least down off the high idle to 1500 or so prior to taking off - it is much easier to drive -
* I have found if it is down right cold outside I almost have to warm it up before going anywhere or as soon as you give throttle it snorts and pops.