holley 4175 setup
Thread Starter
Le Mans Master
Joined: Jun 2019
Posts: 5,361
Likes: 2,108
From: Loveland
holley 4175 setup
I have a 68 327/350. It has a 4175 holley carb. The car came from sea level with 57 jets. In looking up the carb, the stock jet is a 62. I live at 5000 FT. I installed 60 jets for 5000 FT. When I drive the car untill it's hot, let it set for a while, I have to do a flooded start. Hold the peddle to the floor and crank crank crank. Other than that, it starts right up. Is this normal? I adjusted the main float just a tiny bit low. Any other suggestions from the carb guys?
Melting Slicks
Joined: Mar 2006
Posts: 3,456
Likes: 102
From: Piedmont Va
St. Jude Donor '11-'12-'13,'19-'20
Check the lash on the accelerator pump. It's should have .010 at least. If it's too tight it will cause a fuel dump. Have you tried firing it off in this condition without touching the gas?
or maybe could be a vapor lock issue
I had a 4175 on my car for a few years before the rebuild. I thought it was a great carb.
Link to user guide
https://documents.holley.com/199r10012-1rev1.pdf
or maybe could be a vapor lock issue
I had a 4175 on my car for a few years before the rebuild. I thought it was a great carb.
Link to user guide
https://documents.holley.com/199r10012-1rev1.pdf
Le Mans Master
Joined: Oct 2007
Posts: 7,422
Likes: 955
From: Tennessee/Rhode Island
I have had a 4175 on my 78 L-82 4 speed since 1985 when I replaced the OEM Qjet carb which was not running correctly at the time. I specifically remembered buying the carb from Summitt racing back then and it was for an emissions 78 L-82. The carb came with idle jet limit screws and 592 (59 jet but emissions, number 2). I long ago switched out the main jets for 62's and tried 63's with the OEM L-82. in 2014, after the L-82 355 rebuilt I have 68 main jets with the 1 7/8 long tube headers and will go to a 70 main jet.
I too have an issue with hot starts after driving on warm days after the recent 2nd 4175 rebuild...I am going to try the adjustment on the accelerator pump rod.
The 4175 is a GREAT carb and perfect for stock engines, even a moderately built 355 I have now runs great with this carb with a minor jet adjustments.
I too have an issue with hot starts after driving on warm days after the recent 2nd 4175 rebuild...I am going to try the adjustment on the accelerator pump rod.
The 4175 is a GREAT carb and perfect for stock engines, even a moderately built 355 I have now runs great with this carb with a minor jet adjustments.
Dr. Detroit
Joined: Mar 2012
Posts: 10,091
Likes: 4,016
From: New Braunfels Texas
Double check the metering block gasket........is it sealing proper? This happened after you change the jets.....did you replace the metering block gasket? A leaky metering block gasket can cause bleed down through the booster when the ignition is shut off......
Jebby
Jebby
Dr. Detroit
Joined: Mar 2012
Posts: 10,091
Likes: 4,016
From: New Braunfels Texas
It is pretty simple to inspect....just look at the two holes at the main body directly back from the boosters......inspect the corresponding holes in the gasket for traces of bleed through......
Jebby
Jebby
Thread Starter
Le Mans Master
Joined: Jun 2019
Posts: 5,361
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From: Loveland
Metering block gasket is a new blue gasket. I did check the acc pump lever. It was preloaded a bit. I sucked up the adjustment to make it .015. In looking at the holley acc pump adjustment DIY, seemed that they were mostly concerned about not bottoming out the acc pump lever. Anyway,, it is adjusted correctly now. I have a red cam on the acc pump shaft. I also found one of the nuts that holds the carb down, just finger tight. Now I get to test drive it.
I thought stock sea level jets in a 4175 were 62. I have 60 in now for 5000 ft. jb78 is doing 70 jets... I only have a 327/350. ????
Edit: I did look it up. The .015 acc adjustment is at full throttle. There shouldn't be any slack in the acc cam arm at closed throttle.
I thought stock sea level jets in a 4175 were 62. I have 60 in now for 5000 ft. jb78 is doing 70 jets... I only have a 327/350. ????
Edit: I did look it up. The .015 acc adjustment is at full throttle. There shouldn't be any slack in the acc cam arm at closed throttle.
Last edited by kodpkd; Jul 29, 2019 at 08:01 PM.
Thread Starter
Le Mans Master
Joined: Jun 2019
Posts: 5,361
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From: Loveland
So I ran the car today,,, 90* out,,, got the engine nice and hot. After it sat for about 20 min, I took the air filter off and started it. It started kind of ok,,,, BUT fuel started shooting out of the top of the carb, just in front of the two forward barrels, inside the air filter. One of 3 things,,,, fuel is boiling in the forward bowl, my float is letting the fuel bowl get to full, or my needle and seat are leaking. Seems this would have something to do with flooding.
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Team Owner
Joined: Oct 2004
Posts: 81,241
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From: altered state
St. Jude Donor '05
Use a holley heat shield;they really do the most while its running/moving but every little bit....that seems to be the norm on carbed stuff with the ethanol gas. Even in the 70s that could happen on a hot day.
Runs ok other than that?
Tried getting it to 200, 205 checked timing then did the adjustment screws it did help quite a bit.
Runs ok other than that?
Tried getting it to 200, 205 checked timing then did the adjustment screws it did help quite a bit.
Last edited by cv67; Jul 29, 2019 at 09:23 PM.
Thread Starter
Le Mans Master
Joined: Jun 2019
Posts: 5,361
Likes: 2,108
From: Loveland
Use a holley heat shield;they really do the most while its running/moving but every little bit....that seems to be the norm on carbed stuff with the ethanol gas. Even in the 70s that could happen on a hot day.
Runs ok other than that?
Tried getting it to 200, 205 checked timing then did the adjustment screws it did help quite a bit.
Runs ok other than that?
Tried getting it to 200, 205 checked timing then did the adjustment screws it did help quite a bit.
Race Director
Joined: May 2006
Posts: 18,626
Likes: 2,553
Needle and Seat
The 4175 came in different versions which had different jets. What list# 4175 do you have? The list number is stamped on the forward side of the choke airhorn.
Thread Starter
Le Mans Master
Joined: Jun 2019
Posts: 5,361
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From: Loveland
It is a 80555-1 1806. I ordered a needle-seat, and float. Cheap to try and see if it helps. I did do a blow-suck test. It seemed to seal. Is the fuel shooting up 6 inches because it's boiling? Seems if it is really boiling, the float would sink because air and fuel is less dense, causing the overflow.
Melting Slicks
Joined: May 2002
Posts: 2,716
Likes: 121
From: Sulphur LA
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
Have you verified that the choke is open when hot and not closed, if the choke is not open all the way when hot it will cause flooding
Neal
Neal
Melting Slicks
Joined: May 2002
Posts: 2,716
Likes: 121
From: Sulphur LA
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
If the choke is working I would look at the fuel line and verify how close it is to the exhaust, if within a few inches I would try insulating the fuel line in those areas
Neal
Neal
Melting Slicks
Joined: May 2002
Posts: 2,716
Likes: 121
From: Sulphur LA
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
If there is a hot spot on the fuel line the hot fuel when it reaches the fuel bowl could cause fuel to flow of the bowl vents,
Neal
Neal
Le Mans Master
Joined: Aug 2017
Posts: 8,336
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From: Cool Northern Michigan
No one asked about the floats, so I will. Are they brass? Sometimes they get a tiny pin-hole in them causing them to sink. When they sink, they hold the needle-valve open too much. Fuel pressure forces gas up and out of the carb vents. Not pretty.
Also, on the accelerator pump gap: yes 0.015 on that, at full throttle. But a disagree with zero slack at closed throttle. Setting 0.010 > 0.012 will keep the pump from dribbling into the main stream every time you go over a bump or accidently bumping the gas pedal.
Also, on the accelerator pump gap: yes 0.015 on that, at full throttle. But a disagree with zero slack at closed throttle. Setting 0.010 > 0.012 will keep the pump from dribbling into the main stream every time you go over a bump or accidently bumping the gas pedal.