Holley Carb Install Help
Thread Starter
Instructor
Joined: Dec 2005
Posts: 196
Likes: 0
From: Burlington WI
Holley Carb Install Help
OK, I know the Qjet is the way to go on 81 computor Vette. I tried 2 all ready and runs great in all ranges except loadup on long hot idle. Both have been rebuild my me and dwell setting and Idle Position right
on and still rich idle. Pull vac plug that could run the dist. vac advance
it speeds up 150 rpm but dwell goes to hell. Anyway, I bought a Holley 4175 , list 9895. After looking at it I see all sorts of problems that is not a direct fit as advertized. First very little room for studs under the float bowls. Is the stock 81 carb metric threads or american as I used a metric wrench to remove stock bolts. Also no
throttle studs . Gas pedal no problem but I have automatic 350. I know the clutch won't work when I replace the dist and disconnect the
computor. So what to do with kickdown. How about the cruise cable.
Power brake port is a little small but can rig up to stock vac line. Already bought the carb and MSD Dist. so this change is going to happen. Anyone that has done this conversion please help. Also , do I used the stock thick base gasket or a thinner runing with the Alum plate
inbetween. Like I said , all computor readings were right on and still got
a rich loping smelly idle when the computor starts to adjust the M. solnoid when hot. So the Holley & dist is going to be installed. Not stock engine but bought car with new goodwrench 350 ?? Jay
on and still rich idle. Pull vac plug that could run the dist. vac advance
it speeds up 150 rpm but dwell goes to hell. Anyway, I bought a Holley 4175 , list 9895. After looking at it I see all sorts of problems that is not a direct fit as advertized. First very little room for studs under the float bowls. Is the stock 81 carb metric threads or american as I used a metric wrench to remove stock bolts. Also no
throttle studs . Gas pedal no problem but I have automatic 350. I know the clutch won't work when I replace the dist and disconnect the
computor. So what to do with kickdown. How about the cruise cable.
Power brake port is a little small but can rig up to stock vac line. Already bought the carb and MSD Dist. so this change is going to happen. Anyone that has done this conversion please help. Also , do I used the stock thick base gasket or a thinner runing with the Alum plate
inbetween. Like I said , all computor readings were right on and still got
a rich loping smelly idle when the computor starts to adjust the M. solnoid when hot. So the Holley & dist is going to be installed. Not stock engine but bought car with new goodwrench 350 ?? Jay
Intermediate
Joined: Feb 2005
Posts: 35
Likes: 0
I can help only a little. I have an 1980 without a computer. My 4175 runs much better than my qjet ever did. Even after rebuild by Lars. He is legendary but my qjet has demons
Anyway. I used the thin spacer. My throttle bolted right up. I didn't put cruise linkage on because I have not toyed with it enough to figure out how...very different than my qjet. My gas line hooked right up. My nuts were half inch so not metric. It is tight. I had to grind down the sides of a 1/2 inch open end wrench to get them all tight. I keep this wrench in my drawer for when I need to remove the carb...so far I have not. Also, my bracket on the rear that holds the throttle cable...you know, the one that the carb studs actually go through before you put the nut on them...I had to grind that bracket down a little bit...not much but it would not fit without a little metal removal. It interfered. It has been 2 years since I did this swap. I will go now and take a couple pics for you so you know what I mean. I will pm them to you.
Anyway. I used the thin spacer. My throttle bolted right up. I didn't put cruise linkage on because I have not toyed with it enough to figure out how...very different than my qjet. My gas line hooked right up. My nuts were half inch so not metric. It is tight. I had to grind down the sides of a 1/2 inch open end wrench to get them all tight. I keep this wrench in my drawer for when I need to remove the carb...so far I have not. Also, my bracket on the rear that holds the throttle cable...you know, the one that the carb studs actually go through before you put the nut on them...I had to grind that bracket down a little bit...not much but it would not fit without a little metal removal. It interfered. It has been 2 years since I did this swap. I will go now and take a couple pics for you so you know what I mean. I will pm them to you.
Melting Slicks
Joined: Mar 2006
Posts: 3,456
Likes: 102
From: Piedmont Va
St. Jude Donor '11-'12-'13,'19-'20
I just installed a 4175 on my 73 but other than the stud/bowl issue and having to make a new fuel line I didn't have many problems.
Holley has some adapters and brackets their web site which may help with the trans cable at least...sometimes you can "alter" your Qjet brackets and make them work as well.
I think Holley will tell you the 4175 was not intended to go on a computer controlled vehicle...in fact they specifically advertise it for "non-emissions applications"...
You should have received new studs and nuts with the carb if you bought it new....and yes the nuts are tight under the bowls, I had to lift the carb up slightly to get the right rear nut in and started......you must use the Holley length studs tho...if the stock studs are too long you will have an issue. The other thing is they say torque them .060in/lbs?
Good luck getting a torque wrench on them. I just snugged them up to a reasonable but not overtight guestimate and check them again after a few miles. No problems so far.
Hope this helps a little.
Holley has some adapters and brackets their web site which may help with the trans cable at least...sometimes you can "alter" your Qjet brackets and make them work as well.
I think Holley will tell you the 4175 was not intended to go on a computer controlled vehicle...in fact they specifically advertise it for "non-emissions applications"...
You should have received new studs and nuts with the carb if you bought it new....and yes the nuts are tight under the bowls, I had to lift the carb up slightly to get the right rear nut in and started......you must use the Holley length studs tho...if the stock studs are too long you will have an issue. The other thing is they say torque them .060in/lbs?
Good luck getting a torque wrench on them. I just snugged them up to a reasonable but not overtight guestimate and check them again after a few miles. No problems so far. Hope this helps a little.
