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#1
10-22-2021, 01:33 PM
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Carb Recommendation?
So it turn out that my Holley 650cfm is in need of attention and/or replacement. I have a 4175 model (P/N 80555-1) which has its limitations and - so I'm told - a legion of less than satisfied users. Needs a new power valve and one of the idle mixture screws is not working / has no effect.
Not sure if it's worth a rebuild or just a swap to a different carb? Someone recommended an Edelbrock unit. Engine is your basic early 70's 400 - nothing special. Stock internals as far as I know. This engine is not in my long-term plans as I have found a date-correct 428 that I will soon start working on. So what do y'all recommend?
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Mark Las Cruces NM ___________________________ Current Project: '67 Catalina Convertible 400 4-spd Last edited by markpj23; 10-22-2021 at 01:53 PM. |
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#2
10-22-2021, 02:05 PM
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After thinking this through a bit more....
The idle mixture screw has no effect so likely a bad power valve. Maybe just a cheap rebuild kit and new power valve is the easiest / cheapest solution...
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Mark Las Cruces NM ___________________________ Current Project: '67 Catalina Convertible 400 4-spd |
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#3
10-22-2021, 02:09 PM
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Quadrajet.
Glad you figured out that the carb is junk. Now source a good known vintage quadrajet.
Even if your carb were NOT screwed up, it would be a night-and-day difference. With the bad carb, the difference will be 'award-winning'. I'd check with Cliff R or shaker455 and see what they have for sale currently in a ready-to-go configuration. Just saw your 2nd post - you could try a rebuild kit and see what happens. Or just plan on swapping the carb and get on with driving your Pontiac. My choice would be to get rid of THAT Holley and let someone else mess with it (the Holley). Good luck! |
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#4
10-22-2021, 02:24 PM
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Quote:
Please explain your analysis process for the mixture screw having no effect vs the bad power valve. The power valve is not on at idle. The later carbs all had a Power Valve Blow-out Protection check ball and spring installed in them. So if the PVBP was properly installed and working it would be next to impossible for the Power Valve to fail and have any effect at idle. Now if the power valve diaphragm was destroyed by bad gas or "additives" to the gas then that is another story. All that said, get rid of the POS and install something else. A decent running Q-Jet would be a great starting point. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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#5
10-22-2021, 02:49 PM
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Here you go... might be a little rich for your current needs, but maybe the seller can install smaller rods and jets?
https://r.tapatalk.com/shareLink/top...ink_source=app Sent from my SM-G965U using Tapatalk
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68 Firebird-- Street/Strip - 400/461 Eagle Forged Bottom End & Ross Flat top pistons. KRE 325 CFM D port, Ultradyne 263/271 @.050, .4267 lift. Crower Solid roller lifters and 1.65 stainless rockers. Quickfuel 1000 on Torker2 intake and 2" open spacer. Hedman 1.75" headers. TH400 w/brake. Ford 9" w/3.80 gears & 28x9 Hoosier pro bracket drag radial. Best ET: 1.35 60ft, 6.29 @ 107.20 mph, 9.99 @132.33 mph. 3,300 race weight |
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#6
10-22-2021, 03:02 PM
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Quote:
__________________
Mark Las Cruces NM ___________________________ Current Project: '67 Catalina Convertible 400 4-spd |
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#7
10-22-2021, 03:05 PM
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Quote:
__________________
Mark Las Cruces NM ___________________________ Current Project: '67 Catalina Convertible 400 4-spd |
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#8
10-22-2021, 03:49 PM
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I would definitely try to rebuild it, cheapest option if it works out. AED makes a GREAT Holley and Quick Fuel is good , too. I personally like the double pumpers but lots of people prefer vacuum secondaries. No offense to the Qjet faithful.
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Chris D 69 GTO Liberty Blue/dark blue 467, 850 Holley, T2, Edelbrock Dport 310cfm w Ram Air manifolds, HFT 245/251D .561/.594L, T400, 9" w 3.50s 3905lbs 11.59@ 114, 1.57/ 60' |
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#9
10-22-2021, 03:59 PM
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Quote:
You could spent several hundred to over a thousand getting anew carb built, or you could do it yourself and learn a lot about your carb in the process.
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 1965 Pontiac LeMans. M21, 3.73 in a 12 bolt, Kauffman 461.
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#10
10-22-2021, 04:05 PM
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Pull both idle screws out, and flood the holes with spray carb cleaner, using the straw, go drive it, see what happens...............
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1977 Black Trans Am 180 HP Auto, essentially base model T/A. I'm the original owner, purchased May 7, 1977. Shut it off Shut it off Buddy, I just shut your Prius down... 
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#11
10-22-2021, 04:09 PM
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If your next carb will also be run on the 428 then it’s also time to think about what intake manifold might be run on it in terms of duel or single plane.
A duel plane intake especially once you get up to 428 cid could make good use of a 800 to 850 cfm carb depending also on your rear gears,
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#12
10-22-2021, 04:18 PM
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Quote:
__________________
Mark Las Cruces NM ___________________________ Current Project: '67 Catalina Convertible 400 4-spd |
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#13
10-22-2021, 04:19 PM
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Quote:
__________________
Mark Las Cruces NM ___________________________ Current Project: '67 Catalina Convertible 400 4-spd |
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#14
10-22-2021, 04:21 PM
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Quote:
__________________
Mark Las Cruces NM ___________________________ Current Project: '67 Catalina Convertible 400 4-spd |
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#15
10-22-2021, 09:42 PM
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Keep in mind the 4165-4175 series carbs have reverse idle screws. Turning them in makes it richer, out is leaner.
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#16
10-22-2021, 10:31 PM
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You’ll be fine with a rebuild and it may need nothing at all other than squaring up the throttle blades with the transfer slots and adding idle air via the secondary idle speed screw under the carb.
Every non-emissions Performance engine from Chevy and Ford ran Holley carbs. The majority of issues are the result of using a universal calibrated carb without tuning it. 9 times out of 10, they will bolt on and run fine and the 1 problem out of 10 will be a misapplication or user’s lack of tuning experience. Of course a rebuilt and correctly calibrated $750 Qjet is going to work well compared to a used, Holley of unknown calibration … it had better or you wasted your money. Pay that same attention to a Holley and you have a beast of a carburetor. Concentrate on the position of your throttle blades compared to transfer slots. Too much transfer slot exposure makes for over-rich low speed operation and idle mixture screw that do not respond to input changes.
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Triple Black 1971 GTO |
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#17
10-23-2021, 07:51 AM
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If that 428 was not a 67 model and has the correct Q-jet on it then your all set carb wise as long as it can be rebuilt.
It will likely need throttle shaft bushings , or be right on the edge of needing such, so just do it!
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#18
10-23-2021, 08:22 AM
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Quote:
__________________
Mark Las Cruces NM ___________________________ Current Project: '67 Catalina Convertible 400 4-spd |
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#19
10-23-2021, 08:27 AM
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Quote:
__________________
Mark Las Cruces NM ___________________________ Current Project: '67 Catalina Convertible 400 4-spd |
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#20
10-23-2021, 09:48 AM
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Quote:
Turning the screw in removes AIR from the air flue mixture on spreadbore carbs. Turning the screw removes Fuel and Air on square bore carbs and most other carbs. Well worth the price of one of Mike Urich Holley Books to know this as it has been in print since the first Holley Spread Bore carbs were sold and written about. There are even little special tags on the metering blocks that help you know this. Tom V.
__________________
"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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