i want to find out how to jet this carb. I have searched almost everywhere and i still cannot find anything that tells me what jet, what bleed does what at what rpm.Can anyone point me in the right direction?
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
Holley/Weber carb jetting...
- Thread starter daves66nova
- Start date
- Status
- Not open for further replies.
Dunno what model you have, & I didn't realize that Holley & Weber had any joint efforts- but here's a start from HP books. Also scroll down the page & see if anything in the cusomers also bought" listings looks useful. One of the reviews mentions another book that may also be useful. good luck.
Link: http://www.amazon.com/Weber-Carburetors-HP-Books-774/dp/0895863774
Link: http://www.amazon.com/Weber-Carburetors-HP-Books-774/dp/0895863774
the first rule to fallow is ONLY change a jet OR a mettering rod. DO NOT change both at the same. also a little is a lot. i have tuned this carb for street and racing a LOT. i dont have space or time to say how to tune them. not that the ideas for tuning are hard to understand. i have a hard time typing a lot. [email protected] may be we could talk on the phone sometime
Kestas
Staff member
During idle, the mixture is controlled by the idle bleed screws. Off idle, the mixture is controlled by the main jets. Like morris suggested, jetting is a bit of an art.
It would help if you specified what make & model carburetor you're trying to jet. If you're not sure what you have, just copy the information stamped on the choke housing starting with the "LIST" number. (The other information is the build date and the OEM part number.)
Holley has all types of specific information for their carburetors in their technical section, but you must know which model you have.
Check out this link on Holley carburetor books. (I recommend the Mike Urich book for understanding how Holley carburetors work.)
Hope this helps!
Holley has all types of specific information for their carburetors in their technical section, but you must know which model you have.
Check out this link on Holley carburetor books. (I recommend the Mike Urich book for understanding how Holley carburetors work.)
Hope this helps!
daves66nova
Thread starter
Originally Posted By: Kestas
During idle, the mixture is controlled by the idle bleed screws. Off idle, the mixture is controlled by the main jets. Like morris suggested, jetting is a bit of an art.
Yes, i know How to jet ,but what i need to know is which is which.There are about 6 to 8 adjustable "jets" on this carb.
During idle, the mixture is controlled by the idle bleed screws. Off idle, the mixture is controlled by the main jets. Like morris suggested, jetting is a bit of an art.
Yes, i know How to jet ,but what i need to know is which is which.There are about 6 to 8 adjustable "jets" on this carb.
Also consider float level, air bleeds, and power valves.
But most old carbs were designed for GASOLINE, not gas and alcohol.
They require a 5% jet increase right off the bat.
But most old carbs were designed for GASOLINE, not gas and alcohol.
They require a 5% jet increase right off the bat.
daves66nova
Thread starter
yes, this is for a gasoline engine,I only need to know about gasoline,not alcohol.This carb came off a 70's Chevy or ford 4-cyl.
Last edited:
I think most people can only give you general info of limited use without knowing the exact model of carb and where in the driving range you need adjusted or problem you have.
Generally the idle circuit-idle screw, idle air bleed, and idle jet and transition circuit are active at quite high speed. The metering rods are for high speed cruise, and the main jet is for near full throttle power enrichment. But they all work hand in hand and it helps if the metering rod and main jet are in the ballpark for idle and transition circuit adjustments.
Generally the idle circuit-idle screw, idle air bleed, and idle jet and transition circuit are active at quite high speed. The metering rods are for high speed cruise, and the main jet is for near full throttle power enrichment. But they all work hand in hand and it helps if the metering rod and main jet are in the ballpark for idle and transition circuit adjustments.
I'll take a guess from your last post that you have a Holley 5200 (Weber DGV 2 bbl. carb) that was popular in the 70's with Pintos, Cortinas, Capris, Vegas, and Monzas.
Each side (Primary & secondary) has a idle jet; however, only the primary side has a curb idle mixture screw. The secondary side has a fixed idle system to help start enrich the air-fuel mixture as the secondary opens. The main jets are in the fuel bowl while the high speed air bleeds (which look like jets and cover the emulsion tubes) are outside the fuel bowl. Both the main jets and high speed air bleeds control the amount of fuel fed into the main and secondary venturis. Holley lists about nine different main jet sizes, four different high speed air bleed sizes, and three different idle jet sizes.
Unfortunately, the Holley 5200 series book by Mike Ulrich is out of print as it is the bible on the subject. You may find one on eBay or Craig's List.
The old Holley Carburetors book by Ulrich from 1972 has a several pages of information that I could scan for you if you send me a PM with an e-mail address to send the files to as PDFs.
Each side (Primary & secondary) has a idle jet; however, only the primary side has a curb idle mixture screw. The secondary side has a fixed idle system to help start enrich the air-fuel mixture as the secondary opens. The main jets are in the fuel bowl while the high speed air bleeds (which look like jets and cover the emulsion tubes) are outside the fuel bowl. Both the main jets and high speed air bleeds control the amount of fuel fed into the main and secondary venturis. Holley lists about nine different main jet sizes, four different high speed air bleed sizes, and three different idle jet sizes.
Unfortunately, the Holley 5200 series book by Mike Ulrich is out of print as it is the bible on the subject. You may find one on eBay or Craig's List.
The old Holley Carburetors book by Ulrich from 1972 has a several pages of information that I could scan for you if you send me a PM with an e-mail address to send the files to as PDFs.
To clarify:
What I was saying was that that carb was made for pure gasoline. We can't get pure gas anymore, as it has alcohol in it.
More volume is needed.
The jetting should be increased by somewhere around 5% to start with.
What I was saying was that that carb was made for pure gasoline. We can't get pure gas anymore, as it has alcohol in it.
More volume is needed.
The jetting should be increased by somewhere around 5% to start with.
Is everything clean? The base settings should be pretty close if it is in its original application and float level is correct and things are not sloppy and seals are good ( I have seen bad effects from loose butterfly shafts (vacuum leak). I would make sure every passage is clean and any jets/passages do not have any buildup in them (do you have new replacements?). I would also tend to increase fuel a small bit due to the ethanol situation, but it should still run pretty well before this.
I have a habit of running metal picks or even properly sized drill bits (with my fingers) through jets, but I know this is frowned upon and could easily make a bad situation worse.
Are you trying to tune it to get more power or tune it to make it run? There is usually a specific order to tuning as each circuit affects every other circuit to a degree. My experience has been to start with the main jet and work my way down to to the idle circuitry - most of my experience has been with japanese Keihin and Mikuni carbs though with a few holleys thrown in for good measure. And the dual webers on my sand rail.
BTW I know nothing about your specific carb, just general stuff. You can ignore it if it doesn't apply.
I have a habit of running metal picks or even properly sized drill bits (with my fingers) through jets, but I know this is frowned upon and could easily make a bad situation worse.
Are you trying to tune it to get more power or tune it to make it run? There is usually a specific order to tuning as each circuit affects every other circuit to a degree. My experience has been to start with the main jet and work my way down to to the idle circuitry - most of my experience has been with japanese Keihin and Mikuni carbs though with a few holleys thrown in for good measure. And the dual webers on my sand rail.
BTW I know nothing about your specific carb, just general stuff. You can ignore it if it doesn't apply.
Last edited:
on a smaller engine the TINIEST vacuum leak will really confound you trying to set the carb.
And as Mechtec keeps saying you are going to be lean as heck already.
And as Mechtec keeps saying you are going to be lean as heck already.
SteveSRT8 realy hit the nail on the head.
One more thing, improper air filters will confound you.
People put tiny air filters on with no headroom. Reversion, pressure disparities for air bleeds, lack of flow at WOT, etc. are problems.
Carburetors like as high as you can get above it, and with as large an air cleaner as you can fit.
People put tiny air filters on with no headroom. Reversion, pressure disparities for air bleeds, lack of flow at WOT, etc. are problems.
Carburetors like as high as you can get above it, and with as large an air cleaner as you can fit.
Another great point.
I guess since very few of us still have anything with a carb on it we are losing our edge!
The air cleaner paradox was well demonstrated on my 1970 240z with a triple Weber conversion. It came with stupid little itty bitty air cleaners for each carb.
The day I put plain velocity stacks on it I could not believe the difference!
I guess since very few of us still have anything with a carb on it we are losing our edge!
The air cleaner paradox was well demonstrated on my 1970 240z with a triple Weber conversion. It came with stupid little itty bitty air cleaners for each carb.
The day I put plain velocity stacks on it I could not believe the difference!
At car shows, I can't believe how many ridiculously wrong air filters are on expensive modified engines.
You can look and KNOW they are not going to work right.
You can look and KNOW they are not going to work right.
- Status
- Not open for further replies.
Similar threads
- Replies
- 14
- Views
- 867
- Replies
- 11
- Views
- 1K