Carbs: Edelbrock vs. Holley
12-09-2019, 08:36 PM
#21
Platinum Member
Platinum Member
Okay, it's a lot easier to "learn" jetting with an Edelbrock than it is with a Holley. The Edelbrock fueling charts are easy-peasy. Fine tuning a street Edelbrock can involve peening and redrilling the air bleeds, but for most stuff with wide lobe separation cams and decent idle vacuum an Edelbrock usually doesn't need much other than jets, springs, and needles.
I like Holleys, too. But they are a lot harder to "learn" than an Edelbrock. The biggest issue is that a lot of guys have "some" experience jetting Holleys since they have been exposed to them for years, and what they know about Holleys doesn't transfer over to Edelbrocks.
For Fine Tuning, Holley offers carbs with replaceable air bleeds, different booster styles, different squirters, squirter cams, and different pump sizes. But to get ALL of the adjustability you have to get the HP carbs and plan on mixing and matching parts across series numbers.
The Edelbrock is pretty darn simple when you get down to it.
Idle should allow throttle plates to close almost all the way. Idle mix screws handle most of the idling chores, but the low speed air bleeds ALSO affect idle some. The idle feed ports are fine for motors with good vacuum, but a big cam will require you to drill the idle circuit feed ports and maybe peen/drill the low speed bleeds a touch smaller, but then you have to reset the idle mix screws. Off-idle with low vacuum is the toughest place on an Edelbrock, and some people elongate the slots above the throttle plate, but you can usually get all of the off-idle problems fixed with the low speed bleeds without having to file the slots. Good vacuum, and you won't even notice the off-idle problems. Upper end of primaries, you will have to play with the high speed bleeds to smooth the transition into the secondaries (on a car). You don't generally have to do this on a boat, due to the load curve the motor sees at the transition point. Secondary springs are usually all you have to mess with on a boat to get the transition to behave.
Most weirdest problem on an Edelbrock is using an air filter with a lid that is too close to the bowl vents. Screws up all sorts of midrange stuff. Marine flame arrestors are USUALLY open enough, but you still have to keep it in mind.
They make Stub-Stacks for Edelbrocks, but they amplify the bowl vent problem even worse. Stub Stacks require even more clearance around the bowl vents, or else they hurt more than they help.
Edelbrock doesn't offer a large pump capacity. It's generally enough, but your only tuning aid is linkage and squirter jet size. Boats don't suffer on this front as much as a 4-speed hotrod does. As long as your pump feeds enough for you to hammer at 2500 rpm without bog, then you're gold with a boat. Know also that secondary springs are a balancing act with the accel pump. Best to disconnect the secondaries completely when setting up your accel pump, to get the squirt volume/duration worked out for the primary bores, and then juggle secondary springs to make sure you don't bog going into the secondaries.
Holleys THESE DAYS come with Chinese metering blocks. I've seen more than one with casting flash and junk in the secondary side (the primary side is usually checked out better I guess).
So, if you have a carb issue that is only on ONE engine (the beauty of twins), then once you determine that both carbs are setup the same, you now can start disassembling and looking for crap that made it past the sleeping QC guy. It can often be "tuned around" but any time you have to set up the carbs differently on twins, you have a problem in the carb circuits, vacuum leaks somewhere, or something is up in one of the motors. If one motor is giving you fits, just swap carbs. If the problem follows the carb, it's in the carb. If the problem stays with the motor, it's not the carb.
M
I like Holleys, too. But they are a lot harder to "learn" than an Edelbrock. The biggest issue is that a lot of guys have "some" experience jetting Holleys since they have been exposed to them for years, and what they know about Holleys doesn't transfer over to Edelbrocks.
For Fine Tuning, Holley offers carbs with replaceable air bleeds, different booster styles, different squirters, squirter cams, and different pump sizes. But to get ALL of the adjustability you have to get the HP carbs and plan on mixing and matching parts across series numbers.
The Edelbrock is pretty darn simple when you get down to it.
Idle should allow throttle plates to close almost all the way. Idle mix screws handle most of the idling chores, but the low speed air bleeds ALSO affect idle some. The idle feed ports are fine for motors with good vacuum, but a big cam will require you to drill the idle circuit feed ports and maybe peen/drill the low speed bleeds a touch smaller, but then you have to reset the idle mix screws. Off-idle with low vacuum is the toughest place on an Edelbrock, and some people elongate the slots above the throttle plate, but you can usually get all of the off-idle problems fixed with the low speed bleeds without having to file the slots. Good vacuum, and you won't even notice the off-idle problems. Upper end of primaries, you will have to play with the high speed bleeds to smooth the transition into the secondaries (on a car). You don't generally have to do this on a boat, due to the load curve the motor sees at the transition point. Secondary springs are usually all you have to mess with on a boat to get the transition to behave.
Most weirdest problem on an Edelbrock is using an air filter with a lid that is too close to the bowl vents. Screws up all sorts of midrange stuff. Marine flame arrestors are USUALLY open enough, but you still have to keep it in mind.
They make Stub-Stacks for Edelbrocks, but they amplify the bowl vent problem even worse. Stub Stacks require even more clearance around the bowl vents, or else they hurt more than they help.
Edelbrock doesn't offer a large pump capacity. It's generally enough, but your only tuning aid is linkage and squirter jet size. Boats don't suffer on this front as much as a 4-speed hotrod does. As long as your pump feeds enough for you to hammer at 2500 rpm without bog, then you're gold with a boat. Know also that secondary springs are a balancing act with the accel pump. Best to disconnect the secondaries completely when setting up your accel pump, to get the squirt volume/duration worked out for the primary bores, and then juggle secondary springs to make sure you don't bog going into the secondaries.
Holleys THESE DAYS come with Chinese metering blocks. I've seen more than one with casting flash and junk in the secondary side (the primary side is usually checked out better I guess).
So, if you have a carb issue that is only on ONE engine (the beauty of twins), then once you determine that both carbs are setup the same, you now can start disassembling and looking for crap that made it past the sleeping QC guy. It can often be "tuned around" but any time you have to set up the carbs differently on twins, you have a problem in the carb circuits, vacuum leaks somewhere, or something is up in one of the motors. If one motor is giving you fits, just swap carbs. If the problem follows the carb, it's in the carb. If the problem stays with the motor, it's not the carb.
M
12-11-2019, 06:33 PM
#22
Chevy-Harley fan
Charter Member
Okay, it's a lot easier to "learn" jetting with an Edelbrock than it is with a Holley. The Edelbrock fueling charts are easy-peasy. Fine tuning a street Edelbrock can involve peening and redrilling the air bleeds, but for most stuff with wide lobe separation cams and decent idle vacuum an Edelbrock usually doesn't need much other than jets, springs, and needles.
I like Holleys, too. But they are a lot harder to "learn" than an Edelbrock. The biggest issue is that a lot of guys have "some" experience jetting Holleys since they have been exposed to them for years, and what they know about Holleys doesn't transfer over to Edelbrocks.
For Fine Tuning, Holley offers carbs with replaceable air bleeds, different booster styles, different squirters, squirter cams, and different pump sizes. But to get ALL of the adjustability you have to get the HP carbs and plan on mixing and matching parts across series numbers.
The Edelbrock is pretty darn simple when you get down to it.
Idle should allow throttle plates to close almost all the way. Idle mix screws handle most of the idling chores, but the low speed air bleeds ALSO affect idle some. The idle feed ports are fine for motors with good vacuum, but a big cam will require you to drill the idle circuit feed ports and maybe peen/drill the low speed bleeds a touch smaller, but then you have to reset the idle mix screws. Off-idle with low vacuum is the toughest place on an Edelbrock, and some people elongate the slots above the throttle plate, but you can usually get all of the off-idle problems fixed with the low speed bleeds without having to file the slots. Good vacuum, and you won't even notice the off-idle problems. Upper end of primaries, you will have to play with the high speed bleeds to smooth the transition into the secondaries (on a car). You don't generally have to do this on a boat, due to the load curve the motor sees at the transition point. Secondary springs are usually all you have to mess with on a boat to get the transition to behave.
Most weirdest problem on an Edelbrock is using an air filter with a lid that is too close to the bowl vents. Screws up all sorts of midrange stuff. Marine flame arrestors are USUALLY open enough, but you still have to keep it in mind.
They make Stub-Stacks for Edelbrocks, but they amplify the bowl vent problem even worse. Stub Stacks require even more clearance around the bowl vents, or else they hurt more than they help.
Edelbrock doesn't offer a large pump capacity. It's generally enough, but your only tuning aid is linkage and squirter jet size. Boats don't suffer on this front as much as a 4-speed hotrod does. As long as your pump feeds enough for you to hammer at 2500 rpm without bog, then you're gold with a boat. Know also that secondary springs are a balancing act with the accel pump. Best to disconnect the secondaries completely when setting up your accel pump, to get the squirt volume/duration worked out for the primary bores, and then juggle secondary springs to make sure you don't bog going into the secondaries.
Holleys THESE DAYS come with Chinese metering blocks. I've seen more than one with casting flash and junk in the secondary side (the primary side is usually checked out better I guess).
So, if you have a carb issue that is only on ONE engine (the beauty of twins), then once you determine that both carbs are setup the same, you now can start disassembling and looking for crap that made it past the sleeping QC guy. It can often be "tuned around" but any time you have to set up the carbs differently on twins, you have a problem in the carb circuits, vacuum leaks somewhere, or something is up in one of the motors. If one motor is giving you fits, just swap carbs. If the problem follows the carb, it's in the carb. If the problem stays with the motor, it's not the carb.
M
I like Holleys, too. But they are a lot harder to "learn" than an Edelbrock. The biggest issue is that a lot of guys have "some" experience jetting Holleys since they have been exposed to them for years, and what they know about Holleys doesn't transfer over to Edelbrocks.
For Fine Tuning, Holley offers carbs with replaceable air bleeds, different booster styles, different squirters, squirter cams, and different pump sizes. But to get ALL of the adjustability you have to get the HP carbs and plan on mixing and matching parts across series numbers.
The Edelbrock is pretty darn simple when you get down to it.
Idle should allow throttle plates to close almost all the way. Idle mix screws handle most of the idling chores, but the low speed air bleeds ALSO affect idle some. The idle feed ports are fine for motors with good vacuum, but a big cam will require you to drill the idle circuit feed ports and maybe peen/drill the low speed bleeds a touch smaller, but then you have to reset the idle mix screws. Off-idle with low vacuum is the toughest place on an Edelbrock, and some people elongate the slots above the throttle plate, but you can usually get all of the off-idle problems fixed with the low speed bleeds without having to file the slots. Good vacuum, and you won't even notice the off-idle problems. Upper end of primaries, you will have to play with the high speed bleeds to smooth the transition into the secondaries (on a car). You don't generally have to do this on a boat, due to the load curve the motor sees at the transition point. Secondary springs are usually all you have to mess with on a boat to get the transition to behave.
Most weirdest problem on an Edelbrock is using an air filter with a lid that is too close to the bowl vents. Screws up all sorts of midrange stuff. Marine flame arrestors are USUALLY open enough, but you still have to keep it in mind.
They make Stub-Stacks for Edelbrocks, but they amplify the bowl vent problem even worse. Stub Stacks require even more clearance around the bowl vents, or else they hurt more than they help.
Edelbrock doesn't offer a large pump capacity. It's generally enough, but your only tuning aid is linkage and squirter jet size. Boats don't suffer on this front as much as a 4-speed hotrod does. As long as your pump feeds enough for you to hammer at 2500 rpm without bog, then you're gold with a boat. Know also that secondary springs are a balancing act with the accel pump. Best to disconnect the secondaries completely when setting up your accel pump, to get the squirt volume/duration worked out for the primary bores, and then juggle secondary springs to make sure you don't bog going into the secondaries.
Holleys THESE DAYS come with Chinese metering blocks. I've seen more than one with casting flash and junk in the secondary side (the primary side is usually checked out better I guess).
So, if you have a carb issue that is only on ONE engine (the beauty of twins), then once you determine that both carbs are setup the same, you now can start disassembling and looking for crap that made it past the sleeping QC guy. It can often be "tuned around" but any time you have to set up the carbs differently on twins, you have a problem in the carb circuits, vacuum leaks somewhere, or something is up in one of the motors. If one motor is giving you fits, just swap carbs. If the problem follows the carb, it's in the carb. If the problem stays with the motor, it's not the carb.
M
__________________
Pete
Pete
12-11-2019, 10:39 PM
#23
Platinum Member
Platinum Member
Did you ever find that Pontiac HO intake? Really don't know anyone not running billet metering blocks anymore. Not that I would touch a good running Holley if it's already been setup for your engine. Was never impressed with a Edelbrock carb other than the one piece carburetor body, but would rather use a Quadrajet if I wasn't going to run a Holley.
And I cut my teenaged teeth drilling jets and bending needle hangers on Qjets for all my buddies' rides after they installed headers and duals on their pontiacs and chevys. I like Qjets.
MC
12-13-2019, 10:16 AM
#26
Registered
iTrader: (1)
Best carb or EFI is the one the owner or mechanic is most comfortable with.
That said, love Holley based carbs when engines are modded from mild or bigger.
That said, love Holley based carbs when engines are modded from mild or bigger.
