Carburetors - Gary's Musings

[fljab]

In Bill's case his background means he's the most qualified person around on carbs. But I'll still argue with him about Holleys and Carterbrocks.

I've always messed with Holleys, but am interested in going Carter or Edelbrock on Big Whitey eventually, so Bill's advice there would be great. I am no expert at all on carbs, but like many of us, have some shade tree messing around back in the day. Other than rebuilding the Carter 1 bbl on the '81, I really haven't done that much with them for some time now as anything made in the last 30 yrs is pretty much all EFI, including my motorcycles.

 

[Gary Lewis]

In Bill's case his background means he's the most qualified person around on carbs. But I'll still argue with him about Holleys and Carterbrocks.

I've always messed with Holleys, but am interested in going Carter or Edelbrock on Big Whitey eventually, so Bill's advice there would be great. I am no expert at all on carbs, but like many of us, have some shade tree messing around back in the day. Other than rebuilding the Carter 1 bbl on the '81, I really haven't done that much with them for some time now as anything made in the last 30 yrs is pretty much all EFI, including my motorcycles.

I think the Holley's are best for max power, and Carters/Edelbrocks for daily driving - for two reasons. First, in my experience the Edelbrocks come out of the box jetted closer to how I want one. Rusty had a stock Holley 1460 on him when I got him, and the MPG was poor. So I installed an Edelbrock 1406 and not only got better MPG but better part-throttle acceleration. Later I installed an air/fuel ratio meter and found that the Holley was very rich, even though that it had stock jetting. But the Edelbrock's air/fuel ratio was very close to what the engine wanted and provided a much more "crisp" feeling. However, it gave away some power at WOT. Yes, I could probably have tuned the Holley's AFR to get it closer to what the engine needed, especially since Holley's have more things to tune, but why when the Eddy was essentially there out of the box?

The other reason is reliability. In my experience Holleys are prone to problems because they hold gas in with gaskets or fabric. In my youth the bowl gaskets were made of cork, and when the carbs ran dry the cork shrank and you had a leak. Today the better kits have gaskets that don't shrink, but you can still have problems if a ham-handed "mechanic" has over-tightened the bowl screws and warped the bowl or main body. In addition, there's the design flaw of no check valve in the vacuum passage to the power valve. Holley admitted it was a flaw by installing a check valve on newer carbs, and kits are available to fix it on older ones. But forums all over the place have people writing in who have blown power valves due to one backfire because many of the carbs out there have not had the check valve added.

To me the choice is simple - if I'm racing I'll use a Holley, but for my daily driver I'll use an Eddy. Or, the newer Street Demon, which is similar to a Carter or Rochester.

[fljab]

To me the choice is simple - if I'm racing I'll use a Holley, but for my daily driver I'll use an Eddy. Or, the newer Street Demon, which is similar to a Carter or Rochester.

I was looking at the Street Demon carbs on the Summit site; they have 625 cfm versions similar to this one:

https://www.summitracing.com/parts/dem-1900/overview/

They look interesting, but again, I know little about it. I'm still looking for a good used dual plane intake and having no luck locally, but for now I'll be happy to get the stock setup running better.

 

[Gary Lewis]

To me the choice is simple - if I'm racing I'll use a Holley, but for my daily driver I'll use an Eddy. Or, the newer Street Demon, which is similar to a Carter or Rochester.

I was looking at the Street Demon carbs on the Summit site; they have 625 cfm versions similar to this one:

https://www.summitracing.com/parts/dem-1900/overview/

They look interesting, but again, I know little about it. I'm still looking for a good used dual plane intake and having no luck locally, but for now I'll be happy to get the stock setup running better.

I have the 750 CFM version of that carb with the polymer bowl to keep the gas cool. But it is on Dad's engine and that is at Tim Meyer's shop, although it will be delivered on Sept 15th, so I don't have any experience with it yet.

However, Tim has dyno'd the engine extensively and says that the carb performed very well. In fact, it gave almost as much HP as a 780 CFM Holley. But the small primaries that give such good part-throttle performance don't do as well on the top end as the larger ones on a Holley. And the huge secondary that makes up for the small primaries can't meter as precisely as the smaller individual secondaries of a Holley. Again, if I'm going racing (boogity, boogity, boogity) I'll run a Holley.

[Gary Lewis]

I have the 750 CFM version of that carb with the polymer bowl to keep the gas cool. But it is on Dad's engine and that is at Tim Meyer's shop, although it will be delivered on Sept 15th, so I don't have any experience with it yet.

However, Tim has dyno'd the engine extensively and says that the carb performed very well. In fact, it gave almost as much HP as a 780 CFM Holley. But the small primaries that give such good part-throttle performance don't do as well on the top end as the larger ones on a Holley. And the huge secondary that makes up for the small primaries can't meter as precisely as the smaller individual secondaries of a Holley. Again, if I'm going racing (boogity, boogity, boogity) I'll run a Holley.

Guys - Should this carb discussion be moved to a new thread out on the main page? Maybe "Gary's Thoughts On Carbs" or somesuch? Doesn't seem to belong here.

[fljab]

Guys - Should this carb discussion be moved to a new thread out on the main page? Maybe "Gary's Thoughts On Carbs" or somesuch? Doesn't seem to belong here.

Sure, might be good to get it as a main topic.

 

[Gary Lewis]

The following discussion was originally in the New Member's section under Darth Vader, which is Bill/85lebaront2's truck. Therein I said "In Bill's case his background means he's the most qualified person around on carbs. But I'll still argue with him about Holleys and Carterbrocks. As yet he's not risen to the bait, but Jim/fljab did, as show below....

[Gary Lewis]

Guys - Should this carb discussion be moved to a new thread out on the main page? Maybe "Gary's Thoughts On Carbs" or somesuch? Doesn't seem to belong here.

Sure, might be good to get it as a main topic.

Ok, does this work? (Wow, that was easy! I just created the new thread, got its permalink, and put that in the proper field in the Move dialog on your post. And it moved not only that post but all that followed. )

So, Jim, should I now delete my question to you, your response, this response to you, and your to-be response?

[ArdWrknTrk]

Ok, does this work? (Wow, that was easy! I just created the new thread, got its permalink, and put that in the proper field in the Move dialog on your post. And it moved not only that post but all that followed. )

So, Jim, should I now delete my question to you, your response, this response to you, and your to-be response?

This is the other Jim.

I just tore down a 650 cfm Edelbrock 'Thunder' AVS today.

Seems pretty simple, but all the linkages are a little fiddly.

I'm used to Holley's and use the blue gaskets so i don't have "fabric" or any of the leaks Gary alludes to.

I guess I can give a full report when my fuel line comes in next week.

I think Demon is OK, having learned to put my issues with Barry Grant behind me.

[Gary Lewis]

This is the other Jim.

I just tore down a 650 cfm Edelbrock 'Thunder' AVS today.

Seems pretty simple, but all the linkages are a little fiddly.

I'm used to Holley's and use the blue gaskets so i don't have "fabric" or any of the leaks Gary alludes to.

I guess I can give a full report when my fuel line comes in next week.

I think Demon is OK, having learned to put my issues with Barry Grant behind me.

Jim - I think you know, but the Street Demon is a completely different design than the other Demon carbs, which are similar to Holley's. But the Street is a Carter-style carb, designed by an ex-Carter engineer about 10 years ago. Kind of a cross between an AVS and a Thermoquad.