dual carbs and chokes

[4tford]

Pros and cons on chokes on dual carb setups. Both chokes fixed open? One fixed open and one functional? Both functional? What is the best way and why.

[Charlie ny]

Usual choke on rear carb only.......seems to work on all setups I have built.
Charlie ny
PS
Still controversial, leave chokes in place or remove them on carbs
that aren't choked.....
Charlie ny

[chap52]

CharlieNY X2

Want to stir another pot?, I was advised to block off both PV's in my 94's and it works great.

[Tim Ayers]

Originally Posted by Charlie ny

Usual choke on rear carb only.......seems to work on all setups I have built.
Charlie ny
PS
Still controversial, leave chokes in place or remove them on carbs
that aren't choked.....
Charlie ny

Somewhere I remember reading article that the chokes should be left in. The article did flow testing and it was shown that the air flow is disrupted or lacked direction without the chokes.

No harm in leaving them in and, as Charlie said, only making one operational.

[PeterC]

I run twin 48's - rear choke operational - front choke in present but fixed open - the 284ci 59a runs like a top in this configuartion

[Mike51Merc]

Sponsored Links (Register now to hide all advertisements)

Dual 48s, both chokes operational, linked together. No cons.

[scooder]

Originally Posted by chap52

CharlieNY X2

Want to stir another pot?, I was advised to block off both PV's in my 94's and it works great.

What main jets you running? When I tried blocking the power valves, the damn creation would pull a greased stick out of a pig's arse! Hardly got our of the garage!
This was a dual setup.
Martin.

[adileo]

Originally Posted by chap52

CharlieNY X2

Want to stir another pot?, I was advised to block off both PV's in my 94's and it works great.

I have dual Edlebrok 94s rebuilt by Charlie. He blocked off my pv and increased the jet size. Car runs great!!!

Btw my choke only on rear carb.

[zzlegend]

Originally Posted by Mike51Merc

Dual 48s, both chokes operational, linked together. No cons.

Same here on two 94's. Barely close the chokes, to warm up. Starts easily.

[Bored&Stroked]

Power valves are really designed to provide enrichment at full-throttle - or close to it.

The reason blocking the power valves probably worked was because it was running really rich - due to both of them having the wrong vacuum settings and dumping too much raw fuel into the engine at the wrong time. The stock power valves (or the ones supplied with kits) will open at too high of a vacuum level (too early . . . or all the time). With a single carb, the standard valve is probably about right - with multiple carbs, they usually need to be changed. Also, many of the carb kits supply valves with no damn numbers on them . . . so one can maybe guess they are a 6.5 or a 7.5, but who knows.

In a perfect world, one would use a vacuum gauge (inside the car) to monitor the vacuum levels and then select the correct power valves to match the vacuum signals of your particular engine. The old Holley rule was to take a vacuum reading at idle and then cut that number in 1/2 - to select a power valve number . . . this MIGHT get you in the ballpark with a single carb, but using a vacuum gauge when you are driving the car is a better way (along with a WB02 meter if you happen to have one hooked up )

You'll probably find that switching to somewhere around a 3.5 to 4.5 power valve with dual carbs will work well. With that said, many of the modern power valves don't seat quite right (too much radius in the gasket corner area) - so I take the radius out of the gasket area on my lathe. I've seen pictures of this process posted someplace - just don't remember where?

I think you'll find that if you get them right, you'll have the best of both worlds - good economy when at partial throttle and good power at full throttle.

B&S

[willowbilly3]

Kinda OT here but I run chokes on both of the 2100s on my 260. 2 choke knobs. But my carbs set sideways on an efi intake and both run all the time.

[flat 39]

I am running dual 94's and choke both carbs. The main reason I do this is I pull the choke out part way for high idle feature until the engine warms up.

[outlaw]

Originally Posted by Bored&Stroked

Power valves are really designed to provide enrichment at full-throttle - or close to it.

The reason blocking the power valves probably worked was because it was running really rich - due to both of them having the wrong vacuum settings and dumping too much raw fuel into the engine at the wrong time. The stock power valves (or the ones supplied with kits) will open at too high of a vacuum level (too early . . . or all the time). With a single carb, the standard valve is probably about right - with multiple carbs, they usually need to be changed. Also, many of the carb kits supply valves with no damn numbers on them . . . so one can maybe guess they are a 6.5 or a 7.5, but who knows.

In a perfect world, one would use a vacuum gauge (inside the car) to monitor the vacuum levels and then select the correct power valves to match the vacuum signals of your particular engine. The old Holley rule was to take a vacuum reading at idle and then cut that number in 1/2 - to select a power valve number . . . this MIGHT get you in the ballpark with a single carb, but using a vacuum gauge when you are driving the car is a better way (along with a WB02 meter if you happen to have one hooked up )

You'll probably find that switching to somewhere around a 3.5 to 4.5 power valve with dual carbs will work well. With that said, many of the modern power valves don't seat quite right (too much radius in the gasket corner area) - so I take the radius out of the gasket area on my lathe. I've seen pictures of this process posted someplace - just don't remember where?

I think you'll find that if you get them right, you'll have the best of both worlds - good economy when at partial throttle and good power at full throttle.

B&S

B&S, Do you have a picture of one of your power valves showing where & how much you turned off in your lathe? I'm gonna need to do this at some point, just havn't got to that point yet. Thank you. Bill

[4tford]

seems the post got turned into power valves. But with the other replies it seems it is best to run with one functional choke. Thanks Guys.

[Bored&Stroked]

Back to chokes! I am running both chokes on my 32 (Eddie Meyer manifold). The simple reason is that it makes it easy to make a linkage that connects both chokes and still picks up the stock 32 choke rod (which ends up 1/2 between the two) . . . so this is the route I've taken. I surely can't see where having two will hurt anything - and it would give a more consistent (richer mixture) to all cylinders . . . instead of some being rich and some lean.

[Bored&Stroked]

B&S, Do you have a picture of one of your power valves showing where & how much you turned off in your lathe? I'm gonna need to do this at some point, just havn't got to that point yet. Thank you. Bill

No - but I just happened to be out in the shop yesterday, organizing a bunch of carbs and pulled two power valves out (one a stocker and one a modern replacement from Holley). I did this with the intention of showing the differences and necessary modifications. Over the weekend I'll modify one on my lathe and document the process and specifics.

I need to do it anyway - as I'm setting up a couple new 2110's for some dyno testing against my Stromberg 48's.

[chap52]

CharleyNY suggested I run #52 jets in both. Got new jets from him and they run great.