Thoughts on this Carb for Blown Hemi?

jayfire · Jun 8, 2021

I have a 68 GTX. Original 440, 4 speed, Dana 60. Now has a blown 68 426 Hemi with stage V heads and 6-71 Weiand blower. I was told this carb was a Dominator 1050cfm. Only 30 miles on engine in last 31 years, so no real good test drives. My problem is that it will not idle. It constantly revs up and comes back down. No vacuum leaks found. Previous owner said it did that on the 440 before being swapped, which leads me to believe its the carb itself. He said the carb was sent to BDS to be compatible with this engine combo, so no telling what they did to it. I am not a carb guy, other than tweaking a smaller Edelbrock carb. I want this to be more streetable as a cruiser if possible. Should I go with a Holley EFI? Try a different carb? Thanks

Fran Blacker · Jun 8, 2021

Calling @HEMI-ITIS .

33 IMP · Jun 8, 2021

Classic blower surge. Some people like it, says it sounds powerful.
If you dont like it, google "how to cure blower surge"

jayfire · Jun 8, 2021

33 IMP said:
Classic blower surge. Some people like it, says it sounds powerful.
If you dont like it, google "how to cure blower surge"

Mine does not sound like this kind of blower surge. I wish it did! Mine idles low for a few seconds, then revs up for a few seconds, then slowly comes back down again. PO mentioned possibly a blown power valve. Would that do the erratic idle? Thanks

33 IMP · Jun 8, 2021

Im no carb guru, but there are several here and fabo. But as i understand it, a blown power valve won't have an effect on idle. Its easily checked. Pull a bowl off, take the power valve (or valves, but i doubt there is a pv on the secondary side) and test it. Or, you could simply plug it, and fatten the jetting up four steps. You would have to ask someone else here about the wisdom of a power valve on a blown motor.

33 IMP · Jun 8, 2021

I dont think either number in the pics in post #1 identify the carb. Look for a "list" then a four digit number, or just L xxxx. Though your carb has been messed with. It looks very early because of the raised area above the throats, (might have had a choke) but the bowls and metering blocks are much newer. Has a secondary idle mix adjustment too.

jayfire · Jun 8, 2021

33 IMP said:
I dont think either number in the pics in post #1 identify the carb. Look for a "list" then a four digit number, or just L xxxx. Though your carb has been messed with. It looks very early because of the raised area above the throats, (might have had a choke) but the bowls and metering blocks are much newer. Has a secondary idle mix adjustment too.

Can not find a list number anywhere. That is all the numbers around the horn. I have no clue how to adjust anything on this carb except throttle screw!

HEMI-ITIS · Jun 8, 2021

33 IMP said:
Im no carb guru, but there are several here and fabo. But as i understand it, a blown power valve won't have an effect on idle. Its easily checked. Pull a bowl off, take the power valve (or valves, but i doubt there is a pv on the secondary side) and test it. Or, you could simply plug it, and fatten the jetting up four steps. You would have to ask someone else here about the wisdom of a power valve on a blown motor.

Blown power valve will make it run very FHAT......
Appears you are using a single 4 bbl on a 426 Hemi??
EFI depends on yer wallet :bananaweed:

jayfire · Jun 8, 2021

HEMI-ITIS said:
Blown power valve will make it run very FHAT......
Appears you are using a single 4 bbl on a 426 Hemi??
EFI depends on yer wallet

View attachment 1121526 View attachment 1121527

What do you recommend for an EFI setup? If it makes it more cruiser friendly, I’ll do it. Otherwise, I may try to sell the whole engine and buy a more streetable hemi.

HEMI-ITIS · Jun 8, 2021

I don't see a 30 year old dominator being the ticket. A pair of good carbs set up for your combo have to be $2000 or more ,EFI on the cheap side must cost$3000 plus. Not too hard to get the carbs to idle and perform well.

33 IMP · Jun 8, 2021

jayfire said:
What do you recommend for an EFI setup? If it makes it more cruiser friendly, I’ll do it. Otherwise, I may try to sell the whole engine and buy a more streetable hemi.

HEMI-ITIS said:
I don't see a 30 year old dominator being the ticket. A pair of good carbs set up for your combo have to be $2000 or more ,EFI on the cheap side must cost$3000 plus. Not too hard to get the carbs to idle and perform well.

Holley has a dual 4150 sniper setup, self tuning, seen for $2100 and change, maybe less. But, by the time you get a new tank and fuel setup, throttle linkage, and a new blower top, you will probably have what hemi-itis says , at least three grand. Holley has specific blower carbs for gmc blowers, 750cfm, but just like hemi says you will have at least a couple grand in them .
I would be tempted to see what a real sharp carb tuner can do with yours. The main body IS very old, but the rest.......? I would recommend Thumper carbs, Dom definately knows his way around a dominator, except i dont know if he does blower carbs. Sure worth a phone call.

jayfire · Jun 11, 2021

Well, like I said previously, I am not a carb expert! I changed both power valves and it did nothing. I adjusted all four mixture screws 1 turn out and idles just fine now. I guess playing with it more and doing more research will definitely help with the learning curve of carburetors. Thanks for the responses.

Thoughts on this Carb for Blown Hemi?

jayfire

Well-Known Member

Fran Blacker

FBBO Gold Member

33 IMP

FBBO Gold Member

jayfire

Well-Known Member

33 IMP

FBBO Gold Member

33 IMP

FBBO Gold Member

jayfire

Well-Known Member

HEMI-ITIS

STREETER on LI

jayfire

Well-Known Member

HEMI-ITIS

STREETER on LI

33 IMP

FBBO Gold Member

jayfire

Well-Known Member

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