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Holley 750 Dominator Booster Change Over

General engine tech -- Drag Racing to Circle Track

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1980RS
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Holley 750 Dominator Booster Change Over

Post by 1980RS » Sun Jul 26, 2020 5:35 pm

I have decided to take my 750 Dominator that is collecting dust and swap over to the new 12 hole Boosters. I got a set of the billet ones from Allstate and look pretty easy to put in. My Question is what jet to start with as a base line as I am sure it will be lean with the stock 750 jetting. I was going to do this with my 3 circuit 1050 but this route on the 750 makes it's muck easier as it's a 2 circuit already.

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Re: Holley 750 Dominator Booster Change Over

Post by Walter R. Malik » Sun Jul 26, 2020 6:23 pm

1980RS wrote:
Sun Jul 26, 2020 5:35 pm
I have decided to take my 750 Dominator that is collecting dust and swap over to the new 12 hole Boosters. I got a set of the billet ones from Allstate and look pretty easy to put in. My Question is what jet to start with as a base line as I am sure it will be lean with the stock 750 jetting. I was going to do this with my 3 circuit 1050 but this route on the 750 makes it's muck easier as it's a 2 circuit already.
It is all about the "skirt" diameter ... or no "skirt" at all.
http://www.rmcompetition.com
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Re: Holley 750 Dominator Booster Change Over

Post by 1980RS » Mon Jul 27, 2020 12:57 am

Walter R. Malik wrote:
Sun Jul 26, 2020 6:23 pm
1980RS wrote:
Sun Jul 26, 2020 5:35 pm
I have decided to take my 750 Dominator that is collecting dust and swap over to the new 12 hole Boosters. I got a set of the billet ones from Allstate and look pretty easy to put in. My Question is what jet to start with as a base line as I am sure it will be lean with the stock 750 jetting. I was going to do this with my 3 circuit 1050 but this route on the 750 makes it's muck easier as it's a 2 circuit already.
It is all about the "skirt" diameter ... or no "skirt" at all.
There will be no skirts on the new booster and the new change will make it a true 1050.

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Re: Holley 750 Dominator Booster Change Over

Post by Walter R. Malik » Mon Jul 27, 2020 10:25 am

1980RS wrote:
Mon Jul 27, 2020 12:57 am
Walter R. Malik wrote:
Sun Jul 26, 2020 6:23 pm
1980RS wrote:
Sun Jul 26, 2020 5:35 pm
I have decided to take my 750 Dominator that is collecting dust and swap over to the new 12 hole Boosters. I got a set of the billet ones from Allstate and look pretty easy to put in. My Question is what jet to start with as a base line as I am sure it will be lean with the stock 750 jetting. I was going to do this with my 3 circuit 1050 but this route on the 750 makes it's muck easier as it's a 2 circuit already.
It is all about the "skirt" diameter ... or no "skirt" at all.
There will be no skirts on the new booster and the new change will make it a true 1050.
I would say 86's with power valves would be a good place for a start.
http://www.rmcompetition.com
Specialty engine building at its finest.

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Re: Holley 750 Dominator Booster Change Over

Post by jmarkaudio » Tue Jul 28, 2020 10:34 am

If you want to make it run well look over the following link. It needs t-slot restrictions, lowered idle feeds, and opened up angle channels to be ideal.


http://www.motorsportsvillage.com/forum ... f=6&t=3742
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Re: Holley 750 Dominator Booster Change Over

Post by 1980RS » Tue Jul 28, 2020 2:40 pm

Walter R. Malik wrote:
Mon Jul 27, 2020 10:25 am
1980RS wrote:
Mon Jul 27, 2020 12:57 am
Walter R. Malik wrote:
Sun Jul 26, 2020 6:23 pm


It is all about the "skirt" diameter ... or no "skirt" at all.
There will be no skirts on the new booster and the new change will make it a true 1050.
I would say 86's with power valves would be a good place for a start.
Thanks

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Re: Holley 750 Dominator Booster Change Over

Post by 1980RS » Tue Jul 28, 2020 2:43 pm

jmarkaudio wrote:
Tue Jul 28, 2020 10:34 am
If you want to make it run well look over the following link. It needs t-slot restrictions, lowered idle feeds, and opened up angle channels to be ideal.


http://www.motorsportsvillage.com/forum ... f=6&t=3742
Thanks for the info on this but the 750 is a 2 circuit carb already so would I still need do all of this? It's the same as my 1150 2 circuit. I thought all one had to do on these 2 circuits was change to a better booster and get the jetting and air bleeds right.

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Re: Holley 750 Dominator Booster Change Over

Post by jmarkaudio » Sat Aug 01, 2020 11:00 am

Yes, even being a two circuit they respond to the same things. There are baselines in that post that give you some starting points. Just understand I've probably reworked over 100 HP Dominators, they all can respond differently. You can build two seemingly identical bodies and have to tune each differently for the idle and part throttle metering on the same engine. Sometimes small, but occasionally drastic differences. T-slot length, width, and position high or low in the body varies from one casting to the next. I've seen the t-slot exposed .030-.040" below a completely closed blade, I had one .100" above the closed blade. And then there have been porosity issues...
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Re: Holley 750 Dominator Booster Change Over

Post by Walter R. Malik » Sat Aug 01, 2020 11:04 am

1980RS wrote:
Tue Jul 28, 2020 2:43 pm
jmarkaudio wrote:
Tue Jul 28, 2020 10:34 am
If you want to make it run well look over the following link. It needs t-slot restrictions, lowered idle feeds, and opened up angle channels to be ideal.


http://www.motorsportsvillage.com/forum ... f=6&t=3742
Thanks for the info on this but the 750 is a 2 circuit carb already so would I still need do all of this? It's the same as my 1150 2 circuit. I thought all one had to do on these 2 circuits was change to a better booster and get the jetting and air bleeds right.
If you simply change the boosters, your carb will act very similarly to a 0-8082-1 Dominator 1050cfm.
http://www.rmcompetition.com
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Re: Holley 750 Dominator Booster Change Over

Post by PRH » Sat Aug 01, 2020 11:36 am

I’ve only messed with one of those carbs. Pre-HP vintage(not sure if there were HP versions or not*).

Pulled the boosters out, mildly blended away the ridge in the venturi, installed the std style boosters, ..... jetted accordingly...... worked fine on the owners BBC bracket car.

This was a long time ago....... so all the details are a little fuzzy.
I used to install adjustable air bleeds in many of those old carbs...... so there’s a good chance that happened as well.

*Edit- I see there is a thread from not long ago discussing these carbs...... and in that thread I posted a pic of an HP version of the 4500 750...... so they exist.
Somewhat handy with a die grinder.

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Re: Holley 750 Dominator Booster Change Over

Post by 1980RS » Sat Aug 01, 2020 11:56 pm

The 1050 8896-2 test did not work out today. I think it's just too fat and my new parts for the 750 conversion don't show up until Monday. I think using a good 2 circuit with the right parts in it will be better than this 8896. Taking out the intermediate bleeds did help a lot though.

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Re: Holley 750 Dominator Booster Change Over

Post by PRH » Sun Aug 02, 2020 10:42 am

My experience has been that installing T-slot restrictors is a very effective way of cleaning up the low speed operation on Holley 4500 carbs.
Somewhat handy with a die grinder.

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Re: Holley 750 Dominator Booster Change Over

Post by jmarkaudio » Sun Aug 02, 2020 11:53 am

1980RS wrote:
Sat Aug 01, 2020 11:56 pm
The 1050 8896-2 test did not work out today. I think it's just too fat and my new parts for the 750 conversion don't show up until Monday. I think using a good 2 circuit with the right parts in it will be better than this 8896. Taking out the intermediate bleeds did help a lot though.
I was an ASE certified mechanic 30 years ago. Rebuilt my share of carbs but not really any mods. 2007 I got frustrated with my 8896, it was the reason I started messing with carbs... Calibration in that one is bad.
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Re: Holley 750 Dominator Booster Change Over

Post by PRH » Sun Aug 02, 2020 2:26 pm

Calibration in that one is bad.
Some of the Holley 4500’s seem so bad ootb you have to wonder what was the engine combo used to come up with the baseline calibration?
It seems like they’re often pretty awful on just about anything I’ve run them on.

Getting them “okay” at wot isn’t often that hard, and they usually seem to be able to idle alright....... but at any throttle blade setting between closed and wot they’re just fat pigs.

You can’t really get the motor to clean out...... any throttle movement and it’s obvious how rich the mixture is...... until you get close to wot.

I know there are tons of people who just live with them being that way...... but to me, they’re just unusable like that.
Somewhat handy with a die grinder.

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