83 turbo hot hair setup with carb

[forcefed3.8's]

You boost reference with draw through superchargers, which is the same idea. The power valve enrichens at a set low vacuum point (determined by which power valve you have), but your draw through set up will have consant vacuum under boost, and the carb will never enrichen. You can richen the carb at WOT, but it will be too rich under cruising conditions.

 

[jimski]

You boost reference with draw through superchargers, which is the same idea. The power valve enrichens at a set low vacuum point (determined by which power valve you have), but your draw through set up will have consant vacuum under boost, and the carb will never enrichen. You can richen the carb at WOT, but it will be too rich under cruising conditions.

The carb has a stock power valve i bought it new never took it apart to actually see thou but im assuming it is stock,isnt constant vacuum exactly how a carb works anyways,if it where blow thru the concept changes for how the power valve works becouse air is being forced in it not vacuum.Im totally confused reading around the net alot of sites say it will be fine becouse it is draw thru which is the same concept on how a carb works it draws vacuum,thanks for bringing this to light thou becouse i never heard anything about this boost reference power valve stuff..I still really do not understand the concept of it .If u could explain in high detail so i can understand it and how it works with turbo chargers. thanks.

 

[jimski]

I see thanks for youre input

This is a 1983 setup not a 79 to 80 thou so the carb that i saved witht the setup is electronic

 

[jimski]

Should i just use an edelbrock carb instead of this power valve stuff.

 

[Freddie's Buick]

All carbs have a power system. The differance on turbo carbs is that the plumbing is differant. No power valve is used on an electronic carb. The up and down movement needed is controlled electronically.

The internal mixture control needles on non-electronic carbs need a vacuum source in order for the carb to work.

They use engine vacuum as a load indicator that determines rich/lean mixture. The more load one puts the engine through, (throttling up, WOT), the richer the mixture needs to be. Vacuum is less at WOT, so the needles are pushed up due to spring action on the power valve.

During idle, there is no load, thus the mixture is leaner and the engine vacuum is at it's strongest and pulls the power valve down.

The problem with turbos is that the vacuum source needed to control mixture is routed from a differant port. More than likely on the intake manifold rather then internally as in non-turbo carbs.

Can someone explain the reason for this? (I know why but I've already written too much). :biggrin:

 

[dr_frankenstein]

Most of these Carburetors are intended for use with superchargers, and have a unique capability that allows their power valves to reference the intake Manifold vacuum below the supercharger. This allows the power valve to operate as it should, based off intake Manifold vacuum. A power valve provides further enrichment to the main metering system under load (low vacuum) conditions. Without this external referencing, the power valve would be "reading" the Supercharger boost pressure, which has no bearing on the engine load.

I dont know if these style of carbs can be used with turbos due to the nature at which they operate. theroreticly it should beable to operate properly as long as its used in a draw thru application.

I could guide you thru the modifactions to a holley for boost referencing if needed.

A.j.

P.S. Im jealous though, Ive been looking for an 83 hot air setup myself!

LOL

 

[jimski]

Most of these Carburetors are intended for use with superchargers, and have a unique capability that allows their power valves to reference the intake Manifold vacuum below the supercharger. This allows the power valve to operate as it should, based off intake Manifold vacuum. A power valve provides further enrichment to the main metering system under load (low vacuum) conditions. Without this external referencing, the power valve would be "reading" the Supercharger boost pressure, which has no bearing on the engine load.

I dont know if these style of carbs can be used with turbos due to the nature at which they operate. theroreticly it should beable to operate properly as long as its used in a draw thru application.

I could guide you thru the modifactions to a holley for boost referencing if needed.

A.j.

P.S. Im jealous though, Ive been looking for an 83 hot air setup myself!

LOL

Heck if i do not need to boost reference since this is a draw thru setup,it should work normally then as i thought it would to the engine still pulls vacuum thru the carb even thou it has a compressor on the other side as well.I would still like to know how it is done,do i have to screw a nipple on the carb somewhere and connect a vacuum line to the intake manifold so it bypasses the compressor vacuum????

 

[dr_frankenstein]

Heck if i do not need to boost reference since this is a draw thru setup,it should work normally then as i thought it would to the engine still pulls vacuum thru the carb even thou it has a compressor on the other side as well.I would still like to know how it is done,do i have to screw a nipple on the carb somewhere and connect a vacuum line to the intake manifold so it bypasses the compressor vacuum????

well the idea is that the powervalve become "Load Sensative" when its set up to be boost referenced.

the powervalve wont work as it is set up in a stock holley because the vacuum signal is always present when it reads it from the base of the carb, even in low boost the carb reads vacuum..... at high boost it still reads vacuum which wont allow it to open causing a lean situation.

by boost refrencing the valve, and plumbing it to the intake - it corrects the problem. high boost causes the valve to open riching it up, while vacuum/ low or no boost causes it to stay closed.

as for the modification, theres some ports that need to be plugged, some channels that need to be milled out and some new holes drilled.

if you have a steady hand, and are decent with a dremel its not too hard. let me take some pictures and what not to explain it better and i will guide you threw it.

:biggrin: A.j.

 

[jimski]

well the idea is that the powervalve become "Load Sensative" when its set up to be boost referenced.

the powervalve wont work as it is set up in a stock holley because the vacuum signal is always present when it reads it from the base of the carb, even in low boost the carb reads vacuum..... at high boost it still reads vacuum which wont allow it to open causing a lean situation.

by boost refrencing the valve, and plumbing it to the intake - it corrects the problem. high boost causes the valve to open riching it up, while vacuum/ low or no boost causes it to stay closed.

as for the modification, theres some ports that need to be plugged, some channels that need to be milled out and some new holes drilled.

if you have a steady hand, and are decent with a dremel its not too hard. let me take some pictures and what not to explain it better and i will guide you threw it.

:biggrin: A.j.

Great im pretty handy when it comes to modifying stuff. I see the concept of why it will not work there is always vacuum and it will never open even at high rmp when a regular engine loses vacuum which in turn opens the valve up,great stuff.Hey will an edelbrock carb work it has needles on top which control enriching or does edelbrock use vacuum too. Or will any other carb work which would probally be easier then modifying the holley..

 

[dr_frankenstein]

Great im pretty handy when it comes to modifying stuff. I see the concept of why it will not work there is always vacuum and it will never open even at high rmp when a regular engine loses vacuum which in turn opens the valve up,great stuff.Hey will an edelbrock carb work it has needles on top which control enriching or does edelbrock use vacuum too. Or will any other carb work which would probally be easier then modifying the holley..

I cannot say for an edelbrock, my dads the expert on those and I will talk to him tonight about forced induction applications and weather its possible to boost reference as well..

As far as I can tell though, i have never seen an AFB style carb used in any type of real compettion that uses forced induction, so im assuming (bear with me if im incorrect) that there not a favored design for that type of use. most AFB styles i have only seen on N/A applications as there an excellent street carb.

I hope this Info helps out a bit... I cant say im a real HotAir guy since I run a Blower but i feel like its the same concept so i think what i have learned should help.

A.j.

 

[jimski]

I cannot say for an edelbrock, my dads the expert on those and I will talk to him tonight about forced induction applications and weather its possible to boost reference as well..

As far as I can tell though, i have never seen an AFB style carb used in any type of real compettion that uses forced induction, so im assuming (bear with me if im incorrect) that there not a favored design for that type of use. most AFB styles i have only seen on N/A applications as there an excellent street carb.

I hope this Info helps out a bit... I cant say im a real HotAir guy since I run a Blower but i feel like its the same concept so i think what i have learned should help.

A.j.

It is ok thou if i can route that power valve to the manifold vacuum then we both know for sure it will work i was just inquiring about edelbrock deal becouse they are cheaper if i screw it up :biggrin: lol plus it will fit the mount a little better than the huge holley

 

[dr_frankenstein]

It is ok thou if i can route that power valve to the manifold vacuum then we both know for sure it will work i was just inquiring about edelbrock deal becouse they are cheaper if i screw it up :biggrin: lol plus it will fit the mount a little better than the huge holley

well the nice part about the holley, is if you do screw it up, its just the metering block that your modifying. if you make a mistake simply replace the metering block. OR .... if you dont like the way it performs yank it off and go back to regular style metering.

Hooray for Early HotAir!!!!!! Let give the intercoolers a run for there money!

:biggrin: A.j.

 

[jimski]

well the nice part about the holley, is if you do screw it up, its just the metering block that your modifying. if you make a mistake simply replace the metering block. OR .... if you dont like the way it performs yank it off and go back to regular style metering.

Hooray for Early HotAir!!!!!! Let give the intercoolers a run for there money!

:biggrin: A.j.

I agree my 82 buick i had this setup inside i was smoking alot of cars in that time till my bro smashed the front.:biggrin:

 

[fc227]

Greetings everyone!

Hope I am still allowed here :smile:


How big is that carb? , I found on my setup, if I went over ~ 600 cfm, the car would buck and stumble.

I ran a Holly 780, but I had the secondary limited to open only about 1/2 way. And it was a vacuum secondary.

I also ran the HEI Dist. with the ESC for knock control, until I switched over to a Moroso Billet dist., but I had to modify the electronics to make the ESC still work.


Do not go to big with the cam.

 

[jimski]

Greetings everyone!

Hope I am still allowed here :smile:


How big is that carb? , I found on my setup, if I went over ~ 600 cfm, the car would buck and stumble.

I ran a Holly 780, but I had the secondary limited to open only about 1/2 way. And it was a vacuum secondary.

I also ran the HEI Dist. with the ESC for knock control, until I switched over to a Moroso Billet dist., but I had to modify the electronics to make the ESC still work.


Do not go to big with the cam.

I think this is an 850 double pump,I was kinda thinking the last few days if it was too extreme but it sounds as if youres was starving for gas thou.

What have u done to an after market carb to make it work with youre draw thru and what cam do u recomend

 

[mach.80]

Not sure if this helps but, I had an 87 Mazda Rx7 with a Blow through turbo set-up.

We used a 48mm Webber sidedraft. Blew threw it ensuring we pressurized the float bowl. Two factory intercoolers up front.

We used a Malory FPR with the diaphram for pressure.

For electronics We used MSD 6al and BTM boost timing master. With a locked distributor.

The car made 411 horsepower with a 1.3 litre engine.(Wankle Power)

The most fun car I've ever owned.

 

[fc227]

Comp cam's "206”. I know Jim S. as had issues with Comp Cams. I have not.

Contact Mr. Cotton. He can set you up.


As for my setup starving for fuel, it is possible I was running a stock mechanical fuel pump. My setup was a draw through. Best Et was 13.202 @ 100.42 MPH when corrected to sea level was a 12.97.

I blocked the base plate feed for the power valve on the Holley and used a reference signal from the intake for the power valve. I used a check valve with a small bleed off that when to the top of the carb. Because I keep popping power valves. To keep the power valve from seeing boost.

 

[jimski]

Comp cam's "206”. I know Jim S. as had issues with Comp Cams. I have not.

Contact Mr. Cotton. He can set you up.


As for my setup starving for fuel, it is possible I was running a stock mechanical fuel pump. My setup was a draw through. Best Et was 13.202 @ 100.42 MPH when corrected to sea level was a 12.97.

I blocked the base plate feed for the power valve on the Holley and used a reference signal from the intake for the power valve. I used a check valve with a small bleed off that when to the top of the carb. Because I keep popping power valves. To keep the power valve from seeing boost.

how did u hook the vacuum to the carb from the manifold for the power valve this is exactly what i have to do and is the final step.I have located the power valve hole with the ball bearing in it (check valve).But how do reroute the vacuum.

 

[fc227]

Ok, I am going off memory here so… (It has been a few years).

On the bottom of the carb, the throttle plate you should be able to locate the passage that goes up to the power valve. There should also be a passage from this same location that runs to a port on the front of the carb. You have to block the port in the base (throttle plate) so it will not see any vacuum under the carb only from the port. I used epoxy, but I do not remember how I keep the hole to the front port open. I think I drilled it after the epoxy dried. Exercise extreme caution here. If you make a boo-boo you could ruin the throttle plate or base. I had to use a milled down adaptor plate from the Q-jet to the Holley for hood clearance. I should have taken pictures back then but I did not.

I also ended up using the little ball valve /check valve like you mentioned. After going though my 5th power valve. I believe I also used a 7.5” or 6.5” valve I cannot remember.

I hope this helps. This setup worked well for me.

 

[jimski]

Ok, I am going off memory here so… (It has been a few years).

On the bottom of the carb, the throttle plate you should be able to locate the passage that goes up to the power valve. There should also be a passage from this same location that runs to a port on the front of the carb. You have to block the port in the base (throttle plate) so it will not see any vacuum under the carb only from the port. I used epoxy, but I do not remember how I keep the hole to the front port open. I think I drilled it after the epoxy dried. Exercise extreme caution here. If you make a boo-boo you could ruin the throttle plate or base. I had to use a milled down adaptor plate from the Q-jet to the Holley for hood clearance. I should have taken pictures back then but I did not.

I also ended up using the little ball valve /check valve like you mentioned. After going though my 5th power valve. I believe I also used a 7.5” or 6.5” valve I cannot remember.

I hope this helps. This setup worked well for me.

the holley i have has the ball in the hole and i see what u mean the vacuum port right where the power valve hole is cover that hole area and drill to make a tunnel sounds logical