I am going down to Little Rock, today, to do some test-n-tune on the induction system of that thing, so maybe will have some news one way or other for you, tonight. :banghead:
Wish me luck...
Its Time To Build Some BOOST!
- Thread starter srixon4406
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I am going down to Little Rock, today, to do some test-n-tune on the induction system of that thing, so maybe will have some news one way or other for you, tonight. :banghead:
Wish me luck...
MiradaMegaCab
Well-Known Member
:thumbup:Best of luck!!
Aaron,
We took the carb off and raised the jet sizes 5 sizes on both primaries and secondaries because the A/F ratio was really lean (14.5-16:1) at full throttle (No meth injection.)
That gave us 82s in the primaries and 97s in the secondaries.
I know that seems rich, but the A/F ratio was so lean (sometimes 16:1) we just wanted to fix that...
We ran out of time for a real world test because upon re-assembly, unbeknownst to us, the primary float had hung (at the bottom) on the power valve bracket (not enough free room when it's on the bottom of the float bowl) which made it unable to close the needle in its seat. This floods\ed the foat bowl and squirted gasoline, verticlly, out the vent tube.
We'll try again tomorrow.
Sorry...
We took the carb off and raised the jet sizes 5 sizes on both primaries and secondaries because the A/F ratio was really lean (14.5-16:1) at full throttle (No meth injection.)
That gave us 82s in the primaries and 97s in the secondaries.
I know that seems rich, but the A/F ratio was so lean (sometimes 16:1) we just wanted to fix that...
We ran out of time for a real world test because upon re-assembly, unbeknownst to us, the primary float had hung (at the bottom) on the power valve bracket (not enough free room when it's on the bottom of the float bowl) which made it unable to close the needle in its seat. This floods\ed the foat bowl and squirted gasoline, verticlly, out the vent tube.
We'll try again tomorrow.
Sorry...
srixon4406
TURBO TOAD
No need to be sorry Bill its a process, as far as the jet size that does seem like alot of jet if the larger jets don't make it richer try and find a paper clip or something close to the diameter of your high speed air bleeds and plug the primary side that will activate your boosters sooner.
I was doing some testing after I first got the valiant road ready with a 750dp and was having close to the same problem but it had adjustable air bleeds and i plugged them with blanks and it helped alot. But I was told on multiple forums that the 750dp was to much carb for my application. I'm wondering if the 650 im running now isn't to big.
If I remember Toms running a 600, and Ryan is running a 650 demon that flows around 580cfm. Also I believe Ryan run a low 11 second 1/4 mile on the primaries only that equals about 280 cfm.
Just food for thought Bill keep at it we will get there.
Aaron
Thanks, Aaron.
If this doesn't do the job, we may try a different carb (600?) as 750 does sound a bit on the largish size, but the one on my supercharged 360 seems pretty happy and it only makes a bit over 500 hp at the flywheel...
I'll keep you posted!:coffee2:
If this doesn't do the job, we may try a different carb (600?) as 750 does sound a bit on the largish size, but the one on my supercharged 360 seems pretty happy and it only makes a bit over 500 hp at the flywheel...
I'll keep you posted!:coffee2:
stop the beast
Well-Known Member
sounds like you all are making good progress. keep up the good work.
Thanks; this is uncharted waters for us, as we have never had a turbocharged ANYTHING, nor a slant six car before.
Just got tired of V8s and wanted to try something different.
Well, it's different all right! LOL!:banghead:
Well, we went for a ride today and were amazed to find A/F ratios in the 16-18:1 range at full throttle, from 3,500-5,500 rpm but it made 8 pounds of boost like that !!!
That's a sure-fire recipe for detonation, so we went back to the shop and removed the carb, after checking the float levels. (They were right on...)
Tomorrow (Sat.), I will take the blow-thru carb off my 360 Magnum-powered '72 Valiant and install it on the /6 car, as an experiment.
That carb is also a 750 DP (but, from the Carb Shop) and is a $900.00 unit that was never quite rich enough to get rid of a stumble at part-throttle tip-in, at cruise. Also, it was not happy stall starting, going lean at about 2,000 rpm and stumbling pretty badly, bit unless you actively worked the accelerator pump.
Overall driveability was poor, but it made 445 RWHP with that original Carb Shop jetting on a chassis dyno.
I tried to fix the mixture issues, to no avail.
In an effort to fatten it up...
I raised the float levels.
I installed more aggressive accelerator pump (plastic) actuating ramps
I went richer on all main jets by about 5 sizes
Changed out the accelerator pump squiters to bigger ones
I installed significantly smaller (richer) hi-speed air bleeds
I tried some warmer plugs
Nothing I did got rid of that stumble.
Nothing.
But, it IS pig-rich, now, and should wake up the boost on that slant six motor.
I never had the F.A.S.T. O-2 sensor on the V8, with that carb, nor did I ever have a timing light on it; so, I have NO IDEA where the timing is, but it runs good (lucky guess!) and is relatively fast.... low 11's in a 3,300-pound car (without driver.)
I won't take chances like that with the /6 car. I watch that A/F ratio like a hawk while Fredddie drives.
I'll have a report on this debacle for you, Sat. night.
Wish me luck...
All this is with 18 crankshaft-degrees (locked plate) ignition timing.
Oh well, like I told Freddie; if it were easy, everyone would do it!!! :blob:
srixon4406
TURBO TOAD
Bill you never answered my question in a previous post were is your brpv referenced in relation to position on the carb hat?
I'd total plug the hsab that should active the boosters sooner.
Have you heard about adding vent tube extention?
http://www.theturboforums.com/threads/317547-Vent-Tubes-VS-BRPV
You will notice Shaker posts in this thread Pm me if you want some pics
Keep at it BILL we will get it
I'd total plug the hsab that should active the boosters sooner.
Have you heard about adding vent tube extention?
http://www.theturboforums.com/threads/317547-Vent-Tubes-VS-BRPV
You will notice Shaker posts in this thread Pm me if you want some pics
Keep at it BILL we will get it
Is this what you're looking for?
What is an hsab?
Tomorrow (Sat.) I am taking the carb from my V8 Valiant (another 750DP with blow-thru mods by "The Carb Shop") to Little Rock for installation on the /6 for more experimentation as regards the A/F ratio.
Maybe it will put some fuel in there...:coffee2:
What is the necessity for vent tube extension?
srixon4406
TURBO TOAD
OK bill first I'd change the brpv ref point to the rear of the carb hat were the flow of the charge will follow the contour of the carb hat. And that's were your going to receive your best signal.
Remember that's your enrichment circuit that's normal controlled via vacuum, now it needs the the best signal possible, there's guys running a line straight to the compressor housing of the turbo and not using hat pressure. Also that's how the crutch works but you plumb a outside air source to the brpv cavity. Because there reports of internal pressure in the carb shutting the brpv under higher boost application so that's why thee CRUTCH was introduced.
HSAB is high speed air bleeds, if you are looking down at the top of your carb and if you have adjustable bleedsscrews there the inner bleeds like in the pic I posted a couple days ago.
Vent tube extention are easy to make and all you need is a piece of 5/16 brakeline about three feet long and cut it into two pieces and cut and bend to fit like this
You will need to pull the short vent tubes out and us some epoxy resin to set the new ones into place
Remember that's your enrichment circuit that's normal controlled via vacuum, now it needs the the best signal possible, there's guys running a line straight to the compressor housing of the turbo and not using hat pressure. Also that's how the crutch works but you plumb a outside air source to the brpv cavity. Because there reports of internal pressure in the carb shutting the brpv under higher boost application so that's why thee CRUTCH was introduced.
HSAB is high speed air bleeds, if you are looking down at the top of your carb and if you have adjustable bleedsscrews there the inner bleeds like in the pic I posted a couple days ago.
Vent tube extention are easy to make and all you need is a piece of 5/16 brakeline about three feet long and cut it into two pieces and cut and bend to fit like this
You will need to pull the short vent tubes out and us some epoxy resin to set the new ones into place
OK bill first I'd change the brpv ref point to the rear of the carb hat were the flow of the charge will follow the contour of the carb hat. And that's were your going to receive your best signal.
Vent tube extention are easy to make and all you need is a piece of 5/16 brakeline about three feet long and cut it into two pieces and cut and bend to fit like this
You will need to pull the short vent tubes out and us some epoxy resin to set the new ones into place
Now all I need to know is the purpose of these extensions and where they vent to; your picture just shows them ending in ambient air, and I know that's not right.
srixon4406
TURBO TOAD
Bill the extension are to equalize fuel bowl pressure. I'm sure your aware that the fuel supply to the carb is a must and it all starts in the fuel bowls if you have a float set to high and a/F ratio might read fat or rich or you may even over flow the vent tubes, and if the floats are set to low chances are you will starve the motor of fuel and read lean a/F ratio.
Now with blow thru carbs sometimes there's inconsistencies in flow in a carb hat so the stock vent tubes don't always see equal pressure by bring them up into the mouth of the hat it keeps that positive pressure on the fuel bowls.
I hope this explanation helps here's a pic
Bill I was also thinking have you and Freddie thought about unhooking the secondaries and trying to tune on the primaries only? Ryan started this way and ran low 11's if you do the math for cfm calculations a slant calls for around 400 cfm that's only Alittle more then half your 750 its just a thought.
Aaron
Bill the extension are to equalize fuel bowl pressure. I'm sure your aware that the fuel supply to the carb is a must and it all starts in the fuel bowls if you have a float set to high and a/F ratio might read fat or rich or you may even over flow the vent tubes, and if the floats are set to low chances are you will starve the motor of fuel and read lean a/F ratio.
Now with blow thru carbs sometimes there's inconsistencies in flow in a carb hat so the stock vent tubes don't always see equal pressure by bring them up into the mouth of the hat it keeps that positive pressure on the fuel bowls.
I hope this explanation helps here's a pic
Bill I was also thinking have you and Freddie thought about unhooking the secondaries and trying to tune on the primaries only? Ryan started this way and ran low 11's if you do the math for cfm calculations a slant calls for around 400 cfm that's only Alittle more then half your 750 its just a thought.
Aaron
Aaron,
Thanks for the picture and explanation. Now, I understand, (I think.)
I swapped carbs, putting the blow-thru carb off my 360 on this slant six as an experiment and under full throttle, it was a lot richer than the other (original) carb, showing A/F ratios of 14:1... that was as lean as it got.
I know that the desired A/F ratio under full throttle is more like 11:1, so tomorrow or the next time I get a chance to work on it, some "two steps richer" jets are going into the primaries and the secondaries. I am sure that will help some. If it's not enough to get us into the "good" 11:1 range, I'll increase the jet sizes some more to see if that helps.
General driveability was good (generally, 12:1) with this carb, so we're going to go with it for a few times around the block and see if we can get the A/F ratio where we want it by enlarging the main metering jets.
This carb (this one from the Carb Shop) has a small-diameter steel-braided hose that is plumbed into the top of the float bowl extensions which can only be there to equalize float bowl pressure, I would think. Having that hose already installed, I am wondering... we may not need the vent extensions you described; what do you think?
Oh, btw, this carb does NOT have a BRPV. Just a stock one, with Carb Shop mods.
We might try disconnecting the secondary butterfly linkage just to see how it affects performance. We might need a 600cfm Holley 4-bbl, but, Gerry, up at the G-Pop Shop said that he thinks this engine NEEDS a 750 to generate the 500HP we are looking for. We took all of the turbo mechanisms (blower, waste gate, hat, carb, intercooler, meth injector, etc.) to him for his inspection and advice.
He has a LOT of experience with these things, so when he talks, I tend to listen, but anybody can be wrong...I think he may have had a lot to do with Ryan's engine build; not sure.
Today we made 8 pounds of boost out on the hiway, after filling the fuel cell up with some 110-octane VP fuel, ($10.00/gal.!) and putting pure meth in the Boost Cooler. I am not sure, but our waste gate may be set on 8 psi, and that may be the reason the boost didn't climb higher. It got up to 8 in a hurry...
That waste gate adjustment will be the next thing we check, after the carb re-jetting. We don't have the mechanical boost controller installed into the system, yet, but we will...
FYI, this car will see VERY LITTLE street driving, with the great bulk of its miles coming on the drag strip, so "driveability" and gas mileage are not important to us; output IS.
Thanks for all your help and advice; we're gettin' there.... that 8 pounds of boost felt pretty good on the seat on the pants... :blob:
:wack:
Lookin' for 20...
srixon4406
TURBO TOAD
That's great your making progress Bill keep at it. I have a concern about you running the other carb with the stock PV. The stock PV is only good to run around 12 psi of boost and after that the boost pressure and the increased fuel pressure seen in the fuel bowls forces the stock PV closed and if it happens while your under load bad things can happen
Just my 2 cents Bill all info given is strictly from what I've read from real world experience
Just my 2 cents Bill all info given is strictly from what I've read from real world experience
player1up
Well-Known Member
I don't chime in much, as I have about the most rigged turbo build ever, but I have to agree with the vent tube extensions. Now I'm only running a 350 Holley 2bbl and 7 psi of boost, but I couldn't get mine out of the 14 range under boost without the extension ( or without going to a 80 or 90 something jet ) . I went from 14.1 to 11.5 with just the vent extension installed. Oh, and if the float level is too high....your wideband wont be able to read that rich 
I am curious as to what YOU think of this pressure-equalization setup on this Carb Shop 750 blow thru carb.
Will it do the same thing as the modified vent extension you are talking about?
I am curious because the poster who talks about his A/F ratio being limited to 14:1 before he installed these extensions sounds exactly like our experience. I'd like to know what you think.
I hear you on the OEM-typr power valve, but we haven't YET, gotten anywhere near 14 pounds of boost (but, we will.)
If I have to install a C-02 crutch I will...
Right now, we have 8 pounds of boost, but our A/F ratio is at 14 under full throttl=e and boost. I know that needs to be 11:1.
Saturday, I will again experiment, this time with totally blocking the secondary high speed air bleeds to see if that will fatten it up a little. Gonna stuff some round toothpicks in the secondary high speed air bleeds to see what happens.
I'll let you know.
srixon4406
TURBO TOAD
Bill im not a 100% sure about the difference between the vent tube extension and the way your carb is setup. But I believe the idea behind the vent tube extension is to bring the opening of the vent tubes up into the mouth of the carb hat is so they will see a clean air flow. Alot of what I've read guys report kind of like a swirling affect in some carb hats and this will eliminate that. You can also try and turn the ones in the carb in relation to the position of the mouth of the hat. This theory was derived from aviation technology that is called Pitot tubes I think that's how it's spelled.
Have you tried to get ahold of Shaker?
As fair as my valiant goes it looks like we have some nice weather headed our way this weekend upwards of 60 degrees so maybe I'll get some more testing in myself I have to get some new plugs installed before I do anything though. I did some tuning yesterday and im curious to see the results. Maybe I can get the wife out with the video recorder and get some video.
Have you tried to get ahold of Shaker?
As fair as my valiant goes it looks like we have some nice weather headed our way this weekend upwards of 60 degrees so maybe I'll get some more testing in myself I have to get some new plugs installed before I do anything though. I did some tuning yesterday and im curious to see the results. Maybe I can get the wife out with the video recorder and get some video.
I have no time at th moment to write a response, but I'll get back to you later today.
Thanks for the help!:cheers:
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