View Full Version : help with yaw carb

03-07-2002, 01:24 PM
ok, im screwed, I had to go and buy a 2nd set of regulators, pressure gauge, fuel pump, now im into those three items for 500 dollars,
oh well,live and learn
So, I have a superbitchin paul yaw carb, minus his regulator, pressure gauge, fuel pump, without any clue as to what to do with it or a baseline setting to start with, I havnt even figured out where the fuel mixture screw is.
have 8 days till drivers school, can anyone help?

Dave Damouth
03-07-2002, 02:06 PM
Step 1: bolt on the carb.
Step 2: What do you have on the car right now for a regulator, pump, and did you put a return line in the fuel cell?

We'll get you there. Do you want to start the thread back at mazspeed or stay here?

03-07-2002, 03:57 PM
thanks, heres fine.
ok everything is done, ready to start the motor,
I have the holly regulator and a auto meter fuel pressure gauge, but the first number on the gauge is 3 pounds so the lowest i can read is 2.1 psi, and the return line is going to a tee between the tank and pump as we discussed before and a new stock fuel pump, and the backflow valve is in stock location.
has two inline fuel filters one between tank and fuel pump and another between reg and carb.
all are on the car and hooked up, will flip on pump and check for leaks this afternoon pst
thanks Dave, I was getting worried.

[This message has been edited by 7'sRracing (edited March 07, 2002).]

Dave Damouth
03-07-2002, 04:43 PM
Ok, Lets get it started. I don't know what the deal is going to be with the T loop, but lets assume it will be fine and forget about it for now. I'm a little worried about the filter between the reg and carb, so at some point in the next few days, I'd move the filter to before the regulator. Is the regulator near the carb?

The stock fuel pump is scaring me a little also. It will get you through driver school, but you'll probably want to go to a bigger pump when you start really leaning on it. If you want to go to a bigger pump, Summit racing et.al. can overnight one to you. In the mean time, lets sort out what you've got. Let me know if you need a part number for a carter pump. Also, are you certain which Holley regulator you've got? Holley's standard regulator is around 3-7 psi, and the low pressure one is 1-4 psi.

If everything's hooked up, leave the air filter off and throw a brick or something on the gas pedal, have someone hold it, whatever. Do this with the engine off. Please. Look down the primary (smaller) venturi's and make sure the throttle plates are straight up and down. If they are not, consider whether or not you need to adjust the throttle cable until the throttle plates open all the way. It's adjusted with the lock nut you tightened when you put the cable on the carb bracket. Also make certain it shuts all the way when you let off the pedal. There is also a pedal travel limiter on the firewall if you get desperate, but you usually don't need to mess with it. While the throttle plates are open, make sure you can fully open the back ones to straight up and down by rotating the linkage manually.

If you think the throttles are opening fully and everything is bolted down tight, get the pump to fill the carb and fire it up. Let it warm up, make sure nothing leaks. Check the level in the float bowls, it should be just below the center mark in the windows. If the idle needs to be adjusted, its the screw hidden down on the linkage assembly at the back of the carb. Don't worry about jetting, fuel pressure, ect. until you get it to idle good, no leaks, float levels. If one of the float bowls is overfilling and it tries to flood at idle, don't worry. The needles sometimes seat poorly right after UPS gets done abusing it. Try tapping on the bowl lightly, keep the revs up with your right foot, let it run for a few minutes and then recheck. Worst case, take the float bowl cover off, make sure nothing is in the seat, blow off the needle, reseat and try again. sometimes they work fine, sometimes you need to talk nice to them.

When you get done with all that, hopefully you'll be feeling better due to the fact it at least runs. Let me know which regulator you have and I'll give you an idea of what to do next. The gauge you've got is probably going to be accurate to +or- 3psi at the range you're looking for, so if its not already on the car don't worry about it.

Have fun! The stressful part shouldn't come until you practice starts. And assuming this is your IT car, do you have the steering lock drilled, cage is right, belts and helmet dates are ok?

03-07-2002, 05:40 PM
well guess what just came in the mail, now i have two of everything, spares you might say.
yes its my ITA car, stock ports and all(should be)legal.
ok, ill do everything you said, do i hook up pauls fuel pressure gauge on the return or on the regulator?, change the spring in the holly regulator as that is the only difference between the two, move the filter to before the regulator(makes sense) and get back with you noonish your time tommorow.
thanks Dave, I REALLY appreciate this.

Dave Damouth
03-07-2002, 06:31 PM
Start by just Teeing Pauls gauge into the supply line, temporary install. Use it to dial in 2 psi or thereabouts, check what your cheapy gauge says(probably zero). Once you get it happy, gently pack Pauls gauge away in your tool box, well protected. If you ever need to verify or change pressure, put the gauge back on. Mine uses rubber hose to the carb still, so I leave 2 chunks of hose and a Tee attached to the gauge, pull it out when I need it. Did a big carter pump come in the mail also? There is a place on the frame rail that the bracket can attach to that will let you mount it upright and still keep it out of harms way. It needs to mount upright. The stock pump wire harness will supply enough juice to run it without popping fuses or anything, at least on mine.

03-07-2002, 09:58 PM
yes the carter pump came as well, im going to get it started before i install the new pump since everything is already hooked up back there, i have never heard this motor run yet so it would be reasuring to know if it still has working seals and all, my new motor is still in pieces and will go together after the school before my first race.

03-08-2002, 10:29 PM
IT LIVES!!!!!!!!!
started right up, a few problems to work out, front float is stuck, amp meter showing no charge, couple small water leaks but IM STOKED.
5 days left to debug everything, got a trailer lined up, gotta get back at it.
thanks Dave, im about the happyest guy in socal right now.

Daryl Brightwell
ITA Mazda #90

03-08-2002, 10:41 PM
Daryl, congrats on the near completion for school. http://Forums.ImprovedTouring.com/it/cool.gif It's always nice to enjoy the journey (the prep) & the event (the race weekend). http://Forums.ImprovedTouring.com/it/smile.gif

Have fun


Dave Damouth
03-08-2002, 11:07 PM
I'll keep checking back this weekend. email me a phone number at home if you run into a problem.

[email protected]

03-09-2002, 02:26 PM
thanks Dave and Dave, I have some little stuff to do today to finnish the safty requirements, drill and bolt down lap belts per GCR, bolt bumpers on, retape windsheild, put 20 more screws into my front spoiler(only has 4 now), add a screen in front of oil cooler/radiator.
tommorow ill fix the float and set fuel pressure and check timing.
what should I set the timing to?
and what exactly should the fuel pressure be set at?

03-09-2002, 03:51 PM
im having trouble with GCR wording on lap belt mounting, walked up and down my culdesac asking all my neibors (10 people in all,pilots, RN's, school teachers,) if they understood this sentence and nary a one could say WTF it meant.

"3.0 min/max to centerline of lap belt at seat back/bottom junction, lap belt should continue in a strait line to anchorage"

while everyone clearly understood this
"lap belt should continue in a strait line to anchorage"

virtually no one understood this
"3.0 min/max to centerline of lap belt at seat back/bottom junction"

does it mean the bolt must be 3.0 inches, no less,or no more from the junction?
when I sit in my seat and put the lap belt in a strait line it should anchor right at the junction, im stuck.
for such a important and common(in all classes) rule you would think scca would speak english.

[This message has been edited by 7'sRracing (edited March 09, 2002).]

Dave Damouth
03-09-2002, 07:45 PM
I don't pretend to speak for the person that labelled that drawing, but I interpreted it to mean that the centerline on the lap belt can be up to +or- 3 inches from the seat back/bottom junction. If you have an aluminum seat with the bevelled juction, good luck determining where that juction is....

What I think they're trying to get you to do is prevent dumping of the belts. If the belt comes down off your lap, thru the cutout in the seat, and to the floor without hinderance, life is good. If the belts are mounted too far back, they end up taking the load of an impact on the edge of the belt where it rubs against the seat cutout.

Use really big beefy steel plates under the floorboard. Don't try to use the stock seat belt mounting points, in most seats they are too far back and won't work.

Did you remember to drill the steering lock? Directions are in the facts section at mazspeed.

Kill switch done?

BTW, once you get the float settled down and the idle set, you're done with the carb for now. Take a printed set of tuning instructions and your spare jets in case you get really bored, but you won't be thinking about jetting much. It will run fine....

Dave Damouth
03-09-2002, 07:55 PM
Fuel pressure 2 psi.
24 degrees leading, 16 degrees trailing. If you have vacuum and centrifugal advance still, loose the vacuum and get the rpms up over 4500 before setting timing. Set the leading to 24, and lock the distributor down. If the trailing is way off, you adjust it inside the distributor. Close counts on trailing for now.

03-09-2002, 08:10 PM
Daryl, Dave could very well be correct on the 3.0 min/max interpertation.

Install the harness per the manufactures instructions.... Not a slam Dave but I dought the SCCA knows more about installing the harness than the manufacture ???????

Daryl, call 1-414-453-0929 if ya would like to talk over an issue. Leave a messag & I will call you back.

Have Fun


Dave Damouth
03-11-2002, 12:10 PM
Getting stressed yet Daryl?

Focus on safety requirements. When you get through school, we'll start the thread on everyone's nightmare week before driver school stories.

Keep after it! Its too nice of a car to sit in the driveway.

03-11-2002, 04:11 PM
boy howdy http://Forums.ImprovedTouring.com/it/smile.gif
yes just a few little things for today, done with the lap belts, you could hang a CAT D9 from them, sandwitched the floor with 1/4" x 4" steel plates and bolted them together with 5/16th bolts, belt eye plate has a 1/2" thread grade 8 with a lock washer and a stove nut.
the emergency kill was done last week, have a halon system as well as a 2# dry with a quick release.
today im doing winshield clips, changing fuel pump and setting fuel pressure, adding a screen to spoiler opening and changing altinator.
tommorow im taking it out to buttonwillow raceway for a chassis dyno tuneup at 7's only racing.
i think my ass end is too low so im going to put some spacers in the rear springs tommorow.
hell i dont have time to be nervous about school, ill sweat that on the way up there thursday.

03-11-2002, 04:34 PM
:i think my ass end is too low so im going to put some spacers in the rear springs tommorow.:

Daryl, hustle tends to make the a$$ hang low but why are you putting spacers in the car to lift your a$$ ? http://Forums.ImprovedTouring.com/it/tongue.gif

Enjoy your weekend


Dave Damouth
03-11-2002, 05:19 PM
Make sure you take any spare jets and air bleeds you have to 7's with you, and make sure they know the air bleeds are adjustable.

If you have a tri-link on the rear, think twice before raising it. I spent an 8 lap qualifying race hanging on for dear life because I wanted to see what a 1/2" rear ride height would do. Not fun. If it's a standard 4 link, higher is probably better.

Sounds like you're way ahead of the game. Most of us would be trying to get the engine back in right now.....

Speed Raycer
03-11-2002, 08:29 PM
<font face=\"Verdana, Arial\" size=\"2\">Most of us would be trying to get the engine back in right now..... </font>

That's no kidding! We just got the engine fired yesterday in our ITA 7... 18 days til my 2nd drivers school, and we still need paint, exhaust, seatbelts, cage padding, regulator and a bunch of other stuff, not the least of which is fixing our oil cooler which cracked around the lower fitting yesterday while tring to fire it up http://Forums.ImprovedTouring.com/it/frown.gif

It's not what you build... it's how you build it
http://home.swbell.net/srhea66/AllThreeProjectsRealSmall.jpg (http://www.angelfire.com/mo2/radrodder)

Izzy's Custom Cages (http://www.izzyscustomcages.com)

[This message has been edited by Speed Raycer (edited February 27, 2004).]

03-12-2002, 03:37 AM
no time for butt draggin David, 60 hrs to transit time, im a little worried about decible levels though, ran it with pass door open(which is where exhaust exits) and my right ear still hurts.
Dave, I havnt had time to install g-force tri-link( gotta pull the rear end for top bracket welding) so I think I should raise the ass end up a bit or it might be a handful.
yes i dug out my jets and bleeds and ill let ya know how it dynos out.

Daryl Brightwell
ITA Mazda #90

Dave Damouth
03-12-2002, 12:04 PM
Daryl- Assuming its a Dynojet you're using, take a spare floppy with you. Ask the operator to copy the runfiles onto the floppy. Then you can use the viewer from the Dynojet website to compare future runs, other peoples runs, ect. If you don't get it this time, you can always stop by some other time and get a copy.

Don't worry as much about peak as range. You need to fill out the top end as much as possible. 7900 shift point drops you back to 5600. If you get it close, the power at 7900 will be about the same as 5600, which will only be 4-5 hp less than peak.

Air/fuel ratio is going to start going rich at around 7200, and will just keep getting richer until you shift. This is normal, don't worry about it. You won't get rid of it with jetting, so don't deadend the session chasing after it.

Higher in the rear is safer until you get the rest of the suspension in.

03-12-2002, 07:53 PM
Brother D!

I came back for a quick visit. Actually, I put a post about a cheap hot lap system for sale on the FFU (Formula Ford Underground)

Where's your school at that you are worried about the dB limit?

Re: rear ride height: Measure the distance from the highest point of your wheel opening to the bottom of your rear wheel (not ground). If you want to e-mail me off forum...I'll let you know what my set-up was. No guarantees, but it worked for me. With basic ground control suspension and an IT legal motor I ran official times at Willow and Buttonwillow less than 1 second off of Ron Haase's ITA lap records.
1.36.9 at Willow and 2.06.2 at Buttonwillow.

-Daryl DeArman
edited because I can't spell worth a she-ott

[This message has been edited by Quickshoe (edited March 13, 2002).]