Need Jetting Advice
 

Ok guys I am looking for some help on dialing in my single 1050 Dominator. The carb has been boost referenced and the current jetting is 92 for the primary's and 92 for the secondarys. She is sitting on top of a TBS 250 Blower with a 540ci stroker. As I start giving her stick she she lights up and wants to run hard, but around 4100 she starts laying down. I know I have a problem with my fuel pickup being a 3/8" tube and will have to address it with 1/2" pickup, but that should only affect longer run times. I know I have enough fuel volume to handle shorter runs the fuel pressure barely drops below 8.0 lbs when i give her a full stick of throttle.

Blownhavasu and myself took her out yesterday the air was a mild 102 water temp was a cool 67 we cruised for a while letting the oil temp warm up and when she was ready we ran her hard and produced around 4lbs of boost till she started laying down . We immediately pulled a plug and the ground strap showed heat, however the plug looked lean. We built this motor to run around 5600rpm with 750hp. I know this monster wants to run you can feel it and hear it. What do you guys think the jetting should be?

We think we should start by jumping the secondary's to 98's and then adjusting accordingly. Unfortunately I will not be at the boat till next Friday and would like to get a variety of jets. Can someone tell me where I can purchase them and get them delivered to California by Thursday.

Thanks.

Re: Need Jetting Advice
 

ttt

Re: Need Jetting Advice
 

Just guessing, I would say it's lean. My 540's with 1050 Holley uses 90 primary, 92 secondary.

PatriYacht
 

Is your 540 blown with a single dominator?

Re: Need Jetting Advice
 

The fuel pick-up is of major importance!!! I had my fuel tanks replaced and experienced the same "laying down" you did, and lost 500 rpm. I took the pick-ups from the old tanks and sure enough I was back up to 5300 rpm and motors ran great.

My motors are procharged 502s with head porting, running 5+ lbs of boost. My jetting is 78 primary, 96 secondary

Hope this helps

Re: Need Jetting Advice
 

Call Dean Nickerson.

Re: Need Jetting Advice
 

No n/a. That's why I'm guessing you're lean. Summit and Jegs sell jet assortments on a card. You get a pair of each size from 80 to 90, 90 to 100 etc. They could get them to you on time, even over night.

Re: Need Jetting Advice
 

Ran her again this weekend and changed the jets in the secondarys to 98's and i gained 10% i made it to 5000 rpm's and she started to lay down again. We looked at the plugs and she just was starting to creat some heat, so I changed the primarys to 94's. Ran her again and she once again started to laydown at around 4200.

Changed the plugs went back to the primary's at 92 and changed the secondarys to 96's. No gain was seen and she started to lay down at 4100.

My question is when i first changed the secondary's to 98's i saw an increase in performance and she started to gain some heat which was good. But when i changed the primary's to a bigger jet she stated to lay down. I realize that becuase this is a boat and we idle at low rpms's we need to have smaller jets in the primarys so we do not foul plugs. How do we feed the right amount of fuel to the motor with what jet combinations on a single blown 540?

I originally purchased the carb from CPPerformance and gave them my engine requirements, they sent the carb to Blake Carbureation in NC. I spoke with these people and they are the nicest people, but informed me that they mostly do race cars and until recently have done a whole lot of carbs for boats. That would explain why it came with 92's in both the primary's and secondary's. That would be the perfect setup for a race car.

Anyone have Dean Nickerson's number. I am going on vacation this Friday and will have an entire 10 days to tune this sucker, so any advice will definitely be appreciated. I am going to lake shasta in Northern California and i believe the elevation will be around 11,000 i guess. I usually boat at 500 ft above sea level in Lake Havasu AZ.

PatriYacht thanks for the 411 on getting the jets.

PureEnergy, I am curious when you were losing RPM's did you fuel pressure drop, mine is still showing 8lbs.

thanks guys.

Re: Need Jetting Advice
 

I think you are wasting your time with jetting until you fix the fuel supply side. I had a drag boat that had the same problem. I was up to 140's and still flattened out.I went up to 9/16 line without any success. Finally was told to open up the air vent on the feul tank and the problem went away and I went down to 95's.This was in an 11 second 1/4 mile with a very light flat bottom (no hull drag). Fix your pick up and check your tank vent or you will be doing all the work again.

Re: Need Jetting Advice
 

My fuel pressure did not drop! It was very frustrating to diagnose.

Re: Need Jetting Advice
 

like LLyod Said
The most important thing overlooked in adding blowers is fuel.
You are wasting your time jetting until you get proper fuel to the carb.
I just went through the similar situation. I replaced my tubes with 1/2
inch. I also had to run returns and bigger vents. If I remove the fuel feeds to the carbs I fill a 1 gallon container in less then 13 seconds. The fact that your only running one carb actually requires more then someone running two carbs per engine. I have fuel pressure gauges on dash and didnt see them
drop either. But it was still starving for fuel.

Good luck
Remember lean is mean.
Gerry

Re: Need Jetting Advice
 

I think you guys have convinced me that it is a fuel supply problem. I can easily get to my fuel tank and vent tube. What precautions must I make prior to removing and replacing the tube. Is there any special tube i need to get other than 1/2 tube.

What steps should i take, I just towed the boat 300 miles from my lake house and it still has 3/4 tank. The gauge was showing empty or barely moving so before we tested we dropped another 25 gallons, then the damn gauge popped back to life and i was at full tank again.

I would like to tackle this project prior to leaving, any advice.

Thanks again.

Re: Need Jetting Advice
 

I was afraid you were going to say that!

Re: Need Jetting Advice
 

I have the standard 3/8 npt 90 degree brass fitting coming out of the fuel tank. I will post some pics tommorow.

Re: Need Jetting Advice
 

My fuel pressure did not show a drop on the gage either.

Re: Need Jetting Advice
 

This is what I ended up doing. I have 3/8npt female welded bungs in the tank.The restrictive 3/8 alumminum tubes slid into these with a 3/8 brass
90 on the top. I removed and tossed these tubes and brass 90,s. I went to the local hobby shop and puchased 15/32 thinwall brass tubes.
these are 1/32 less then 1/2 inch id. They fit perfecly in a double male 3/8
npt nipple. I "mean perfect" I measured the correct depth off old tubes.
allowing for the threads on the nipple. I cut a 45 degree on the bottom of the new brass tubes and solderd the nipple on top. Dropped them in the 3/8npt tank bungs. Threaded a non restrictive brass elbow on the top then went with aeromotive # 10 pipe adapters to the # 10 hose. then to wix
high flow filter heads 1/2 npt.

This procedure allowed me to increase the pickup tubes without any cutting or drilling.
If you have the same on your tank dont hesitate to call me ill walk you through it.
Hope this helps
Gerry
401-255-5242

Re: Need Jetting Advice
 

I might just be doing that, I am on the west coast what timezone are you located?

Anyway here are some pics as promissed of my fuel system starting at the tank.

Re: Need Jetting Advice
 

img4 shows the fuel separator after the fuel pump, and 5 shows you the level of the fuel line to the pump if you look real close.

Thanks guys.

Hey Blownhavasu, you ready to work tonight?

Re: Need Jetting Advice
 

This is the baby that is causing me and BlownHavasu so much greif and the sad part is that we have our wifes with us on the weekends so they want to play and we want to dial in this engine!

Thanks again OSO brothers.

Re: Need Jetting Advice
 

Im on the east coast its 2:00 pm here Are those 3/8 npt threaded in tank???

Re: Need Jetting Advice
 

Yes, before i put the adapter npt into the brass fitting a 3/8 nipple came out and it had the 3/8 diameter.

Re: Need Jetting Advice
 

this is the restricted setup I had. This threaded into the 3/8 female bung
that is welded to the top of my tank.

I tossed it !!

Re: Need Jetting Advice
 

this 3/8 nipple has a inside diamiter of .495 the brass tube fits perfectly
into this with a 32nd under 1/2 inch id. Go to a hobby shop and get the (15/32) correct lenths then solder it into this nipple this will drop in and thread into your 3/8 female tank then thread the appropriate adapter to the top. I cannot show the thinwall tubing cause there now in my tank.
Dont forget to cut the bottom of tube to a 45 incase your off on your depth
measurement.

Re: Need Jetting Advice
 

Caveman thanks I will let you know what i find tonight.