Went to the dyno yesterday.

[jeffwiebe]

We were digging most of the day for a popping sound. Found out it was a lean pop. We finally got to make some pulls after jetting up 14 sizes. It made the most power at 41* timing. Its a 468 with BB2 Extra heads, 13-1, 722 lift roller cam. We used a 1150 Dominator with 99 jets, no power valves and its still lean according to the oporator. It made 679 hp at 6800 rpm. The dyno oporator told me i should have a 950 carb. This was my first time at a dyno so really don't know what ideal air fuel should be. It started at 14.5 and ended up at 12.8. Were not done yet, we only made 5 pulls. I'm going back tomorrow to try and get it to 700hp. Also there is no windage tray in the motor and the oil pressure would jump around. I'm thinking a tray would free up some hp. It also has a vac pump pulling 6" at 7000 rpm. Any thaughts from the pro's ?

[sunsation540]

please tell me that the cam in the 468 is the lunati 722 308/316 no the 316/320 ? also say super sucker spacer and what intake is on it? loosen lash and ck the compression if lash is tighter than .028

[jeffwiebe]

Cam is Lunati 722/722 lift, advertised duration 312in/320ex installed at 106. It is a Dart 4150 intake with Super Sucker below carb and reducer spacer at the intake. We had lash at 26 and backed them off to 30. How the heck did you know it had a Super Sucker on it??? We did a leak down, it was 10-20%, cranking compression was even on all at 175psi. This is a new motor so i'm thinking the leak down should get better after a few more pulls. Is the Super Sucker giving us the lean air/fuel?

[sunsation540]

jeff, what does this go in dragster door car??/

[jeffwiebe]

Its going in a back half 69 Chevelle. We made another ten pulls last night trying different carbs and spacers. There was no gain going to a 4150 carb as the oporator suggested. The super sucker made 8hp and 5 ft pounds torque over a straight through spacer. We did gain 8hp with #24 center air bleeds. I don't know what was in there, can't see any numbers on them. Air/fuel went down to 12.14 and peak hp jumped to 6900 rpm from 6800rpm. We didn't reach our goal of 700hp but i think with a windage tray it should be close.

[fourtenposi]

Was that 1150 you tried a 3 circuit carb, Heard alot of people have issues with those carb never being able to give it enough fuel. This thread details why there is an issue. I have heard that those with this issue, can actually take out the jets and it will still be lean.

http://motorsportsvillage.com/forum/vie ... php?t=3283

If that engine is truely making that kind of power, it will like a dominator better. If you can, hook up a vacuum gauge so you can read the plenum vacuum. If its reading over 1.25 you are leaving power on the table.

Sounds pretty stout so far. Good luck

[sunsation540]

you can find the leaner mid and richer upper by making the IAB larger or take it out compleatley this will pull more to the top and clean up the middle...i took out the intermed bleeds on a 9375 on a 496 made 11hp more when removed, same jet...this is not your problem , the cam you have is way to big!!! turn that little 468, 8500 and it will pick up hp.. that cam is for a light car, super comp or super gas =2300.-2600 lb car no torque required.. with a larger head smaller displacment small bore it has no velocity, not pulling enough air to make a strong signal.... thats also why it wants to much timing, cam overlap killing cranking compression and cylinder filling...i really hope your chevelle has a 3 speed trans and a 4.88 gear it will run in the mid to upper 10.s not to be a dick or too much of one, that cam is over 20years old, it has a place in a 540 SC dragster,,in the past 5 years there have been way to many improvments not to take advantage of.them .Sorry

[jeffwiebe]

I know the cam is old and could use something more current. Last year with iron heads the car ran 9.96 135mph waighing in at 3100lbs shifting at 7400 and going through at 7400 with 5.13 gears, and it had a broken sprag. This year the car is 2800 lbs with me in it and the only change to the motor is the Brodix heads and a freshion up. I'm hoping for mid 9's, and i just ordered a new converter. One of the reasons a wanted to go to the dyno was to get the right converter.
The carb is a Carb Shop 3 circuit 1150. I had problems last year at part throttle on the return road and in the pits. It was loading up, burbling and farting. I'm no carb expert so i had a buddy look at it. Whatever he did worked and its working fine now. Here's a pic from last year with the iron heads.

[sunsation540]

the cam you have is way to big!!! turn that little 468, 8500 and it will pick up hp.. that cam is for a light car, super comp or super gas =2300.-2600 lb car no torque required.. @3100 and with a 5.13 it will do the job but i still feel you left more on the table....if it takes 7500 to pull the car through the traps why didn't you dyno it to 7600??? what oil pan are you running?? and it take around 600+ hp @ 3100 to go 135mph you may still see some fair gains>.HELL you got a post car ME TOO.. not to many of these turds around>>>

[jeffwiebe]

My first time at a dyno so i just went with the flow. I did tell him it went through at 7400 rpm. I don't know why he stopped the pull at 7000 rpm. The hp stopped climbing at 6900 rpm and the torque peaked at 5800 rpm. Maybe thats why he stopped it at 7000 rpm. If i picked up hp from last year, and with the car being lighter it will rev higher at the top end now. I'm thinking around 7600 rpm.
I'm running an old Hamberger pan with trap door, no kick out and no tray. I have a Milodon tray coming and i'll use the same pan this year.

[sunsation540]

if you would have raised the rpm to 72-7400 i bet you would have gotten that 700hp hard to not rev past 7 and shut the throttle all at once if you know what i mean..by 6900 the throtle was already closing!! good luck let us know how it goes,,,

[jmarkaudio]

Was that 1150 you tried a 3 circuit carb, Heard alot of people have issues with those carb never being able to give it enough fuel. This thread details why there is an issue. I have heard that those with this issue, can actually take out the jets and it will still be lean.

http://motorsportsvillage.com/forum/vie ... php?t=3283

If that engine is truely making that kind of power, it will like a dominator better. If you can, hook up a vacuum gauge so you can read the plenum vacuum. If its reading over 1.25 you are leaving power on the table

Bill beat me to this, he is correct that some factory Dominators will run lean because the idle tubes in the mainwells restrict the fuel. Usually the bigger the engine or more air it is capable of pulling in, the harder it is to get enough fuel metered in to match. An easy test would be to pull the jets completely out, if it is still not rich enough you have found the issue. You can replace the metering blocks with 3 circuit blocks from BLP that don't have the restriction because the idle circuit is relocated, however the 2 circuit conversion at MSV Bill mentioned would be a better solution. Here is a picture of what the issue is.

[jeffwiebe]

Thanks for the tip jmarkaudio. I took the dyno sheets to an engine builder that i know very well. He figured that the motor is low on compression. With the pistons i'm running with 44cc domes, 123cc chambers and 0 deck its only 10-1 ish compression . That would explain the 175psi cranking compression. It should be at least 230psi. The BB2 Extra comes with 119cc chambers but i had to take out a bunch in the chambers to clearence them for the pistons. I'm taking the heads there today to see if they can be milled to 110cc and still clear the piston. According to him that would bump it up to 13.5-1 compression and give me over 700hp where it should be. I wish i'd known this before i went to the dyno. .

[jeffwiebe]

I made some runs on the weekend. After i figured the converter doesn't like to be flashed on the start. (i think its a bit tight stalling at 5200) I took out the starting line chip and it 60' 1.38 and ran 9.82 at 136 mph. This was with last years tires and a really cold track. I think it will improve with some fresh tires and better conditions. I'm very happy though. Not bad for a little 468.