Ran my 66 chevelle for the first time. Have a few bugs to work out.First problem to sort out is, the car pulls hard at launch and second gear. When I get into 3rd gear the car lays right down and then picks up and pulls real hard for the last 100 feet of the run. :confused:Best run was a 12.47 E.T., 107 mph. 177 60 ft.
Motor is a 468, 10.38 to 1, Ultradyne solid cam, 251,259 at .50 600 intake,625 exhaust lift on 108 L/C. Mild ported oval heads, Holly strip dominator, with a Barry grant preped holly h/p flowing 1080 cfm. Running 1/2" line from tank to carb, with a 172 gph carter mecanical pump.Need your guys help with this. Other imfo, 3500 stall turbo 350 trans, 12=bolt posi 4:11s. Dick Miller complete rear supension with anti body roll bar. 90/10 front shock. full roll cage. 3900# with driver.

sorry for the long post, but I need some help here and though I would answer some of the questions I was sure would comeup.

Looking to go 11.50/11.60, Is this possibly with this combo?


Thanks guys, graemlins/hurray.gif any help I can get is really welcome


first

what type of ignition are you using? hei stock coils run out of steam at high rpms,if you have a stock hei coil you should replace it with a high output msd or accel super coil.

I run a modified HEI with locked out timing and a 50,000 volt coil and shift at 6200.

when you say it lays down, does it feel like a "bog" or do the RPMS really drop?

I would look at adding an electric pump out back to help move the fuel to the mech. pump, or go to an elec. pump totally. I have read that big fuel lines hold a lot of gas, and it can "stall" in the line due to the forces of accelleration. (thats working against the mech. pump).The fuel is heavy, and since it has to pull fuel all the way to the front, the pump just can't keep up.
Your combo should run easy mid 11s, so you are losing a full second of E.T. That could give the pump enough time to fill up the carb. again to make that last charge.

Tom, It feels like the car just slows down, with my foot tight to the floor. Kind of like it is out of fuel in the secondarys. When the car comes back to life in the last 100 feet hold on.

That is exactly what it soounds like it is doing ;)
My money is on the fuel system. If it isn't a problem it will be :D
In drag racing it is always better to push rather than try to pull the fuel.
And before someone gets on here & tells you NASCAR runs an engine pump with 800 HP so you should have no problem I'll just say they ain't putting the forces on the column of fuel you are.
There is more to a fuel system than GPH
Do yourself a favor & build a good fuel system so you no longer have to consider it as a potential problem

I think MeanKen hit this right on the money. That's a classic sign of inadequate fuel delivery.
After staging, the bowls are full. Then as the car accelerates, the bowls drain and the car lays down. Then the system has time to replenish the bowls and away you go in high gear.
if the tank is a stock tank, be sure it is over 1/2 full when you race it(the fuel runs away from the pickup under acceleration and uncovers the pickup). Check for kinks in the system. Check the fuel filter. Then, raise the floats a couple of flats from where you're at now. If it picks up, you know you have a fuel delivery problem.

Randy

Thanks Mike for the info. I run this car on the street in the summer months. Is an electric pump going to hold up and if so, can you recomend an electric pump setup that will work for me?

If I add an electric pump between the tank and the mechanical pump will I need a regulator between the electric pump and the mechanical pump. I am think about the 140 gph Mallory.

Do away with the mechanical pump altogether and put the regulator near the carb. This will eliminate fuel pulsing caused by the mechanical pump.
The Aeromotive Street Rod pump also works very well in continuous duty applications like street cars.

Randy

sounds like lack of fuel,with a stock tank you have to extend the fuel tank pickup close to the rear of the tank by removing the factory sock setup and using a compression fitting and some steel fuel line.A winston cup car will run in the 10's with that pump and proper gearing.

i ran the carter street hi volume mech pump with the stock 3/8 line and a 4/speed in my 68 with a very similar setup to yours . it ran 11.39's at 121mph. now i run a sumped tank ,holley black, elect pump, 1/2 line(8-an) and run 11.21 at 121 mph, i spent 700 bucks on the changeover and did not pick up mph. you must have something obstructing your fuel delivery.no one believed that little carter pump would give out those numbers but it did ,i can vouge for that.

Don't really want to turn this into a I did this & he did that debate so I will just leave it with a few comments.
First, it is a fuel system.
In my opinion a 3/8 line & mechanical pump is marginal at best with a combo like yours.
Not saying it can't or won't work just that it's marginal.
Now,,,If you change from a 3/8 line to a 1/2 inch line before a mechanical pump & then accelerate you will have more fuel weight in the 1/2 inch line to overcome. So what worked with a 3/8 line may well not work with a 1/2 inch line.
I would do as a few here suggested & build yourself a good fuel system so you no longer have to wonder if you left anything on the table.
It isn't going to hurt & it may just help.
If not now then when you get the urge to go faster you will already have it done ;)
As has been suggested,get a good electrical pump & filter, check your tank & lines for kinks & restrictions. If it is a stock tank deal keep it half full & sump it when you can. Or put in a fuel cell.
Most of this is a repeat of what others have already said but it is good advice.

Guess it turned into more than a few comments,,, :D

mike, i agree with you there is no question that
a good FUEL SYSTEM will be in his best interest.
his mph is waaaaay down from where it should be.
and if he is on a tight budget i'm just suggesting
he can make his current SYSTEM work if he goes thru it.ray

Do you have a fuel pressure gauge? What fuel pump pushrod are you running? Stock? Your current fuel system you have should feed that car way into the 10's the way it is...maybe the sock in the tank is clogged..

I agree with others that I would look at the fuel system first.

For comparison I ran 11.30's at 117 mph with a stock 3/8 line, stock original pickup and original sock out of my original tank with the 172 carter.

I modified my fuel system to a new stock tank with a welded in sump and -10 braided line to the front...I kept the same Carter 172 (3 years old now) and ran it all of last season. I have a fuel pressure gauge inside the car and it reads 5 to 6 now at the top end.

Kwik66, if you have the stock pickup and sock, that may certainly be your restriction. by modifying the pickup tube as others have said you may solve your problem. Someone else said the line may be kinked, and that would do it also.

Are you sure the pump is in good shape? Do you have another to try out? fuel filter clogged, do you have the sintered brass filters in the bowl inlets?

Harold INSISTS on 1/2" fuel line to his cams, sounds like you now know why....

If you're already running 1/2" line, then look at your pump, or upgrade all at once. Harold may pipe in here with a comment, but I know he's very strongly recommended fuel supply upgrades with his cams.

like i said before i have run 11.39 at 121mph with an ultradyne 612/630 solid cam and a carter hi volume street pump and stock 3/8 line. still no faster with a 1/2 line and holley black. next season i will try harolds suggestion of 2 pumps in line to feed each bowl just to put some real comparasons to the table. my setup is almost identical to this guys. same cam, same ign, only i run a 4/speed. the carter street pump only flows 120 gph and has tiny 1/4 npt ports.

I think its over carburetion...1080 cfm?? with a 468 and 4.11 gears, you don't need to shift much over 6000....I would think 800-850 cfm would get the job done graemlins/thumbsup.gif

Hi guys,just got the change to get back on line.To answer some of the things you have brought up. I will go over my fuel system. I have the stock tank with a sump welded in the rear.The outlet on the sum is 3/8". I sized it up to except a 1/2" aluminum line, this 1/2" line goes to the 172 gph carter mechanical pump. From there to the carb I am still running the 1/2" line.I have the Nascar inline filters going to the front and rear bowls. I have 7 lbs. of fuel presure, that only drops to 6 lbs. through the traps.I don't have jet extentions in the rear bowls and the rear power valve (5.5) is still in the carb.92# jets in all four corners and a 5.5 power valve in the front. I think I have that covered. sorry for the long post, but you guy had a lot of ground for me to cover. You guys have been super, thanks for all the help. I'll get this thing in the 11's yet.

I have the Nascar inline filters going to the front and rear bowls.

dump the filters and get a steel filter not paper.

1.77 60ft times?? you don't need jet extensions,,,92 jets :eek: I'm running 78's square in my hp950...again I say,,way over-carbureted graemlins/thumbsup.gif