I went racing last night and when I turn the car off my car will continue to run. Also, by the time I near the 1/4 mile, my car will die off at wide open throttle. It only dies when I am almost at the 1/4 mile mark. The RPMs will drop down and it feels like I just took my foot off the gas. Also, I think it is backfiring at the 1/4 mile. At the line, I got a huge backfire out of my carb then the car died... it started right back up. I lowered the fuel pressure to 8psi and the timing is advanced 10 degrees at 600RPM. I also put springs and bushings in my MSD distributor (will this cause it?). Anything will help.

 

it sounds like it may be related to timming, I know having timming too far advanced at idle will cause the motor to run on. check your vacuum advance and make sure its hooked up to a ported vacuum source. it sounds like the timming is too far advanced at idle and not far enough at WOT. hooking it up to a constant source will cause these symptoms. IMHO.

 

Well I dont have a vacuum advance because its a mechanical holley 750 DP. The weird thing is atht it only dies towards the end of the 1/4 mile and not at any other time. I have to be on the car at WOT for about 8 seconds straight then it dies off.

 

It's not timing. Leave the buzzword out of it.

There's no reason why a Holley mechanical secondary carb requires you not to use a vacuum advance. The car will run a whole lot better on the street with vacuum advance than without.

You have a fuel delivery problem. That's why your car dies at the end of a run, it's running out of gas. It doesn't matter what the fuel pressure is if you don't have enough flow, which is what the real problem is, not the pressure.

Your carb will work a whole lot better with about 5-6 psi of fuel pressure like all the rest of us use.

Backfiring through the carb is another symptom of running lean, except under different conditions. With a single plane intake and a large carb, you will need an enormous pump shot, because the air velocity at low RPMs isn't enough to keep the fuel vaporized; it condenses out, the only thing that makes it to the cylinders is air, i.e. a massive lean condition. Driver technique is very important there... you can't drive a single-plane intake by just leaving it in gear and stomping it, it won't work, I don't think you'll ever be able to get enough pump shot to overcome that. You need to learn how to flash the converter at the line, so the engine is already at the TC stall speed long before you launch.

Again, leave the timing alone until you get the fuel issues worked out. None of what you have described is a "timing" problem, and most especially, you will not "fix" it by twisting the distributor around.

 

You have a good point there and that thought already ran through my mind. I have the stock intank fuel pump in my car. I used the mallory 3-port regulator when I converted from TPI to carb. I think your right.. it may be dieing out from the massive load.
-What are your suggestions now? I plan on running nitrous. Do I keep the intank just for nitrous and put in an electric fuel pump or ditch the intank and run just one fuel pump. If I run just one fuel pump, which do you recommend (summit sells a 140gph kit w/ regulator and lines for $270) and how do I do it? Do I just get a sump and hook it up?
-How do I hook up a vacuum advance? I have an MSD pro billet distributor and digital 6+. I know there is a vacuum line on the carb for advance.

 

Ditch the in-tank, definitely. Sump the tank and run either one huge electric pump for both carb & nitrous, or a mech pump for the carb and electric for nitrous, or something like that.

What kind of ET and MPH and 60' does the car run? That should give a fairly good idea of the fuel consumption. and consequently the flow rate you need.

 

Ok heres a time slip from my best run which is kinda pathetic considering the mods. Will the 140 gph be good for the motor and nitrous?
R/T .837
60' 2.083
330 5.717
1/8 8.728 MPH 81.5
1000 11.351
1/4 13.625 MPH 96.6

 

That is kind of pitiful, but that's OK, ya gotta start wherever you are and get better.

Looks to me like you have somewhere ner about 280-290 crank HP right now, depending on how much your car weighs. Your motor, properly tuned, should do most of twice that. It takes somewhere near .0015 gallons per horsepower per minute, or about half a gallon per minute to make as much power as you're making now, so that's around 30 gph. Get it dialed in, it will probably want 50 gph before nitrous (which I wouldn't do to that motor with its 11½:1 CR if I was you - that's not a nitrous-built motor). So I'd guess the 140 gph should do.

Before you just start buying parts though, look for restrictions. You can buy stuff all day long, but if the pickup sock in the tank is all built up with crud, or the lines are encrusted with the gas tank crusties, or something else is wrong where you can't see it and the solution dosen't look all romantic and blue or red anodized, then all the fuel pumps and expensive hardware that you can see won't do a bit of good.

You should be having massive, unbelievable, uncontrollable wheel hop and tire spin off the line. What have you done so far to address the 60' issue? That's real quick payoff directly in ET right there without opening the hood.

 

That was basically my first real run with the car. I ordered the 140gph summit fuel kit and Im going to run it independant from the intank pump. Im going to put an aluminum line in the tank and hook up the pump to it. Ill just keep the intank pump for my nitrous setup for now. I plan on going with a sump but money and time is short because Im heading back to school.
-As far as the 60' time, I have absolutely no traction. I could spin my tires about 300 feet. I am looking into the MT street slicks and new rims, but again thats more $$. I thank you for all the help.
-Im pulling out my rear end today and dropping the tank. I have a Moser 9" ford rear in my garage with 4:11s that Im putting in. This will help alot. By any chance, can a 9 bolt disc brake kit fit on a moser 9" ford? Some guys told me it will work but Moser said it wont.

 

Ok guys, I put the fuel pump in and the new rear end. When I went to the track it still died off towards the end of the track and I only ran a 13.9. This is slower than last time. Do you have any suggestions? Its a 140gph pump. Do you think I have to rejet my carb? I am clueless now. Timing is at 10 degrees initial advance and 36 degrees total advance at 2500 RPM. Fuel pressure is at 6psi. Plugs are gapped at .050. I can not think of anything else that is causing this.

 

Are you still running your stock fuel lines? You would need at least 3/8" all the way from pickup to carb. Do you have the lines located close to the headers/exhaust? Your pressure regulator could be malfunctioning also.

96 MPH with that combo Something really isn't running right. That motor should be good for 550HP+

 

The whole fuel line and components are new. I have a 3/8 steel line going into the tank. This line goes stright to a 6AN stainless steel braided hose to filter to fuel pump fuel pressure regulator then to the Carb. Its the summit fuel pump kit.

 

Oh by the way, I still have the prom in the computer and the computer in the car to avoid VATS problems. I highly doubt this could cause anything because nothing is hooked up to it as far as distributor or fuel pump. Just an aside.

 

Moser is right, you need a 4th Gen disc brake setup to fit. The 4.11's will make your 60' times worse without slicks or DRs.

 

I ended up using the wilwood disc brake system, works great and looks great.

 

I just found out another problem today. This might be causing everything hopefully. The spark plugs I have in there are the Accel shorty plugs with a .46 reach. I need a .75 reach plug for the heads. All the plugs I get touch my headers and Accel doesn't make a shorty plug with .75 reach, the .46 each is the highest. Anyone know if other companies make shorty plugs?

 

I would also check the valve lash, I assume you are running a solid roller. How much valve seat pressure are you running? That's a pretty high lift cam for a small block. You could be floating the valves on the top end. which would make it pop also.

 

Im pretty sure its a hydraulic roller. Its lunati cam p/n 50169

 

Looks like it is a Solid Roller, I would make sure the valve lash is .020-.022, and I would also use one of those Valvetrain geometry checkers. I thought that cam was too big to be a hydrolic roller, they have limits because of the extra weight of the hydrolic parts

www.lunaticams.com

ROLLER, Good idle. Excellent street rod cam. Good throttle response.
2500-6500
281°
285°
248°
252°
.606"
.585"
.404"
.390"
110° Sep
106° Int C/L
18°BTC 52°ABC /
60°BBC 12°ATC
50169
$271.00




-
.020"
.022

 

Mr. Happy thanks for the info. I wasnt sure. Now as far as valve lash. I do not know how to adjust it. My valve covers are off now so its the best time to check. What do i have to do?

Also, I got new plugs, they are .75 reach over the .46 reach I had. This will make a big difference. Whats do you guys think for gapping? I was thinking .050 because Im running an MSD box and distributor. My CR is 11.5:1

 

Pull the power from the ignition then bump the motor until the valvle you want to adjust is on the base of the cam (lowest point) then there should be a .020-.022" gap (you need a feeler gauge) between the rocker arm and the valve stem. Also the motor needs to be warm as the lash changes with tempature. If your lash was adjusted like it was a hydralic it would make the car backfire as it would essentially keep the valves from closing probably would cause vavle float. I would start at .035 on the spark plugs then play with gap later. Be sure you are not running too hot heat range of the plugs also, this will cause high speed missfire. Consider running a Annular discharge Holley, the 830's are pretty cheap and really run it made a big difference on my 396.

Mike

 

Hes got a tough ign., isnt .035 a little small? ive always thought if you have a strong coil that you can gap the plugs up around .050 for optimum power. my engine feels alot stronger at .050. im using an accel super coil on and HEI.

 

I tend to go conservative when I have a motor that have may a ignition problem the less gap you run the less load you put on the ignition system. Gta, what did the plugs look like after the run? Maybe you need to jet up the secondaries. Is that a known good carb? If the plugs are ash white after the run you are lean. Best way to check is to shut the motor down at the end of the track, don't let it Idle and pull a plug. You will get a good look at the mixture and timing. See how far down the burn line is on the plug, on the second thread is normally around 38 degrees. Yours maybee different with those long thread plugs.

Mike

 

The carb is one month old so I know its not bad.
When I pulled the old Accel plugs today, some plugs were black, a couple tan and 3 or 4 grey ( maybe even ashy). Im hoping that with these new plugs(champion RC12YC) the car will run good. The heads called for these plugs. Also the heads need plugs with .75 reach. My old Accel shorty ones were only .46. This should make a difference.

 

Some carbs work others don't just because they are new is no reason to trust them. I would check and see what it is jetted at. If you have a friend with similar carb that works good, I would try it. Carb may need to be recurved to your application. Its amazing how much difference a carb can make. 750 maybe a little on the small size for your motor because long stroke motors need more breathing than say a destroked 400 (377). I would jet up the secondaries a couple of steps.

Mike

 

Thats what alot of guys are saying. What jet should I start with and why just the secondaries (is that generally where to start)? If I go with a new carb, which one should I get? Ill spen about 500. How are the demons? My bro might buy this one for his mopar.

 

The one I have is Holley 510-O-9381 $382 from jegs. To me the demon carbs are overpriced, as is everything barry grant makes. I do not know what the stock jetting is. It seems to me it probably is not lean part throttle so I would start with secondaries. Go up a two sizes and read the plugs if you need more jet up the primaries.

Mike

 

Mr Happy thanks for all your help, I will be ordering the holley jet assortment this week. I am going to get the car running saturday. I just put in an NX nitrous kit and did the plugs.

 

this is old i no but what was the problem?? i have the same problem with my car almost but i am think its my egnition/ also mine is getting worse. so what was the problem???