[Deeznuts]

So now that the "offical" drag racing season is done besides a few races for some... what are you racers planning on upgrading or fixing in the off season?

I am planning on chasing down a problem that started at the last 2 races on the car.... after launch it falls flat at about 5500 rpm in 1st gear, no missing, or popping, or anything else.. just falls flat. Revs clean to 6000 for 2-3 shift and crosses the stripe at 6300 with no issues.... plan is to get a fuel pressure gauge in the car that I can monitor to see if that is the problem..... and I am going to put on a new set of Slicks. I currently run Hoosier Quick Time Pro D.O.T tires, but they wear out really quick.

 

[bracketchev70]

So now that the "offical" drag racing season is done besides a few races for some... what are you racers planning on upgrading or fixing in the off season?

I am planning on chasing down a problem that started at the last 2 races on the car.... after launch it falls flat at about 5500 rpm in 1st gear, no missing, or popping, or anything else.. just falls flat. Revs clean to 6000 for 2-3 shift and crosses the stripe at 6300 with no issues.... plan is to get a fuel pressure gauge in the car that I can monitor to see if that is the problem..... and I am going to put on a new set of Slicks. I currently run Hoosier Quick Time Pro D.O.T tires, but they wear out really quick.

A fuel pressure gauge is a good idea, but I would expect the car to have more fuel problems in high gear as the engine load is higher. This is strictly a footbrake car right and the 60' is still the same?

 

[Gregs72]

I had issues similar to that with my car at one point.....check your fuel filters.


Upgrades to my Sportsman car........Change the oil, compression test and set the valves.

Goal is to have my TOP ET car on the track by spring and use this as a test year to work out all the bugs.

 

[Qwk]

A new front end is my goal fro the Winter!

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[Deeznuts]

Thanks for the replies. I too thought that if fuel related it would be worse in high gear. I was told that when the car leaves the added g forces can make a bad pump not be able to overcome the force of the fuel being forced back in the line. I am not so sure that this car leaves hard enough for that to really be a factor.
I started out the season running the trans brake. At the end of the season I decided to slow the car down and run the non electronics footbrake class which has a 12.0 cut off. I put a smaller carburetor (removed the 800dp and put on a 600 dp) and put weight in the car. I have also wondered if the smaller carburetor could be a contributing factor too...
I have pulled the fuel filter apart and it is clean. Adjusted the fuel pressure up and down with no change.

It makes the ET swing .08+ if you cant make the shift before 5500 in 1st gear... kind of hard when the converter flashes to 5200... very small window.

 

[Gregs72]

Throw the old carb on for a pass. see if it still does it......if it doesn't then you know its the carb.

 

[Qwk]

Dumb question, Do you have Jet Extensions in the rear of the carb?

 

[Deeznuts]

Dumb question, Do you have Jet Extensions in the rear of the carb?

Yes, it does.

 

[Deeznuts]

Throw the old carb on for a pass. see if it still does it......if it doesn't then you know its the carb.

I had the 800 on it and it was giving me problems on the footbrake, it had a bog that was an issue but it was fine on the trans brake.

I put the 600 on it before I got the bog figured out with the 800.

 

[bracketchev70]

I was wondering if it could be trans or converter related. Don’t know if the transbrake can leak by and drag in first gear.

 

[Deeznuts]

I was wondering if it could be trans or converter related. Don’t know if the transbrake can leak by and drag in first gear.

You are right on my second guess. The car had a similar issue where it felt flat at 6000 rpm off the brake on the 1-2 shift. But I shift at 6000 for 2-3 and go through the lights at about 6300. I thought it might need some valve springs??? But I am not so sure now.
I got the car from a guy who was in way over his head.... he got the car with the trans in it and I heard from the engine builder that the trans was good... but the guy I bought it from had his local regular transmission shop go through the transmission... not sure what he did... but I have found that the TH400 needs a approximately. 060 bleed hole in the direct drum in a race application or it can drag at around the 5000 rpm range.

So... fuel pressure 1st take out the trans and dig in to confirm the bleed hole in the direct drum 2nd...
Any other ideas?
I just cant have this thing swing this much et... it's a bracket car and not a good one right now.

 

[bracketchev70]

You are right on my second guess. The car had a similar issue where it felt flat at 6000 rpm off the brake on the 1-2 shift. But I shift at 6000 for 2-3 and go through the lights at about 6300. I thought it might need some valve springs??? But I am not so sure now.
I got the car from a guy who was in way over his head.... he got the car with the trans in it and I heard from the engine builder that the trans was good... but the guy I bought it from had his local regular transmission shop go through the transmission... not sure what he did... but I have found that the TH400 needs a approximately. 060 bleed hole in the direct drum in a race application or it can drag at around the 5000 rpm range.

So... fuel pressure 1st take out the trans and dig in to confirm the bleed hole in the direct drum 2nd...
Any other ideas?
I just cant have this thing swing this much et... it's a bracket car and not a good one right now.

I know what you mean I chased an issue in mine for a year. Mine would without fail screw up on pass #4 of the day. I could win 1st round and then second round the car would stutter at the top of 2nd gear. I mean rpm would stop climbing for a split second, enough to lose a couple .01. If I got to 3rd round, it would do it in second and third. And then I was .06-.08 off. I usually never got past round 3. I thought it was somehow heat related because I was hot lapping the car at that point. But you name it, I changed it. Ultimately it was a bad carburetor after being told REPEATADLY by the builder it couldn't be. A new carb and first time out was in to round 5.

 

[Deeznuts]

I took about a 10 year break from racing, I was still in touch with my old racing buddies... they said come back... it will be fun.... lol.

In all seriousness it is challenging not only to build a competitive car, but to keep it competitive. I think that is what keeps us doing it.
I will figure it out, it will just take some patience time and good analysis, but most of all some really good luck.
Thanks

 

[camhead]

I took my car to the body shop last February to have damage fixed & to be painted. I went thru the engine & trans last Winter while the car was away & still never got the car back yet. I'm hoping to get it back & just reassembled by next season, it was so depressing sitting last season out & not even having the car to drive.

 

[rickb]

I want to put a front 3 gal fuel cell. So I can use the space in the rear to put in an ARB.

 

[ZNova]

I am planning on chasing down a problem that started at the last 2 races on the car.... after launch it falls flat at about 5500 rpm in 1st gear, no missing, or popping, or anything else.. just falls flat. Revs clean to 6000 for 2-3 shift and crosses the stripe at 6300 with no issues.

I chased my tail for 2 years with a similar problem, usually at high air temps, and after some trial and error, zeroed in on fuel delivery. I have a 67 with stock fuel tank, and had the original 3/8" line to Carter mechanical pump. At the time my motor was making about 450 HP and everyone said the fuel system should be adequate. It wasn't. So over a period of several months, I replaced all the fuel filters, changed to a 1/2" tank pickup, 1/2" aluminum line to fuel pump, then switched to a 130 gph mechanical pump with 1/2" inlet/outlet and fuel regulator. Problem solved, but can't say which of the changes solved the problem. Most likely it was all of the above.

 

[Deeznuts]

Well I finally started working on my car to get the issue sorted out... my cousin suggested doing the 1 gallon of fuel test..
Take off feed lines to carb and see how long it takes to fill a 1 gallon gas container.
It should be-
10 second car 25 seconds
11 second car 30 seconds
12 second car 35 seconds

Well my pump was 49 seconds.
Problem identified.
New pump is on order. And I went with a Mallory 110 pump to replace the old Holley Blue.
I ran the same Mallory on one of my previous cars and it was very reliable and super quiet.
Hopefully will be going to the track at end of the month.

 

[bracketchev70]

Maybe it was slower due to daylight savings time!!!!