Chasing a gremlin!

[338d]

I am looking for some input from anyone as I am about to go jump off a bridge! I have been fighting a gremlin with my car for a couple weeks now that I am lost with. The car is a 2700lb corvair wagon, powerglide, 477 BBC, alcohol, BLP beltdrive pump, Ken Jones carb, MSD 7AL ignition, crank trigger, and can give more info if needed. I have ran the same combination all season and have not made any changes until this sudden issue arose. A few weeks ago car was running fine as usual and I was down to 6 cars in 1/8 class and 3 cars in 1/4 class. On my 1/8 run the car left normal and right before the shift it just lays over. I clicked it into high and aborted the run. Had just a couple minutes to check a couple things before going up for the semis of 1/4 mile. Car seemed fine, it reeved up and was very responsive and no abnormal oil pressure or noise, so I went up for the 1/4 run. On that pass the car makes a fine run and I break out. The temperature that evening was in the upper 90's so it was hot. When loading the car I noticed that the tranny had puked a little fluid out of the vent, so I got thinking that maybe the tranny got a little hot and maybe started slipping on that pass it fell over. That week I changed the fluid, put new tranny lines on it, and installed a bigger tranny cooler. The next week 1st pass the car launches and instantly noses over like a throttle stop was on it. We take carb off and go thru it, check fuel pressure and everything seems good, so next pass it launches fine, but lays over around 150 feet out, so I decided to stay in it this time to see what it does and it just labored almost like you were going down the track getting in and out of the throttle. Now I am thinking converter rolled a sprag or something, so have the transmission gone thru that week and it looks like new and I put my other converter in the car. I go to the track and 1st pass it makes it down the track. Around 1000 ft the car had a slight surge but not sure how much it effected the run. Temperatures were in the upper 80's and kinda humid, so figured the car should run low to mid 5.80's on the 1/8 and upper 9 teens or low 20's on the 1/4. It ran 5.84 116.5 and 9.19 145. The mph's were a little off, but the new converter in the car was a little looser, so I was thinking maybe that was it. Next pass right before the shift it noses over again! No more runs that night. Take fuel pump off and clean out the internal bypass on it to make sure it wasn't sticking and put a new set of plugs in it. Go down last night and 1st pass the car makes the most crisp and clean pass the car has made in weeks and runs 5.79 at 118.70 and 9.12 at 148mph. I am ready to do cartwheels I am so happy now! I go make a 2nd pass and the car gets out around 200ft and begins to labor like I am letting in and out of the throttle. The air was good last night, so it is doing this in good and bad air. The car is not popping at all it actually feels and sounds like you are getting in and out of the gas, but for some reason it really liked the new plugs and it seems to only have the issue under a load. I can tack it down the return road at it is fine and it is fine in the burnout. Somebody has had to have a similar issue before and just looking for a route to go. Starting to think ignition related now, but I have always had a popping or misfire with ignition issues in the past. Any help would be appreciated.

[drphillips309]

Sounds kinda similar to what dorag had happen to him 10 years ago with his dragster and the belt drive pump. His was fine in the burnout but when he launched either the supply line or the return line I can't remember was collapsing shut . Maybe Offerman can explain better . But Keith changed fuel lines and was fine.

[bracketracing]

I run an electric pump. I had similar issues long time ago. Floats soaked up fuel and caused it to run out of fuel after resetting floats. Another idea check distributer internal be sure rotor didn't come loose. Mine has done that also.

[338d]

Aug 20, 2015 9:26:00 GMT -6 bracketracing said:

I run an electric pump. I had similar issues long time ago. Floats soaked up fuel and caused it to run out of fuel after resetting floats. Another idea check distributer internal be sure rotor didn't come loose. Mine has done that also.

I have not checked the dist yet, but when the carb was apart floats seemed ok. They are brass floats.

[jeremy341a]

fuel filter?

Crank trigger pickup?

[548h]

Check ignition system. Coil, crank trigger, distributor, any possible EMI being introduced to the trigger wires (if you're not sure MSD makes a grounded lead for protection), MSD power/ground, battery, (charging system if equipped).

Check your rear gears, brakes, drive shaft, rear wheels/tires, etc for any binding.

You may end up having to put the car on a dyno to test systems under a real load.

Feel free to call the shop if you want Clay. 636-282-5700

[bracketracing]

Clay I had a brass float fill with fuel. It bounced off the jet extension and cracked the bottom. But that would make it flood.

[moparsz]

Aug 20, 2015 10:03:39 GMT -6 548h said:

Check ignition system. Coil, crank trigger, distributor, any possible EMI being introduced to the trigger wires (if you're not sure MSD makes a grounded lead for protection), MSD power/ground, battery, (charging system if equipped).

Check your rear gears, brakes, drive shaft, rear wheels/tires, etc for any binding.

You may end up having to put the car on a dyno to test systems under a real load.

Feel free to call the shop if you want Clay. 636-282-5700

Hey now, get back to work on mine. Just kidding lol

[396z]

Stab in the dark, but could there be some moisture in your fuel?

[338d]

I have been using the fuel out of the same drum as another racer and they have had no issues, but I have had bad fuel in the past before.

[548h]

I remember Barclay had a similar problem in the big blue olds. Turns out there was a screw that usually holds the float retainer to the bowl that was loose and would get sucked into the main jet on a hard pull. It was intermittent and sounds like what you are experiencing. What happened was the lock washer fractured. When it did there was no longer any tension on the screw. Eventually it fell into the bowl. And then, under a high load, would get drawn in to the jet. Instant three barrel.

[358t]

Aug 20, 2015 8:29:11 GMT -6 drphillips309 said:

Sounds kinda similar to what dorag had happen to him 10 years ago with his dragster and the belt drive pump. His was fine in the burnout but when he launched either the supply line or the return line I can't remember was collapsing shut . Maybe Offerman can explain better . But Keith changed fuel lines and was fine.

Yes, Kieth and several customers have had problems with a pumps suction hose. In some cases it has even been new hose and fittings. In Kieth's case the hose was collapsed inside sorta like a brake hose can do. Another customer recently had the same thing. His was noticable by squeezing the hose as a soft spot could be felt. Sometimes the hose can look wavy on the outside also and would indicate its collapsing. In the past I've also helped troubleshoot customers through problems that ended up being the swivel type 90 or swivel type 45 degree fittings. They would allow the pump to suck air but wouldn't noticeably leak fuel. If at all possible do not use swivel type 90 or 45 degree fittings on the inlet side of a pump, especially a belt pump. Also, no-name brand or some house brand hoses have been problemmatic.

Clay and I talked about his issues last week. I believe has also talked to several others. Many of the things being discussed here have been brought up as possibilities already. Something that hasn't been brought up here and we didn't think of last week and that happened to a customer of mine recently is the fuel pump pulleys slipping, either on the crank mandrel or at the pump.

Clay, do you have a fuel pressure gauge in drivers view that you can look at while you feel it bogging or surging? This could verify or rule out the fuel supply system.

We can't quite rule out the trans yet. If the stator support tube is not a tight and solid press fit anymore and is able to spin it will act just like a failing or broken sprag in the converter which also match Clays symptoms. Would also cause the trans to run hotter than normal. I believe Dirk Sutton had a stator support tube problem a couple years ago that about made him pull all of his hair out before they found it.

Scott

[bracketracing]

Yes we changed dirks pump at the bracket finals

[jim0602]

Definantly a good place to start would be making sure the fuel pressure isn't dropping off when the problem occurs and there is no sign of the pressure dropping off under heavy load in high gear when the fuel demand is highest. Pressure doesn't always show a volume issue but it's an easy test that can lead you in the right direction

[sg3526]

Aug 20, 2015 14:21:24 GMT -6 358t said:

Aug 20, 2015 8:29:11 GMT -6 drphillips309 said:

Sounds kinda similar to what dorag had happen to him 10 years ago with his dragster and the belt drive pump. His was fine in the burnout but when he launched either the supply line or the return line I can't remember was collapsing shut . Maybe Offerman can explain better . But Keith changed fuel lines and was fine.

Yes, Kieth and several customers have had problems with a pumps suction hose. In some cases it has even been new hose and fittings. In Kieth's case the hose was collapsed inside sorta like a brake hose can do. Another customer recently had the same thing. His was noticable by squeezing the hose as a soft spot could be felt. Sometimes the hose can look wavy on the outside also and would indicate its collapsing. In the past I've also helped troubleshoot customers through problems that ended up being the swivel type 90 or swivel type 45 degree fittings. They would allow the pump to suck air but wouldn't noticeably leak fuel. If at all possible do not use swivel type 90 or 45 degree fittings on the inlet side of a pump, especially a belt pump. Also, no-name brand or some house brand hoses have been problemmatic.

Clay and I talked about his issues last week. I believe has also talked to several others. Many of the things being discussed here have been brought up as possibilities already. Something that hasn't been brought up here and we didn't think of last week and that happened to a customer of mine recently is the fuel pump pulleys slipping, either on the crank mandrel or at the pump.

Clay, do you have a fuel pressure gauge in drivers view that you can look at while you feel it bogging or surging? This could verify or rule out the fuel supply system.

We can't quite rule out the trans yet. If the stator support tube is not a tight and solid press fit anymore and is able to spin it will act just like a failing or broken sprag in the converter which also match Clays symptoms. Would also cause the trans to run hotter than normal. I believe Dirk Sutton had a stator support tube problem a couple years ago that about made him pull all of his hair out before they found it.

Scott

Just did a trans for a customer last week with the same issue, he thought he had a dead converter and took everything out to have it all gone through. Brought the trans up to me and when we took the pump apart the stator tube looked a little odd. Reached down to grab it and it moved, Little additional pressure and it fell out he is now waiting for BTE to get done with his converter.