Engine goes flat in second gear

[Dan Stryffeler]

Not sure what is happening, but under fairly heavy acceleration, (highway on ramps, etc.), the car pulls strongly through 1st gear, but falls flat after shifting into second.

At first, I thought my shift linkage might have loosened up and I was jumping from 1st to 4th, but that's not happening.

MSD box has rev limiter set at 5500rpm, which I am hitting. Will the box cut the ignition for a few seconds or does it fire-in instantly after you drop below the limit rpm?

The clutch is not slipping, car is not missing, just no umph...

Accelerates well when passing in all gears.

Help!

Thanks,

Dan

[Clois Harlan]

The problem is probably not with your MSD box however, pull your distributor cap and check to see of the two screws that hold down your rotor cap are tight. I have seen a loose rotor cause this problem. Just guessing but I think it is in your carb., you may be flooding out during hard excelleration. Can you speed shift your car from first to second at say 3500 or 4000 RPM and the problem is eliminated? How about from second to third etc.?

What kind of carb are you running? What size jets? What cam are you running? These are some of the questions these guys that can help may need to know.

Good luck,


Clois

[Edbo]

So you shift to third and.........what? It's normal again? Or still flat?

What I hear you saying is that it falls flat when you hit the rev limiter. 5500 is pretty low BTW.

Ed

[Dan Stryffeler]

Clois,

I'm running an old, (probably 1964), set of Ford tri-power 2 barrels (2300 series). The primary carb has a #62 jet, secondaries are #64. I had gone to smaller jets last fall and the car had no power at all. The carbs flow about 225 to 250cfm each as I recall. Secondaries kick in at about 3000rpm.

With the cam that I'm running; Crower 15513, power usually dosn't come on until 2500rpm or so... as long as I stay 3000+ rpm shifting/power is fine.

Heads are 1968 302 with 1.90" intake, (flow 186cfm) and 1.60" exhaust, (flow 129cfm). Volumn 61cc, compression is 10:1

Ed,

After a couple seconds, everything works fine. Yeah, 5500 is fairly low, but I've been told that strokers+high rpm is not a good mix. When the engine was dyno'ed - it made peak horse power at 5750rpm so I thought 5500 was a good stopping point.

I can't tell you how many times I've felt like replacing the trip's with a single modern 4 barrel.

Thanks,

Dan

[wilf leek]

I wonder if this is actually a fuel starvation problem? Is the fuel pump not keeping up with demand? Blocked filter in the line somehwere?
Have you ever kept it WOT in top at high revs for a reasonable length of time? that would be another time when lack of fuel flow would show up.

It's the "Ok after a couple of seconds" thing that is leading me down this road. Could be worth fitting a fuel pressure gauge and seeing what that shows during the "fault" condition.

[Hotfingrs]

Dan, I'm with Wilf on this one...look for a fuel problem. If you need help, let me know.

[Dan Stryffeler]

Thanks Jack, would appreciate the help... maybe meet at a car show in the next few weeks (weather permitting - ugh!) and let you take it for a spin.

Typically, will be going up to Avon Commons on Saturdays and QS&L on Sundays. Never been to the cruises in Elyria, Amherst, Lorain, etc. - could meet you pretty much anytime at one of those.

Never had this problem before, just the usual too fat or too lean at idle.

- Dan

[Edbo]

What Wilf said..fuel supply prob.

I have a 6000 rev limiter on my 393, with a 5700 shift lite. I'm going to bump it up to 5900/6200. It's really starting to pull STRONG right before the shift lite.

I highly recommend a shift lite. You don't have to watch the tach and with the proper 'buffer' you never hit the rev limiter.

Ed

[Clois Harlan]

Hi Dan,

I just got off the phone with a friend of mine that said he had a similar problem and it turned out that his inline fuel filter had a bunch of junk in it. He also went to an electric fuel pump and claims the problem is solved.

I hope this helps.


Clois

[Dan Stryffeler]

Clois,

Looks like bad weather for the next few days, so will have plenty of time to get under the car and route around - will check the fuel filter.

Never been particularly happy with my electric pump - 'Holley Red'.
Holley claims 7psi in their literature - real world experience with mine shows 4lbs at idle, 6-7lbs at about 3500rpm (pressure guage is mounted on my fuel rail). I can only guess that the pressure change occurs because of alternator speed; i.e. higher rpm = higher amps = faster pump speed.

I've been told that Holleys, in general, like about 5 to 5-1/2lbs pressure (max). So I was thinking about a higher pressure pump, and putting a regulator on it to stabilize the pressure a bit. I have no provision for a return line to the tank, so I have to assume that I may shorten the pump life a bit by regulating the pressure down.

Thanks again,

Dan

[Clois Harlan]

Dan,

If you decide to change fuel pumps Summit sells a knock off of the Aeromotive electric fuel pump that is capable of 18 psi w/ regulator for $135.00. Just a thought if you need to switch pumps.

Clois

[Dan Stryffeler]

Sunday afternoon, I fiddled with the carbs a bit; closed the mixture screws on the front/back carbs, effectively cutting them out of the idle circuit - also closed the throttle plates; they were originally opened about 1/2 turn of the screw.

To achieve idle, had to open throttle plate on center carb about 1 full turn on the screw and richen up the mixture screws by about 3/4 turn each.

Checked the fuel filter, no problems there...

Car is idling great (just a little rich) at 1000rpm and is accelerating fine through all the gears. Had a new (small) problem with the carb linkage binding, but got that sorted out.

Still not sure what the problem was... by closing the throttle plates on the front/back carbs, it would just mean that they open a little later during acceleration. The mixture screws should'nt have had any effect, because they only affect idle (or am I missing something?). Maybe the plates were just getting stuck open, who knows...

Thanks for all the input.

- Dan