427 L68 Tri-Power Engine Failure - leaking carb Fuel Lock

[Timothy B.]

Re: 427 L68 Tri-Power Engine Failure - leaking carb Fuel Lock

My thoughts are if the downhill parking causes the fuel level to overcome the float needle then what's the difference between the tripower carbs and just a single four barrel carb car.

[Larry M.]

Re: 427 L68 Tri-Power Engine Failure - leaking carb Fuel Lock

My thoughts are if the downhill parking causes the fuel level to overcome the float needle then what's the difference between the tripower carbs and just a single four barrel carb car.

Answer should be "none".

Larry

[Timothy B.]

Re: 427 L68 Tri-Power Engine Failure - leaking carb Fuel Lock

The only logical thing I can think of is there are three fuel entrances into the engine vs only one.

[Patrick B.]

Re: 427 L68 Tri-Power Engine Failure - leaking carb Fuel Lock

Answer should be "none".

Larry

Maybe the end carbs with the plastic foam floats are more susceptible to this problem than the center carb and all the Holley 4 bbls I have seen which have brass floats.

[Larry M.]

Re: 427 L68 Tri-Power Engine Failure - leaking carb Fuel Lock

The only logical thing I can think of is there are three fuel entrances into the engine vs only one.

Tim:

The four barrel carbs have two needle and seats

[Skip N.]

Re: 427 L68 Tri-Power Engine Failure - leaking carb Fuel Lock

YES, the net chatter is front & rear floats are the culprits:

- there have been Tech discussions nytrophil floats sticking causing bowl (s) to leak down
- the front & rear floats apparently also have marginally shorter fulcrum on floats ; therefore have more tendency to stick & leak
- have not measured fulcrum difference center to end carbs ; just stating what I have read

I guess a Holley expert could confirm

[Skip N.]

Re: 427 L68 Tri-Power Engine Failure - leaking carb Fuel Lock

Interesting - SO...you think maybe the starter has enough torque to bend a Rod?

My car definitely had some combustion (maybe only 1 or 2 cylinders fired before hydro lock)

[Patrick B.]

[Gary C.]

Re: 427 L68 Tri-Power Engine Failure - leaking carb Fuel Lock

Regarding questions about 4 barrel equipped Corvettes
a. Those with center pivot bowls & metering block for rear bowl (L88 all three years, LT1, LS6, 65 list 3124, 66 list 3247) had same brass float as front bowl, thus no difference in float capability with needle/seat
b. Those with side pivot bowls had same float as front (64/65/66/67 model 4160), these cleared metering plate, thus no difference in float capability with needle/seat
c. The only Holleys on Corvettes that had the nitrophyl floats were the tri-power front/rear carb. These front/rear tri-power did not have metering block but had a metering plate so it needed the nitrophyl float to clear the metering plate with center pivot bowl, thus the loss of moment arm (center of buoyancy point on float is closer to pivot pin). This buoyancy point shift weakens the needle/seat sealing capability. Change of float style (nitrophyl vs brass) plus change in moment arm in front/rear carb vs. center carb makes front/rear carb on tri-power the worst case
d. Other cars that had center pivot bowls without rear metering block like some models of list 3310 (780s) that you get from speed shops would have the nitrophyl float in the rear bowl but a difference in fuel tank height/sending unit/fuel line design/geometry vs. carburetor so they would not have the issue of tri-power Corvette on a downhill. For one, when I pull my Corvette rubber fuel line by fuel pump, it always pours gas out whereas my 68 Camaro & 70 442 do not have this phenomena.

When my 69 L89 has it's issue, I could see that the front carb was the culprit. I was using 100LL gas (which has the blue dye) and blue dye was all over the front carb base plate area. This makes sense since the front carb is the lowest point on the three carbs when on a downhill slope. I have never had an issue with the car level or on a uphill slope.