What gears to use?

[Double Venom]

Ok,
Lets review.
New build -- with a very special "X" crankshaft. (Don't ask me what was different about it, except the whole thing was polished. It looked exactly like the original)

-40 lbs of hand torque to turn the complete engine over by hand, minus tranny.

Perceived problem: No oil pressure immediately after start up, engine reaching rpm Idle.

Oil pump is of the vertical type, twin gears with relief valves and springs built into the timing case cover. Driven directly off the crank shaft.

"My" First clue that I should have paid attention to, was the oil warning "light!". As Niles mentioned, we build the DV's with redundant guages. All the critical areas are guarded with guages and warning lights, and some times a buzzer is added.

The "Oil Light" lit at power but went out almost immediately at start up. Never did re-light! (Should have paid attention to this!)

Ok -- Oil guage #1, pressure would immediately go to 80+ lbs. then drop off to +/- 10.

Oil guage #2 repeated. Both guages were electrical

Two new sending units installed with the same results.

By-pass valves and springs replaced in the oil pump.

Tried both guages again, still read the same.

Pulled the timing cover off. Did a full "mike" of the gears and the timing cover walls. (No bearing here!) Well within specs. Decided to replace the cover plate and both gears.

Again, re-fired with the same results, using both guage #1 & #2 and mixing up the now new sending units. (Aint this getting redundant? )

Nothing to do now but to get out a MECHANICAL guage that has been in my tool box for years and give it a try.

Ten minutes later, (I can change the whole set up in my sleep by now! ) and it PEGS OUT AT 85 LBS. & doesn't drop off!

The motor had always idled and ran under full load at 70 to 80 lbs.!

The guage doesn't go any higher than 85 lbs and it is sitting right on the peg! I then inspect both of the stock guages and they only go to 80 lbs.! (This is why the oil warning light never came on..the oil pressure never was low!)

I then purchased a 100 psi oil pressure guage, hooked it up and the motor sits right at 85 +/- lbs. of oil pressure!

The original oil sending units, made for a max. of 80 psi. The inner rocker "needle" in the sending unit was being shoved off it's base once the pressure exceeded 80 psi! This is what caused the dash gauge to drop to 10 psi!


Two weeks, couple of hundred bucks, about 60 hours aggravation.... You gotta love this hobby!

DV -- 300 Cobras is NOT enough! You know what...we're going to make it!

[justa6]

Oh well who woulda "thunked" it...

Boy am I glad that it didn't happen to me on either the Cobra or the GN.

You would have thought that they would have had some kind of "Stop" for the sending unit so that it would peg and then when the oil warmed up or the RPM dropped it would then indicate correctly again. Which brings me to ask what kind of gauge is it? Reason I ask is my "mini motor" goes up to around 100psi as I go through the traps and I don't want any "surprises" on the roll out.
(Its got a 100 # gauge and sending unit.

Regards and good luck,

[petek]

Well ok then, I don't feel too bad at all about not getting this one - heck, it took you two weeks

Frankly I like this sort of thread, gives me a chance to LEARN something!

[Dominik]

DV,

the pressure exceeding the instruments limit ...

What a rip-off!

That is defenitely worth putting into the lessons learned folder.

Dominik

I am not really well organised yet to join the forum as before due to limitations in the internet capability (speed) of the south african sytems.

You may send me links to interesting topics it you like.

[Double Venom]

The gauges were Stewart Warner and Autometer, the Mechanical one that was finally used was an old Sun gauge..remember them?

It was not the gauges fault guys. Every gauge has its limits, I just exceeded the limits. I mean we're talking Mobil 1 oil at idle, with 85 psi. I did talk to a Viper engine designeer and the first question he asked was, "where did I get the crank"? After much hem-hawwing around, and telling him Santa Claus dropped if off last winter, he just smiled and told me that was normal oil pressure.

Who would have thunk it !? I now have a new Stewart Warner gauge 0 to 100!

DV

[justa6]

Glad it all worked out.

I do not agree though on the subject of maxing out the gauge.

There should be a "peg" or stop of some kind that just allows the rheostat in the sender to give a max voltage equalling the 80psi no matter how much pressure it senses (within limits) that way if you had thick oil on a cold day and exceeded the 80 psi it wouldn't damage the gauge's sending unit. Kind of like on some gauges they have a simple "peg" that keeps the gauge within its physical limits.

Speaking of limits its kind of like the Rev limiter. They are nice to have.

Just an opinion. Lets keep the "good ideas" like this thread coming. We can all learn a LOT from each others experience.

On a different subject. My son brought his 66 Big block Corvette over yesterday to check an oil leak. (Valve cover) He just had a new FRAME put under the car with a lot of "underneath" work done while it was off. I lifted the hood on the 427 and couldn't believe the physical size of the motor. I'm so used to the V6 in the Cobra that it seems "normal" to me now. We both were laughing about the Cobra having 83 more horsepower. He whined "a little"

He's now "plotting" nitrous but it won't "save" him

[Double Venom]

Just to keep the records straight. The "gauge" does have a peg to limit its travel. It was actually the sending unit that created the problem. These are sensitive little buggers and can only move so far. It's when the internal rheostat, if you will, goes past its normal range is where the gauge get the false reading.

Love those old BB Vettes!

[Dominik]

I love those BB Chevys also.
My upholstery buddy in LA (San Juan d C) has a L-72 conv.

I gave him one of my aluminum blocks for storage. I haven't heard from him since ... ;-)

Thanks for the thread,

Dominik