Fresh Motor And Carbs

[anthony_c]

after a 3-year absence my 260 is now off the lift and back on the road with a fresh rebuild of the motor and carbs.

any thoughts on what mpg numbers i should be seeing?

 

stock 2.8L, bored .020

Round-tops

5-speed

[rcb280z]

Depends on driving style and how she is tuned. When I was running 72' SU's on my 77 L28 I was getting 15/20. But it was tuned to run so to speak. With the F.I. back on I see 16/26. These numbers are approx numbers.

Again it depends on how you have it tuned. Condition of dizzy & vac can, ignition, etc. If everything is in tip top condition you could see numbers around 17 city/25 hwy. Again, approx numbers here.

[anthony_c]

i've only cleared the first tank of gas, but your numbers line up with what i've observed so far.

 

after 166 miles of normal in-town and 2 lane back-road driving i managed 17.7 mpg.

no extended highway miles yet but it looks like i'm on track for the 25 mpg you suggested.

 

• it has a new cap, rotor, and wires, rubber fuel lines, filters, vacuum lines, hose clamps, and everything else i could throw at it.

• the heat riser tube from the manifold to the stock air cleaner is missing, but since the car came with a mixture of 240 and 260 intake parts i'm not certain how or if the vacuum motor in the stock air cleaner will work.

• the tubes that carry coolant through the intake have been cut-off as well.

 

any thoughts on switching to a 240 air cleaner with the manual summer/winter lever? in cold weather it takes about 2-3 minutes of idling before it settles in becomes driveable.

[rcb280z]

You will only get good hwy mileage if the timing is right and vacuum advance works.

I just used the chokes until mine warmed up. If you dont have them hooked up you may want to consider it or just wait a few minutes before driving it.

I had the K&N round air filters on mine.

That is a descent city mileage.

[anthony_c]

so i took the car out for its fourth break-in run today and two curious things happened.

1. the oil pressure went up and remained elevated

2. the brake booster failed, making the trip that much more exciting

 

unless someone has really creative and ingenious explanation i'm going to assume that the booster was at the end of its life, and the timing of these two events was purely coincidence.

 

but is it normal for oil pressure to go up when breaking in a new motor?

[madkaw]

I can't imagine that being normal. DO NOT trust stock gauge- mount a direct oil pressure gauge.

The stock gauge is slow to react. How high are the numbers?

[siteunseen]

When I rebuilt my 2.8 it had good oil pressure and only got better.  It stays 3/4s of the gauge when driving and only drops down at idle.

 

Maybe you could put a vacuum gauge on the brake bung?  Part stores loan them out.  

[anthony_c]

still running the stock gauge so no numbers,

 

but after the "bump" yesterday:

- the needle is about a 1/4 inch past the midway point while at speed.

- at idle the needle drops back to just below the midway point.

[Oiluj]

My bored-out 2.7 L6 gets about 24+ mpg on the freeway, but only about 12 mpg city, probably because of the performance cam, (and the driver).

 

My oil pressure is typically well above the mid-point "at speed", but at idle sometimes drops to zero, even though it's got oil pressure.   , because that's how the newer type oil pressure sender operates.

[siteunseen]

still running the stock gauge so no numbers,

 

but after the "bump" yesterday:

- the needle is about a 1/4 inch past the midway point while at speed.

- at idle the needle drops back to just below the midway point.

Same as mine.  But now after a few thousand miles the idle pressure is lower than midway, about a fourth of the gauge, but comes right back up with a little pedal push.

[Patcon]

Many times the booster dies because brake fluid leaks from the rear of the master cylinder into the booster. The fluid destroys the rubber diaphragm in the booster so it no longer holds vacuum. The diaphragms are basically not available. Booster rebuild companies don't want to sell just a few and wholesalers I've found want a 1500 minimum order...

Charles

[anthony_c]

just testing new upload function