1972 911T Is my newly built motor…toast?

[GeminiBlue911T]

1972 911T with PMO carbs. Mostly stock except pistons are higher compression from a 2.2 and the carbs. Originally built to be a reliable driver.

I just turned it over and oil pressure was showing 60 at idle then calmed and went down to 40. The 60 went on for about a minute. Like something was stuck? Maybe?

It sounds rough, but I personally couldn’t pinpoint the misfire, 2 others could that are more experienced. I just figured it was running rough for break in.

If the engine is lunched, where should I start first? What should I look for before I pull the engine out.

I know this is a very vague question. But I’m not sure where to start at this point.

[PeteKz]

Oil pressure is fine. When the oil is cold, it’s thicker, so the pressure typically decreases as it warms up. However, 60 then 40 at idle is much higher than normal. Does it ever go above 60? If so, you might have the wrong sender for your gauge.

[Bill Douglas]

It sounds rough, but I personally couldn’t pinpoint the misfire,

Assuming the oil pressure is OK, next the missfire. Start with the simple. Are the spark plug leads on right and the correct leads to the plugs.

[GeminiBlue911T]

It went up to 100 at one point when it was revving up. What would be considered normal at idle?

Leads appear to be correct.

[proporsche]

what plugs did you use on the oil pressure relief valve and safety relief valve?
The one with the groove must go to vertical valve and without to horizontal (on the left)
here is some reading

Ivan
Ultimate Oil Pressure Relief Valve Thread

[yelcab1]

Who did the rebuild? Why is that person not contributing?

[colingreene]

If you do rev the motor at stone cold, I dont advise it but yes 100 psi is not out of the question.
It will however also take you a long time to get the oil fully up to temp just idling in the garage.
That being said the only way to know for sure if your gauge is correct is to put a mechanical gauge on it and check it that way.
Rough running could be a number of things on a new motor, such as carb or ignition set up, loose wires, mis ordered wires, not tight spark plugs.
or poorly set up carbs.

[tk32]

My dad recently had a freshly built air-cooled (4 cylinder) motor get worse and worse and worse until the car was totally undrivable. Backfiring, missing, unburnt fuel, it would barely start. When we first installed it ran very well if a bit rich, puzzling. He went through everything while I searched the internet and tried to come up with ways a new engine could be broken. The conclusion was: rip it out and start over, that brand new engine is forked

Meanwhile he checked and re-checked the grounds, plugs, coils, relays, CDi box, wiring, timing, fuel, tune ... In the end it was the distributor points that went out of whack, how, why? Who knows. It was left in the hands of a reputable shop to adjust the points and for a good carb tune (above our pay grade), she runs like a top. Also the wiring is now bulletproof

Things I learned: 1. It's usually fairly simple, these things are really not all that complicated. 2 It is critical to isolate each system and go one by one until the culprit is uncovered, unfortunately at this point it could be almost anything causing misfiring, backfiring, general poor running. Oil pressure? seems fine for heavy weight oil in a stone cold engine ... good luck!

[Mike O'Meara]

'72 2.4 here in the midwest driving season(over now) running 20w50 Castrol will definitely hit 100lbs pressure when revved cold (motor). As it warms the pressure falls into the 15lbs per1000rpm range, and barely registers at warm idle. HTH

[PeteKz]

I'm still thinking your gauge and sender are mismatched.