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Technical Cold start idle

Discussion in 'The Hokey Ass Message Board' started by 83Squarebody, Jun 24, 2019.

  1. 83Squarebody
    Joined: Jun 4, 2018
    Posts: 91

    83Squarebody
    Member
    from Arizona

    iChevy 350 with edelbrock AVS2 650, if that matters. Engine is already broken in and Ive put about 40ish miles on flat tappet.

    Ive read letting a new/rebuilt engine with flat tappet cam high idle too long on cold start is not good. Should I wait for the choke to settle on its own once hot enough or stomp the gas after a shorter period of time to settle idle fairly quickly on cold start up?

    I hope this makes sense?
     
  2. gene-koning
    Joined: Oct 28, 2016
    Posts: 2,037

    gene-koning
    Member

    OK, how cold is a cold startup in AZ, in the summer?

    Here in the Midwest, in the winter, when it gets near 0 degrees (or below), I would let the cold start run about 30 seconds before I kick it off fast idle and go. Some cars are more temperamental, and they would stumble and fall on their face if you tried to go too soon, those I would give a little more time before it was time to go. Some people like to let the ride run for 10 minutes so the car gets warm inside before they want to go anyplace.

    If the choke is properly adjusted and everything works as designed, at an outside temp of about 50 degrees, the choke should really be pretty much opened on its own after a minute or two of running time. Of course most of the stuff I had had an automatic choke, very few had a manual choke.

    The manual choke was closed for the motor to start, then opened about 1/4 of the way after the car started. After a couple minutes, I opened the choke fully, unless the motor stumbled. Then I would open it full after some more running time. Gene
     
  3. squirrel
    Joined: Sep 23, 2004
    Posts: 46,901

    squirrel
    Member

    You should be on your way (meaning you need to push the gas pedal) in less than a minute. The choke probably won't release the fast idle cam until you touch the gas pedal, anyways.
     
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  4. 83Squarebody
    Joined: Jun 4, 2018
    Posts: 91

    83Squarebody
    Member
    from Arizona

    I figured. I just read all this weird stuff in regards to flat tappet cams.

    Also seems odd to me, that for 500 miles you cant keep and constant rpm for long distances. Why? If you put this engine in your daily driver assuming you have freeway travel how could you avoid that? Constant speeding up slowing down, doesnt seem practical.
     

  5. 1946caddy
    Joined: Dec 18, 2013
    Posts: 1,705

    1946caddy
    Member
    from washington

    I heard you break in a flat tappet cam with a twenty minute run in time at 2000 RPM's
     
  6. seb fontana
    Joined: Sep 1, 2005
    Posts: 6,614

    seb fontana
    Member
    from ct

    Pretty much....
     
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  7. s55mercury66
    Joined: Jul 6, 2009
    Posts: 3,980

    s55mercury66
    Member
    from SW Wyoming

    If you want to follow that procedure you may need to re-route your trip.
     
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  8. 83Squarebody
    Joined: Jun 4, 2018
    Posts: 91

    83Squarebody
    Member
    from Arizona

    Break in yes for 20-30min at 2000-2500 rpm with the break in oil.....
    Then I read and recommend by builder, after intial breakin. You drive for roughly 500 miles staying below 4500rpm for long distances. Long distances seems relative to me, 5 miles 50 miles?? I dont know.

    Ive read others say after that initial break in, just go drive it. Still maintaining zinc oil but a mild detergent type like Lucas hot rod oil.

    I just find it odd you have to br careful driving with a flat tappet after break in, when that initial break in is the most crucial part. Id assume once past that along eith zinc oil you should br good. I dont know
     
  9. Truck64
    Joined: Oct 18, 2015
    Posts: 4,153

    Truck64
    Member
    from Ioway

    In the "old days" piston rings were sometimes hard to get seated, to get run in against the cylinder walls. The idea there is to get the engine under load right away after cam & lifter break-in. Idling won't do this, and cylinders glaze over. Supposedly modern ring materials and cylinder finishes don't have this problem.
     
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  10. gene-koning
    Joined: Oct 28, 2016
    Posts: 2,037

    gene-koning
    Member

    When I was a youngster oh so many years ago, my old boss at the largest service station in town, told me to break in the cam first, then take the car out to a back road and make 10 runs in a row from idle up to 4,000 rpm at wide open throttle to break in a motor. Then change the oil and filter and run it the way you planned on using the motor. He also always insisted that you never abuse a motor until it reached operating temp of 180 degrees. He also told me that if you run a car hard, parts break.

    His formula for breaking in motors has worked out pretty well for me for the last 44 years. He was right about breaking parts as well. I don't break as many parts as I used to. Gene
     
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  11. 83Squarebody
    Joined: Jun 4, 2018
    Posts: 91

    83Squarebody
    Member
    from Arizona

    That seems far more reasonable and logical. 500 miles just comes across as overly excessive. For a non daily, 500 miles can be an enternity. I get it warm and have driven it to a spot and go back and forth about 5-6 times accelerating upto roughly 3-4000rpms-ish then coast down to a crawl. I have done this for 30-40 miles so far, with the city cruising.

    I get warming it up and not going nuts on a cold engine. I also live in AZ so, its really not cold right now and wont be for many months to come.
     
  12. 83Squarebody
    Joined: Jun 4, 2018
    Posts: 91

    83Squarebody
    Member
    from Arizona


    Right, I understand that. But is that really a thing today? Or does the age of the block factor into this?
    If its bored .30 over etc etc... but new rings etc, can the cylinder still glaze over if you push it hard after initial break in?

    If I were rich I wouldnt sweat shredding a lobe. But i have to make this new rebuild last, or at least try.
     
  13. Back in the Day Chet Herbert Recommended 30 minutes a 3000 RPM.
     
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  14. Truck64
    Joined: Oct 18, 2015
    Posts: 4,153

    Truck64
    Member
    from Ioway

    No, it's excessive idle time, before the rings have had a chance to seat, that causes cylinders to glaze over.

    Under compression, under load on the road, the cylinder gases force the piston rings outward tightly against the cylinder walls. When everything is new, there are microscopic gaps before the mating surfaces wear in. That's partly what the cross-hatch finish is for. Lots of blow by until everything gets settled in. At idle there's no load, old school moly rings esp. won't seat against the cylinders walls.

    The problem is cylinder glazing is more or less permanent practically speaking. If you've ever seen it, a very hard, smooth almost glass like surface finish that fills in the cross-hatching and allows blow by, the engine will likely also be a permanent oil burner.

    So break-in is kind of a one time deal to get right early on, directly after cam break-in. This was the situation back in the day anyway. Just like the service station boss said above. Take it out somewhere and give it several full throttle accelerations in a row, to load it up. Avoid lugging the engine, avoid high revs. That's it. Long term a proper break-in will result in a smoother, quieter engine and probably last a lot longer before an overhaul is required.

    There was a guy on another forum who was having an issue with a smoking rebuilt engine, a real mosquito fogger. Turns out what happened, he had the engine on a stand because he couldn't install it right away.

    He liked to hear it run it though. So every now and then (for over a year) he'd fire it up on the stand. He estimated maybe 10 hours total accumulated idle time or something like that. Oops.
     
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  15. After I break in the cam at 3000 RPM for 30 minutes. I change the oil. I don't use any break in oil just whatever oil I plan on using. Then I drive and use it like I intend too. And change the oil in about a 1000 miles. The oil changes are just to remove any debris or lint ect. from the assembly process. after the first two oil changes I resume normal oil changes. I use molly rings. molly rings on a properly honed cyl will seat very good. There Is a guy on U TUBE. Vice Grip Garage. He just did a Ring job on a 307 chevy. Used two different grit dingleberry hones. installed HO 305 heads. and a new cam. It made 290 Hp on the Dyno.
     
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  16. 83Squarebody
    Joined: Jun 4, 2018
    Posts: 91

    83Squarebody
    Member
    from Arizona

    gotcha! So if i may ask? what is the reason for the concern, warranted or not for not driving at high RPMs for long distances on this often cited 500 mile brake in? Is it the load?
    Thanks.
     
  17. woodhawg
    Joined: Apr 11, 2009
    Posts: 1,019

    woodhawg
    Member
    1. S.F.C.C.

    45821C8D-4F16-4533-941F-D4783D08936F.jpeg
    You REALLY want to do this!
     
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  18. Truck64
    Joined: Oct 18, 2015
    Posts: 4,153

    Truck64
    Member
    from Ioway

    I always heard it as avoiding "steady speeds", the idea being not to take a brand new car and lock it down at 55 mph for a long highway trip. I expect this is similar to a no load condition. It actually takes very little horsepower to maintain speed on level road in high gear once it gets there, maybe 50. This is why the "vary speed occasionally".

    The motocross guys always beat the piss out of a new or rebuilt engine to get a good ring seat. I suppose engine clearances have something to do with what people can get away with RPM wise. Years ago my aunt took us to Detroit to watch cars being built at a GM plant. I don't remember a whole lot, but I do remember they didn't seem to baby the new cars too much driving them off the line, they were squealing the tires and zooking!
     
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  19. 83Squarebody
    Joined: Jun 4, 2018
    Posts: 91

    83Squarebody
    Member
    from Arizona

    Yes, i miss-typed. The gentleman who built my engine, said
    “Not one steady rpm for long periods only upto 4500 rpm for first 500 miles”

    So yes. Its more constant rpms for long distances, than what rpms youre driving at. Just dont red line the engine the first 500 miles Im guessing.
    I would assume that steady rpms is the issue.
    Im guessing as well, that a constant RPM is equivalent to no load, like idle.


    Then again, Ive read guys who say after intial break in, drive like youre going to, but still change the oil after 500 miles.
     
    Last edited: Jun 26, 2019
  20. Blues4U
    Joined: Oct 1, 2015
    Posts: 4,882

    Blues4U
    Member
    from So Cal

    This is correct. To the OP, man, you're taking things far too literally and to the extreme. Once the cam is broken in there is no need to worry about cold start idle time, fire it up, allow the fluids to start circulating, and go. Take it easy as the engine comes up to operating temperature, don't go crazy with it. For the first 500 miles or so, if you take it on long trips, then vary the speed while you're driving. If you're just going short distances to a local cruise, a hang out, drive in, or to work, just drive it normal. It will be fine.

    Man, when I used to work in heavy equipment repair, we would put brand new or rebuilt engines to work at full load almost immediately. Once we fired up a rebuilt engine we gave it a quick check for oil/coolant leaks, and if none were found we'd bring it up to operating temperature with a light load, then once up to temp we'd put it through it's paces, checking oil pressure, high idle (diesel engines are governed at fast idle speed, you need to check it), low idle, converter stall speed and full stall speed (converter + hydraulic), check fuel pressure, check boost pressure and blow by. Compare readings to spec's, and if all are good retorque the head, reset the valves, give it a once over, put the sheet metal all back on and put it to work, immediately at full load for the duration of the shift, no babying at all. We might change the oil & filter after 100 hours, and after that at whatever the normal interval is (used to be 250 hours, now it can be up to 1000 or more). These are engines in excess of $30k, and the downtime can cost even more. No break in oil used, just 15W-40 diesel engine oil. Coming from a car background I was amazed at this, but it's normal practice. And as long as the engine was built right there were never any failures from lack of babying it. In fact, if it's gonna fail they want to know ASAP. That thing needs to move dirt and earn it's keep, there's no time for foolin' around.
     
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  21. 83Squarebody
    Joined: Jun 4, 2018
    Posts: 91

    83Squarebody
    Member
    from Arizona


    Lol... yes I know and youre 100% right. I just like to have a firm understanding of things. Which at times bogs me down from just driving the darn thing and having fun... I find engines fascinating. So I may go overboard in taking things too literally.


    I guess most of my reservations and my 90000000000 questions, is that I want to understand this “flat tappet break-in and running” so I dont screw this engine up. I cant afford a replacement or a fixin’of it. It took all I had to buy it. Also, I dont want to void my warranty on it.

    Your comfort in this comes with the experience I dont have. I’ll get there, eventually...

    But yes, your point and observation, still stand. Lol.
     
    Last edited: Jun 26, 2019

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