New motor, light blue smoke

[Jeff B.]

I've got my 1964 327-300 HP motor back in the chassis, the body is still off. The motor was rebuilt: new pistons, rings, valve guides, valves, guides, seals, springs, pushrods ect. All stock parts inlcuding crane 300 HP bluprinted restoration cam and lifters. I have about 30 minutes on the motor at 2000-3000 RPM but with no load. After it warms up there is light blue smoke when you open the throttle. I changed the intake manifold gasket just to make sure but there was no change. Compression is good in all cylinders and it runs great and idles perfectly smooth. Has original AFB just back from Holly custom shop. I'm trying to decide if I should move forward assuming the rings have not seated yet or stop and pull the motor and have it put on a dyno and checked out. Any thoughts?

[Ridge K.]

Re: New motor, light blue smoke

Jeff, before spending money and/or a lot of time, I would allow a little more time for the rings to "set".
It's getting late this evening, but I'm sure that by tomorrow some of our most experienced mechanic/fellow members will share their thoughts.
Keep us posted. Ridge.

[Jeff B.]

Re: New motor, light blue smoke

That's what I'm thinking also, but I would just hate to have to deal with pulling the motor once the newly painted body was back on. It's kind of the chicken / egg thing. I may not be able to seat the rings without actually driving it, but once it's back together and driveable it's much harder and risky to pull the motor. If I did not mention it, this is part of a complete resto. Here are a couple pictures. Pay no attention to the battery, radiator and wooden temporary radiator mount!

[Timothy B.]

Re: New motor, light blue smoke

Jeff, I seem to recall the same thing with my 63, the cranking compression pressure is 165 to 175lbs. I would say your motor needs to be run!!!

Your work looks great, did you do the rebuild or someone else? No one can tell you exactly what to do except to say if the motor is put together according to spec all should be fine. No way I would tear a engine apart after 30 minutes of running time unless I had a good itching something is wrong.

If your attention to detail is as good inside as outside it will be fine. Lots of things need to burn off, seat, get adjusted etc. Make sure it's leak free and coolant level stays constant.

NICE WORK!

[Jim L.]

Re: New motor, light blue smoke

. The motor was rebuilt: new pistons, rings, valve guides, valves, guides, seals, springs, pushrods ect.

What kind of rings were installed?

Jim

[Stuart F.]

Re: New motor, light blue smoke

Even new exhaust systems have some protective oil residue inside that will burn off - as stated by my learned colleagues, there are a lot of things to seat in yet and/or burn off, i.e. assembly oils, etc. If you first run it in the chassis in an enclosed environment, as opposed to getting out on the road right away, you will see these telltale signs of some oil burn. Wait until you have a chance to run it up more at least until doing something drastic.

Stu Fox

[Jeff B.]

Re: New motor, light blue smoke

Timothy, I did most of the work on the car but the motor long block was done by a shop and his favorite machine shop. It's a bit frustating though because I'm so used to doing everything myself and double checking everything I and just have to trust the motor builder on this one. On the heads, I pulled one spring and noticed they used both the o-ring seal and an umbrella seal so I would not think oil is getting in through the guides. I think I will do a leak down test and if that checks out, call it good.

[Jeff B.]

Re: New motor, light blue smoke

For some reason, the shop that built it can't find the purchase record for the new rings. I remember seeing them in boxes sitting next to the new pistons when they were assembling them but I don't know if they were molly or chrome. I would think molly but can't be sure.

[Timothy B.]

Re: New motor, light blue smoke

Jeff,

I bet they are moly rings as chrome is not used much anymore, racing applications may be different. A leak down test may put your mind at ease. Do you recall the cranking compression pressure.

[Jeff B.]

Re: New motor, light blue smoke

With 3 compression strokes for each test, between 160 & 175. I used the stock 10.5/1 pistons.

[Timothy B.]

Re: New motor, light blue smoke

Jeff,

Your cranking pressure sounds about the same as my 63 300HP when tested. I forgot to open the throttle blades so I had to crank longer and at the end the starter was not spinning as fast. I think my lowest reading was approx 165 and the highest 175, my engine is .060 over bore.

[Jamie F.]

Re: New motor, light blue smoke

An essential part of ring break in and sealing is loading under acceleration, and unloading under deceleration.
As your engine is under no load you really haven't given the rings the opportunity to properly break in.
All out of car engine break ins such as on a dyno put the engine through different loads for just this reason.
I would wait until you have something for that new motor to drag around before condeming it and yanking it out.

[Michael H.]

Re: New motor, light blue smoke

An essential part of ring break in and sealing is loading under acceleration, and unloading under deceleration.
As your engine is under no load you really haven't given the rings the opportunity to properly break in.
All out of car engine break ins such as on a dyno put the engine through different loads for just this reason.
I would wait until you have something for that new motor to drag around before condeming it and yanking it out.

With todays piston rings and PROPER cylinder reconditioning, there really isn't a breakin period. Rings seat almost immediately IF the cyl's are prepared correctly and rings installed correctly. Ring breakin is a thing of the past.
If the engine builder doesn't have an automatic feed precision hone machine, there's a good chance the cyl surface has not been prepared properly. Most low volume engine builders don't have this expensive equipment.

If you have blue smoke after 20-30 minutes of running, you have a problem.

I would start by inspecting all of the spark plugs to see what's happening in each cyl. If they show oil, I would look at valve seal issues first because that's the easiest.

But, as Stu mentioned, I would look into the simple items first. I would guess that 30 minutes of running would have burned off any oil in the exhaust pipes but I suppose it is possible that some remains.

[Jamie F.]

Re: New motor, light blue smoke

With todays piston rings and PROPER cylinder reconditioning, there really isn't a breakin period. Rings seat almost immediately IF the cyl's are prepared correctly and rings installed correctly. Ring breakin is a thing of the past.
If the engine builder doesn't have an automatic feed precision hone machine, there's a good chance the cyl surface has not been prepared properly. Most low volume engine builders don't have this expensive equipment.

If you have blue smoke after 20-30 minutes of running, you have a problem.

I would start by inspecting all of the spark plugs to see what's happening in each cyl. If they show oil, I would look at valve seal issues first because that's the easiest.

But, as Stu mentioned, I would look into the simple items first. I would guess that 30 minutes of running would have burned off any oil in the exhaust pipes but I suppose it is possible that some remains.

I would think that any Shop still in business, especially a "favorite Shop" that can't correctly hone the cylinders on a small block Chevy they would have been long gone...
A friend pulled the heads on his 427 because he thought he had a blown head gasket as white vapor was coming out of the side pipes after 15 minutes. Put them back together and still white vapor... He let the engine run for a while and it went away because it was coolant in the exhaust pipes burning off that poured in there when he pulled the heads, both times.
Don't away suspect the worst, oil in the head, sticky ring, hard chrome rings. Many things could cause this initially.

[Michael H.]

Re: New motor, light blue smoke

I would think that any Shop still in business, especially a "favorite Shop" that can't correctly hone the cylinders on a small block Chevy they would have been long gone...
A friend pulled the heads on his 427 because he thought he had a blown head gasket as white vapor was coming out of the side pipes after 15 minutes. Put them back together and still white vapor... He let the engine run for a while and it went away because it was coolant in the exhaust pipes burning off that poured in there when he pulled the heads, both times.
Don't away suspect the worst, oil in the head, sticky ring, hard chrome rings. Many things could cause this initially.

I'm not saying that the rings or cyl wall finish is the problem. However, IF the cause of oil huffing IS a cyl finish issue, it will never completely go away.
The oil burning may be reduced quite a bit in time but if the engine is smoking after 30 minutes of operation, something isn't right.
As mentioned, the problem may indeed be something else, and likely is something else. However, if it boils down to ring/cyl wall finish, it won't ever go away completely.