blue smoke

oldae82
Club4AG Enthusiast
Posts: 111
Joined: Sun Apr 07, 2013 5:38 pm

blue smoke

Postby oldae82 » Tue Oct 25, 2022 5:01 pm

I have a 4ag I've recently put back together. I used Tomei 264.8.15 cams, intake and exhaust. I used weisco pistons, used, with rings, rods, and new rod bearings. The seller of the pistons was unsure of the compression ratio, thought it might be 10:1. He said the engine he'd installed them in spun a crank bearing and he lost enthusiasm for the project. He thought maybe 150 miles on the pistons, but I suspect more, looking at carbon. Pistons looked good, rings looked good, had sharp edges. All assembled and running. Engine is showing 215-220# compression without the butterfly open, warm engine, on all 4 cylinders. Engine shows 195-210# on cold compression test.

Problem is this. I was driving on the interstate at about 4k in 5th, went to slow down for traffic, downshifted, and was enveloped in a cloud of blue smoke. Further playing/testing on back roads shows blue noticeable smoke on hard acceleration. Engine sounds good, pulls hard to redline, and shows good compression. I am running 93 octane fuel. Any idea as to cause of this embarrassment?

totta crolla
Club4AG Pro
Posts: 651
Joined: Tue Mar 26, 2013 5:21 am
Location: Oxford U.K

Re: blue smoke

Postby totta crolla » Wed Oct 26, 2022 12:32 am

Check to see how much comes out of the engine breather when you rev it to approx 4k in neutral.
I would have fitted new rings and honed the bores (as a minimum) before installing the pistons.
Can we assume that this blue smoke comes from the exhaust?
Greta will pop by and spank your arse for driving this car about...

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oldeskewltoy
Club4AG MASTER
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Joined: Wed Jan 09, 2013 4:44 pm
Location: Portland, Oregon

Re: blue smoke

Postby oldeskewltoy » Wed Oct 26, 2022 9:31 am

typically....... smoke on decel - valve seals. Smoke on accel... oil control rings.
OST Cyl head porting, - viewtopic.php?f=22&t=300

Building a great engine takes knowing the end... before you begin :ugeek:

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