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Old 10-17-2011, 07:14 AM
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Thx Bud, ya i was expecting to see rough looking bores or damaged piston. thx for the ring advice.

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Old 10-17-2011, 09:11 AM
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When I broke mine it was not obvious until I removed them. Dont forget to mark everything
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Old 10-19-2011, 10:06 PM
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Yes sir i found the problem two pistons with cracked lands. Time to put flat top pistons and not trust someone else. My figures with my heads should be about 9.5 to 1 much better for the street. Good news is bores still look good. thx and surprise it ran as good as it did.
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Old 03-13-2013, 06:15 PM
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Yep. I was just going to comment that as a general rule, 9.5:1 for cast iron heads on pump gas. 10.5:1 for aluminum. Aluminum heads allow for more compression due to their inferior thermal efficiency. I generally stay down at the 10.2 mark even on aluminum just for safety and to allow a little more flexibilty with fuel trims and timing. Remember also, the Vortecs are a "fast burn" design, meaning that they want less ignition lead by design.

As far as what happened in your engine during those 90 miles, I am concerned for you that you didn't hear that. It had to be ringing pretty hard. I would urge you to pay very close attention to the tone of the engine as you run it. No radio. And remember also, unless you break a motor in on the dyno, you generally want to run it easy for the first 1,000 miles anyway, focusing on seating the rings so you don't end up with an oil burner.
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Old 03-13-2013, 11:44 PM
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Thanks for the sense of reason post.We have taught our driver a good "seat of the pants" dyno on new builds is invaluable.After all your in that situation can't hear much over open heads.Same applies to street rods.So let the fun begin after the first 1,000.
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Old 03-14-2013, 04:17 AM
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Quote:
Originally Posted by stegman View Post
Yes sir i found the problem two pistons with cracked lands. Time to put flat top pistons and not trust someone else. My figures with my heads should be about 9.5 to 1 much better for the street. Good news is bores still look good. thx and surprise it ran as good as it did.
Stegman,
When you say not trust someone else, are you implying that the installer, that wasn't you, broke the pistons when they were installed?

I'm curious of the ring gap on the bad cylinders?


To the rest of you,
Do you think these are broken due to install, detonation or something else?
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Old 03-14-2013, 05:41 AM
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Detonation or ring ends butting would be the top two. Rod bearing damage could point to detonation. Inspecting the rings might show if they butted.
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Old 03-19-2013, 08:57 AM
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Are the rings gapped correctly? Easy to check once the pistons are out.
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Old 03-19-2013, 09:26 AM
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Originally Posted by stegman View Post
I have a fresh 383 stroker in my roadster and after tuning and general cam breakin with a couple of short drives iam getting some blowby with and without the pvc. i know i should get some until its broke in, but it seems a little excessive to me. i pulled the plugs and they look even and pretty good telling me no broke rings. could timing effect blowby, iam running 76cc heads on 8cc dome pistons with a compression ratio of about 10.5 on 93 octane. does anybody think race gas or 100 octane avfuel would help. total timing is only 32 advance. thanks agian........
You need to break the engine in, short drives will not accomplish that. The engine and the oil need to get up to operating temps and stay there for a considerable period. You need about five 100 mile drives or one 500 mile drive at mostly moderate RPMs, with a few blasts on throttle to ge there. If you don't, it is easy to have an engine that will always have high blow by and perhaps oil consumption, though these are two different issues with their own as well as some common causes. What was used for rings is very important, chrome rings can be hard to seal up, these take more aggression on the throttle to bed them in than moly and certainly plain iron. A good engine builder would keep track of these things and advise the engine's owner/operator accordingly.

Short drives are very hard on an engine especially a fresh one. You can get a lot of blow by till the rings and cylinder walls get seated into each other. No 100 octane fuel will not help. If this doesn't settle down after a handful of long drives then you can start to consider problems in parts and/or machining.

Bogie
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