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Author Topic: '71 350 Engine Rebuild troubles...need ideas  (Read 3881 times)

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FastRandy67

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'71 350 Engine Rebuild troubles...need ideas
« on: July 19, 2008, 08:40:08 PM »
I'm new to this board, but have owed a '71 Firebird (350) for about 2 years.  The trouble I'm having is with a full rebuild.  The car uses 1qt of oil every 400 miles.  The shop has torn down the engine three times replacing rings, the entire valve train, etc.  I also get a lot of condensation and large amounts of soot from the exhaust on a cold start up.  The engine doesn't visibly smoke and there are no leaks.  Looking at the tops of the pistons (replaced with new) through the spark plug hole, there is a some oil or dark substance on the concave areas.

The shop is at a loss on what the issue is.  They've done this rebuild three times in the past 16 months...Does anyone on this board have any ideas as to the cause of the soot and oil consumption?  Also, I'm in the SF Bay Area, so if there are engine rebuilders you'd recommend, by all means let me know.

Thanks,
FastRandy

plmcrzy

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Re: '71 350 Engine Rebuild troubles...need ideas
« Reply #1 on: July 20, 2008, 01:23:14 PM »
this may not be the problem, but worth a try, did you peplace the PCV valve ?
I DON'T DESERVE TO BE CONCIOUS RIGHT NOW

FastRandy67

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Re: '71 350 Engine Rebuild troubles...need ideas
« Reply #2 on: July 20, 2008, 03:28:40 PM »
Unfortunately, there were no PCV Valves on these engines.  I have a K&N Crankcase Breather on it.  So, I don't think that's the problem.  Thanks for your suggestion, though.

-FastRandy67

plmcrzy

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Re: '71 350 Engine Rebuild troubles...need ideas
« Reply #3 on: July 20, 2008, 03:52:45 PM »
as far as the black soot goes sounds like the air/fuel ratio is to rich, do you foul out spark plug often?
I DON'T DESERVE TO BE CONCIOUS RIGHT NOW

FastRandy67

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Re: '71 350 Engine Rebuild troubles...need ideas
« Reply #4 on: July 21, 2008, 09:22:12 AM »
I apologize regarding the pcv valve...it does have one and it is new and working properly.  I had a brain f*rt before and was thinking EGR.  I've set the air/fuel mixture as lean as possible (just before stumble at idle) and the problem is back and the car has less power than a 1983 Ford Escort with the A/C on.  One other thing, when I pull the plugs, they look great (grayish white ends), but when looking into the plug hole the top of the pistons have either oil on them or black-ish stuff in the concave areas.

Could the heads be bad?

FastRandy67

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Re: '71 350 Engine Rebuild troubles...need ideas
« Reply #5 on: July 21, 2008, 08:29:13 PM »
I checked the PCV Valve tonight, and there is a bit of oil at the base and a bit of oil inside the connecting hose.  Is this normal?  Also, I spoke with another engine rebuilding shop and the guy spent 20 mins. with me brainstorming issues.  He though there could be a hugh end-gap if the stock size rings were put on...also thought there could be a large side gap with the rocker arms.  Finally, he was surprised that they didn't bore our the cylinders and just honed them.

-FastRandy

National Firebird and Trans Am Club Message Board

Re: '71 350 Engine Rebuild troubles...need ideas
« Reply #5 on: July 21, 2008, 08:29:13 PM »


 

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