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Low Compression Street Engine's & Tuning Techniques Idea's...How Too's on low compression Engines.

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Old 09-03-14, 01:56AM   #16
sprint250
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I still own a 1974 Ford truck that I picked up in 1975.It has a low compression 300"six.
The engine would ping on any fuel.
Could not get out of its own way.
In the flat it could barely get past 80mph
The reason was not the fuel.It was the POS Carter YF one barrel carb. It was literally falling apart on the manifold.
All kinds of un-meterd air leaks.
I would fix it and 6 months later trouble again.
Also figured out the Intake manifold had leaks too.

All that lean running/pinging an possible detonating eventually wiped out the bearings by 1986 at 140K.
When we tore it down in 88 all the bearings were into the copper.

Re-assembeled it at home after sending the block & head to reputable machine chop.
Different cam grind ,new Offenhuaser manifold and Autolite 2V carb w/ 6cyl split headers.
It ran smooth , had more power than ever before,it would run with out pinging or dieseling on shutdown even on 87 oct.
That truck would now easily peg the 100mph speedo and was able to maintain that speed uphills as well, something it could never do in the past with the original Ford factory build and tune.
We now call it "the other 5.0".
The second build lasted 300K before another teardown in 2008.
The bearings were worn but nowhere near as bad as they were in 1988.
I'll attribute that to no air leaks in the induction system plus adequate fuel delivery.
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Old 08-03-15, 11:15AM   #17
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Quote:
Originally Posted by 1967 Tempest View Post
Can a low Compression engine Ping?

Yes. Cam profile has a lot to do with compression and ping. I try and stay under 165psi cranking compression to control cylinder pressures. Max I like is 175/180 safely.
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Old 08-03-15, 01:29PM   #18
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I think I have a combo of exhaust leak and lifter tap. Building a new engine right now. I will know more once I get into this engine.
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Old 03-29-17, 07:55AM   #19
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turns out it was both an exhaust leak from the down pipes and lifter noise...
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