460 Autotec forged piston slap and how I reduced it - 460 Ford Forum
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post #1 of 7 (permalink) Old 07-18-2019, 06:51 PM Thread Starter
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460 Autotec forged piston slap and how I reduced it

I have Autotec forged pistons and my builder told me that for the first minute or so I would have to endure piston slap due to tolerances and piston design. I removed all the smog before the engine build. I did everything I could think of to reduce internal friction losses including full-floating pistons.

My builder was correct and there was piston slap. One smog device I believe to actually benefit an engine and that is the ported vacuum switch which is downstream of the thermostat and sits on top (of mine) of the t'stat housing. One set of ports will block the vacuum advance until coolant temperature opens the thermostat; I have the smog port blocked off. This facilitates a faster warm up of the engine. So I decided to reconnect it and found that the retarded timing helps to reduce and eliminate piston slap on my 466 on a cold start. It's a cheap fix and worth a try.

BTW, I just got 14.88 mpg but my thread on how I did it got a 'Closed Thread' for some reason. I will try to avoid it in the future. Pretty good for 6,000#+ F-250 High Boy 4x4 at 4,000' elevation. Stock T-19, 3.54 gears and Dana 70 rear end.

When I can buy a better piece of hardware than what I have and it is approximately the same cost as reworking my old, tired and stressed part then I feel I am ahead of the game.
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post #2 of 7 (permalink) Old 07-18-2019, 09:13 PM
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Cool

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Originally Posted by BigBlueBrutus View Post
I have Autotec forged pistons and my builder told me that for the first minute or so I would have to endure piston slap due to tolerances and piston design. I removed all the smog before the engine build. I did everything I could think of to reduce internal friction losses including full-floating pistons.

My builder was correct and there was piston slap. One smog device I believe to actually benefit an engine and that is the ported vacuum switch which is downstream of the thermostat and sits on top (of mine) of the t'stat housing. One set of ports will block the vacuum advance until coolant temperature opens the thermostat; I have the smog port blocked off. This facilitates a faster warm up of the engine. So I decided to reconnect it and found that the retarded timing helps to reduce and eliminate piston slap on my 466 on a cold start. It's a cheap fix and worth a try.

BTW, I just got 14.88 mpg but my thread on how I did it got a 'Closed Thread' for some reason. I will try to avoid it in the future. Pretty good for 6,000#+ F-250 High Boy 4x4 at 4,000' elevation. Stock T-19, 3.54 gears and Dana 70 rear end.

We've used auto tec pistons with no issues at all at .0035" piston to wall. What is your clearance?



SJ
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post #3 of 7 (permalink) Old 07-18-2019, 09:27 PM Thread Starter
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The shop that did the block did not tell me and I forgot to ask. This guy has 50 years of experience and at 7k miles I have no problems with compression nor oil consumption.(now that I ditched the FelPro intake manifold gaskets for the OEM Victor--another story) so it is safe to assume he got it right. I was impressed with AutoTec's customer service during a phone call and ability to build exactly what I wanted which was a 9:1 C.R. with my heads and quench; they dished the pistons accordingly. Kinda neat the laser etching of information under the piston.

When I can buy a better piece of hardware than what I have and it is approximately the same cost as reworking my old, tired and stressed part then I feel I am ahead of the game.
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post #4 of 7 (permalink) Old 07-19-2019, 08:43 AM
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HI, ?? never heard of piston slap after a proper rebuild?? I think the old man may have done something wrong.. piston slap is NOT normal unless parts are miss-matched.
good luck
tim

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post #5 of 7 (permalink) Old 07-19-2019, 01:56 PM
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Cool

Autotec pistons are forged from 4032 high silicone content aluminum. They need to run tighter because the do NOT expand as much.

Do you have a build sheet that outlines piston to wall clearance as well as ring gap? As a consumer you have a right to that information.

Every performance crate engine build we've done gets a build packet and a copy in our office for reference.



SJ
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post #6 of 7 (permalink) Old 07-19-2019, 02:12 PM Thread Starter
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HI, ?? never heard of piston slap after a proper rebuild?? I think the old man may have done something wrong.. piston slap is NOT normal unless parts are miss-matched.
good luck
tim
Piston slap is a common occurrence with some builders and 'experts' claiming that they know how to fix, cure or prevent it. Please use duckduckgo and search for piston slap forged pistons . I had a Toyota Tacoma, late model, that I bought new and it had piston slap on cold starts which I found out later was common to that V-6 engine; I went from 0w30 to 10w30 which helped reduce most of the noise and that was GM's 'cure' for piston slap in the early LS-1 engine. My piston slap was on cold startups, not warm starts.

When I can buy a better piece of hardware than what I have and it is approximately the same cost as reworking my old, tired and stressed part then I feel I am ahead of the game.
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post #7 of 7 (permalink) Old 07-19-2019, 02:14 PM Thread Starter
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no and I forgot to ask. It has been several years since the build. No problems with the timing vacuum delay and no audible slap.

When I can buy a better piece of hardware than what I have and it is approximately the same cost as reworking my old, tired and stressed part then I feel I am ahead of the game.
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