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How much reversion is too much??

Old 10-05-2016, 07:41 AM
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Thanks everyone for the info. So, while I have everyone's attention, I have another question.

This combo also makes some pretty high EGT's(1500+)@WOT, which I posted about in the past. Apparently its not causing an issue with the engine's reliability and the conclusion was there wasn't much that can be done to lower them w/o changing the combo. I was however wondering if the extended time with the high heat was taking its toll on the exhaust, and exhaust valves. Throw in reversion, and hence my worries on dropping an exhaust valve.

However, this year I did pull the egt sensors out of the riser's a little with some o2 extenders(my O2 bungs are welded in right above the riser flange). Egt's dropped by over 200/300* across the board, and maybe its because the sensor is shielded a little bit more, or just closer to the outer circumference of the riser, Idk.

With that being said. Are there any heat formula's out there to give me an idea of what the actual egt is coming out of the port? Does the heat multiply as the cylinders combine in the riser? Does the turbulator create more heat? Is it hotter in the middle of the riser then toward the outer edge?

Any thoughts?


LE
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Old 10-05-2016, 08:13 AM
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If you went with daytona sensors ignitions, you could have all the timing you want at idle, custom map it, pull some timing in the midrange, and add some timing up top . 28 deg total at wot is pretty low, unless you are running a ton of boost, or a vortec style chambered head. I running 34-35 total timing on my supercharged engines from 5500-6000rpm. Between 5000-5500, about 32-33.
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Old 10-05-2016, 09:26 AM
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Originally Posted by MILD THUNDER
If you went with daytona sensors ignitions, you could have all the timing you want at idle, custom map it, pull some timing in the midrange, and add some timing up top . 28 deg total at wot is pretty low, unless you are running a ton of boost, or a vortec style chambered head. I running 34-35 total timing on my supercharged engines from 5500-6000rpm. Between 5000-5500, about 32-33.
I melted some pistons in 2008, and then again in 2013, because I didn't learn my lesson in 2008. It seems my combo is really fast at 30* of timing, and really expensive at 31* of timing.. 9.3 to 1 CR, and 8lbs of boost at 5900rpm. Maybe the cams, heads, higher egt's, Idk. I do know its a crap shoot at 31*s.

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Old 10-05-2016, 09:28 AM
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Usually melting pistons is from being lean. What kind of air fuel ratio were you running ?
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Old 10-05-2016, 09:57 AM
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Originally Posted by MILD THUNDER
Usually melting pistons is from being lean. What kind of air fuel ratio were you running ?
Wasn't monitoring AF in 2008, and I did have a carb issue when I put this combo together in 2007, which I believe helped along my piston issue in 2008. But I do keep a pretty good log of where and what, an I had 31/32* of timing when it melted in 08'(new carbs after that).

In 2013, I was monitoring AF, and its always been on the rich side, between high 10's and mid 11's at WOT. Played with timing on Sat(actually chasing high EGT's) and melted 2 pistons on Sunday with 31*s timing.

I must admit, I've been in the maintain and have fun mode for awhile. Not interested in going full speed all the time, and keeping things a little conservative. I've had good docking, driving and speed with the blow thru carbs, but my next combo is going to be fuel injected with some kind of data logging.


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Old 10-05-2016, 03:38 PM
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methanol injection / check afr like running now / air gap tunnel ram w blocked exhaust heater / we have lil chev marine makin frost ice on a hot day
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