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Thread: Post Mortem analysis - Let's all learn !

  1. #1
    Fuel Injected!
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    Post Mortem analysis - Let's all learn !

    What I did right - I feel as though I put quality parts in this build, my guy has many many years of experience ( not to say he can't make a mistake) , engine ran like a bitch on the dyno with a carb. consistent pulls all within 2hp. It seems that his experience trumps my stupidity. I would have to point to some sort of setup as opposed to part failure or build failure

    These guys normally do carb stuff so enter the rookie - ( Me), engine goes in truck, after 4 cycles of the key , fuel line feels cold, turn key , the 355 fires right up, I mean fires right up like it had been a cohesive unit for years. So I'm thinking , wow, I got this.. we set the timing unplugging the little plug deal , plug it back in, seems fine under no load. good... gas is old, so let's hook up the ole Moates deal and take a ride.. before I left I was looking at the data logger dashboard deal as it sat on my center console, spark advance increased with rpm, Learn monitor was bouncing into yellow but not far. all other items were fine, ( at least not yellow), still no CEL , get going down the road, 6 miles to wawa, real low on gas... put a 30 spot of premium in her and head back. temperature never above 180 , so I glance over at the dash and see the MPG , amazed that it's getting 23mpg at 50mph on cruise, she's purring like a kitten... come up to a stop sign, take off gradually and notice spark advance in dropping under accel , seems odd still no other warning signs, so I hammer on it but not bad get it up to 75 or 80, she still seems smooth, next stop sign I hammer it, yellow in the corner of my eye, CEL in the corner of my other eye... and that's the end. exhaust # 6 stuck open, more than likely she got caught by the TRW piston I so cautiously lubed up and installed with its new rings in a beautifully honed cylinder just a month ago.

    Interesting QUESTION - What condition would cause spark advance to decrease, I would of expected a lot more timing , I firmly believe this is the issue, so we goofed in this area. I'm wondering if I should of put more timing in it from the get go.. having no baseline and no experience with the tuning s/w I have no clue what the required results should of been. I should of taken it to someone instead of being an idiot and trying to learn something I know nothing about or got a holley sniper and let it do the work.

    I think now Im going to have the engine pulled, sell it back to the builder , sell the truck with no engine and include the old one with it , which ran fine for a 190hp tbi head old girl. The only reason Im abandoning ship is because I move 1700 miles away on thursday of next week.

    Part of my medicine is to write about my woes, so thank you for reading or at least scanning over this mess.. lol

  2. #2
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    I would not expect the tune is the problem. Valves can go this quickly with valve <-> piston collisions, valve guides too tight, or when high compression meets wrong octane fuel. If you're not running stock pistons and heads I'd look at valve guides, especially if RPM was in the upper range when the engine failed.

    Timing will drop as vacuum drops or when knock occurs. Sounds like ecm was doing what it was supposed to.

    Too bad you can't throw the engine into a crate and take it with you. You're gonna find a bunch of clean trucks in SD and you'll want to start playing again pretty quickly. If your builder is willing to redo it, maybe help figure out what went wrong, then you might try leaving the engine with him for a few months. 3400 miles could be done in a weekend with two drivers.

  3. #3
    Fuel Injected!
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    Ive done it 15 times. my best time is 26 flat in a rental Impala. 26 1/2 , 27 a few times. Option Im leaning to is to have it sent to me and put it in something else, im changing my mind at a rapid pace here...lol

  4. #4
    Fuel Injected!
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    When I logged this thing I used an XDF file and some other extension to get the logger to work. Could those things effect engine performance in logging mode? no changes made to stock BIN.. I dunno, im hunting for clues.

    We spent so much time on those heads, honing, checking, resurfacing seal seats, measuring valve height, shimming, not to mention the valve job itself, it's not like we just slapped it together ya know?

  5. #5

  6. #6
    Fuel Injected!
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    I feel for you. It sucks having a new build have issues. In theory, the exhaust valve might stick if the timing was retarded and the mixture on the lean side. That combination puts extra heat into the exhaust side. In practice, it's very unlikely it was the tune.

  7. #7
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    Did you use brand new lifter? Any chance the valves were adjusted when the lifters had no oil? This could cause the lifters to open the valves too far.

  8. #8
    Fuel Injected!
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    That actually makes sense, we did run the crap out of it on the dyno, pulling to 5800. I would think it would of went then ( carbed on the dyno- FYI)

  9. #9
    Fuel Injected!
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    I was watching that spark advance under accel it dropped like a dead horsefly

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