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Old 04-16-2002, 06:09 PM
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Unhappy bad vibes

Just had my new 454 with 8-71 blower dynoed and tuned and have a bad vibration that rattles out my block to trans dowels and loosens all my exhaust bolts, even though they have lock washers. engine was supposably balanced. it has a crank hub that bds blower recomends instead of a damper. so far just running it in my garagr I have cracked a turbo 400 trans bellhousing,flattened a cam in 4 minutes of running, and chased loose nut and bolts every time I start it for a few minutes. I pulled the oil pan to check if it was balanced, and I see that alot of metal was removed from the crank with a drill so it was balanced but I'm afraid somthing went wrong. Could they have balanced it with the crank hub 180 degrees out since it has 2 keyway grooves? I also see some scoring on the cylinder walls and when I scratch across them with my fingernail they seem pretty deep> Is that common for a engine that's only run for about a hour or are my forged pistons swelling when they heat up and getting so tight that thier scoring the walls due to incorrect bore size for the forged pistons? Let me know what you think. I'm about to go to battle with the machin shop and need some pro advice. thanks

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Old 04-16-2002, 07:05 PM
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scored cylinder wlls sounds like a broken ring.is the motor fresh?first time run? I would raise H### with the shop that put it together
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Old 04-16-2002, 07:11 PM
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Big block Chevy's can be either externally balanced or internally balanced, you have a combination of components (flywheel, crank, crank pulley) that do not match. Sounds like when they rebalanced your motor they internally balanced the motor to match you blower crank pulley but you may have an externally balanced flywheel, you can check by rotating the flywheel and looking for spot welded plates close to the ring gear. If you remove these you will now have an internally balanced flywheel plate, it would be best to replace the flywheel if you find you have a mismatch of parts. What does the shop say?

As for the scoring, they need to redo your engine. Hope you don't need a lawyer. Scoring as you describe in the first hour of run-in is not normal and will mean a very short lived engine if and when you get it running right. Forged pistons need 0.0015" to 0.0025" clearance per inch of cyl dia, blower engines should be on the high side. This means 0.0065" to 0.0105" clearance on the 4.25" bore. It is possible the shop honed the engine for clearance with a cast piston. If so they might be able to hone out the scoring and get you the correct clearance, but the pistons better be replaced if they were the ones who screwed up. You should remove the heads and measure to see what is there so you will know before they try to feed you a line.
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Old 04-16-2002, 07:55 PM
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4jaw is dead on this one...it just so happens i just pulled a 454 out with the BDS counter weight you talk about(its got a BDS blower on it) If you want a pix of the flywheel e-mail me.Its going back in thursday. They internally balanceed this motor and the flywheel is off a smallblock. Ask the machine shop if it externally balance or internal balanced. Also if it broke the trans....now this is a long shot...the block may not be indexed to crank. They make offset dowels to do this if the motor was line bored. Sounds like you have a balance problem. If you need any pix of the BDS set up just yell. This one is a bear and runs well.Just had to pull it to fix some frontend stuff.
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Old 04-17-2002, 05:28 AM
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It is my understanding that the crank is externally balanced due to it having drill holes on the counter weights insted of being filled with mallory metal. the flex plate is weighted, and the crank hub is also the BDS external balanced hub. In reference to the bore size; what should the bore measure for a 454 bored .030 over and running a blower. you mention a very loose piston fit. Why is this neccesary with a blower. The shop that did the work wants the engine back so they can go thru it, but I'm reluctant to let them have it because so far the owner has made excuses as to why I've been having all these problems, and none of them involve his work. He also told me, when I asked him whether my engine was internally or externally ballanced that a 454 can only be externally balanced. This shop specializes in repairing broken heads for deisel trucks, and hind sight tells me that they don't know anything about high performance engines, or at least not enough to machine them corectly. If I bring it back to them, we all know that thier not going to admit that anything they find wrong on thir part caused my problems. And if I have sombody else do the job over the right way then the judge will say that I didn't give the origional machine shop the chance to resolve the dispute by correcting thier mistakes. I know cause Ive been there. I don't think a lawyer will make a difference other than more money spent on a already expensive lesson.Guess I'm pretty good at wasting thousands of very hard and labor intensive dollars.Makes me want to crawl back in bed.
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Old 04-17-2002, 02:40 PM
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Engines running forged pistons need more clearance due to the higher expansion rate of forgings, blower engines and turbo engines should be clearanced on the high side due to the extra heat these components put into the chamber, if you have scoring on the cyl walls there will be particles floating around in the oil so I would check ALL the bearings to be sure none are damaged. Something else to check.

Cylinder bores should be around 4.287"-4.290" assuming the engine had never been bored before. Remember piston size is the ultimate determinant in sizing the bore and that should be your guide. The shop should have given you a build sheet telling you what they did to the motor and the sizes of the parts installed, is there an ID plate on the engine block?

Perhaps the flywheel counterweight is out of phase with the crank balancer weight, sounds like you have the correct parts (external balance balancer, external balance flywheel, drilled crank for external balance etc.). Since the flywheel weight has the most effect and you have had trans problems (Phat was right about the offset dowels make sure to check particularily if the engine was aligned honed) I would guess the flywheel is out of phase. Maybe Phat could provide some photos of the correct phasing of the crank balancer and flywheel counterweight at TDC so you could compare. Nice to have another engine to look at!

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[ April 17, 2002: Message edited by: 4 Jaw Chuck ]</p>
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Old 04-17-2002, 04:35 PM
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Phat and 4JawChuck are right on. It definetely sounds like a severe balance problem. As far as the crank front balancer counterweight is concerned, if the engine is externally balanced It should have the front vib dampner counterweight and should have been balanced with the flywheel and the front counterweight attached. As far as some of the Blower companies not using a balancer on the front of the engine, this is only for internally balanced engines like small block 283, 327, 350's or big blocks like 396, 402, 427 or early chysler 440's and 426 hemis. The thought on this is that the gilmer belt drive acts as a vibration dampner.
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Old 04-19-2002, 05:04 PM
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Hey phat those pictures would be great. I'm taking out the engine this weekend and I think the pictures would help alot. thanks
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