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1987-1991 Parley with regards to your 1987 to 1991 Bonneville, Olds 88 or Buick Le Sabre Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 04-01-2005, 01:12 PM   #1
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im having a 3800 borred .20 over and i was wondering where i could get some good pistions and rods




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Old 04-01-2005, 04:33 PM   #2
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Not sure about the rods yet but I have hypereutectic pistons you can get from the link in my sig.

You can get a fresh set of stock pistons from a number of places, and if you're just looking to rebuild it they work nicely. Not sure if they're available in oversizes though.
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Old 04-01-2005, 08:53 PM   #3
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thanks for the help




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Old 04-04-2005, 03:06 PM   #4
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Welcome to the club! shes pretty :P
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Old 04-04-2005, 10:37 PM   #5
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You should have the pistons you intend to use before the machine work as the pistons should have a piston to bore dimension recommendation. Hypereutectics will usually have a tighter clearance due to the limited expansion which is good for ring life as the pistons rocks less in the bore. I used SilvoLite 1744h pistons (vin L) which have an approx. .050" greater compression height for a compression ratio of 9.1:1. One other thing, use stock head gaskets if possible. The cylinder hole in the Fel Pro gaskets I got with the overhaul kit have an almost 4" diameter, about .015" greater than the stock gaskets and this will cost you at least a couple of tenths in compression ratio. The rest of the Fel Pro set is first rate.
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Old 04-05-2005, 02:44 AM   #6
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ok thanks for the help i built a 344 for my old 84 half ton chevy and i didnt know where i went wrong it was BALLESS and im trying to make this one not lol

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Old 04-05-2005, 10:14 PM   #7
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From the investigation I did at the time I did the 3800 rebuild, I found you cannot trust a lot of the published information from some manufacturers. Many stock replacement pistons are "destroked", meaning they are shorter than stock. My guess would be they assume the head or block will be decked and the pistons are shortened to compensate. That dereases the compression ratio substantially if no machine work is required. The other problem was the size of the dish in the piston. I tried three different manufacturers and cc'd them myself and all were greater volume than listed. The combination of the large hole head gasket from Fel-Pro, the shortened pistons and larger dish would have actually dropped the compression ratio 1/2 of a full number, or down to 8.0:1. All things being equal, with a match to the stock piston in the correct overbore size, compression ratio should rise due to the larger swept volume of the larger diameter. One other small item is the balance between cylinders. I cc'd all of the combustion chambers and the piston dish. By swapping the smaller dish pistons into the larger chambered cylinders I got the total compressed volume to vary .6 cc'* high to low. If I had not measured them, they could be off by up to 2.5 cc'*. Maybe picking nits, but it takes little time to blueprint as best you can, even using relatively generic parts. Only my .02 but measure the parts to be sure you are getting what you paid for. If not, reject them. A fully machined piston should be more accurate, especially in the dish size, but it is best to double check.
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Old 04-07-2005, 03:10 AM   #8
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thank you very much for telling me that i could have made a big mistake
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