3.8 bottom end rebuild options - TCCoA Forums
 
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post #1 of 9 (permalink) Old 09-26-2005, 04:26 PM Thread Starter
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3.8 bottom end rebuild options

I have to rebuild the bottom end of my mom's 1992 3.8 Cougar and need some insight. Basically I have a perfect top end on the motor, car still looks and drives like it came from the dealership floor, original cold R12 AC, etc.

The motor has about 200K at the moment. I did the head gaskets 2 years ago and the motor was pristine inside, bore taper about 0.001", just needed to take 0.005" off the heads, minor clean up on the valve seats, etc. Head gasket gave way on the passenger side rear cylinder at the back and was shut right off so no overheating.

But that new fricking rod knock on cold start lets me know I am getting dirty again :-( I was hoping it was only the oil pump, but it is perfect inside as well I just found. The motor was always a little ping happy, so I am expecting to find most of the rods out of round.

What are the options for the bottom end only? Can I drop in a 4.2 bottom end keeping the 3.8 oil pan, etc? Don't want to do the split valve stuff, this car doesn't get used much anymore as my parents are retired, so don't want to waste money either. Basically a stock rebuild. Whats the word on replacement rods, pistons, etc., if I just rebuild what I have? I am thinking a new set of stock bore pistons, re-worked rods, rings, bearings, etc.
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post #2 of 9 (permalink) Old 09-27-2005, 02:00 AM
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I'd suggest just getting a bottom form a 96+ 3.8. I'd say anything else wouldn't be cost effective.

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post #3 of 9 (permalink) Old 09-27-2005, 02:59 PM
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Punch it .030 over and put an RV cam in it? If you could find an old 3.0 SC, Steal crank and decent rods. You could also stroke said steal crank?

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post #4 of 9 (permalink) Old 09-27-2005, 05:09 PM
 
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I am doing a rebuild on a hydrolocked 4.2... All I did was replace the rod that was bad and put new pistons in it. I also had the crank checked and everything was ok.

4.2 cranks are cheap through ford brand new.

RIP Joel Bender and Preston Smith. The world will never be the same without you.
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post #5 of 9 (permalink) Old 09-27-2005, 05:18 PM
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litnig, is the 4.2 crank a drop in 3.8 block? I was reading about this in an article in Muscle Mustangs & Fast Fords.
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post #6 of 9 (permalink) Old 09-27-2005, 05:19 PM
 
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yes and no... there might be some modification needed to the block for clearance.

RIP Joel Bender and Preston Smith. The world will never be the same without you.
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post #7 of 9 (permalink) Old 09-27-2005, 06:49 PM
 
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the stud girdle isn't a requirement, but recommended...

The oil pan would only be in issue if you went with the above girdle and studs

Yes, it is internally balanced, so you would need a new balancer and flexplate (get a 4.2 balancer from a 97 or 98, that will allow you to use the stock lower pulley). For the flex plate, you can get one from a mark VIII and bolt up a gt converter, marauder converter, etc.

RIP Joel Bender and Preston Smith. The world will never be the same without you.
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post #8 of 9 (permalink) Old 09-27-2005, 07:06 PM
 
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I do now know about the AOD converter issue. I will ask Dirtyd0g to chime in next time I talk with him.

As for the girdle, yes it does act as a windage tray. Keep in mind, if you decide to get the girdle you will need to get main studs for a 4.2 98+ and an oil pan from a 2001+ mustang 3.8

RIP Joel Bender and Preston Smith. The world will never be the same without you.
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post #9 of 9 (permalink) Old 09-27-2005, 07:10 PM
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Any stock 4.2 flexplate will work fine.
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