how can i tell a sc 3.8 from a na 3.8???

sendeth

Registered User
are the casting numbers different on the different engines??? i have a guy who says he has a 3.8 motor built for a supercharger with only 20k miles. i want to make sure that this guy isn't an idiot trying to sell a normal 3.8. my friend says i can take oil pan off and look at the seam on it. he said the forged crank will have a thicker seam, almost a 1/4 across. are there any other ways i can tell if this is infact built with forged parts without taking it apart???

----sendeth@hotmail.com
 
Heads have "SC" cast in them on the outside lip just below the valve cover facing up.

Block has SC cast into the back right side bank of cyclinders (when looking at the back, or tranny side, of the block)

Crank??? Sorry I don't remember real well. But I do recall a forging die parting line on the balancing weights. Or the place where the forging dies seperated, almost looks like a casting die parting line. Oh, almost forgot, the rear main bearing of the crank will be 0.010 inch less than the other main bearings.
 
Looking at the crank it is easy to tell them apart also. The N/A crank does not have the large counter weights that an SC crank has. On an SC crank, each pair of cylinders has large counter weights. On an NA crank, only the first and last ones do as I recall. Anyway, they look TOTALLY different.
 
crank

you can tell a cast crank from a forged crank by tapping it with a hammer. If it makes a short diiiinnng then it is cast, forged will be more like diiiiiiiiiiiiiiiiiiinnnnnnnnnnnnnnnnnngggggggggggggggg. If you know what I mean. To test set the crank on end on cement and balance it with your finger and tap it lightly with a metal hammer. O yeah if the crank goes THUD, then its cracked.
 
Re: crank

M90TAURUS said:
you can tell a cast crank from a forged crank by tapping it with a hammer. If it makes a short diiiinnng then it is cast, forged will be more like diiiiiiiiiiiiiiiiiiinnnnnnnnnnnnnnnnnngggggggggggggggg. If you know what I mean. To test set the crank on end on cement and balance it with your finger and tap it lightly with a metal hammer. O yeah if the crank goes THUD, then its cracked.

Or you can set it on a folded up towel.

There is also "SC" on the front of the block

Jeff
 
thanks

thanks for all the replies. i've been reading through the site also. and thanks for the picture, that helped a lot. about those roller rockers, there is a group but post about some roller rocker i was thinking about getting. are they worth it??? and i think they are the 1.73's. what kind of hp gain do you get???
 
No appreciable gain in HP has been recorded. 1.8RR's were worth 10rwhp on my 340rwhp fully modded motor. On a stocker it is a waste of money.
 
Yeah he's right. I got them thinking they would give me sick HP. I got gain that was noticable, but not like what I was expecting. I never dynoed it with just those added because I also got my throttle body and intake on at the sametime. But I still like them. I just wish they weren't covered by the valve cover because they are pretty.


oh and they are SCP 1.73 rr's
 
Both sides on the front of my block had SC cast into them as well. Here is the passenger side.

passMMinst.jpg
 
3.8

The 3.8 SC heads are aluminum, are the 3.8 n/a heads iron, if so, they should be a good bit heavier than the SC heads.
 
heads up

Oh, well then that would make it a little harder to tell them apart. I did notice mine had the SC stamp on them when I did my head gaskets in January.

David
 
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