4.1 vs. 3.8

[cooled85T]

Im sure this thread has come up before but I cant find it. I was wondering what the difference between an NA 4.1 and a 109 3.8 engine are. I bought a 4.1 off of a guy. He says he used a 109 crank and rods and hyper pistons. I want to get the pistons out of there and was just wondering what all was going to be invovled in this. Also does the RJC girdle work fine on a 4.1

 

[Black Power]

You need to drill and tap a hole for the oil drain from the turbo to the block. Also forged slugs for a 4.1 are going to be big bucks, they are custom pieces as no one carries them on the shelf.

There is a girdle that someone makes that will work with the 4.1s 14 bolt pan. I think it is by RJC.

The 4.1 uses the same rods and crank, it's the same thing but a bigger bore. There are differences in the blocks, but in short the 4.1 will work for a turbo engine.

 

[Joe Kelsch]

I've read somewhere that you may want to drill out the first couple of threads out of the deck for the head bolts. Something about the deck getting pulled up under boost which cracks the deck.

 

[cooled85T]

The motor is .030 over. Nobody sells pistons for these? How much are custom pistons and where would I get them?

 

[sixgun86gn]

The motor is .030 over. Nobody sells pistons for these? How much are custom pistons and where would I get them?

About $650-$800

The hypers will be fine,I have them in my 4.1 thats in my T and they have taken 26# so far no sweat.

If you absolutely have to have the forged pistons you will need to buy some from JE,CP, or maybe diamond. They can all make them,but they are not an off the shelf piston.

 

[charlief1]

If you want a real headache try my combo. 4.1 bored .035 over to 4" with 6.5" or 6.65" rods. I asked if there was a chevy piston that would work with this combo and there is no option, I have to go custom. If you go to a 4" bore you can get a better choice of piston and might save a few $ but if you're looking for power it's what you have to do.

 

[49-blues]

I have a set of forged ross pistons-like new from billy anderson-set up for a stroker combination with a 4.00" bore and piston compression height of 1.205"-$300. shipped

 

[charlief1]

What kind of dish do they have? Not trying to hijack your thread cooled85t.

 

[bison]

If the block is a 484 casting i wouldnt waste my time. The decks seem to crack often. What are your performance goals? If you want a strong 4.1 by a stage 2 block.

 

[sixgun86gn]

If the block is a 484 casting i wouldnt waste my time. The decks seem to crack often. What are your performance goals? If you want a strong 4.1 by a stage 2 block.

Thats funny because thats all I use. The oil holes are bigger and I haven't had a problem with cracking yet.

 

[cooled85T]

I am looking to build the motor for high 10s. I wanted to put forged pistons, girdle, and a good balance in it. Any other opinions on the 484 block. Its what I have.

 

[49-blues]

charlief1-the pistons are recessed like stock or the trws.hth.

 

[49-blues]

cooled85T-I would put a cat crank or eagle in it along with some good rods-also I would use some steel caps vs the girdle.

 

[boostingbuick]

484 block here with girdle and stock caps going high tens at 128. Stock crank and rods. And that is with a cracked deck. The cracks have never been an issue. I knew it was cracked when I bought it and has had more than a 100 passes on it since.

 

[wickedtt]

484 block here with girdle and stock caps going high tens at 128. Stock crank and rods. And that is with a cracked deck. The cracks have never been an issue. I knew it was cracked when I bought it and has had more than a 100 passes on it since.

That's what I let to here, just keep it simple and with a cracked deck too

 

[SVT F15O]

I pushed my last setup(4.1 with stock crank and rods) to a 10.30 @ 131.
Next time out will have a stroker rotating assembly and a little bigger bore. I am hoping for deep in the 9's.

 

[BOSS 6]

whats the difference in the two blocks

 

[cooled85T]

cooled85T-I would put a cat crank or eagle in it along with some good rods-also I would use some steel caps vs the girdle.

I would love to put all that in it but I was trying to keep this simple. Will those pistons work with my setup?

 

[Otto J]

I pushed my last setup(4.1 with stock crank and rods) to a 10.30 @ 131.
Next time out will have a stroker rotating assembly and a little bigger bore. I am hoping for deep in the 9's.

And it has a cracked deck!
The heads and cam assembly are installed.
Just waiting on a few gaskets from Mat to finish.
This is a 4.1 production block with a 3.625 stroker crank:biggrin:

 

[cooled85T]

So I guess a cracked Deck is nothing to worry about?