3.8 or 4.1? Opinions wanted.

[BuickMike]

I know there is plenty of info on this, but I'm looking for opinions based on my situation.

First off, my original motor is still running. It has 133k miles on it, but is in need of a rebuild. It smokes a bit at startup (has to be worn valve guides)and has quite a bit of blow-by.

I'm not driving the car right now, so leaving it sit without a motor is not an issue.

I'm looking to do a mild build, ARP Studs, mild ported heads and cam, TRW forged if a 3.8, SpeedPro Hypers if a 4.1, stock crank and rods.

I'll be looking to step up to #50 injectors and a bigger turbo like a TE61 in the future, but that's about it.

Basically, I just want a solid 11 second car that will be fun to drive on the street, reliable, and handle well.

I'm leaning towards using my current motor for the rebuild because I know I have a good core, however the results people are getting with the production 4.1's is very tempting to me.

What do you folks think?

 

[MY3TTYPES]

I'd like to hear what kind of results people are getting from the 4.1 and what parts they are using in them. Anybody?

 

[SHADOWII]

here are some links you might find interesting and informitive.
www.turbobuicks.com/forums/showthread.php?t=44909
www.turbobuicks.com/forums/showthread.php?t=24399
www.turbobuicks.com/forums/showthread.php?t=44128
www.turbobuicks.com/forums/showthread.php?t=44481&page=1&pp=15&highlight=4.1
this one is a step by step by Bruce Plecan's
www.bacomatic.org/~dw/bp41/bp41.htm :biggrin:
hope these come up?

 

[CTX-SLPR]

Here is my 4.1 in final assembly. Everything is there but pushrods but nothing is torqued down and I've having some problems with the keyway on Eagle crank. Enjoy the freshly painted pictures.

 

[BuickMike]

Thanks for the replies.

I see alot of votes to stick with the 3.8, but no posts about it.

I juess it all boils down to is the extra power worth it if I already have a perfectly food 3.8?

 

[cool 84]

4.1 hands down for a street car. It's proven it will easily stand up to an 11 sec combo. I would run it just for the difference in spool up alone. I ran the exact same combo on the 3.8L and rebuilt a 4.1 and bolted everything on. There is a noticable difference, especially in spool of decent sized turbo. I even brought the stall down from 3,500 to 3,000 and it spools great. It's a little more torquey both off and on boost. I have mine bored .035 putting it at a 4.00" bore so the cost of pistons came way down. I think I paid ~$500 for my forged JEs with pins. I would run a 3.8 if I was trying to knock off a 9sec stock block timeslip but for anything else, 4.1.

 

[SHADOWII]

personally, I lean towards the extra inches. I have had a 4.1+.020 sitting in my closet for about 3years now, it has already been rebuilt, but I have decided to put a girdle on it, and go w/224 cam. I don't have the funds to rebuild it(the required machining) yet, as I am still working on the house.(another money pit) I don't think you can beat the extra torgue available, especially on the street. It is difficult to see the 4.1 straining at the same hp levels of the 3.8. w/the sme mods.

 

[VadersV6]

Isnt building a 4.1, an all around bigger PITA? Not the same availability of parts? Seems like it would be so much cheaper to just build a 3.8. Plus the 3.8 will hold up fine, and who wants to go through the hell of going with a 4.1 when the payoff isnt worth the effort?

 

[Squid4life]

Some say it is worth the effort, and there really isn't much difference in parts. Well, I guess no more than converting a HA longblock to IC'ed.

Pistons, rings, head gaskets, isn't that it?

14 bolt pan, new front covers are either 14 or 20, or you can drill and tap it.

I don't know for sure, I have yet to do it. I have most everything to try it. STD block, hyper pistons (coated), spare crank, spare 2 dot rods. Or Imay sell it all before I move to Cali...



EDIT>>> CTX- motor look sgreat! Very nice job!

 

[CTX-SLPR]

Isnt building a 4.1, an all around bigger PITA? Not the same availability of parts? Seems like it would be so much cheaper to just build a 3.8. Plus the 3.8 will hold up fine, and who wants to go through the hell of going with a 4.1 when the payoff isnt worth the effort?

Piston, rings, and headgaskets you are correct as unique 4.1 parts, the rest are shared with the 84-85 "Hot-Air" motors. If you are going high zoot then yes, a 4.1 is a ton more work with custom pistons especially, my custom Diamonds were around $700 for piston, rings, and pins. But if you are wanting a bit more power without adding a ton of big stuff to the engine then its worth it. Actually what got me started was a set of eBay pistons I bought and ended up passing along when the project went from low buck motor built out of junkyard and backyard welded stuff to a serious project with durability requirements.
Thanks for the compliment on the motor, now to just finish it up then start collecting electronics to make it run, a turbo to make it powerful, and custom tricks to make it even more different.

 

[Squid4life]

I guess I got lucky and posted a WTB ad for 4.1 pistons and a few guys had them. Got hypers that are coated, used for dyno time I think, then swapped in favor of forged. I have a STD block, the STD pistons were $80. Then collected an old turbo motor with 2 dots and a turbo crank. Mine is low budget, no custom NASA pistons for me.

 

[cool 84]

The 4.1 is just as easy as the 3.8 to build. Yes, the pistons, rings, and headgaskets are different but those are parts you replace anyway. I've done both builds and I would never go back to a 3.8L unless it was a stage motor.

 

[87GNSteve]

Go with the 4.1 and save the 3.8 for later if/when you want to go back to original many years from now when blocks are hard to find. I have a feeling the availablity of production 4.1 and 3.8 will get pretty scarce.

 

[VadersV6]

I would never throw hypers in any performance motor. Especially boosted. Those things are as brittle as glass. As everyone knows, they're not very forgiving with detonation.

 

[cool 84]

I would never throw hypers in any performance motor. Especially boosted. Those things are as brittle as glass. As everyone knows, they're not very forgiving with detonation.

I wouldn't run hypers but my dad has hypers in the fairly well modded daily driver. That thing has detonated worse than any TR I've heard and it's still going strong. Mine on the other hand got a few degrees of knock retard with forged pistons and broke a ring land but these cars hate me anyway.

 

[broke1]

I would run the 4.1 with a 4" bore and the 6" rods that Mike Licht sells.Talk about torque!!!

 

[sixgun86gn]

You could do what I did and find some used forged pistons from an old stage 2 build.I paid $150 for some,threw in a 218/218 comp hyd cam and some decent main studs,bore and hone cost me $80,all total i had maybe $800 at the most in my 4.1 shortblock.

Had no girdle or steel caps and had no sweat putting down 500 hp/500tq at the rear tires on only 20# of boost.

I broke the trans before I could find out how fast I could get it to go but it still ran 127 in the 1/4.Ran 7.1-7.2's consistently on pump gas and 16# at the local 1/8 mile track at 96-97 mph,6.8s at 20# with some timing.

all in all the 4.1 block is fairly strong and can be cheap to build,I didn't use any special head gaskets,the ones at O'Reilly's are the same for both 3.8 and 4.1.

 

[The Don]

hmmm this is seeming to be good info!

 

[blackplague]

I would run the 4.1 with a 4" bore and the 6" rods that Mike Licht sells.Talk about torque!!!

Even better yet!! 4.1L block .035 over for a standard 327 chevy pistons coupled to 425 buick rods offset on one side to fit. A super torque monster :biggrin:

 

[Ttype6]

No one is mentioning that using the larger bore of the 4.1 unshrouds the intake valve.