Thinking of going 4.1 what are the goods and bads??

T

thunderace31

Banned
Joined
Sep 2, 2002
Ok I am looking at either rebuilding my 3.8 and stroking it to a 4.1-4.5 or purchasing a 4.1 and going that way.

What eles is need to for the 4.1 to go in?? Dif headers motor mounts??

What I want to do is run High to mid 9's next year

But I also want to be able to drive the car on the street (Cruise nights and a little stop light action!)

Now here is my big one 4.1 and 3.8 are off center blocks??? How hp much can a 4.1 take before it goes boom!

Both look to be about the same $$ to build just dif oil pans I think???

What heads should I go with?? GN1 or Posted stock?? What cam would be best??

I already have a TE65a on the car now it runs really well and should be in the low 11's maybe high 10's this year on the stock unopened block! Its slowly dieing and has some blow by so its time to do something for next year

I also did a search on here and came up with only 2 threads that didnt answer to many of my questions but then again I seem to have problems with searching for some reason lol Im really not the best at computers or key wordsd I guess

Thanks for your help and info
Derek
 
The #4291 blocks are supposed to be the best of the 4.1 production blocks as far as strength goes, i have front three main billet caps/arp studs -with a steel crank should be good to 800 HP. i might consider selling mine-i have to much stuff and not enough time to complete everything.i was told by Dan Strezo that a girdle wouldnt be necessary but if you got extra dough i would go for that as well.
 
Someone posted recently about a 4.1 and the pics showed the block had cracked, near the deck.
 
the #4291 has the most meat in the deck area and there are other steps that can be taken to avoid the cracking in the deck area.like drilling the bolt holes down alittle so the studs grabs the deck at a lower location thus stronger.
 
49-blues said:
the #4291 has the most meat in the deck area and there are other steps that can be taken to avoid the cracking in the deck area.like drilling the bolt holes down alittle so the studs grabs the deck at a lower location thus stronger.
Click to expand...

How far can they be board out?? .20 .30 .40???

What about the oil drain back for the turbo?? And the oil pan is a 20 bolt right??

Everything else fits (IE Oil pump timing cover same cams and lifters ect.)

They also look like at the one end there is no cooling passage?? How do these run on the street hot or normal??

Should I consider Aluminum heads if I went this route??

Thanks for the info
 
High to Mid 9's. I would build your 109. I am building a 4.1L production block but I plan on just running it 90% of the time on pump gas. My block will be bored .040 over, girdle, hypo's, stock rods, turbo crank, steel heads, 14-bolt pan, etc. I will be running a 70BB, stock TB, PFM and the cam I haven't decided on yet. It should run decent until I decide to build my 109. My intentions are to have a very strong running street motor low 11 maybe mid 10's :D
 
4.1

i wanted to build one for my car but the guy that does my machine work and he knows turbo buicks very well, talked me out of it. the cracking of the decks and the cylinders are very close together. i am very hard on my car so i am going to build a 109 stroker with billet caps with no girdle. i think for a street car the 4.1 is good with the occasional trip to the track. With the strokers kits they have now i think staying with a 109 block is a no brainer but this is just my opinion.....hth.........Bob
 
I have heard the exact same thing from a local GOOD buick builder... and have seen it happen.. I'd build the 3.8


Super6 said:
i wanted to build one for my car but the guy that does my machine work and he knows turbo buicks very well, talked me out of it. the cracking of the decks and the cylinders are very close together. i am very hard on my car so i am going to build a 109 stroker with billet caps with no girdle. i think for a street car the 4.1 is good with the occasional trip to the track. With the strokers kits they have now i think staying with a 109 block is a no brainer but this is just my opinion.....hth.........Bob
Click to expand...
 
doesnt the 4.1 have 14 bolt holes? Or are we not talking about a stage motor? I dont know anything other than the 109
 
Imo

I have used both 4.1 and 3.8
The 4.1 makes a great STREET eng.
The 3.8 is better suited for a RACE eng.
The biggest drawback to the production 4.1 is the thin deck. Limit boost to around 18-20 psi and stay away from detonation and it will hold up well.I wouldnt recommend dumping a lot of $ in a 4.1. Best of luck.
 
Lee Thompson said:
I have used both 4.1 and 3.8
The 4.1 makes a great STREET eng.
The 3.8 is better suited for a RACE eng.
The biggest drawback to the production 4.1 is the thin deck. Limit boost to around 18-20 psi and stay away from detonation and it will hold up well.I wouldnt recommend dumping a lot of $ in a 4.1. Best of luck.
Click to expand...

Thanks Lee I was just looking at what to do and I guess I got my answer :)

I really want to go 9.90 thats my magic # I have 2 other 10 sec. cars so I want to move just a little faster.

I beat the **** out of my T even on the street if the road is clear it to the mat! lol. So I want something that will hold up well. All my chips are burned for alky or race gas and there 24-27 punds of boost :)

I guess Ill look for another 109 and build the stroker I was thinking about :)

GN1 alum. heads and maybe a webber racing short block ??? There prices seem a bit out there but I have heard good things about there motors.

Other option is to pull mine in the fall and hope its done by spring :confused:
 
The stock bore of the 4.1 is 3.965 so boring out .035 would make a 4.00 bore with a stroker crank ,the proper rods and pistons a 274 cu in motor-run it at 18 lbs of boost on pump gas and add alcohol injection for about 24 lbs of boost , with billet caps and possible a 14 bolt rjc girdle .and you would have a very potent possibly 9 second motor.also you already have most of the parts you could transfer into a stage2 4.1 block later if something goes wrong.
 
49-blues said:
The stock bore of the 4.1 is 3.965 so boring out .035 would make a 4.00 bore with a stroker crank ,the proper rods and pistons a 274 cu in motor-run it at 18 lbs of boost on pump gas and add alcohol injection for about 24 lbs of boost , with billet caps and possible a 14 bolt rjc girdle .and you would have a very potent possibly 9 second motor.also you already have most of the parts you could transfer into a stage2 4.1 block later if something goes wrong.
Click to expand...

Interesting what do you mean Id have all the parts for a 4.1 Stage 2 motor Im lost on that one because I thought that Stage 2 was way dif. than this or a 3.8 :confused:

4.1 also uses the same 3.8 motor mount or is that wrong 2 ??? :confused:

Is there any place I can read up on these things just want to learn more about them :)
 
A off center 4.1 stage 2 is basically the same as a production 4.1 only much stronger so almost all the parts would be interchangeable. Motor mounts should be the same only difference is the bores.
 
I just got my 4.1 yesterday, I havent tore it all the way down but its the #4291 block and the #6293 heads. I havent pulled the crank but it should have the rolled fillet crank right, and the 763 rods? Are the 6293 heads any better than the 8445s?
 
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