4.1=3.8 turbo crank



Not that I need one but a cheap spare would be nice. Do all 4.1 have the hard to find turbo crank? If so, what cars to look at for a 4.1?
From what I understand, Yes. I just picked up a 4.1 for $20 from a '84 NA Regal. It had the rolled fillet crank, and 8445 heads.

From the Before Black Website:

GM cars with the Buick 4.1 V6 (252 ci)
(Easily identified from 3.8 Litre by Quadrajet)

80 STD-Electra, OPT-LeSabre
81 STD-Electra, Riviera, OPT-LeSabre, Riviera T Type
82 STD-Electra, Riviera, OPT-LeSabre, Regal Note: Included in Grand National Package
83 STD-Electra, Riviera, OPT-LeSabre, Regal
84 STD-Electra, Riviera, OPT-LeSabre, Regal

81 OPT-All except Limo
82 OPT-Seville, Eldorado, DeVille, Fleetwood
(NOTE: badges will say 4.1 for V6, 4100 for Cad V8)

81 STD-98,Toronado
82 STD-98,Toronado
83 STD-98,Toronado
84 STD-Toronado

82 OPT-Bonneville, Grand Prix
Be aware that if the 4.1L has been rebuilt by a mass rebuilder(Jasper's, etc), it *MAY NOT* still have the rolled fillet crank in it...Just pop the oil pan off and pull a rod cap to make sure that it still is a rolled fillet crank...Usually, the major rebuilder's will epoxy some kind of ID tag somewhere on the block for warranty purposes...If a tag is there, chances are good that a regular 3.8L crank is in there...
Does anybody know the block casting number on those early 4.1 blocks with the rolled fillet crankshafts? The cranks were # 229,
i think ? ThX.
All 4.1L motors had the rolled rod journal fillet cranks(if motors hadn't been rebuilt by mass rebuilders, then it's a crap shoot whether the rolled fillet crank is still there)...

The desirable 4.1L blocks had casting #25506484...I believe that was for the '83/4 blocks...'84 for sure...They have the oiling system upgrades...The other casting # for the 4.1L that I know of were #25506818...They were '80/2 blocks...

You can't just go by the casting # on the cranks and ASSume you are getting a turbo crank...I've seen the #229 cranks, I also have a turbo crank with #877...You have to visually inspect the crank for the rolled rod fillets...All the cranks(NA and turbo) were made from the same crank castings...It is just the turbo cranks and the 4.1L cranks that recieved an extra manufacturing step(the pressure rolled rod fillets) that distinguishes them from the NA cranks...

If you are thinking of getting a crank out of a 4.1L motor, make sure you pull the oil pan and a rod cap and visually check for the rolled fillets...These motors are now 20 yrs old and there's a good chance that the motors have been rebuilt and the cranks replaced with a NA 3.8L crank...A very easy way to identify a 4.1L motor w/o having to crawl under the car is look for the factory alum. 4 bbl intake...If the intake is there, then crawl under and look for the casting # to doublecheck that it is a 4.1L...Swapping a 4 bbl intake on a 3.8L is a very quick way to make more power w/ the 3.8L...

Also, if you are looking to build the 4.1L into a turbo motor, pull a cyl head and check the piston tops for overbore numbers...If it isn't a stock bore block, you won't be able to use it...I've seen some that are .060 over at salvage yards...

Go here for more info...


Hope this helps...
If the car is an 83 or newer with a 4.1, take the whole engine!!! You can sell it to some other TB member who wants to build a 4.1. I bought an 83 4.1 engine at the local yard for $160. Just my luck that I sold it to Cool 84 before I realized that it had stage 1 heads. So Cool 84 scored a standard turbo crank, standard 4.1 and stage 1 heads for $160. Lucky for him I guess...........
According to the Buick Power Source manual, true Stage 1 heads have the intake face of the head filled in(no egr or heat crossover provisions)...the coolant passages at the ends of the heads are bridged, where the production head was not...Also, they have the same casting number as the production head(25506293)...Reinforced deck surface, intake port wall on the short-side radius is revised to allow increased airflow when ported(Both the water jacket and intake port core have been revised)...

Unless those heads had these features, I doubt they would make it on a production motor from the factory...Those heads were probably big bucks and were maybe worth more than the production motor they were put on(if they actually did make it on the motor)...If they are, then GOOD FIND!!! We should all hope to be so lucky...Stranger things have happened...

Cool84, can you actually verify that using the description of the heads from the Buick Source manual???
Where do I find the 109 casting #? I found an 86 GP at the yard and just want to make sure it's a 109 with the 8445 heads before I pull it all apart. TIA
Originally posted by Carolinaturbot6
The picture there shows the rolled fillet. The arrow points to it. It makes the crank stronger.

This may be a dumb question but...Is the rolled fillet the only difference and can they be machined into a NA 3.8 crank?
The rolled rod fillet is the only difference between the turbo crank and the NA crank...

The fillet cannot be machined into it...It must be pressure rolled into the crank...It's kind of like forging but they are just compressing the material in the corners of the journal...The corner of the journal is where the cranks will break, if they break...That is the weak spot...By compressing the metal in the corners, it makes the material more dense and stronger there...
Turbo Crank

Are this turbo rolled filet cranks forged or cast, also who makes a good forged after market crank for the 86/87 gn 109 block??? Thanks.
The stock turbo rolled fillet cranks, if I remember right, are Nodular cast iron...

Not sure who would have forged cranks in stock, if they're even available...Some billet cranks may be floating around though...

With TA Performance making the new alum V6 replacement block, they are supposed to start into getting new cranks and rods made to be able to hold up to the power that the new block is supposed to be able to support...They do have new heads coming out really soon(next couple of months)...
If you are looking for a billit crank T/a performance has crower billits in stock also he is taking orders on the new aluminum block.If you don't want to get a billit crank from T/A, you could get a scat like i did but you will probably wait "9 MONTHS"to get it."Cryogenically Frozon 109"
Another dumb question. I have looked at the pic on gnttype, but it is not clear. I don't really understand what the rolled fillet looks like compared to the N/A. Does anyone happen to have clear pics of both?