W ell i am on debate I have a buit 3.8 in my gn ight now,scat crank, all 4 billet mains and rjc gridle,20 over pistons and cryo rods.I also have roller cam in it and ta s roller lifters. i recently got a brand NEW 4.1 block with caps ad am thinkng of selling my 3.8 and building 4.1. But i am unsure on what is all different if built and swapped out. Like are heads off my 3.8 interchangable etc or do ihave to buy specific stuff. cuz i am thinking of doing a strocker kit and having cam donto match turbo etc. So anybody done something similar andwhat you all have o change on swappin in.
3.8 or 4.1
- Thread starter kraus
- Start date
- Joined
- May 26, 2001
Everything from your 1987 block will work on the 4.1 except the pan. The timing cover will work also if you drill and tap 2 holes for the different oil pan. 
All your 3.8 internals will fit in the 109 block except the pistons.
You WILL see much more than marginal gains, especially on the street in the low end and mid-range HP and torque!
All your 3.8 internals will fit in the 109 block except the pistons.
You WILL see much more than marginal gains, especially on the street in the low end and mid-range HP and torque!
dartguy340
T-Type guy
- Joined
- Oct 2, 2010
Everything from your 1987 block will work on the 4.1 except the pan. The timing cover will work also if you drill and tap 2 holes for the different oil pan.
All your 3.8 internals will fit in the 109 block except the pistons.
You WILL see much more than marginal gains, especially on the street in the low end and mid-range HP and torque!
x2...
Well my thought nick were to either sell my shortblock complete after built this. I mean i girdle and 4 billet capped this one along with the crank. So i was thinking a stroker kit and billet mains and more agressive cam. Its mostly a streetcar but i would like to try and get in 9s or super low 10 teens consistent. But i am trying to do on a radial tire,and not blow my bank account up. Buy knowning i can swap crank and rods out into this block,i can save some money. So know i just have to talk yo more people with knowledge like yourself nick.
Nasty Wendy
Perverted Lurker
- Joined
- May 24, 2001
So you are considering building a stock stroke 4.1? Think about this. A stock stroke 4.1 is ~ 252 cubes. If you put a stroker crank into your built 3.8 you'll be at 249 cubes. Considering the strength that the capped and girdled 3.8 will have over the 4.1 you would be better off stroking your existing 3.8.
Look into whether you'd need new pistons or if there is a rod length that would work for you to use your current pistons. If you could use your current pistons and only need a crank and rods and have a steel crank to sell to recoup some cost then stroke your 3.8. You didn't list what rods your 3.8 use but if they aren't the 2dots then you could sell those to recoup more cost. I have a 4.1 and love it. If some one wanted to trade me straight up for a capped, girdled, & stroked 109 I wouldn't hesitate. Jason White has been in the upper 8's with the stroked 109. I remember Dick Kerney going pretty freakin' fast with a stroked 109 as well (9.0s maybe 8.9?). Whats the fastest a production 4.1 has lived to brag about?
- Joined
- May 26, 2001
The reason I am a big fan of the 4.1 block over a 3.8 because my personal experience over 20 years with building and using them has been superior performance especially on a street car, and never yet had one give up on a street strip build even into the 9's.
Certainly the added displacement is helpful, but the most important advantage is the larger bore. Almost all racers will take increased bore over stroke for added performance as it will allow better breathing especially in our case with a V-6 Buick as it moves the cylinder wall away from the valves to reduce restriction and un-shroud the air flow in-and-out of the cylinder.
When you stroke a 4.1 and add about 20 cubic inches, this will certainly add more power, but it will not come into play until you reach a higher RPM range usually over 6000 which is not where you would be often with a street car.
I have built MANY 4.1 production engines over the years and personally about 6 of them for my personal use in various Regals.
Currently I have a 4.1 production block in my race car as well as one in a street car.
The race car has a 70mm turbo and has developed 650 HP on the dyno at 18 psi, and the street car with a 66mm turbo about 100 HP less, and both are on E-85.
Personally I will not post tech info or comments unless I have personal knowledge or experience, and if I have an opinion on a subject, I will state it as such. It is amazing how many "experts" tell what is best, or good/bad, but not actually "been there, done that"?
Certainly the added displacement is helpful, but the most important advantage is the larger bore. Almost all racers will take increased bore over stroke for added performance as it will allow better breathing especially in our case with a V-6 Buick as it moves the cylinder wall away from the valves to reduce restriction and un-shroud the air flow in-and-out of the cylinder.
When you stroke a 4.1 and add about 20 cubic inches, this will certainly add more power, but it will not come into play until you reach a higher RPM range usually over 6000 which is not where you would be often with a street car.
I have built MANY 4.1 production engines over the years and personally about 6 of them for my personal use in various Regals.
Currently I have a 4.1 production block in my race car as well as one in a street car.
The race car has a 70mm turbo and has developed 650 HP on the dyno at 18 psi, and the street car with a 66mm turbo about 100 HP less, and both are on E-85.
Personally I will not post tech info or comments unless I have personal knowledge or experience, and if I have an opinion on a subject, I will state it as such. It is amazing how many "experts" tell what is best, or good/bad, but not actually "been there, done that"?
Tom Walker
Tommy2Tone
- Joined
- Jul 18, 2004
Years ago, I built a 400 SBC with a 350 steel crank, .030 to net a 377. A builder of Nascar engines gave me the insight on unshrouding the valves with a larger bore. With the same Crane cam, carb, headers, etc... in both Novas, mine walked off and left a 383 chevy in the quarter. I'm a firm believer in bore over stroke when looking for power. I'm sure the 4.1 story is much the same.
I was thinking of stroking the 4.1 new everything originally and sell my complete 3.8. Buy i was thinking just building the 4.1 without stroking is still more cubes then mine. My motor npw has dot 2 rods that are cryp treated,with a 20 over piston. The only thing i thinl that i would change in it is the baby 208 210 cam. Maybe have one designed to go more with the 6765 turbo i added 5months ago. The car is fun bit i got the 4.1 and was weighing options. Like said its a streetcar full interior ac,cruise etc. i may just sell the block and spend money on cam swap.
Mike Licht
I was here first
- Joined
- May 23, 2001
my 4.1 street car is awesome. For a street car they are tough to beat. I am building 3 for customers right now
Mike
Mike
Mike Licht
I was here first
- Joined
- May 23, 2001
I am not sure anyone has ever pushed a 4.1 the way a 109 has been pushed by the TSM guys but there is plenty in the 9's holding up just fine
