Which way to go ...109 stroker or 4.1 ??

[dynoman]

You are absolutely correct that a 4.1 build will make it "easier" to reach goals especially with a street/strip build.

We have done 10 4.1 engine builds over the past year and can positively say it is much more responsive and pulls harder on the street with the massive amount of torque at low RPM and keeps pulling to high RPM.

I seriously doubt that the ones saying "stay with the 109" have any experience with a properly set up 4.1?

One of my production 4.1 builds can run 9.90's at 18 psi and a 70mm turbo with over 3000' altitude, which a make that ~ a 9.7 at sea level.

As far as 3.625" stroke on a 4.1, you will not see any significant performance increase until you reach the upper RPM range.

Since all 4.1 turbo pistons are a custom piece, the stroker pistons we use are about $200 more for the set, and you will spend a few hundred more $$$ in clearancing and mock-up costs.

Nick, if I can't find a good 4.1 block is it worth it to stroke the 109 . Either way I go ...4.1 , stroked 109 , or stock stroke 109 , they will be run on E85.

 

[dynoman]

Make sure to get the block checked as I have come across many cracked ones over the years. I was building these motors back in the early 90's for myself and customers, then no one wanted them. I am surprised these are making a big comeback 20+ years later.

Dave, where are the cracks usually , on the deck from the head bolt holes ?

 

[87WE4BOOSTED]

Nick, if I can't find a good 4.1 block is it worth it to stroke the 109 . Either way I go ...4.1 , stroked 109 , or stock stroke 109 , they will be run on E85.

I say you'll be fine if you don't find one soley based on you goals.

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[dynoman]

Can I my JE pistons on a stroked 109 , or is there a difference in pin loction on a stroker ? My pistons are low mileage and could save $$$ if they could be reused.

 

[David Husek]

Here is a picture of the engine when it arrived

Dave, where are the cracks usually , on the deck from the head bolt holes ?

They do crack from the bolt holes to the water jackets. The ones I came across were cracked from the main to the cam bore on number 2.

 

[David Husek]

Can I my JE pistons on a stroked 109 , or is there a difference in pin loction on a stroker ? My pistons are low mileage and could save $$$ if they could be reused.

The JE pistons use a 1.850 comp height. They are too tall for a stroker setup, you would need a connecting rod 5.85" long. I have a killer deal on a stroker setup for a 109 if interested.

 

[dynoman]

Thanks Dave, but I'm not going to build the motor myself, I'm going to leave that to the experts !! I don't want to hand a builder a bunch of parts and say can you put it together for me. I hope someone on here will build my motor once I decide which way to go.

 

[dynoman]

The JE pistons use a 1.850 comp height. They are too tall for a stroker setup, you would need a connecting rod 5.85" long. I have a killer deal on a stroker setup for a 109 if interested.

Well it looks like reusing my pistons is a non issue due to the hole I spotted in one of them when I pulled the oil pan last night.

 

[TTipe]

You are absolutely correct that a 4.1 build will make it "easier" to reach goals especially with a street/strip build.

We have done 10 4.1 engine builds over the past year and can positively say it is much more responsive and pulls harder on the street with the massive amount of torque at low RPM and keeps pulling to high RPM.

I seriously doubt that the ones saying "stay with the 109" have any experience with a properly set up 4.1?

One of my production 4.1 builds can run 9.90's at 18 psi and a 70mm turbo with over 3000' altitude, which a make that ~ a 9.7 at sea level.

As far as 3.625" stroke on a 4.1, you will not see any significant performance increase until you reach the upper RPM range.

Since all 4.1 turbo pistons are a custom piece, the stroker pistons we use are about $200 more for the set, and you will spend a few hundred more $$$ in clearancing and mock-up costs.

Nick I tend to disagree from a longevity aspect. Race engines are continuously "freshened" so perhaps longevity is not an issue. The head studs/bolts are closer to the cylinder bore walls than the 109. Even with countersinking the thread bore into the deck (and all the other smoke and mirrors) the clamping force radiates out from the center of the head stud. There is less material (deck) with the 4.1L block than the 109 therefore the bore wall will be pulled easier toward the cylinder head stud/bolt. This could compromise bore sealibility since the bore shape will begin to look like a clover leaf. I know because I used to see the bore shape from the Buick Engineering Lab cylinder bore studies. The apparatus used was a "Talley Round" which produced a logarithmic (exaggerated) result. Also as more power is built into these 4.1L engines the siamesed bore walls will like to push on each other more.

 

[TTipe]

You are absolutely correct that a 4.1 build will make it "easier" to reach goals especially with a street/strip build.

We have done 10 4.1 engine builds over the past year and can positively say it is much more responsive and pulls harder on the street with the massive amount of torque at low RPM and keeps pulling to high RPM.

I seriously doubt that the ones saying "stay with the 109" have any experience with a properly set up 4.1?

One of my production 4.1 builds can run 9.90's at 18 psi and a 70mm turbo with over 3000' altitude, which a make that ~ a 9.7 at sea level.

As far as 3.625" stroke on a 4.1, you will not see any significant performance increase until you reach the upper RPM range.

Since all 4.1 turbo pistons are a custom piece, the stroker pistons we use are about $200 more for the set, and you will spend a few hundred more $$$ in clearancing and mock-up costs.

Nick I tend to disagree from a longevity aspect. Race engines are continuously "freshened" so perhaps longevity is not an issue. The head studs/bolts are closer to the cylinder bore walls than the 109. Even with countersinking the thread bore into the deck (and all the other smoke and mirrors) the clamping force radiates out from the center of the head stud. There is less material (deck) with the 4.1L block than the 109 therefore the bore wall will be pulled easier toward the cylinder head stud/bolt. This could compromise bore sealibility since the bore shape will begin to look like a clover leaf. I know because I used to see the bore shape from the Buick Engineering Lab cylinder bore studies. The apparatus used was a "Talley Round" which produced a logarithmic (exaggerated) result. Also as more power is built into these 4.1L engines the siamesed bore walls will like to push on each other more.

 

[TTipe]

You are absolutely correct that a 4.1 build will make it "easier" to reach goals especially with a street/strip build.

We have done 10 4.1 engine builds over the past year and can positively say it is much more responsive and pulls harder on the street with the massive amount of torque at low RPM and keeps pulling to high RPM.

I seriously doubt that the ones saying "stay with the 109" have any experience with a properly set up 4.1?

One of my production 4.1 builds can run 9.90's at 18 psi and a 70mm turbo with over 3000' altitude, which a make that ~ a 9.7 at sea level.

As far as 3.625" stroke on a 4.1, you will not see any significant performance increase until you reach the upper RPM range.

Since all 4.1 turbo pistons are a custom piece, the stroker pistons we use are about $200 more for the set, and you will spend a few hundred more $$$ in clearancing and mock-up costs.

Nick I tend to disagree from a longevity aspect. Race engines are continuously "freshened" so perhaps longevity is not an issue. The head studs/bolts are closer to the cylinder bore walls than the 109. Even with countersinking the thread bore into the deck (and all the other smoke and mirrors) the clamping force radiates out from the center of the head stud. There is less material (deck) with the 4.1L block than the 109 therefore the bore wall will be pulled easier toward the cylinder head stud/bolt. This could compromise bore sealibility since the bore shape will begin to look like a clover leaf. I know because I used to see the bore shape from the Buick Engineering Lab cylinder bore studies. The apparatus used was a "Talley Round" which produced a logarithmic (exaggerated) result. Also as more power is built into these 4.1L engines the siamesed bore walls will like to push on each other more.

 

[TexasT]

So, with this clover leaving, by using a torque plate, and a head torqued on the opposite side along with the mains toqued on it should replicate the shape of the cylinder in the finished block. Or at least it should more than doing the machine work without those things torqued on. And while the casting on the 4.1 is known thinner, I would have to think that it is thick enough or there wouldn't be any driving around and running at the strip.
Anymore cool info from "back in the day" at Buick Motorsports.

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[TTipe]

So, with this clover leaving, by using a torque plate, and a head torqued on the opposite side along with the mains toqued on it should replicate the shape of the cylinder in the finished block. Or at least it should more than doing the machine work without those things torqued on. And while the casting on the 4.1 is known thinner, I would have to think that it is thick enough or there wouldn't be any driving around and running at the strip.
Anymore cool info from "back in the day" at Buick Motorsports.

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I referenced longevity. However my point is supported by leaking the motor. I bet when you leak your new 4.1L and get less than 3% max leak on any cylinder and your maximum variation from any cylinder to any cylinder is less than 1% I'm sure you are satisfied. Leak the engine after 5k miles of weekend racing, normal driving and proper oil changes and you may be surprised. Heat cycling ,thrust forces ,rod offset loading and chamber pressure work on deck plate honed & temperature regulated (load the jackets at coolant temp) bores regardless of money spent and good wishes. Deck plate honing sets the bore statically at a chosen set of saddle and deck loadings. Heat cycling ,reciprocating load forces and chamber pressures are dynamic and cumulative. Deck plate honing and optimal saddle loading help, but ultimately the thinner bore walls and decks are the issue since the loading of the head fasteners are still pulling. Bend a piece of sheet metal compared to a piece of cardboard. The 4.1L block had the most "unstable" (as shown by the Talley Round) bores. The most stable was the 3.3L on center MFI blocks. Do you see a relationship forming?? Bore center to center is constant. Bore stability decreases as bore wall thickness decreases. Obviously this comment excludes P/N 25500016.

 

[Jay J]

Great thread. Did you do testing on the later, FWD 3.8 V6 as well?

 

[TTipe]

Great thread. Did you do testing on the later, FWD 3.8 V6 as well?

Yes

 

[20psiofevil]

Very nice post! Did you do any metallurgy testing between the 2 blocks?


Also from my stand point I would look to gain around 50 rwtq going from 232ci to 250ci. I gained nearly 80 going from a 232 to 260 myself.

 

[KevinB]

Are you all using stock cranks for these low 10/high 9 builds? Girdle? Caps?

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[Jay J]

TTipe: Have not seen any posts that have gone into the depth that you have regarding the Buick blocks. Most of us are stuck with a dwindling supply of rebuild-able (junkyard) cores. That is why I asked about the FWD 3800 series, because we need an affordable, viable place to put all this great stuff--stroker cranks, good rods, pistons, etc. that are now available. Would appreciate hearing about what you found when you tested the later CI blocks... And any opinions you may offer regarding the preservation of these cars.

Thanks-

 

[TexasT]

Great info. I haven't assembled one yet. Though I do have a block that passed a magnaflux by my machinist. I understand the limits. I understand the thinner deck and cylinder walls. I also understand that 5k miles of weekend racing/cruising might be over a decade of time. Using a forged crank and main caps to try and control the flex and thus control or at least put off busting out the webs for a while. Then maybe move over to a ta block. But at that $, I'll stick with production stuff I find in the wrecking yards and Craig's list for the budget I work with. Just the pistons equal what I spent on the block, crank, machine work, cam bearings and gasket set.
I am glad you are adding to the mix, lots of good info you provide. No replacement for displacement, or we would all be hunting 3300 blocks and going for longevity.


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[Jay J]

One other point--have you guys ever noticed that a new engine always seems to run better after 5k miles or more?