Anybody ever destroke a stock "109" block motor?

[Scott231]

Originally posted by Chris McDade
You won't see any 4.1's in TSM....Unless someone has changed the rules

Hmm, let's re-visit some of the relevant TSM rules -

• "A factory stock appearing part is a GM part that came on a 1981 to 1987 Buick Regal..."
• Buick V6 production block casting (generally the 25526109 block, although, older non-Stage blocks allowed). <250CID maximum

And some quick research on gnttype reveals that the 25506484 4.1L block was available in 1984. Accordingly the block meets the first rule. And since the 4.1 block (stoke stroke and bore) is just under 250 cubic inches, the second rule listed is met. Now if you overbore a 4.1, even just 10 over, you fail the second rule listed above. And thus (the moral of this post), an overbored 4.1L block will have to be de-stroked to be TSM legal.

I am aware of two de-stroked motors in the initial stages for 2004 TSM competition - 1 is a 109 and 1 is a 4.1. If the individuals involved wish to make their names known, they will announce it, not me.

 

[Chris McDade]

Scott,
Way to to put me in my place. I guess I should read all the rules and not just some.

I didn't know that you could run production 4.1 blocks.

Bring them on

Thanks Scott

 

[86brick]

Looks like Walt wasn't the one smoking the good stuff

Thanks for clearing that up Scott

 

[Chris McDade]

I guess my smoke is better

 

[86brick]

Originally posted by Chris McDade
I guess my smoke is better

Yup you gots that really good shiznit

 

[turbo nasty]

In this post late.
But (short stroke)high rpm motors are usaully HP motors were as long stroke motors are tq pigs.

 

[turbofish38]

Scott, If I get out my calculator out and figure 3.965 bore with a 3.400 stroke that comes out to roughly 252 cubes. Does this mean you can not use a 4.1 production block in TSM?

The 3.0 production Buick V-6 was a shorter deck 3.8. 3.80" bore with a 2.66 stroke. Even though the crank has the smaller FWD flywheel flange has anybody done any parts swapping to de-stroke? It also uses shorter rods and uses the same main and rod bearings.

Eric Fisher

 

[quickt]

Originally posted by turbofish38
Scott, If I get out my calculator out and figure 3.965 bore with a 3.400 stroke that comes out to roughly 252 cubes. Does this mean you can not use a 4.1 production block in TSM?

Eric Fisher

Hummm I just looked in 2 books. The Motorsport book I have says 3.960 and the speed pro piston cat says 3.965. The 4.1 block would be legal as long as the CID is 250" or less. That would require a destroke to stay under the 250" limit. It seems that there are some advantages to the short stroke motors. Hi RPM HP over a broad rpm range.

 

[Louie L.]

LOL i guess i should start too.

 

[chevyII]

destroke

If people are using a 4.1 then destrocking them to meet the rules<max cid> I doubt they care about loosing torque and more concered about the larger bore unshrouding the valves. I dont know all the buick stroke,rod lenghts but on a sbc a 4" to 4.125 bore increase does wonders for flow,add a destroked crank and the longest rod possible and your in buisiness. As far as a 109 block its not going to be cheap custom crank and rods $$$$$. thats my 2 cents

 

[Scott231]

I just visited the Buick Power Souce Manual and an online Engine Displacement calculator....and must now recant my earlier post. A completely stock4.1 maesures out to 252 cubic inches and would thus be illegal. Even if you use the 3.960 bore number thatLonnie lists above, that equates to 251 cubes.

As such, IN ORDER TO RUN A 4.1L Buick motor, it MUST BE DE-STROKED.

Any 4.1L motor will be checked with a P&G meter

 

[Whitettype86]

I guess that answer my question on a 4.1 for TSM racing