M20 B3x Naturally Aspirated Stroker build past, present and future

[Sh3rpak!ng]

Oh no :( :( :( not the kind of update I ever want to see

[digger]

was minding my own business then boom, someone crashed into me....its making me reassess my plans. we will see what happens

[Bearmw]

What happened?

[digger]

The details in this thread..... Can't wait to get my stroked finished.


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I hear you, unfortunately I may never finish. Recent events have put a rather large obstacle in my way, such that it all seems so far away at this point.

[digger]

After seeing these results and part throttle goodness I definitely want that 2nd harmonic with my upcoming m20! Do you think a y pipe would act similarly? I have parts for either 3rd harmonic with factory h pipe precat or I can put my y pipe after the giant factory cat for 2nd.

Yes, y pipe will be same, similar to h as well . I'd do y they flow better if you're happy to use a single pipe

[MrBurgundy]

The details in this thread..... Can't wait to get my stroked finished.


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[whitebulat22]

The harmonic lengths I obtained from pipemax are primarlily a function of the peak hp rpm so for an engine with peak hp in the 6250-6750rpm regardless of other specs the numbers are approx

4th harmonic: 400-425mm
3rd Harmonic: 800-850mm
2nd Harmonic: 1600-1700mm

Torque

After seeing these results and part throttle goodness I definitely want that 2nd harmonic with my upcoming m20! Do you think a y pipe would act similarly? I have parts for either 3rd harmonic with factory h pipe precat or I can put my y pipe after the giant factory cat for 2nd.

[digger]

for reference this is the manifold sitting on a spare stock 885 head showing the change in port entry size, so port entry is not much bigger despite expected power about double stock b25. Equivalent to ~ D39-40mm

[Nutzy]

Stellar work Digger! Looking forward to seeing the results. :)

[digger]

The limitation on stroke is the clearance to the intermediate oil pump shaft. im getting a custom one made as even with slim rod shoulders of the Molnar rods it needs to neck down too much for my liking with crappy quality material (cast iron?) its made from becoming apparent when you start to cut into it

[ForcedFirebird]

Bang up!

[digger]

didn't think you could go bigger than the s52 crank. Are you running the 135mm rods?

The longest rods I've heard is the MM stroker kit which are like 137mm so this crank will really shorten that piston!

135mm rods, which coincidentally is the same length rods that the donor engine had. This means the piston compression height is larger than my MM pistons which use a 138mm rod.

[downforce22]

didn't think you could go bigger than the s52 crank. Are you running the 135mm rods?

The longest rods I've heard is the MM stroker kit which are like 137mm so this crank will really shorten that piston!

[FredK]

Wow. That is a tasty burger!

[digger]

incredible. where did you source the Alpina crank?

eBay, a new one cost about 5k from alpina and you need a VIN, you could get a custom one for that so i waited a couple years until one came up on ebay