[Race gas vs pump gas]

I have a 421 cub making 99.8hp on pump gas at 5800ft it has 35mm pwk carbs shearer s/b inframes and 4° advance on timing! If I get smaller cc domes to run 110 and bigger carbs will there be a significant gain in hp to justify the money spent? Will mostly be used for drag racing!

 

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[Race gas vs pump gas]

I have a 421 cub making 99.8hp on pump gas at 5800ft it has 35mm pwk carbs shearer s/b inframes and 4° advance on timing! If I get smaller cc domes to run 110 and bigger carbs will there be a significant gain in hp to justify the money spent? Will mostly be used for drag racing!

 

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[Dmc on 421 serval]

When it’s built hit me up with your jetting. I’ve had issues with my 28s being super finicky between pipes. I bought some 33s I may switch over. Might just be my carbs though …

What would you say the jetting should be at?
I am at just little over 6000ft.

Could order the jets and get them so long will only be building it at the end of the year when I go back home

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[Dmc on 421 serval]

He said fabulous.


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Who's he?

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[Dmc on 421 serval]

You’ll lose as much as 7-10 hp I’m guessing from the Shearers. As you mentioned, they do best with inframe drag pipes, the DMC will be awesome for trails no doubt. 
I pulled 87 hp with SLP amd 91 with Shearers with the exact same set up as what your about to build. My numbers are in the dyno section 

Thank you Sir

Went and checked it out would be good enough for trail riding as far as I'm concerned with the 28's will probably get good fuel milage too compared to the 35's!
Thanks for your info

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[Dmc on 421 serval]

Sweet!
Thought it would hold it back a lot performance wise

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[Dmc on 421 serval]

I recently acquired 421 serval cylinders with a mx port from redline. I know it would be best to run with a larger volume pipe! 'N have shearer small bore and 35pwk on my redline cub and making almost 100hp on pump gas. But since i got the dmc's and some 28pwk lying around thought 'n might just run them till I can get a set of bigger pipes and carbs! Wanting to know what can I expect from this setup?

 

Pump gas

Vforce 4 reeds

4° advance timing

28 pwk

Dmc alien

 

 

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