What dome size would be optimal for pump on a 421 assassin

[Up north rider]

I’m wondering if I would gain any power from switching from my 24cc to 23 or 22cc domes on my 421 assassin. I don’t plan on running anything higher than pump gas. My cranking psi when I built the motor was around 120. Elevation I ride Is 600-1200 ft. 

[375hp banshees]

@BANSHEE HP

[Up north rider]

It is the low port version as well

[SKEETER]

Just message bill aka bansheehp   

[ClaudeMachining]

I’m wondering if I would gain any power from switching from my 24cc to 23 or 22cc domes on my 421 assassin. I don’t plan on running anything higher than pump gas. My cranking psi when I built the motor was around 120. Elevation I ride Is 600-1200 ft. 

You should always run the least octane your setup can take.

Do a uccr test and report back. Lower than 12, you can put smaller domes.

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[Up north rider]

So correct me if I’m wrong. Uccr means uncorrected compression ratio? 

[SKEETER]

Easy with the big words, claude is only an e n g I n e e r 

[Up north rider]

Lol

[Up north rider]

I don’t even know what it means. 
smh

Edited April 1, 2024 by Up north rider

[ClaudeMachining]

Easy with the big words, claude is only an e n g I n e e r 

I'm way more than a simple engineer. ;-)

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[ClaudeMachining]

I don’t even know what it means. 
smh

Yes UnCorrected Compression Ratio.

Your static compression is kind of low, you can probably use smaller domes, but without uccr test, it's kind of hard to tell.

Bill should know the numbers by heart since he's doing this days in days out.

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[Up north rider]

After talking to driveline, I bought 23cc domes and it made such a huge difference! 
The cranking psi is now 140(cold). I know I should check it again warm just to make sure it’s not too high but I’m sure it’s pretty safe yet. 
I didn’t confirm the squish clearance yet either. .051-.055 is the green zone correct? 
Anyway I thought I’d say it’s running fantastic. 
I had no idea it would be such a drastic change. The cpi pipes that I have on there (I hate to admit it) kind of sucked for playing around and trail riding but now it seems to have way more mid torque. They almost feel like my old t5’s did but in addition to a lot more top end as well. I haven’t touched the jets yet but we’ll see. The thing rips!

[ClaudeMachining]

After talking to driveline, I bought 23cc domes and it made such a huge difference! 
The cranking psi is now 140(cold). I know I should check it again warm just to make sure it’s not too high but I’m sure it’s pretty safe yet. 
I didn’t confirm the squish clearance yet either. .051-.055 is the green zone correct? 
Anyway I thought I’d say it’s running fantastic. 
I had no idea it would be such a drastic change. The cpi pipes that I have on there (I hate to admit it) kind of sucked for playing around and trail riding but now it seems to have way more mid torque. They almost feel like my old t5’s did but in addition to a lot more top end as well. I haven’t touched the jets yet but we’ll see. The thing rips!

Good!!!

I had a DL 421, it was a great engine.

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