What limits the redline on the IDI?

[huggyb1972]

I don't mean that how it sounded I know that the govenor in the pump is what holds back the engine speed. What I am wondering is why did the manufacturer choose 4000 rpm. is the rotating mass so great that it will not tolerate more speed than that? or will the injector pump not function properly at the higher speeds? Anyone know the answers to these questions. Just to be clear here I have a IDI and spare parts so to experiment with it won't cost me as much as a powerstroke would and so far parts are cheap fromwhere I'm sittin.:ford:

 

[kas83]

The fact that it's an IDI is what limits the rpm potential. Since combustion starts in a small prechamber, and then travels into the cylinder, it takes more time to burn. The burn rate is what holds it back.

But, Hypermax's "Super IDI" back in the day was reported to spin 6500 rpm, and it's claimed to have stayed IDI, not converted to direct injection. So who knows.