How many amps to turn an engine over?

[Iamzod]

Quick question, I have googled and come up with wildly different answers of 140 - 400amps so thought I'd try here.

How many amps will be required to start an engine?

2.9L 6cyl Petrol, only thing belt driven is the water & PAS pumps. 9.7:1 Compression.

I am looking for an automotive circuit breaker and want to make sure I get the correct rating.

 

[Iamzod]

Maybe the specifics like make model and brand would help us google for you

It's a Ford Capri but it's running a 24v Granada/Scorpio engine mated to a 2.8i flywheel & starter motor. The aircon & viscous fan are gone.

I did manage to find some starter specs but they state 1100w @ 12v which i work out at only 92amps, can't be right?

 

[Iamzod]

the old 2.9 essex starter in the xr4x4 was 1400w (ive one in the garage) not sure if its the same block as the 24v?

That will have been a Cologne rather than an Essex i think. It's the same block but totally different heads, maybe a beefier starter as they came with things like air-con?

Still only works out at 117A though?

 

[Iamzod]

SO that's the starter figured out, i'm guessing that a petrol fuel pump & the ECU & EFI gubbins isn't going to draw more than 50 amps?

So 200Amp breaker with a 250amp fuse as a backup sound reasonable?

 

[Iamzod]

Don't think it's quite that simple, you'll have a cold cranking amp value that would be required to start the engine - this will be at a really low voltage so amps will be high 300A+

Gah, spanner in the works!

Just to point out, the car won't be seeing the light of day outside of the summer months so it'll never get started in the sort of temperatures we have now.

 

[Iamzod]

The surge on initial crank could be very high. It's very unusual to have a fuse or similar in the starting cable.

Battery is being moved to the boot about 12 feet from it's original location. Don't want a short causing a fire if the cable gets damaged somehow.