Boring out 3.9/4.0 OHC blocks

[Anonymous]

Does anyone know how far you can safely bore the 3.9/4.0 ohc blocks

 

[DYNOED250]

We have gone to using 20 tho over 250 pistons in a 4.0.... its about a 70-80 tho over bore and works ok, havnt split a bore yet

 

[Anonymous]

Thanks , do you know if the 3.9 block is the same, we are looking at building a stout speedway engine using a custom intake manifold and 4 barrell on methanol, what aplication was the 4L you bored , how much horse power. We would be looking for a bit over 400 flywheel.

 

[DYNOED250]

it was a 330 hp 4.0 on methanol with a 650 dp holley. this was dynoed..
HAve fun getting compression high.. "DONT DECK THE HEAD" to much as u end up with valves that are to far out on the pistion due to the angle they run on and the chain tensioner runs out of travel. .
a 400 hp 4.0 will take MEGGA head porting and custom $1500 pistons to get comp up to good level to make use of that nice methanol.
On there next motor its going to be tripple webbers/ solexes on methanol, just gota find some

 

[Anonymous]

Thanks sounds like theres some fun to be had then, we wanna get up to around 13-1. Theres a bloke here runing 55mm sidedraught's on methanol on a 3.9,but the the car hasnt seen the track yet, rumoured to have over 400 hp

 

[Anonymous]

hey HRC wat class is it that your racing in.

 

[Anonymous]

They are called supersix , basically a supersedan but no V8 , limited to a ford holden or hemi six , it is a western australian class, my car has a BA falcon body on it

 

[Anonymous]

ahh ok. it also sounds a little bit like the modified productions.