Hypothetical 5.0L Barra build.

[Changothelion]

I am trying to find answers on whether you can bore and stroke out a BF Barra so that its a 5.0L.

Is it okay to go 0.060 over for bore, or will it cut into the cooling jacket?

Are there kits out there that are already made?

 

Is there even a crankshaft that can give enough stroke to make a difference?

[Puffwagon]

I heard you can take a billet block out to 4.5 litres with stock stroke. I don't know how big you can go with sleeves on a stock block but it would be a 4.2 litre with 2.5mm O/S pistons.

 

Also keef broke the forum

[k31th]

 

The barra engine actually runs better with lowering the "capacity" and de-stroking it, as the stroke is longer than the bore (ratio) so stroking it will make it even more unstable in higher rev ranges, but of course could add some more low-end torque, which the barra really doesn't need as it has plenty already.

[Changothelion]

Thank you that really helps

[Puffwagon]

Define "runs better".

 

If you jump up to 4.2 or 4.5 litres you'll have a lot more low end torque and turbos will come online much faster. Stock stroke engines have been pushed well over 9000rpm with the right cams and with larger displacement you can lower this and still achieve the same result. For a street car it is a no brainer to have more displacement, god knows we've heard enough people whinging about turbo lag on this forum.

 

Spool offers a 4.2 litre stroker kit and there was a car that made all the power with it, all the way through the rev range. 100whp more on the same boost.

[Changothelion]

that's awesome thank you, Im definitely gonna look into that.

[k31th]

23 minutes ago, Puffwagon said:

Define "runs better".

 

If you jump up to 4.2 or 4.5 litres you'll have a lot more low end torque and turbos will come online much faster. Stock stroke engines have been pushed well over 9000rpm with the right cams and with larger displacement you can lower this and still achieve the same result. For a street car it is a no brainer to have more displacement, god knows we've heard enough people whinging about turbo lag on this forum.

 

Spool offers a 4.2 litre stroker kit and there was a car that made all the power with it, all the way through the rev range. 100whp more on the same boost.

Obviously I was using a fairly vague statement with "runs better"... A more "square" engine runs more stably which means it can run up higher revs for much longer and safer.

 

More stroke will make it more unstable in higher revs and put more pressure on the the entire engine and make it more likely to destroy itself. Not saying you can't do either and get a result you might want, but I wouldn't even think of stroking a barra for more displacement, just up the boost/timing haha

 

Also, imagine a company selling a product that spruiks it on their own blog... fair dinkum, find me one person who's even done it and posted about it on the internet independently of sponsorship by spool.

Also, I remember dynomite doing some back-to-back saying just "bigger cams" made 100rwhp across the rev-range... it's not scientific/repeatable if you change more than 1 variable.

 

They (spool & dynomite) say they're trying to keep everything the same but you have to change the tune to take advantage of the "more displacement" or "bigger cams", which invalidates the test unless they're 100% transparent about the specific tune changes.

[Puffwagon]

Yeah there are stuff and things about an engines bore and stroke that make it better or worse for various applications. I for one would definitely prefer to use a 4.2 litre stroker on the street. Making power isn't the issue, you get the benefit of the low down response from a gtx35 with the legs of a gtx45. Sign me up! cough cough...someone tell my wife...